Expression of interleukin 1 alpha and beta, and interleukin 1 receptor antagonist mRNA in the rat central nervous system after peripheral administration of lipopolysaccharides

Interleukin 1alpha (IL-1alpha) and IL-1beta, and the endogenous IL-1 receptor antagonist (IL-1ra) are known members of the IL-1 family. Using in situ hybridization histochemistry we demonstrated that following endotoxin injection (lipopolysaccharides, LPS, 2.0 mg/kg, i.p.) a time dependent expression and partly different expression patterns of the cytokines occurred within the rat brain and pituitary gland. All cytokines were observed in the choroid plexus. In addition, IL-1ra mRNA expressing cells were observed scattered in the brain parenchyma, whereas scattered IL-1beta mRNA expressing cells were restricted to central thalamic nuclei, the dorsal hypothalamus, and cortical regions, such as the parietal and frontal cortex. A strong IL-1beta mRNA expression was found in the circumventricular organs. In the pituitary gland, a low IL-1alpha and a high IL-1beta mRNA expression was observed, with the highest density of cytokine-expressing cells seen in the posterior pituitary. The cell types expressing the mRNA's of IL-1alpha, IL-1beta and IL-1ra were identified as monocytes in the circumventricular organs and the pituitary gland, and as microglia in the brain parenchyma. In conclusion, the present findings revealed that cytokine production in response to a peripheral endotoxin challenge mainly occurs in peripherally derived monocytes in the circumventricular organs and the pituitary gland. IL-1beta is the predominant form expressed, whereas the expression of IL-1alpha mRNA and IL-1ra mRNA is lower. Our observations support the view that peripherally derived IL-1 may play a role in the induction of centrally mediated illness symptoms.     

Stress-induced extracellular Hsp72 is a functionally significant danger signal to the immune system

Extracellular heat-shock proteins (eHsp) such as those belonging to the 70-kDa family of Hsp (eg, Hsp72) have been hypothesized to act as a "danger signal" to immune cells, promote immune responses, and improve host defense. The current study tested this hypothesis. Adult male F344 rats were exposed to an acute laboratory stressor (100, 5-second, 1.6-mA inescapable tail shocks) and challenged with Escherichia coli. The number of colony-forming units (CFU) of bacteria at the site of injection, the levels of eHsp72, the immune response to eHsp72 and E. coli-derived lipopolysaccharide (LPS), and the amount of time required to recover from in vivo bacterial challenge were measured. CFUs were reduced 2, 4, and 6 hours after injection of E. coli in rats exposed to stress. Rats exposed to stress had elevated eHsp72 that was elevated rapidly (25 minutes) and remained elevated in the circulation and at the inflammatory site (2 hours after stressor termination). Both stressor exposure and eHsp72 administration in the absence of stress resulted in a facilitated pattern of recovery after bacterial inflammation induced by subcutaneous E. coli injection. Rats exposed to acute restraint (100 minutes) did not demonstrate elevated circulating eHsp72 or a facilitated pattern of recovery after bacterial challenge. In vitro stimulation of rat splenocytes and macrophages with eHsp72 elevated nitric oxide (NO), tumor necrosis factor alpha (TNF-alpha), interleukin (IL)-1beta, and IL-6, and this effect was specific to eHsp72 because it was not diminished by polymyxin B and was reduced by earlier heat-denature treatment. Stimulation of cells with eHsp72 combined with LPS resulted in a greater NO and cytokine response than that observed after stimulation with eHsp72 or LPS alone. In vivo, at the inflammatory site, the bacterial-induced NO response was potentiated by stress, and NO inhibition (L-NIO) reduced the stress-induced facilitation but had no effect on the control kinetics of bacterial inflammation recovery. Thus, these results lend support to the hypothesis that intense stressor exposure increases eHsp72, which acts as a danger signal to potentiate the NO response to bacterial challenge and facilitate recovery from bacterial inflammation.     

