Rat strain differences in peritoneal immune cell response to selected gut microbiota: A crossroad between tolerance and autoimmunity?

AIMS: Some gut commensals can be protective, whereas others are implicated as necessary for development of inflammatory/autoimmune diseases. Peritoneal immune cells may play an important role in promoting autoimmunity in response to gut microbiota. This study investigated the phenotype and the function of peritoneal immune cells in the autoimmunity-resistant Albino Oxford (AO), and the autoimmunity-prone Dark Agouti (DA) rat strains upon stimulation with their own colonic E. coli or Enterococcus. MAIN METHODS: Rats were intraperitoneally injected with their own E. coli or Enterococcus. Peritoneal cells isolated two days later were tested for nitric oxide (NO) and cytokine production, and for arginase and myeloperoxidase (MPO) activity. The phenotype of cells was determined using flow cytometry. KEY FINDINGS: While the Enterococcus injection did not affect the composition of peritoneal cells in AO rats, the E. coli treatment increased the percentages of activated CD11bintHIS48hi neutrophils, and decreased the proportion of resident (CD11bhiHIS48int/low, CD163 + CD86+) and anti-inflammatory CD68 + CD206+ macrophages. E. coli increased the production of NO and urea, but preserved their ratio in cells from AO rats. Conversely, both E. coli and Enterococcus diminished the proportion of resident and anti-inflammatory macrophages, increased the proportion of activated neutrophils, and induced inflammatory polarization of peritoneal cells in DA rats. However, injection of E. coli maintained the ratio of typical CD11bintHIS48int neutrophils in DA rats, which correlated with the sustained MPO activity. SIGNIFICANCE: The rat strain differences in peritoneal cell response to own commensal microbiota may contribute to differential susceptibility to inflammatory/autoimmune diseases.

Delivery of a Chlamydial Adhesin N-PmpC Subunit Vaccine to the Ocular Mucosa Using Particulate Carriers.

Trachoma, caused by the intracellular bacterium Chlamydia trachomatis (Ct), remains the world's leading preventable infectious cause of blindness. Recent attempts to develop effective vaccines rely on modified chlamydial antigen delivery platforms. As the mechanisms engaged in the pathology of the disease are not fully understood, designing a subunit vaccine specific to chlamydial antigens could improve safety for human use. We propose the delivery of chlamydia-specific antigens to the ocular mucosa using particulate carriers, bacterial ghosts (BGs). We therefore characterized humoral and cellular immune responses after conjunctival and subcutaneous immunization with a N-terminal portion (amino acid 1-893) of the chlamydial polymorphic membrane protein C (PmpC) of Ct serovar B, expressed in probiotic Escherichia coli Nissle 1917 bacterial ghosts (EcN BGs) in BALB/c mice. Three immunizations were performed at two-week intervals, and the immune responses were evaluated two weeks after the final immunization in mice. In a guinea pig model of ocular infection animals were immunized in the same manner as the mice, and protection against challenge was assessed two weeks after the last immunization. N-PmpC was successfully expressed within BGs and delivery to the ocular mucosa was well tolerated without signs of inflammation. N-PmpC-specific mucosal IgA levels in tears yielded significantly increased levels in the group immunized via the conjunctiva compared with the subcutaneously immunized mice. Immunization with N-PmpC EcN BGs via both immunization routes prompted the establishment of an N-PmpC-specific IFNγ immune response. Immunization via the conjunctiva resulted in a decrease in intensity of the transitional inflammatory reaction in conjunctiva of challenged guinea pigs compared with subcutaneously and non-immunized animals. The delivery of the chlamydial subunit vaccine to the ocular mucosa using a particulate carrier, such as BGs, induced both humoral and cellular immune responses. Further investigations are needed to improve the immunization scheme and dosage.

A Mumps Outbreak in Vojvodina, Serbia, in 2012 Underlines the Need for Additional Vaccination Opportunities for Young Adults.

