Blockade of OGFr delays the onset and reduces the severity of diabetic ocular surface complications.

The opioid growth factor (OGF)-OGF receptor (OGFr) pathway is present in the ocular surface and functions to maintain homeostasis of the epithelium. The OGF-OGFr pathway has been reported to be dysregulated in diabetic individuals and animal models, and is reflected in elevations of the inhibitory growth factor, OGF, chemically termed [Met5]-enkephalin. Recently, our laboratory reported elevated levels of OGF and OGFr in the serum and corneal epithelium of type 1 diabetic rats, suggesting that dysregulation of the OGF-OGFr axis may lead to dry eye, abnormal corneal surface sensitivity, and delayed re-epithelialization. Blockade of OGF-OGFr pathway using naltrexone, a potent opioid receptor antagonist, reverses dry eye symptoms and restores corneal surface sensitivity in diabetic rats when used as a therapy. Based on the evidence that both OGF and OGFr are elevated in type 1 diabetic rats, this study examined whether systemic or topical naltrexone treatment initiated at the time of induction of hyperglycemia could protect against the development of diabetic ocular surface complications. Diabetic male Sprague-Dawley rats treated systemically or topically with naltrexone had a delayed onset of dry eye and altered corneal surface sensitivity, and an improved healing rate for corneal wounds, that were comparable to non-diabetic rats. Serum levels of OGF were normal for rats receiving systemic naltrexone, and OGF tissue levels were normal for type 1 diabetic rats receiving twice daily naltrexone drops. OGFr levels remained elevated. These data support the role of the OGF-OGFr axis in regulation of ocular surface complications, and suggest that naltrexone therapy may be beneficial for pre-diabetic and early diabetic individuals.

[Met5]-enkephalin preserves diffusion metrics in EAE mice.

Multiple sclerosis is a chronic progressive neurological disorder that has few distinctive biomarkers associated with disease progression or response to therapy. This research investigated whether non-invasive imaging correlated with animal behavior and morphological indicators of disease in response to serum levels of [Met5]-enkephalin. Using the experimental autoimmune encephalomyelitis (EAE) model, adult female C57BL/6 J mice were randomized to receive daily injections of 0.1 mg/kg naltrexone (NTX) (= low dose naltrexone, LDN), 10 mg/kg Opioid Growth Factor (OGF) (chemically termed [Met5]-enkephalin) or saline beginning at the time of disease induction. Daily composite behavior scores were recorded over a 30-day period based on tail tone, gait, righting reflex, and limb strength. Prior to disease onset (day 7), and at peak disease (day 18), mice were imaged and tissues (blood and spinal cord) collected at day 30 for serum analyses of OGF and morphology. Serum OGF levels of EAE mice treated with saline were significantly reduced from baseline and from normal mice. Longitudinal cohort data demonstrated an increase in fractional anisotropy in all cohorts by day 18. There was a significant decrease in radial diffusivity in the saline group seen at day 18 whereas the axial diffusivity was not altered amongst treatment groups. Treatment with OGF or LDN resulted in mean diffusivity rates that were comparable to baseline (normal) levels at days 7 and 18. Luxol fast blue staining of the lumbar spinal cords demonstrated a 16 % reduction in myelin staining in saline treated EAE animals when compared to OGF and LDN treated EAE mice. Immunohistochemistry with Olig2 (pan-oligodendrocyte marker) and myelin basic protein (MBP) revealed that OGF and LDN treatment restored the area (%) of MBP and number of oligodendrocytes to that of normal spinal cord (∼75 %). Saline treated EAE mice had more demyelination and fewer oligodendrocytes than normal mice. Collectively, these data suggest that a panel of biomarkers including imaging, serum biomarker levels, and behavior correlate with progression of disease, and may begin to validate use of specific non-invasive markers for MS.

Opioid-like peptides and ghrelin mitigation of bariatric results depends on obesity level.