Habitual physical activity facilitates stress-induced HSP72 induction in brain,peripheral, and immune tissues

The mechanism(s) for how physically active organisms are resistant to many damaging effects of acute stressor exposure is unknown. Cellular induction of heat-shock proteins (e.g., HSP72) is one successful strategy used by the cell to survive the damaging effects of stress. It is possible, therefore, that the stress-buffering effect of physical activity may be due to an improved HSP72 response to stress. Thus the purpose of the current study was to determine whether prior voluntary freewheel running facilitates the stress-induced induction of HSP72 in central (brain), peripheral, and immune tissues. Adult male Fischer 344 rats were housed with either a mobile running wheel (Active) or a locked, immobile wheel [sedentary (Sed)] for 8 wk before stressor exposure. Rats were exposed to either inescapable tail-shock stress (IS; 100 1.6-mA tail shocks, 5-s duration, 60-s intertrial interval), exhaustive exercise stress (EXS; treadmill running to exhaustion), or no stress (controls). Blood, brain, and peripheral tissues were collected 2 h after stressor termination. The kinetics of HSP72 induction after IS was determined in cultured mesenteric lymph node cells. Activation of the stress response was verified by measuring serum corticosterone (RIA). Tissue and cellular HSP72 content were measured using HSP72 ELISA in cell lysates. Both Active and Sed rats had elevated levels of serum corticosterone after stress. In contrast, Active but not Sed rats exposed to IS and/or EXS had elevated HSP72 in dorsal vagal complex, frontal cortex, hippocampus, pituitary, adrenal, liver, spleen, mesenteric lymph nodes, and heart. In addition, Active rats exposed to IS demonstrated a faster induction of lymphocyte HSP72 compared with Sed rats. Thus Active rats responded to stress with both greater and faster HSP72 responses compared with Sed rats. These results indicate that previous physical activity potentiates HSP72 expression after a wide range of stressors. Facilitated induction of HSP72 may contribute to the increased stress resistance previously reported in physically active organisms.     

Stress-induced ACTH release after removal of the hypothalamus in rats with atrophied neural lobe.

Twenty-four hours after isolation of the pituitary by surgical removal of the medial hypothalamus, i.e. in rats with pituitary island, E. coli endotoxin significantly increased the plasma corticosterone level. Atrophy of the neural lobe, due to pituitary stalk section performed one month prior to removal of the medial hypothalamus, did not prevent the increase of ACTH release by E. coli endotoxin. E. coli endotoxin-induced ACTH release in MBH-deprived animals does not appear to be a function of mechanisms operating only in the innervated lobe.     

Electrical stimulation of afferent vagus nerve induces IL-1beta expression in the brain and activates HPA axis

Possible roles of the afferent vagus nerve in regulation of interleukin (IL)-1beta expression in the brain and hypothalamic-pituitary-adrenal (HPA) axis were examined in anesthetized rats. Levels of IL-1beta mRNA and protein in the brain were measured by comparative RT-PCR and ELISA. Direct electrical stimulation of the central end of the vagus nerve was performed continuously for 2 h. The afferent stimulation of the vagus nerve induced increases in the expression of mRNA and protein levels of IL-1beta in the hypothalamus and the hippocampus. Furthermore, expression of corticotropin-releasing factor mRNA was increased in the hypothalamus 2 h after vagal stimulation. Plasma levels of ACTH and corticosterone were also increased by this stimulation. The present results indicate that activation of the afferent vagus nerves itself can induce production of IL-1beta in the brain and activate the HPA axis. Therefore, the afferent vagus nerve may play an important role in transmitting peripheral signals to the brain in the infection and inflammation.     

Circulating cytokines and endotoxin are not necessary for the activation of the sickness or corticosterone response produced by peripheral E. coli challenge.