In 2012, mumps was introduced from Bosnia and Herzegovina to Vojvodina, causing an outbreak with 335 reported cases. The present manuscript analyses the epidemiological and laboratory characteristics of this outbreak, identifies its main causes and suggests potential future preventive measures. Sera of 133 patients were tested for mumps-specific antibodies by ELISA and 15 nose/throat swabs were investigated for mumps virus RNA by RT-PCR. IgG antibodies were found in 127 patients (95.5%). Mumps infection was laboratory-confirmed in 53 patients, including 44 IgM and 9 PCR positive cases. All other 282 cases were classified as epidemiologically-confirmed. More than half of the patients (n = 181, 54%) were 20-29 years old, followed by the 15-19 age bracket (n = 95, 28.4%). Twice as many males as females were affected (67% versus 33%). Disease complications were reported in 13 cases (3.9%), including 9 patients with orchitis and 4 with pancreatitis. According to medical records or anamnestic data, 190 patients (56.7%) were immunized with two doses and 35 (10.4%) with one dose of mumps-containing vaccine. The Serbian sequences corresponded to a minor genotype G variant detected during the 2011/2012 mumps outbreak in Bosnia and Herzegovina. Vaccine failures, the initial one-dose immunization policy and a vaccine shortage between 1999 and 2002 contributed to the outbreak. Additional vaccination opportunities should be offered to young adults during transition periods in their life trajectories.

Unopposed Estrogen Supplementation/Progesterone Deficiency in Post-Reproductive Age Affects the Secretory Profile of Resident Macrophages in a Tissue-Specific Manner in the Rat.

PROBLEM: The influence of unopposed estrogen replacement/isolated progesterone deficiency on macrophage production of pro-inflammatory/anti-inflammatory mediators in the post-reproductive age was studied. METHOD OF STUDY: Considering that in the rats post-ovariectomy the circulating estradiol, but not progesterone level rises to the values in sham-operated controls, 20-month-old rats ovariectomized at the age of 10 months served as an experimental model. Estrogen and progesterone receptor expression, secretion of pro- and anti-inflammatory cytokines, and arginine metabolism end-products were examined in splenic and peritoneal macrophages under basal conditions and following lipopolysaccharide (LPS) stimulation in vitro. RESULTS: Almost all peritoneal and a subset of splenic macrophages expressed the intracellular progesterone receptor. Ovariectomy diminished cytokine production by splenic (IL-1ß) and peritoneal (TNF-α, IL-1ß, IL-10) macrophages and increased the production of IL-10 by splenic and TGF-ß by peritoneal cells under basal conditions. Following LPS stimulation, splenic macrophages from ovariectomized rats produced less TNF-α and more IL-10, whereas peritoneal macrophages produced less IL-1ß and TGF-ß than the corresponding cells from sham-operated rats. Ovariectomy diminished urea production in both subpopulations of LPS-stimulated macrophages. CONCLUSION: Although long-lasting isolated progesterone deficiency in the post-reproductive age differentially affects cytokine production in the macrophages from distinct tissue compartments, in both subpopulations, it impairs the pro-inflammatory/anti-inflammatory cytokine secretory balance.

Immune response to gut Escherichia coli and susceptibility to adjuvant arthritis in the rats.

We have investigated the humoral immune response to antigens of predominant gut aerobic bacterial strains (i.e. Escherichia coli) over the course of adjuvant arthritis and oil-induced arthritis in two inbred rat strains: Dark Agouti (DA) and Albino Oxford (AO). We report the presence of antibodies specific to proteins of E. coli in molecular weight range between 20-30 kDa in sera of diseased DA rats, and the absence of these antibodies in the sera of AO rats. In DA rats, CFA and IFA provoked a stronger antibody response to E. coli, especially of the IgG2b antibody class. Intramuscular administration of E. coli preceding the adjuvant arthritis induction had no effect on the development and course of disease, as well as on the activation of T cells in the draining inguinal lymph nodes. Higher serum levels of natural and induced IgA antibodies, combined with a higher CD3+CD26+ cell percentage were found in AO rats. The observed correlation between the serologic response to commensal flora and rats' genetic background as a defining factor for arthritis susceptibility may contribute to the process of creating a favorable (or less favorable) milieu for arthritis development.

Strain differences in the humoral immune response to commensal bacterial antigens in rats.

We have investigated the immune response to commensal bacterial species in the two inbred rat strains: Dark Agouti (DA) and Albino Oxford (AO). The predominant Gram-negative aerobe in our rats' intestinal bacterial flora was Escherichia coli, while Proteus mirabilis was isolated only from DA rat strain. We report that sera from both DA and AO rat strains contain specific IgG against predominant intestinal flora. Intramuscular administration of commensal bacterial antigens provoked only Th1-type antibody response in AO rats while DA rats developed mixed Th1- and Th2-type antibody response to E. coli and Th1-type response to P. mirabilis antigens. Weaker antibody production to own E. coli and higher serum levels of natural IgG and IgA P. mirabilis-specific antibodies combined with higher CD3+ cells proliferation was found in AO rats. Strain difference in the pattern of antibody production and differential regulation of immune response to commensal bacteria may contribute to the marked differences in the immune reactivity of AO and DA rats.