INTRODUCTION: Bariatric surgery, as the only effective treatment of obesity, has strong effects on the metabolism, and nervous and endocrine systems. Thus, based on the different opinions about the efficaciousness of morbid obesity treatments, the aim of the present study was to estimate the association of serum ghrelin and Met-enkephalin (native, five amino acids and cryptic, precursor of enkephalin) concentrations with body mass index (BMI) value in bariatric patients within 30 postoperative days. MATERIAL AND METHODS: The study was performed on 38 female patients divided into two groups: I - BMI lower than 40 kg/m² (n = 18) and II - BMI higher than 40 kg/m² (n = 20). Blood was taken before (-24 h), and 72 h and 30 days after the sleeve gastrectomy. Routine haematological, anthropometric, and metabolic parameters as well as thyroid-stimulating hormone (TSH), ghrelin, and Met-enkephalin values were measured in all patients. RESULTS: There were statistically significant differences between the two groups before the surgery in terms of TSH, both forms of Metenkephalin, triglycerides concentrations, and activity of alanine transaminase (ALT), gamma glutamyltransferase (GGTP), and C-reactive protein (CRP). After 72 h, the serum levels of cryptic Met-enkephalin and CRP, and activity of enzymes varied between the two groups of patients. Thirty days after the surgery, some metabolic and immune parameters were still different in both female groups in favour of patients with lover BMI. However, significant differences were noticed in the levels of ghrelin (increase), and native (decrease) and cryptic Met-enkephalins (increase). CONCLUSIONS: The activity of endogenous peptides in bariatric patients is connected with the degree of obesity. Ghrelin level increases are negatively correlated with native Met-enkephalin changes shortly after bariatric surgery. The interplay of ghrelin and opioids might be considered as a predictor of postoperative weight loss success.

Remote ischaemic preconditioning modifies serum apolipoprotein D, met-enkephalin, adenosine, and nitric oxide in healthy young adults.

Remote ischaemic preconditioning (RIPC) has been employed as a non-invasive protective intervention against myocardial ischaemia-reperfusion injury in animal studies. However, the underlying mechanisms are incompletely defined in humans and its clinical efficacy has been inconclusive. As advanced age, disease, and drugs may confound RIPC mechanisms in patients, our aim is to measure whether RIPC evokes release of adenosine, bradykinin, met-enkephalin, nitric oxide, and apolipoproteins in healthy young adults. Healthy subjects (n = 18, 9 males, 23 ± 1.5 years old; 9 females, 23 ± 1.8 years old) participated after informed consent. RIPC was applied using a blood pressure cuff to the dominant arms for four cycles of 5-minute cuff inflation (ischaemia) and 5-minute cuff deflation (reperfusion). Blood was sampled at baseline and immediately after the final cuff deflation (Post-RIPC). Baseline and Post-RIPC plasma levels of adenosine, bradykinin, met-enkephalin, apolipoprotein A-1 (ApoA-1), apolipoprotein D (ApoD), and nitric oxide (as nitrite) were measured via ELISA and high-performance liquid chromatography. Mean (±SD) baseline levels of adenosine, bradykinin, met-enkephalin, ApoA-1, ApoD, and nitrite in healthy young adults were 13.8 ± 6.5 ng/mL, 2.6 ± 1.9 µg/mL, 594.1 ± 197.4 pg/mL, 3.0 ± 0.7 mg/mL, 22.2 ± 4.0 µg/mL, and 49.8 ± 13.4 nmol/L, respectively. Post-RIPC adenosine and nitrite levels increased (59.5 ± 37.9%, P < .0001; 32.2 ± 19.5%, P < .0001), whereas met-enkephalin and ApoD levels marginally decreased (5.3 ± 14.0%, P = .04; 10.8 ± 20.5%, P = .04). Post-RIPC levels were not influenced by sex, age, blood pressure, waist circumference, or BMI. RIPC produces increased levels of adenosine and nitrites, and decreased met-enkephalin and ApoD in the plasma of young healthy adults.

Enkephalin degradation in serum of patients with inflammatory bowel diseases.

BACKGROUND: Inflammatory bowel diseases (IBD) are a group of chronic and recurrent gastrointestinal disorders that are difficult to control. Recently, a new IBD therapy based on the targeting of the endogenous opioid system has been proposed. Consequently, due to the fact that endogenous enkephalins have an anti-inflammatory effect, we aimed at investigating the degradation of serum enkephalin (Met- and Leu-enkephalin) in patients with IBD. METHODS: Enkephalin degradation in serum of patients with IBD was characterized using mass spectrometry methods. Calculated half-life (T1/2) of enkephalins were compared and correlated with the disease type and gender of the patients. Additionally, statistical analysis was used to examine the dynamics of changes in terms of inhibition of enkephalins degradation within research groups. RESULTS: Our research indicates that the degree of enkephalins degradation depends on the gender of the patients. The difference is most evident for the rate of Met-enkephalin degradation between men (mean T1/2 = 13.61 min) and women (mean T1/2 = 21.84 min) with Crohn's disease (CD). CONCLUSIONS: The most significant alternation of enkephalins degradation in serum samples of IBD patients, compared to control group, were observed in both Crohn's disease and ulcerative colitis (UC) female patients. We suggest that the differences observed between the genders in IBD patients may be explained by regulation of enkephalinases activity by estradiol.