Peripheral administration of a variety of inflammatory stimuli, such as endotoxin or cytokines, induces an orchestrated set of brain-mediated events referred to as the sickness response. The mechanism for how immune products signal the brain is not clear, but accumulating evidence supports the existence of neural as well as blood-borne pathways. Although endotoxin or cytokine administration results in sickness responses, few data exist regarding the role of circulating endotoxin or cytokines in the induction of sickness during a real bacterial infection. Thus the present studies examined whether subcutaneously administered Escherichia coli can activate sickness responses and whether circulating endotoxin and/or proinflammatory cytokines are a prerequisite for these responses. Male Sprague-Dawley rats were injected subcutaneously with one of three doses (2.5 x 10(7), 2.5 x 10(8), 2.5 x 10(9) colony-forming units) of replicating E. coli, a ubiquitous bacterial strain, or vehicle. Core body temperature (Tc) and activity were measured for 3 days after the injection. A second set of groups of animals were killed 3, 6, 12, 18, 24, and 48 h after the injection, and blood samples and brains were collected. Injections dose dependently and consistently increased Tc and decreased activity, with increases in Tc beginning 4 h after the injection. In addition, E. coli significantly increased serum interleukin (IL)-1beta, IL-6, and tumor necrosis factor-alpha and brain IL-1beta levels beginning at the 6-h time point. Corticosterone and endotoxin were first elevated in the circulation at 3 and 18 h after the injection, respectively. Because fever onset preceded brain cytokine induction, we also examined cytokine levels in the serum, brain, and inflammation site 2 and 4 h after injection. Cytokines were elevated at the inflammation site but were not detectable in the serum or brain at 2 and 4 h. We conclude that subcutaneous injection of replicating E. coli induces a consistent and naturalistic infection that includes features of the sickness response as well as increases in circulating, brain, and inflammation site tissue cytokines. In addition, injection of replicating E. coli produces a robust fever and corticosterone response at a time when there are no detectable increases in circulating cytokines or endotoxin. These results suggest that elevated levels of circulating cytokines and endotoxin are not necessary for the activation of the sickness or corticosterone response. Therefore, fever, activity reduction, and corticosterone elevation induced by E. coli infection may have been evoked by a neural, rather than a humoral, pathway from the periphery to the brain.     

Role of extracellular HSP72 in acute stress-induced potentiation of innate immunity in active rats.

Acute stress can compromise acquired, and potentiate innate, immunity. Recent evidence suggests that the impact of stress on measures of immunity can be modulated by the physical activity status of the organism and that extracellular heat shock protein 72 (eHSP72) contributes to the activation of innate immunity produced by stress. Therefore, this study investigated whether physical activity status would impact the immunologically enhancing effects of stressor exposure [inescapable tail-shock stress (IS)] on innate immunity and whether changes in eHSP72 responses could play a role. Adult, male Fischer 344 rats lived with mobile (physically active) or immobile (sedentary) running wheels. After 6 wk, rats were exposed to IS or to no stress. Immediately after IS, all rats were injected subcutaneously with live Escherichia coli. Inflammation was assessed daily, and plasma eHSP72 was measured at various time points. Rats exposed to IS resolved their inflammation faster than nonstressed rats, but the beneficial impact of stress on recovery was greater in physically active rats. All rats had equal increases in circulating eHSP72 after IS. Splenocytes harvested from a separate cohort of nonstressed rats were cultured with eHSP72, and nitric oxide and cytokines were measured. Physically active rats responded to eHSP72 stimulation in vitro with a greater nitric oxide and cytokine response than sedentary rats. Thus physically active rats both recover faster than sedentary rats after bacterial challenge + IS exposure and demonstrate potentiated cellular responses to eHSP72 activation that could be important for bacterial recovery.     

Inhibition of caspase-1 in rat brain reduces spontaneous nonrapid eye movement sleep and nonrapid eye movement sleep enhancement induced by lipopolysaccharide

Evidence suggests that IL-1beta is involved in promoting physiological nonrapid eye movement (NREM) sleep. IL-1beta has also been proposed to mediate NREM sleep enhancement induced by bacteria or their components. Mature and biologically active IL-1beta is cleaved from an inactive precursor by a cysteinyl aspartate-specific protease (caspase)-1. This study aimed to test the hypothesis that inhibition in brain of the cleavage of biologically active IL-1beta will reduce in rats both spontaneous NREM sleep and NREM sleep enhancement induced by the peripheral administration of components of the bacterial cell wall. To test this hypothesis, rats were intracerebroventricularly administered the caspase-1 inhibitor Ac-Tyr-Val-Ala-Asp chloromethyl ketone (YVAD; 3, 30, 300, and 1,500 ng) or were pretreated intracerebroventricularly with YVAD (300 ng) and then intraperitoneally injected with the gram-negative bacterial cell wall component LPS (250 microg/kg). Subsequent sleep-wake behavior was determined by standard polygraphic recordings. YVAD administration at the beginning of the light phase of the light-dark cycle significantly reduced time spontaneously spent in NREM sleep during the first 12 postinjection hours. YVAD pretreatment also completely prevented NREM sleep enhancement induced by peripheral LPS administration at the beginning of the dark phase. These results, in agreement with previous evidence, support the involvement of brain IL-1beta in physiological promotion of NREM sleep and in mediating NREM sleep enhancement induced by peripheral immune challenge.     

