Fibrin(ogen) may be an important target for methylglyoxal-derived AGE modification in elastic arteries of humans.

Diabetes is associated with increased risk of cardiovascular disease. Advanced glycation end-products (AGEs) are considered to be a major pathogenic factor for diabetic vascular complications. The levels of AGEs are increased in diabetic patients. We have studied the presence of the major AGE methylglyoxal (MGO)-derived hydroimidazolone in human aorta and carotid arteries, using immunohistochemistry (IHC), western blotting and mass spectrometry. By IHC, MGO-derived modifications were detected mainly associated with cells in intimal thickenings and cells in microvessels in adventitia. In type V lesions MGO-derived AGE was also present, extracellular in the necrotic core and in cells at the border of the core. The highest degree of modification was probably associated with cell nuclei. By western blotting and mass spectrometry fibrin(ogen), the cytoskeleton-associated protein moesin and the nuclear proteins lamin A and C were identified as putative main targets for MGO-derived modification. LC-MS/MS studies of fibrin(ogen) modified in vitro with low concentrations of MGO identified the sites that were most prone to modification. These results indicate that AGE modifications occur preferentially on specific proteins. The modification of these proteins may play a role in vascular dysfunction and development of atherosclerosis in diabetes.

Troponin I degradation in serum of patients with acute ischemic stroke.

BACKGROUND: Although troponin is a cornerstone biomarker in the assessment and management of patients with acute coronary syndrome, much remains to be learned about the biology of this widely used biomarker, including its post-release modification. Degradation of troponin following release in patients with acute coronary syndrome has been described; however whether such post-release modification occurs in other non-acute coronary syndrome states remains unknown. The aim of this study was to define troponin degradation in patients with acute ischemic stroke. MATERIALS AND METHODS: Troponin I (cTnI) was measured daily during the first 5 days of admission in 244 patients with acute ischemic stroke. Western blot analysis was performed using anti-cTnI antibodies and compared with serum concentrations of cTnI in seven patients and one patient with myocardial infarction (positive control). RESULTS: Elevated levels of troponin were detected in 25 (10%) patients; in all, both intact cTnI and cTnI degradation products were detected, with up to seven degradation fragments found. Samples with the highest total cTnI levels gave the strongest and most numerous western-blotting bands. All fragments were comparable with the degradation pattern of the positive control in terms of position. CONCLUSIONS: Immunoblotting of blood samples from patients with acute ischemic stroke reveals similar degradation patterns of cTnI as has been described in patients with acute myocardial infarction. The biological ramification and potential clinical impact of this finding bears further scrutiny.

Cardiac troponin I degradation in serum of patients with hypertrophic obstructive cardiomyopathy undergoing percutaneous septal ablation.

INTRODUCTION: Troponin has become the most important marker for diagnosing acute myocardial infarction, yet knowledge is scarce regarding appearance of specific degradation fragments in the blood. We have recently described the appearance of intact cardiac troponin I (cTnI) and 7 degradation products in patients suffering from ST-elevation myocardial infarction (STEMI) using Western blot analysis. However, the time resolution in STEMI patients is hampered by the rather vague time point 'onset of pain'. We therefore sought to utilize a time-wise more reliable model of human myocardial necrosis: percutaneous transluminal septal myocardial ablation (PTSMA) of hypertrophic obstructive cardiomyopathy (HOCM). Here the iatrogenic induction of myocardial necrosis occurs in vivo, allowing us to investigate degradation of cTnI by the second. METHODS: Blood samples were obtained from 8 patients with HOCM just prior to initiation of PTSMA and up to 50 h following the procedure. Western blot analysis was performed with subsequent analysis of relative intensities of the bands as compared to the degradation of cTnI in STEMI patients from the ASSENT-2 troponin substudy. RESULTS: We demonstrate intact cTnI and 9 degradation products [molecular weight (MW) 12.0-23.5 kDa]. The bands were comparable in MW to degradation fragments in STEMI. Their early rise in intensity, occurring within few minutes after the alcohol injection, emphasizes how susceptible troponin bands are to chemical/ischemic insults. Moreover, two additional bands were visible in the PTSMA population. CONCLUSION: This work describes the degradation products of troponin I in HOCM patients undergoing PTSMA. The detected bands appear fast and are similar to degradations following STEMI. This model contributes to our knowledge of the degradation patterns of troponin in disease states, and may thus play a role in the interpretation of elevated troponin levels.

Low levels of raf kinase inhibitory protein in growth hormone-secreting pituitary adenomas correlate with poor response to octreotide treatment.