Determination of methionine-enkephalin and leucine-enkephalin by LC-MS in human plasma: Study of pre-analytical stability.

The aim of this work was to assess the influence of preanalytical variables on the stability of two endogenous opioid peptides (Methionine-Enkephalin and Leucine-Enkephalin) in human plasma. For this purpose, first a sensitive LC-MS/MS analytical method was developed and validated for the simultaneous quantitative analysis of these two peptides. The methodology consisted of a simple protein precipitation step followed by UPLC separation and MRM quantitative analysis using a stable isotope labelled Methionine-Enkephalin as internal standard. The method with a limit of quantitation of 10 pg/mL showed good reproducibility with excellent accuracy and precision, and was linear up to 2000 pg/mL. An extensive evaluation of the pre-analytical stability of these peptides in human blood was carried out to ensure an adequate sample collection procedure to obtain reliable results in the analysis of clinical samples.

Featured Article: Modulation of the OGF-OGFr pathway alters cytokine profiles in experimental autoimmune encephalomyelitis and multiple sclerosis.

The endogenous neuropeptide opioid growth factor, chemically termed [Met5]-enkephalin, has growth inhibitory and immunomodulatory properties. Opioid growth factor is distributed widely throughout most tissues, is autocrine and paracrine produced, and interacts at the nuclear-associated receptor, OGFr. Serum levels of opioid growth factor are decreased in patients with multiple sclerosis and in animals with experimental autoimmune encephalomyelitis suggesting that the OGF-OGFr pathway becomes dysregulated in this disease. This study begins to assess other cytokines that are altered following opioid growth factor or low-dose naltrexone modulation of the OGF-OGFr axis in mice with experimental autoimmune encephalomyelitis using serum samples collected in mice treated for 10 or 20 days and assayed by a multiplex cytokine assay for inflammatory markers. Cytokines of interest were validated in mice at six days following immunization for experimental autoimmune encephalomyelitis. In addition, selected cytokines were validated with serum from MS patients treated with low-dose naltrexone alone or low-dose naltrexone in combination with glatiramer acetate (Copaxone®). Experimental autoimmune encephalomyelitis mice had elevated levels of 7 of 10 cytokines. Treatment with opioid growth factor or low-dose naltrexone resulted in elevated expression levels of the IL-6 cytokine, and significantly reduced IL-10 values, relative to saline-treated experimental autoimmune encephalomyelitis mice. TNF-γ values were increased in experimental autoimmune encephalomyelitis mice relative to normal, but were not altered by opioid growth factor or low-dose naltrexone. IFN-γ levels were reduced in opioid growth factor- or low-dose naltrexone-treated experimental autoimmune encephalomyelitis mice relative to saline-treated mice at 10 days, and elevated relative to normal values at 20 days. Validation studies revealed that within six days of immunization, opioid growth factor or low-dose naltrexone modulated IL-6 and IL-10 cytokine expression. Validation in human serum revealed markedly reduced IL-6 cytokine levels in MS patients taking low-dose naltrexone relative to standard care. In summary, modulation of the OGF-OGFr pathway regulates some inflammatory cytokines, and together with opioid growth factor serum levels, may begin to form a panel of valid biomarkers to monitor progression of multiple sclerosis and response to therapy. Impact statement Modulation of the opioid growth factor (OGF)-OGF receptor (OGFr) alters inflammatory cytokine expression in multiple sclerosis and experimental autoimmune encephalomyelitis (EAE). Multiplex cytokine assays demonstrated that mice with chronic EAE and treated with either OGF or low-dose naltrexone (LDN) had decreased expression of interferon-gamma (IFN-γ), tumor necrosis factor-alpha (TNF-α), and the anti-inflammatory cytokine IL-10 within 10 days or treatment, as well as increased serum expression of the pro-inflammatory cytokine IL-6, relative to immunized mice receiving saline. Multiplex data were validated using ELISA kits and serum from MS patients treated with LDN and revealed decreased in IL-6 levels in patients taking LDN relative to standard care alone. These data, along with serum levels of OGF, begin to formulate a selective biomarker profile for MS that is easily measured and effective at monitoring disease progression and response to therapy.