Acute stressor exposure facilitates innate immunity more in physically active than in sedentary rats

Most previous stress-immune research focused on the immunosuppressive effects of stress on acquired immunity. More recently, it has become clear that acute stressor exposure can potentiate innate, as well as suppress acquired, immunity. For example, acute stress improves recovery from bacterial inflammation, a classic in vivo measure of innate immunity. The previous work was done in sedentary organisms. Physical activity status can modulate the impact of stress on immune function. The following studies tested the hypothesis that the effect of stress on inflammation after subcutaneous challenge with bacteria (Escherichia coli) is facilitated by physical activity. The results were that sedentary, stressed rats resolved their inflammation 1-2 days faster and have increased circulating neutrophils compared with their nonstressed, sedentary counterparts. In contrast, physically active, stressed rats resolve their inflammation 3-4 days faster and have increased circulating and inflammatory site neutrophils compared with their nonstressed counterparts. Importantly, the beneficial impact of stress on inflammation recovery and neutrophil migration was greater in the physically active, than sedentary, stressed rats. Thus physical activity status facilitates the positive effect of acute stress on innate immunity.     

Site-specific modulation of LPS-induced fever and interleukin-1 beta expression in rats by interleukin-10

Bacterial lipopolysaccharide (LPS) induces fever that is mediated by pyrogenic cytokines such as interleukin (IL)-1 beta. We hypothesized that the anti-inflammatory cytokine IL-10 modulates the febrile response to LPS by suppressing the production of pyrogenic cytokines. In rats, intravenous but not intracerebroventricular infusion of IL-10 was found to attenuate fever induced by peripheral administration of LPS (10 microg/kg iv). IL-10 also suppressed LPS-induced IL-1 beta production in peripheral tissues and in the brain stem. In contrast, central administration of IL-10 attenuated the febrile response to central LPS (60 ng/rat icv) and decreased IL-1 beta production in the hypothalamus and brain stem but not in peripheral tissues and plasma. Furthermore, intravenous LPS upregulated expression of IL-10 receptor (IL-10R1) mRNA in the liver, whereas intracerebroventricular LPS enhanced IL-10R1 mRNA in the hypothalamus. We conclude that IL-10 modulates the febrile response by acting in the periphery or in the brain dependent on the primary site of inflammation and that its mechanism of action most likely involves inhibition of local IL-1 beta production.     

Effects of lipopolysaccharide on neurokinin A content and release in the hypothalamic-pituitary axis

The administration of bacterial lipopolysaccharide (LPS) markedly affects pituitary secretion, and its effects are probably mediated by cytokines produced by immune cells or by the hypothalamo-pituitary axis itself. Since neurokinin A (NKA) plays a role in inflammatory responses and is involved in the control of prolactin secretion, we examined the in vivo effect of LPS on the concentration of NKA in hypothalamus and pituitary (assessed by RIA) and serum prolactin levels in male rats. One hour after the intraperitoneal administration of LPS (250 microg/rat), NKA content was decreased in the posterior pituitary but not in the hypothalamus or anterior pituitary. Three hours after injection, LPS decreased NKA concentration in the hypothalamus and anterior and posterior pituitary. In all the conditions tested, LPS significantly decreased serum prolactin. We also examined the in vitro effects of LPS (10 microg/ml), interleukin-6 (IL-6, 10 ng/ml) and tumor necrosis factor alpha (TNF-alpha, 50 ng/ml) on hypothalamic NKA release. Interleukin-6 increased NKA release without modifying hypothalamic NKA concentration, whereas neither LPS nor TNF-alpha affected them. Our results suggest that IL-6 may be involved in the increase of hypothalamic NKA release induced by LPS. NKA could participate in neuroendocrine responses to endotoxin challenge.     