CONTEXT: Excessive GH production by pituitary tumors causes acromegaly. Medical treatment of acromegaly with somatostatin analogs (SMSs), like octreotide, is well established, but the clinical effect is variable. One mechanism for octreotide effect is inhibition of the MAPK signaling pathway after binding to the G protein-coupled somatostatin receptor. Nonphosphorylated Raf kinase inhibitory protein (RKIP) binds to and inhibits Raf1 kinase, and thereby attenuates MAPK signaling, whereas phosphorylated RKIP inhibits G protein receptor internalization and degradation due to inhibition of G protein receptor kinase 2. OBJECTIVE: Our objective was to study RKIP levels in pituitary somatotroph adenomas, and relate them to clinical characteristics and response to octreotide treatment in patients with acromegaly. PATIENTS AND METHODS: RKIP level was analyzed by Western blot of proteins extracted from somatotroph tumors frozen a short time after surgery in 51 patients with active acromegaly. An acute somatostatin test was performed in 46 of the patients, and in 21 the IGF-I level before and 6 months after SMS treatment was available. RESULTS: The adenoma RKIP level correlated significantly to both the acute and the long-term octreotide responses on serum levels of GH and IGF-I, respectively. In multiple regression analyses, the RKIP level was a significant determinant for both the GH reduction in the acute test and the IGF-I reduction after approximately 6 months. CONCLUSION: The RKIP level in somatotroph adenomas seems to be important for the clinical effect of SMS treatment, in which low levels of RKIP correlate to poor clinical response to SMSs.

Increased vitreous levels of hydroimidazolone in type 2 diabetes patients are associated with retinopathy: a case-control study.

PURPOSE: As advanced glycation endproducts (AGEs) and the vitreous body are both considered to be involved in the development of diabetic retinopathy and hydroimidazolone is one of the most prominent AGEs, we compared vitreous and serum hydroimidazolone in diabetes patients with proliferative diabetic retinopathy (PDR) to levels in non-diabetes controls, co-measuring vitreous albumin and vascular endothelial growth factor (VEGF). METHODS: In a cross-sectional case-control study design, we used immunoassays to compare vitreous and serum hydroimidazolone and VEGF levels in 23 consecutive type 2 diabetes mellitus patients with a median known diabetes duration of 12 years (range 1-38 years) with those in 32 non-diabetes age-matched controls undergoing vitrectomy. RESULTS: Vitreous hydroimidazolone was increased in the PDR group (median 1.3 U/ml, range 0.5-3.3 U/ml) compared with controls (median 0.8 U/ml, 0.5-2.5 U/ml) (p = 0.026). Hydroimidazolone levels in serum and vitreous correlated (r = 0.49, p = 0.019). In PDR, vitreous VEGF levels were increased (median 1600 pg/ml, range 20-14 700 pg/ml) compared with controls (median 7 pg/ml, range 2-500 pg/ml) (p < 0.001). Similarly, vitreous albumin concentration was increased in PDR (median 1.6 g/l, range 0.7-3.0 g/l) compared with controls (median 0.3 g/l, range 0.08-1.9 g/l) (p < 0.001). Albumin could not explain the differences in vitreous VEGF levels in a logistic regression analysis. No correlation was found between vitreous levels of VEGF and hydroimidazolone (r = 0.12, p = 0.59). CONCLUSIONS: Increased vitreous hydroimidazolone is associated with diabetic retinopathy, possibly due to a blood-retinal barrier breakdown. Irrespective of origin, it may add to the ocular damage and needs further causal investigation. Increased VEGF in diabetic vitreous is probably of intraocular origin. It is not associated with vitreous hydroimidazolone.

Time course of degradation of cardiac troponin I in patients with acute ST-elevation myocardial infarction: the ASSENT-2 troponin substudy.

Although measurement of troponin is widely used for diagnosing acute myocardial infarction (AMI), its diagnostic potential may be increased by a more complete characterization of its molecular appearance and degradation in the blood. The aim of this study was to define the time course of cardiac troponin I (cTnI) degradation in patients with acute ST-elevation myocardial infarction (STEMI). In the ASSENT-2 substudy, 26 males hospitalized with STEMI were randomized to 2 different thrombolytic drugs within 6 hours after onset of symptoms. Blood samples were obtained just before initiation of thrombolysis and at 30 minutes intervals (7 samples per patient). Western blot analysis was performed using anti-cTnI antibodies and compared with serum concentrations of cTnI. All patients exceeded the cTnI cutoff for AMI during the sampling period; at initiation of therapy, 23 had elevated cTnI values. All patients demonstrated 2 bands on immunoblot: intact cTnI and a single degradation product as early as 90 minutes after onset of symptoms. On subsequent samples, 15 of 26 patients showed multiple degradation products with up to 7 degradation bands. The appearance of fragments was correlated with higher levels of cTnI (P<0.001) and time to initiation of treatment (P=0.058). This study defines for the first time the initial time course of cTnI degradation in STEMI. Intact cTnI and a single degradation product were detectable on immunoblot as early as 90 minutes after onset of symptoms with further degradation after 165 minutes. Infarct size and time to initiation of treatment was the major determinant for degradation.