Featured Article: Serum [Met5]-enkephalin levels are reduced in multiple sclerosis and restored by low-dose naltrexone.

Low-dose naltrexone is a widely used off-label therapeutic prescribed for a variety of immune-related disorders. The mechanism underlying low-dose naltrexone's efficacy for fatigue, Crohn's disease, fibromyalgia, and multiple sclerosis is, in part, intermittent blockade of opioid receptors followed by upregulation of endogenous opioids. Short, intermittent blockade by naltrexone specifically blocks the opioid growth factor receptor resulting in biofeedback events that increase production of the endogenous opioid growth factor (OGF) (chemically termed [Met5]-enkephalin) facilitating interactions between opioid growth factor and opioid growth factor receptor that ultimately, result in inhibited cell proliferation. Preclinical studies have reported that enkephalin levels are deficient in animal models of experimental autoimmune encephalomyelitis, a mouse model of multiple sclerosis. Our hypothesis is that serum enkephalin levels are diminished in humans with multiple sclerosis and experimental autoimmune encephalomyelitis mice, and that change in serum opioid growth factor levels may serve as a reasonable candidate biomarker for the onset of experimental autoimmune encephalomyelitis and response to therapy. To address this, we designed a two-part study to measure endogenous opioids in multiple sclerosis patients, and to investigate the temporal pattern of decline in serum enkephalin concentrations in mice with chronic progressive experimental autoimmune encephalomyelitis and treated with low-dose naltrexone. For comparison, we investigated whether low-dose naltrexone exposure in normal mice also resulted in altered enkephalin levels. In both animal models, we monitored tactile and heat sensitivity, as well as differential white blood cell counts as indicators of inflammation. Serum [Met5]-enkephalin levels were lower in humans with multiple sclerosis relative to non-multiple sclerosis patients, and low-dose naltrexone restored their levels. In experimental autoimmune encephalomyelitis mice, [Met5]-enkephalin levels were depressed prior to the appearance of clinical disease, and were restored with low-dose naltrexone treatment. Low-dose naltrexone therapy had no effect on serum [Met5]-enkephalin or ß-endorphin in normal mice. Thus, [Met5]-enkephalin (i.e. opioid growth factor) may be a reasonable candidate biomarker for multiple sclerosis, and may signal new pathways for treatment of autoimmune disorders. Impact statement This report presents human and animal data identifying a novel biomarker for the onset and progression of multiple sclerosis (MS). Humans diagnosed with MS have reduced serum levels of OGF (i.e. [Met5]-enkephalin) relative to non-MS neurologic patients, and low-dose naltrexone (LDN) therapy restored their enkephalin levels. Serum OGF levels were reduced in mice immunized with MOG35-55 prior to any clinical behavioral sign of experimental autoimmune encephalomyelitis, and LDN therapy restored their serum OGF levels. ß-endorphin concentrations were not altered by LDN in humans or mice. Thus, blood levels of OGF may serve as a new, selective biomarker for the progression of MS, as well as response to therapy.

Elevated serum [Met5]-enkephalin levels correlate with improved clinical and behavioral outcomes in experimental autoimmune encephalomyelitis.

Methionine enkephalin ([Met5]-enkephalin, Opioid growth factor (OGF)) is a small neuropeptide with growth-related as well as immunomodulatory properties. OGF is distributed widely throughout the body, is both autocrine and paracrine produced, and has a very short half-life in serum. In addition to its neurotransmitter functions, OGF inhibits cell replication of a wide variety of cells involved in the autoimmune process. In this preclinical study, mice were immunized with myelin oligodendrocytic glycoprotein (MOG35-55) to establish a chronic progressive form of autoimmune encephalomyelitis (EAE), and serum enkephalin levels were assessed throughout the disease as well as in response to OGF therapy in order to determine whether OGF may be a biological marker for EAE and multiple sclerosis. Immunized mice were randomly assigned to groups receiving daily 10mg/kg OGF (n=24) or saline (n=25) beginning at the time of established disease and clinical behavior. Open field activity, rearing, forced swimming, and novel object tests were monitored. Serum levels of peptide were measured prior to immunization, before clinical symptoms were observed, and at the onset and peak period of disease. Spinal cord neuropathology was evaluated 40days after immunization. EAE disease onset occurred on day 9 post immunization when the mean clinical score was 1.5. Peak disease scores for saline-injected EAE mice reached a mean of 5.7 on day 18, whereas mice receiving OGF had a peak clinical score of 2.5. Behavioral tests conducted 5days post-immunization (and before clinical signs of EAE) revealed that EAE mice had reduced serum enkephalin levels related to elevated clinical disease scores. Serum levels of enkephalin collected at peak disease and after 40days correlated with clinical scores. Disease status was associated with activity in the open field, rearing, time associating with a novel object, and pain sensitivity. Clinical signs of EAE correlated with levels of enkephalins such that as behavioral scores increased, serum [Met5]-enkephalin levels decreased. Thus, [Met5]-enkephalin is a novel biomarker that is associated with disease onset and progression, as well as response to therapy in a mouse model of EAE, and may provide new insight into MS.