Modulation of granulocyte functions by peptide YY in the rat: age-related differences in Y receptors expression and plasma dipeptidyl peptidase 4 activity.

It has been acknowledged that aging exerts detrimental effects on cells of the innate immune system and that neuropeptides, including neuropeptide Y (NPY) and NPY-related peptides fine-tune the activity of these cells through a receptor specific mechanism. The present study investigated the age-dependent potential of peptide YY (PYY) to modulate different granulocyte functions. The PYY reduced the carrageenan-elicited granulocyte accumulation into the air-pouch of aged (24 months) rats, and markedly decreased the phagocytosis of zymosan, as well as the H(2)O(2) production, when applied in vivo (20 microg/air-pouch). The anti-inflammatory effect of PYY was less prominent in adult (8 months) and young (3 months) rats. However, the proportions of granulocytes expressing Y1, Y2 and Y5 receptor subtypes were significantly lower in both aged and young rats when compared to adult rats. Furthermore, the aging was found to be associated with the diminished dipeptidyl peptidase 4 (DP4, an enzyme converting the NPY and PYY to Y2/Y5 receptor selective agonists) activity in plasma. In conclusion, the diverse age-related anti-inflammatory effect of PYY in rats originates from different expression levels of Y1, Y2, and Y5 receptor subtypes in addition to different plasma DP4 activity.

The anti-inflammatory effect of neuropeptide Y (NPY) in rats is dependent on dipeptidyl peptidase 4 (DP4) activity and age.

Neuropeptide Y (NPY)-induced modulation of the immune and inflammatory responses is regulated by tissue-specific expression of different receptor subtypes (Y1-Y6) and the activity of the enzyme dipeptidyl peptidase 4 (DP4, CD26) which terminates the action of NPY on Y1 receptor subtype. The present study investigated the age-dependent effect of NPY on inflammatory paw edema and macrophage nitric oxide production in Dark Agouti rats exhibiting a high-plasma DP4 activity, as acknowledged earlier. The results showed that NPY suppressed paw edema in adult and aged, but not in young rats. Furthermore, plasma DP4 activity decreased, while macrophage DP4 activity, as well as macrophage CD26 expression increased with aging. The use of NPY-related peptides and Y receptor-specific antagonists revealed that anti-inflammatory effect of NPY is mediated via Y1 and Y5 receptors. NPY-induced suppression of paw edema in young rats following inhibition of DP4 additionally emphasized the role for Y1 receptor in the anti-inflammatory action of NPY. In contrast to the in vivo situation, NPY stimulated macrophage nitric oxide production in vitro only in young rats, and this effect was mediated via Y1 and Y2 receptors. It can be concluded that age-dependant modulation of inflammatory reactions by NPY is determined by plasma, but not macrophage DP4 activity at different ages.

The effects of corticosterone and beta-endorphin on adherence, phagocytosis and hydrogen peroxide production of macrophages isolated from Dark Agouti rats exposed to acute stress.

BACKGROUND: Given that stressful experiences can change the reaction to a subsequent exposure to stress, we tested the in vitro effects of the stress mediator corticosterone and the opioid peptide beta-endorphin on the function of macrophages isolated from control rats and from rats exposed to electric tail shock stress (ES) or a stress-witnessing procedure (SW) 24 h earlier. METHODS: Peritoneal macrophages isolated from control and stressed rats of the Dark Agouti (DA) strain were treated in vitro with corticosterone or beta-endorphin and tested for adherence, phagocytosis and hydrogen peroxide release. RESULTS: ES diminished adherence and SW decreased phagocytosis. The suppressive effect of corticosterone on phagocytosis was absent in rats exposed to ES and SW, while the suppressive effect of beta-endorphin on adherence was not observed in rats exposed to SW. ES and SW did not affect H(2)O(2) release, neither directly nor indirectly by changing macrophage response to corticosterone and beta-endorphin in this test. CONCLUSIONS: In DA rats early macrophage activation steps, i.e. adherence and phagocytosis, were more sensitive to stress than their effector function, corresponding to H(2)O(2) production. We suggest that neuroendocrine mediators of stress that converge on macrophages might have changed specific macrophage receptors or postreceptor events and alter their response to artificial stressors, represented by corticosterone and beta-endorphin in vitro.