Genetic and functional analysis of the cytK family of genes in Bacillus cereus.

CytK is a pore-forming toxin of Bacillus cereus that has been linked to a case of necrotic enteritis. PCR products of the expected size were generated with cytK primers in 13 of 29 strains. Six strains were PCR-positive for the related gene hly-II, which encodes haemolysin II, a protein that is 37 % identical to the original CytK. Five of the strains were positive for both genes. The DNA sequences of putative cytK genes from three positive strains were determined, and the deduced amino acid sequences were 89 % identical to that of the original CytK. The authors have designated this new cytK variant cytK-2, and refer to the original cytK as cytK-1. The CytK-2 proteins from these three strains were isolated, and their identity was verified by N-terminal sequencing. blast analysis using the cytK-2 gene sequences revealed very high homology with two cytK-2 sequences in the genomes of B. cereus strains ATCC 14579 and ATCC 10987. The differences between CytK-1 and the CytK-2 proteins were clustered to certain regions of the proteins. The isolated CytK-2 proteins were haemolytic and toxic towards human intestinal Caco-2 cells and Vero cells, although their toxicity was about 20 % of that of CytK-1. Both native and recombinant CytK-2 proteins from B. cereus 1230-88 were able to form pores in planar lipid bilayers, but the majority of the channels observed were of lower conductance than those created by CytK-1. It is likely that CytK-2 toxins contribute to the enterotoxicity of several strains of B. cereus, although not all of the CytK-2 toxins may be as harmful as the CytK-1 originally isolated.

A validated method for rapid analysis of ethane in breath and its application in kinetic studies in human volunteers.

Oxidative stress may initiate lipid peroxidation that generates ethane. Ethane, at low concentrations, is eliminated by pulmonary exhalation. Previous methods have not allowed frequent sampling, thus ethane kinetics has not been studied in man. A validated method over the range 3.8-100,000 ppb with a limit of quantitation of 3.8 ppb (CV 9.3%) based on cryofocusing technique of a 60 ml breath sample allowed frequent sampling. Due to a rapid analytical procedure batches of more than 100 samples may be analyzed. In human volunteers (24-55 years) uptake was studied for up to 23 min (n = 9), elimination was studied for 210 min (n = 9). Ethane was inhaled (concentrations varied from 16 to 29 ppm (parts per million)) through a non-rebreathing system; sampling was performed with short intervals from the expiratory limb. Samples were also drawn from the inhalatory limb. Ninety-five percent of steady state (inspired) concentration was reached within 1.75 min. Five percent of the initially inhaled concentrations was found in exhaled air 1.5 min after termination of inhalation. A terminal mean half life of 31 min for ethane was also observed. The data indicate that frequent sampling will be necessary to capture relevant changes in breath ethane.

Comparison of biological effect of the two different enterotoxin complexes isolated from three different strains of Bacillus cereus.

The cytotoxicity of the two different enterotoxin complexes of Bacillus cereus was compared after isolation from three different strains. Protein components of non-haemolytic enterotoxin (NHE) of 39 kDa, 45 kDa and 105 kDa were isolated from all of the three strains, whilst proteins B, L1 and L2 of haemolysin BL (HBL) were isolated from supernatants of two strains (F837-76 and 1230-88). These proteins were not detected in strain 0075-95. Inhibition of protein synthesis in Vero cells was used as a measure of cytotoxicity. The HBL complex from strain F837-76 was highly toxic. This strain also produced the NHE complex. However, when purified, at least two of the components of NHE had to be present in higher amounts than those of the components of HBL to cause the same degree of toxicity. Both complexes purified from strain 1230-88 were cytotoxic. The amount required to cause the same degree of cytotoxicity was approximately equal for the components of the two complexes, except that higher amounts of the 105 kDa protein of NHE had to be present than for the other components. None of the purified complexes from strain 1230-88 was toxic in amounts comparable to those of the HBL complex of strain F837-76 and NHE of strain 0075-95. These results indicate that when measuring cytotoxic enterotoxins from B. cereus at least two different complexes and six different proteins have to be taken into consideration.