The effects of different exercise training modalities on plasma proenkephalin Peptide F in women.

Due to the important interactions of proenkephalin fragments (e.g., proenkephalin [107-140] Peptide F) to enhance activation of immune cells and potentially combat pain associated with exercise-induced muscle tissue damage, we examined the differential plasma responses of Peptide F to different exercise training programs. Participants were tested pre-training (T1), and after 8 weeks (T2) of training. Fifty-nine healthy women were matched and then randomly assigned to one of four groups: heavy resistance strength training (STR, n=18), high intensity endurance training (END, n=14), combined strength and endurance training (CMB, n=17), or control (CON, n=10). Blood was collected using a cannula inserted into a superficial vein in the antecubital fossa with samples collected at rest and immediately after an acute bout of 6 X 10 RM in a squat resistance exercise before training and after training. Prior to any training, no significant differences were observed for any of the groups before or after acute exercise. With training, significant (P≤0.95) elevations were observed with acute exercise in each of the exercise training groups and this effect was significantly greater in the CMB group. These data indicate that in untrained women exercise training will not change resting of plasma Peptide F concentrations unless both forms of exercise are performed but will result in significant increases in the immediate post-exercise responses. Such findings appear to indicate adrenal medullary adaptations opioid production significantly altered with exercise training.

The effects of exercise training programs on plasma concentrations of proenkephalin Peptide F and catecholamines.

To determine if exercise training alters the pattern and magnitude of plasma concentrations of proenkephalin Peptide F and epinephrine, plasma proenkephalin [107-140] Peptide F(ir) and catecholamines were examined pre-training (T-1), and after 4- (T-2), 8- (T-3), and 12-weeks (T-4) of training. 26 healthy men were matched and randomly assigned to one of three groups: heavy resistance strength training (Strength, n=9), high intensity endurance training (Endurance, n=8), or both training modalities combined (Combined, n=9). Blood was collected using a syringe with a cannula inserted into a superficial arm vein with samples collected at rest, after each 7 min stage and 5 and 15 min into recovery. With training, all groups observed shifted plasma Peptide F responses to graded exercise, where significant increases were observed at lower exercise intensities. Increases in plasma epinephrine with exercise were observed in all groups. The Combined group saw increases at 25% at T-3 and for 50% at T-2, T-3, and T-4 which was higher than T-1. The Endurance group demonstrated increases for 50% at T-1, T-2, T-3 but not at T-4. The plasma epinephrine response to graded exercise was reduced in the Strength group. Increases in plasma norepinephrine above rest were observed starting at 50% . The Strength group demonstrated a significant reduction in norepinephrine observed at 100% at T-3 and T-4. Peptide F and catecholamines responses to graded exercise can be altered by different types of physical exercise training. Simultaneous high intensity training may produce adrenal medulla exhaustion when compared to single mode training.

Music and biological stress dampening in mechanically-ventilated patients at the intensive care unit ward-a prospective interventional randomized crossover trial.

PURPOSE: To evaluate the impact of slow-tempo music listening periods in mechanically ventilated intensive care unit patients. METHODS: A randomized crossover study was performed in a 16-bed, adult critical care unit at a tertiary care hospital. Still-sedated patients, mandating at least 3 more days of mechanical ventilation, were included. The intervention consisted in two 1-hour daily periods of music-vs-sham-MP3 listening which were performed on Day 1 or 3 post-inclusion, with a Day 2 wash-out. "Before-after" collection of vital signs, recording of daily sedative drug consumption and measurement of stress and inflammatory blood markers were performed. RESULTS: Of 55 randomized patients, 49 were included in the final analyses. Along with music listening, (i) vital signs did not consistently change, whereas narcotic consumption tended to decrease to a similar sedation (P = .06 vs sham-MP3); (ii) cortisol and prolactin blood concentrations decreased, whereas Adreno Cortico Trophic Hormone (ACTH)/cortisol ratio increased (P = .02; P = .038; and P = .015 vs sham-MP3, respectively), (iii) cortisol responders exhibited reversed associated changes in blood mehionine (MET)-enkephalin content (P = .01). CONCLUSIONS: In the present trial, music listening is a more sensitive stress-reliever in terms of biological vs clinical response. The hypothalamus-pituitary adrenal axis stress axis is a quick sensor of music listening in responding mechanically ventilated intensive care unit patients, through a rapid reduction in blood cortisol.