Methionine-enkephalin modulation of hydrogen peroxide (H2O2) release by rat peritoneal macrophages involves different types of opioid receptors.

We investigated the involvement of specific types of opioid receptors in methionine-enkephalin (MET)-induced modulation of hydrogen peroxide (H2O2) release by rat macrophages primed with sub-optimal concentrations of phorbol myristate acetate (PMA). Peritoneal macrophages in vitro treated with different concentrations of MET were tested for H2O2 release in phenol red assay. In the antagonistic study macrophages were treated with MET and one opioid receptor antagonist, or combination of MET and two or three opioid receptor antagonists. MET decreased H2O2 release in eight individual macrophage samples, and increased it in 10 samples. The increase of H2O2 release induced by MET in macrophages was blocked with combination of opioid receptor antagonists specific delta1,2 and mu receptors, as well as with combination of antagonists specific for delta1,2 and kappa opioid receptors. MET-induced decrease of the H2O2 release in macrophages was prevented by opioid receptor antagonists specific for delta1,2 or mu receptors, and also with combination of two or three opioid receptor antagonists. MET-induced enhancement of H2O2 release was mediated via delta1 or delta2 opioid receptor subtypes, or by mu-kappa opioid receptor functional interactions, while MET-induced suppression involved functional interactions between delta1 and mu, delta2 and mu, or delta1 and kappa opioid receptors. It is possible that individual differences in basal or induced macrophage capacity to produce H2O2 might shape the repertoire of opioid receptors expression and in that way pre-determine the direction of MET-induced changes after the in vitro treatment.

Exposure to acute physical and psychological stress alters the response of rat macrophages to corticosterone, neuropeptide Y and beta-endorphin.

The objective of the present study was to investigate the effect of acute exposure to electric tail shock stress (ES) and a stress witnessing procedure (SW), as models for physical and psychological stress paradigms, respectively on adherence, phagocytosis and hydrogen peroxide (H(2)O(2)) release from rat peritoneal macrophages. In addition, we studied the in vitro effects of corticosterone (CORT), neuropeptide Y (NPY) and beta-endorphin (BE) on adherence, phagocytosis and H(2)O(2) release from macrophages isolated from control rats and from rats that had been exposed to ES or SW procedures 24 h earlier. ES and SW comparably diminished phagocytosis and H(2)O(2) release, but did not influence macrophage adherence. In vitro treatment with CORT and NPY notably suppressed phagocytosis and potentiated H(2)O(2) release from macrophages. BE suppressed both phagocytosis and H(2)O(2) release from macrophages. Previous exposure to ES and SW altered the responsiveness of the isolated macrophages to their in vitro treatment with mediators of stress, making the cells less sensitive to the influence of CORT and NPY and to a lesser extent to BE. It could be concluded that changes in the local macrophage milieu induced by ES and SW 24 h earlier modify macrophage responses to subsequent in vitro exposure to the stress mimics, CORT, NPY and BE.

Reactive oxygen species (ROS), but not nitric oxide (NO), contribute to strain differences in the susceptibility to experimental arthritis in rats.

There is extensive evidence for the critical role of reactive oxygen species (ROS) and nitric oxide (NO) produced by phagocytes in development of inflammatory processes and pathogenesis of numerous diseases, including rheumatoid arthritis (RA). Apart from their function as mediators of inflammation and tissue damage, recent research supports their role as signaling and regulatory molecules. In the present study we have investigated the production of ROS and NO over the course of adjuvant arthritis (AA) and oil-induced arthritis (OIA), by resident peritoneal macrophages of two rat strains: Dark Agouti (DA), susceptible, and Albino Oxford (AO), resistant to induction of AA and OIA. We have compared levels of ROS and NO produced by susceptible vs. resistant rat strain, and investigated their relevancy for arthritis development and severity. In addition, we have stimulated macrophages in vitro with Mycobacterium bovis BCG, and two heat shock proteins (HSP): endogenous HSP47 and mycobacterial HSP71 (mHSP71). Our results suggest a possible contribution of increased ROS production to arthritis resistance of AO rats. The ROS production in AO rats is potentiated by endogenous HSP47, but not with mycobacterial cell and mHSP71, suggesting HSP47 participates in AA control. We have found no fundamental relationship between the magnitude of NO production and AA and OIA susceptibility and severity, suggesting that NO has no effector role in AA and OIA. Our results advocate a regulatory type action of NO molecule might be more significant in arthritis development.