Responses of proenkephalin Peptide F to aerobic exercise stress in the plasma and white blood cell biocompartments.

Proenkephalin Peptide F [107-140] is an enkephalin-containing peptide found predominantly within the adrenal medulla, co-packaged with epinephrine within the chromaffin granules. In vivo studies indicate that Peptide F has classic opioid analgesia effects; in vitro studies suggest potential immune cell interactions. In this investigation we examined patterns of Peptide F concentrations in different bio-compartments of the blood at rest and following sub-maximal cycle exercise to determine if Peptide F interacts with the white blood cell (WBC) bio-compartment during aerobic exercise. Eight physically active men (n=8) performed sub-maximal (80-85% V˙O2peak) cycle ergometer exercise for 30 min. Plasma Peptide F and WBC Peptide F immunoreactivity were examined pre-exercise, mid-exercise and immediately post-, 5-min post-, 15-min post-, 30-min post- and 60-min post-exercise and at similar time-points during a control condition (30 min rest). Peptide F concentrations significantly (p<0.05) increased at 5 and 60 min post-exercise, compared to pre-exercise concentrations. No significant increases in Peptide F concentrations in the WBC fraction were observed during or after exercise. However, a significant decrease was observed at 30 min post-exercise. An ultradian pattern of Peptide F distribution was apparent during rest. Furthermore, concentrations of T cells, B cells, NK cells, and total WBCs demonstrated significant changes in response to aerobic exercise. Data indicated that Peptide F was bound in significant molar concentrations in the WBC fraction and that this biocompartment may be one of the tissue targets for binding interactions. These data indicate that Peptide F is involved with immune cell modulation in the white blood circulatory biocompartment of blood.

Changes in plasma methionine-enkephalin levels associated with a cluster headache episode.

Eighteen male cluster headache (CH) inpatients within a CH series participated in this research. Blood samples were drawn from patients at least 6-hour pain-free after the last acute CH episode and then shortly prior (SP), during, and soon after (SA) a new acute CH attack. Three healthy male, age-comparable drug-free volunteers served as controls; 5 samples were obtained from each of these individual over a 24-hour period. Individual patient's methionine-enkephalin (MET) plasma concentration showed significant changes, and in some subjects, dramatic changes, during the different phases of a single CH episode. Peptide levels followed a general pattern of higher plasma concentration SP to an acute CH attack, followed by decreased levels during the attack itself, and falling even further SA the acute episode. Consistently, 16 of the 18 patients tested showed pre-CH peptide levels significantly higher (arbitrarily the authors considered values 20% or more as "significant") than their own values obtained during the acute CH pain phase, with observed differences reaching 80% or more in 7 of these individuals. For about half of these patients, peptide concentration during the acute CH episode was significantly above the control's range (68.2-87.6 pg MET/mL; control's circulating MET concentration remaining essentially unchanged during a 24-hour period). MET levels were further decreased in essentially all of the post-CH samples, with values falling within (n = 6) or even further below than those in the control's range (n = 11). Neither age, time of CH occurrence, nor patient's use of a number of medications known for failing to influence plasma MET degradation kinetics seemed to significantly influence MET levels. These results might help in the biochemical characterization of the actual phases of a CH episode. Developing drugs modulating MET bioavailability could lead to novel antinociceptive agents useful for the treatment of CH's associated pain.

Endogenous opioids in wound-site neutrophils of sternotomy patients.

BACKGROUND: Postoperative pain management is a critical aspect of patient care. The inflammatory state of the post-sternotomy surgical wound sensitizes nerve endings, causing pain. Unrelieved or improperly managed pain compromises wound healing. Peripheral opioid receptors play a major role in analgesia, particularly under inflammatory conditions where both opioid receptor expression and efficacy are increased. Leukocytic opioid peptides include ß-endorphin (END), met-enkephalin (ENK), and dynorphin-A (DYN), with END and ENK being predominant. METHODOLOGY/PRINCIPAL FINDINGS: This work represents the first study of inflammatory cells collected from post-sternotomy wounds of patients undergoing cardiac surgery including coronary artery bypass grafting (CABG). Wound fluid (WF) and cells were collected from sternal wounds using a JP Blake drain at 24, 48, and 72 hours post sternum closure. Anti-CD15 staining and flow cytometry revealed that polymorphonuclear neutrophils (PMN) are the predominant cells present in wound fluid collected post-surgery. Compared to peripheral blood (PB) derived PMN, significant increases in CD177+/CD66b+ PMN were observed suggesting activation of wound-site PMN. Such activation was associated with higher levels of opioid peptide expression in PMN derived from WF. Indeed, increased level of opioid peptides in sternal wound environment was noted 72 h post-surgery. We demonstrate that WF contains factors that can significantly induce POMC transcription in human PMNs. IL-10 and IL-4 were abundant in WF and both cytokines significantly induced POMC gene expression suggesting that WF factors such as IL-10 and IL-4 contribute towards increased opioid peptide expression in wound-site PMN. CONCLUSIONS/SIGNIFICANCE: This approach provided a unique opportunity to study the cross-talk between inflammation and opioid peptides in PMN at a sternotomy wound-site. Wound-site PMN exhibited induction of END and ENK. In addition, sternal wound fluid significantly induced END expression in PMN. Taken together, these data constitute first clinical evidence that human wound-site PMNs are direct contributors of opioids at the sternal wound-site.

Decreased plasma methionine-enkephalin levels in cluster headache patients.

Results from a longitudinal study (blood drawn at days 29, 64, 89,124, 142, and 182 of the protocol) shows that the concentration of platelet-poor plasma (PPP) methionine(5)-enkephalin (MET) in healthy, drug-free, white male individuals (n = 5) remains within a relatively narrow range, well within the experimental error of the analytical procedures used. Interindividual differences fail to reach statistical significance [x ± SD and range (MET picograms per mL of PPP) of 91.2 ± 15.1, 67.1-113.5; 69.6 ± 7.5, 66.1-90.1; 76.6 ± 12.6, 58.5-93.1; 86.8 ± 10.9, 76.3-107.4; and 84.5 ± 11.4, 68.9-103.4; for subjects 1-5, respectively]. MET levels were similar to those recorded from single samples obtained from a group of 24 white male, age-comparable, drug-free healthy volunteers [x ± SD and range (picograms of MET per mL of PPP) of 83.3 ± 15.1 and 57.4-119.1]. The controls' range for all the subjects (n = 29) was 57.4-119.1 pgMET/mL PPP. Compared with the controls, individual patients with cluster headache (CH) show a much wider variation in PPP MET levels (blood drawn at different time intervals, at least 10 samples per patient, over a period of 221-298 days), with many (slightly over half) of single values below the controls range; no single MET level was above the controls range [x ± SD and range (picograms of MET per mL of PPP) of 56.4 ± 27.7, 6.1-100.5; 72.6 ± 20.5, 43.0-113.0; 46.0 ± 28.5, 10.0-92.6; 53.6 ± 27.5, 13.0-101.0; 52.0 ± 26.1, 17.5-83.6; 63.5 ± 22.3, 21.7-91.3 for individuals A-F, respectively]. Although interindividual differences within the patients' group were not statistically significant, their peptide levels were significantly lower than those of controls. Neither the presence of unspecified "headaches between clinic visits" and "daily headaches" (patients E and F, respectively), nor the use of a number of drugs known to lack inhibitory activity upon the aminopeptidase-MET degradation reaction, seemed to significantly influence MET concentration. The results could lead to a better understanding of the etiology of the pain associated with CH, with the relative changes in plasma peptide perhaps reflecting the patients' vulnerability to such a condition. Pharmacological modulation of MET function may prove useful in the treatment of CH-associated pain, whether the development of such drugs could find useful pharmacological applications remains to be explored.

Met-enkephalins in patients with inflammatory bowel diseases.