The influence of stress and methionine-enkephalin on macrophage functions in two inbred rat strains.

The aim of our current study was to investigate the effect of acute exposure to electric tail shock stress (ES) and to a stress witnessing procedure (SW), as models for physical and psychological stress paradigms, respectively, on phagocytosis and H(2)O(2) production in peritoneal macrophages isolated from Albino Oxford (AO) and Dark Agouti (DA) rats. In addition, we studied the in vitro effects of methionine-enkephalin (ME) on phagocytosis and H(2)O(2) production in peritoneal macrophages isolated from both AO and DA rats that had been exposed to ES and SW procedures. The results showed that peritoneal macrophages isolated from DA rats were less sensitive to the suppressive effects of ES and SW than macrophages isolated from AO rats. In vitro treatment of macrophages isolated from AO rats with ME mimicked to some extent the suppressive effects of ES and SW on phagocytosis and H(2)O(2) production and additionally diminished H(2)O(2) release in macrophages isolated from AO rats previously exposed to ES or SW. ME did not have any effect on phagocytosis in macrophages isolated from DA rats, but changed H(2)O(2) production in a concentration-dependent manner. In macrophages isolated from DA rats previously exposed to stress the effect of ME was dependent on the macrophage function tested and the particular stress paradigm employed. Our results emphasise the fact that both beneficial and detrimental effects of stress on immune system functions could be attributed to the individual variations in the macrophage's response to stress mediators.

Neuropeptide Y (NPY) modulates oxidative burst and nitric oxide production in carrageenan-elicited granulocytes from rat air pouch.

We studied the effects of neuropeptide Y (NPY) and NPY-related receptor specific peptides on functions of carrageenan-elicited granulocytes in vitro and ability of NPY to modulate carrageenan-induced air pouch inflammation in rats in vivo. Anti-inflammatory effect of NPY comprises reduced granulocyte accumulation into the air pouch, to some extent attenuation of phagocytosis, attained via Y1 receptor, and considerable decrease in peroxide production, albeit mediated via Y2 and Y5 receptors activation. Conversely, NPY increases nitric oxide production and this potentiation is mediated via Y1 receptor. It is concluded that NPY Y1 and Y2/Y5 receptors' interaction participates in NPY-induced modulation of granulocyte functions related to inflammation.

Beta-endorphin differentially affects inflammation in two inbred rat strains.

It has been shown that inflammation of rat paws elicits accumulation of opioid peptide beta-endorphin-containing immune cells in the inflamed subcutaneous tissue, contributing to immunocyte-produced pain suppression. However, the possible mechanisms involved in the pharmacological application of beta-endorphin in rat paw inflammation have not been investigated. The present study was set up to explore the effects of intraplantar injection of beta-endorphin on Concanavalin A-induced paw edema in two inbred rat strains, Albino Oxford (AO) and Dark Agouti (DA). Both high dose-induced suppression and low dose-induced potentiation of edema development in AO and DA rats, respectively, were blocked with antagonists specific for delta (naltrindole) and kappa (nor-binaltorphimine) opioid receptors. beta-endorphin in vitro decreased phagocytosis and increased nitric oxide (NO) production in air pouch granulocytes obtained from AO rats. However, in cells from DA rat strain beta-endorphin modulated both phagocytosis and NO production in a concentration-dependent manner. It could be concluded that the strain-dependent opposing effects of beta-endorphin on paw inflammation are mediated through delta and kappa opioid receptors and probably involve changes in the production of reactive oxygen species by inflammatory cells. Our results point to the importance of genotype for pharmacological manipulations and the development of inflammation.

Age-related effect of peptide YY (PYY) on paw edema in the rat: the function of Y1 receptors on inflammatory cells.

It is well documented that neuropeptides participate in local inflammatory reaction and modulate functions of inflammatory cells. The aim of the study was to determine a link between in vivo and in vitro effects of NPY-related peptides on inflammatory response with respect to ageing. Peptide YY (PYY) intraplantarly applied decreases concanavalin A-induced paw edema in 3 and 8 months, but not in 24 months old male rats of Albino Oxford strain. The use of NPY-related receptor-specific peptides and Y1 receptor antagonist revealed that anti-inflammatory effect of PYY is mediated via NPY Y1 receptors. PYY in vitro decreases adherence of macrophages from 8 months, but not from 3 and 24 months old rats and this effect is also mediated via NPY Y1 receptor. Additionally, PYY (10(-6)M) decreases NBT reduction in macrophages from 3 and 8 months old rats, and suppresses NO production in cells from 24 months old rats, albeit regardless of absence of in vivo effect of PYY on inflammation in aged rats. It is concluded that aged rats are less responsive to anti-inflammatory action of PYY compared to adult and young rats, and that ageing is associated with altered NPY Y1 receptor functioning.

Stress applied during primary immunization affects the secondary humoral immune response in the rat: involvement of opioid peptides.

The effect of unpredictable, inescapable and uncontrollable electric tail shocks (ES) on the humoral immune response to bovine serum albumin (BSA) was investigated in the rat. Contributions of the procedures that accompany shock delivery, such as witnessing the ES procedure (stress witnessing, SW) and exposure to the apparatus for shock delivery (apparatus control, AC) to the changes in specific immunity induced by ES were also tested. All procedures were applied during primary and/or secondary immunization. It was demonstrated that exposure to ES during primary immunization with BSA significantly suppressed specific anti-BSA antibody production after secondary and tertiary immunization with the same antigen. Exposure to the SW procedure during primary immunization with BSA enhanced the specific antibody level after secondary immunization, while exposure to the apparatus alone did not influence the development of either the primary or secondary humoral immune response to BSA. Both ES-induced suppression and SW-induced potentiation of the humoral immune response were partially inhibited by prior treatment with the opioid receptor antagonist naloxone. Additionally, treatments with the opioid peptides methionine- and leucine-enkephalin decreased anti-BSA antibody level, mimicking to some extent the effects of ES. It is suggested that ES and endogenous opioid peptides had long-term effects on humoral immunity through mechanisms involving immunologic memory.

Correlation between age-related changes in open field behavior and plaque forming cell response in DA female rats.

We investigated the relationship between immunological and behavioral changes during ageing in Dark Agouti female rats. Results showed that ageing was associated with decreased exploratory behavior and increased emotionality (open field test) and decreased pain perception (writhing assay), but not with altered depression-like behavior (forced swim test). The observed behavioral changes were paralleled with decreased innate immunity in middle-aged and old rats, as revealed by reduced peroxide production of peritoneal macrophages; and decreased specific immunity, measured by the plaque-forming cell response, in old rats in comparison with young rats. Correlation analyses between behavioral and immune parameters demonstrated a significant correlation between the lines crossed in the open field test and the plaque-forming cell response. Taken together, the demonstrated age-dependent association between exploratory behavior and specific immune response suggests a senescent decline of a common neuroimmune regulatory mechanism.

Different effects of methionine-enkephalin on paw edema in two inbred rat strains.

The effect of intraplantarly (i.pl.)-injected methionine-enkephalin (ME) on Concanavalin A (Con A)-induced paw edema in Dark Agouti (DA) and Albino Oxford (AO) rats was investigated. ME suppressed edema in DA rats, which was antagonized with naloxone (non-selective opioid receptor antagonist) and naltrindole (delta opioid receptors antagonist). Potentiating effect of ME in AO rats was blocked by naloxone, nor-binaltorphimine (kappa opioid receptors antagonist) and beta-funaltrexamine (mu opioid receptors antagonist). Dexamethasone suppressed edema in both rat strains. These findings suggest that strain-dependent differences in the effects of ME on inflammation in DA and AO rats could be related to diversity in opioid receptors expression in these strains.

Effect of neuropeptide Y on inflammatory paw edema in the rat: involvement of peripheral NPY Y1 and Y5 receptors and interaction with dipeptidyl-peptidase IV (CD26).

Several lines of evidence suggest that neuropeptide Y (NPY) may exert regulatory effects in local inflammatory responses. Here, we show that intraplantarly (i.pl.) applied NPY, peptide YY (PYY), and an NPY Y5 receptor-selective agonist dose-dependently potentiate concanavalin A (Con A)-induced paw edema in the rat. The NPY Y1 receptor antagonist BIBO 3304 abolishes the pro-inflammatory action of both NPY and PYY while the dipeptidyl-peptidase IV (CD26) inhibitor Ile-thiazolidide exerted synergistic and potentiating effects in vivo. Taken together, the present data reveal an NPY Y1/Y5 receptor interplay and an involvement of CD26 in the NPY-induced potentiation of paw edema in the rat.