PURPOSE: Opioid peptides provide a link between the neuroendocrine and immune systems. They modify the inflammatory process through their effect on the synthesis and secretion of cytokines and on the proliferation of leukocytes to the inflammatory lesion. The evaluation analyzed changes in free met-enkephalin concentration values in the serum and colon mucosal biopsy specimens of patients with inflammatory bowel disease (IBD). MATERIAL AND METHODS: In serum and colon mucosal biopsy specimens, free met-enkephalin levels were determined in 43 patients with ulcerative colitis (UC) and 38 individuals with Crohn's disease (CD). The evaluation analyzed the effect of disease activity, inflammatory lesions of the colon and laboratory parameters, on the level of the investigated marker. The control group consisted of 45 healthy volunteers. RESULTS: Serum free met-enkephalin levels were depressed in patients with CD (85.4pg/ml) and UC (101.5pg/ml) as compared to the controls (119.4pg/ml). Met-enkephalin levels in colonic biopsies collected from inflammatory lesions in IBD patients were significantly higher as compared to sections without inflammatory lesions (6.59pg/mg vs. 2.89pg/mg, p < 0.01 in the CD group and 6.12pg/mg vs. 3.47pg/mg, p < 0.05 in the UC group) and their level correlated with disease activity. CONCLUSIONS: The present investigation is the first study that demonstrates changes in free met-enkephalin levels in IBD that may play a role in the pathogenesis and course of the disease. Further studies are necessary to assess the anti-inflammatory effect of opioid peptides.

Plasma endogenous enkephalin levels in early systemic sclerosis: clinical and laboratory associations.

OBJECTIVE: Met- and leu-enkephalins are endogenous opioid neuropeptides with potent analgesic, vasoactive, immunomodulatory and anti-apoptotic properties. We hypothesised that clinical or immunological variables of early systemic sclerosis (SSc) might be correlated to plasma enkephalin levels. METHODS: Plasma samples were collected at study entry of the Genetics versus Environment in Scleroderma Outcomes Study (GENISOS) cohort (early SSc, n=116). Plasma met-enkephalin and leu-enkephalin levels (microg/ml) were measured by high performance liquid chromatography (HPLC) and correlated to clinical and laboratory parameters in the GENISOS database. Statistical analyses were performed by nonparametric Wilcoxon rank sum tests and Pearson correlation coefficients. RESULTS: Significantly lower plasma met-enkephalin levels were associated with anti-topoisomerase-I seropositivity (6+8.3 vs. 14.9+22.8 microg/ml, p=0.02). Plasma leu-enkephalin levels were significantly higher in SSc patients with digital pulp loss (95.6+130 vs. 64.9+101 microg/ml, p=0.02). Lower mean plasma met-enkephalin levels and inversely higher leu-enkephalin levels were noted in SSc patients with Raynaud's phenomena (p=NS). CONCLUSION: The associations of plasma enkephalin levels to immunologic or clinical pathologies may underscore their vasogenic or fibrogenic significance and potential as therapeutic targets in early SSc.

Topical application of naltrexone facilitates reepithelialization of the cornea in diabetic rabbits.

Delayed corneal reepithelialization is a complication of diabetes, and may lead to ulcers and erosions, which cause ocular morbidity and visual loss. This study examined the efficacy of naltrexone (NTX), a long-acting, potent opioid antagonist, applied topically, to facilitate the repair of standardized corneal abrasions in diabetic (alloxan-induced) New Zealand White rabbits (glucose levels>450 mg/dL). NTX at a concentration of 10(-4)M, or sterile vehicle (SV), was administered topically 4 times per day for 7 days to the abraded eye of uncontrolled Type 1 diabetic (DB), insulin-controlled Type 1 diabetic (DB-IN), or non-diabetic (Normal) rabbits. Wound healing was monitored, and non-invasive (tonopen, pachymeter, hand-held slit lamp, and retinal camera) and invasive (histopathology) measurements evaluated. Corneal reepithelialization in the uncontrolled DB rabbits was significantly enhanced (up to a 47% reduction in wound area) following treatment with NTX relative to both Normal SV and DB SV rabbits at 24, 48, and 56 h following surgery. At 72 h, DB NTX rabbits had residual defects that were 64-82% smaller than Normal and DB SV animals. NTX treated DB-IN rabbits had residual defects that were 9-37% smaller than DB-IN rabbits receiving SV, and 6-40% smaller than Normal rabbits. No signs of toxicity from topical applications were noted. These data confirm and extend those documented in rats that demonstrated a lack of toxicity of NTX at a wide range of dosages, as well as efficacy for enhanced corneal epithelialization. These studies set the stage for clinical trials using NTX as a therapy for diabetic keratopathy.