Effects of physical training on IL-1beta, IL-6 and IL-1ra concentrations in various brain areas of the rat

There is increasing evidence that voluntary physical activity and exercise training have beneficial effects on brain function by facilitating neurovegetative, neuroadaptative and neuroprotective processes. Cytokines are chronically expressed at elevated levels within the CNS in many neurological disorders and may contribute to the histopathological, pathophysiological, and cognitive deficits associated with such disorders. In the present study, we examined the influence of seven weeks of physical training on IL-1b, IL-6 and IL-1ra concentrations in hypothalamus, pituitary, hippocampus, cerebellum and frontal cortex in rats. We determined circulating concentrations of cytokines, corticosterone, prolactin and leptin. Two groups of 10 rats were investigated: one group (trained rats) was progressively trained (5 days/week); the other group (sedentary rats) was used as a sedentary group. The training program induced a decrease of (i) IL-1b concentration in the hippocampus (0.7 +/- 0.16 versus 0.99 +/- 0.14 pg/mg protein; p < 0.05), (ii) IL-6 concentration in the cerebellum (10.7 +/- 1.00 in trained rats versus 14.8 +/- 1.34 pg/mg protein in sedentary rats; p < 0.05), (iii) IL-1ra concentration in the pituitary (245 +/- 14.31 versus 328 +/- 17.73 pg/mg protein; p < 0.01). We also found positive correlations between (i) serum prolactin and the concentration of IL-6 in the cerebellum, (ii) serum leptin and the concentration of IL-1ra in the pituitary. There was no effect of physical training on IL-1b, IL-6, and IL-1ra serum levels. These findings suggest that the decrease in particular pro-inflammatory, central cytokines such as IL-1b and IL-6 induced by the training program may play a role in the positive effects of regular physical activity on the central nervous system.     

Lipopolysaccharide pretreatment of the udder protects against experimental Escherichia coli mastitis

Exposure to pathogen-associated molecular patterns such as LPS can cause an immune refractory state in mammals known as endotoxin tolerance (ET), resulting in a decreased inflammatory response after pathogen contact. This ET concept was used to reduce the severity of an experimentally-induced clinical mastitis. Cows were pretreated with 1?μg LPS per udder quarter and challenged 72?h (group L72EC) or 240?h (group L240EC) later with 500 CFU Escherichia coli. Pretreated animals showed no leukopenia after challenge, no (L72EC), or only slightly (L240EC), elevated body temperature and significantly reduced systemic and local clinical scores compared with cows that were not pretreated. Whereas an increase of milk somatic cell count after the E. coli challenge was abrogated in L72EC animals, it was significantly delayed in the L240EC group. In both pretreated groups the bacterial load in milk was markedly reduced. Based on the expression of inflammation-related genes in lobulo-alveolar mammary tissue, the tolerizing effect of LPS pretreatment is based on the inhibited up-regulation of inflammatory (TNF-α, IL-6, CXCL8, CCL20) and anti-inflammatory genes (IL-10, IRAK-M). These findings indicate that the concept of ET may be usefully applied as mastitis prophylaxis facilitating a rapid response to microbial infection and avoiding dysregulated inflammation.     

Abdominal vagatomy does not modify endotoxic shock in rats

Bilateral subdiaphragmatic vagotomy does not improve the clinical course not the survival of Sprague-Dawley rats injected intravenously with E. coli lipopolysaccharide. These results show that whatever peripheral signals are elicited by endotoxin to generate the centrally mediated hypotensive response, they are not conveyed to the central nervous system by abdominal vagal afferent fibers.     

Cytokines as mediators of neuroimmune interactions

Cytokines regulate numerous physiological and pathological processes in the central nervous system (CNS), i.e. they function both as immune regulators and neuromodulators. Acting upon the CNS via different ways, cytokines, mainly proinflammatory ones IL-1beta and TNF-alpha, can disturb physiological functions of the CNS, cause neurotoxic and neurodegenerative damage and stimulate IL-1beta synthesis in hypothalamus nuclei and posterior pituitary. They can produce stress-like effects upon the CNS and affect the activity of the axis hypothalamus--pituitary--adrenal glands, levels of neuropeptides in hypothalamic regions of brain, synthesis and utilization of central monoamines. These influences can implement the effects of sensitization, which enhances neuroendocrine responses to later stresses. Microglia and astrocytes, secondary messengers and interaction between hypothalamus and anterior pituitary play an important role in range of these processes as well as in the maintenance of Th1/Th2 cytokine balance.     

c-Fos generation in the dorsal vagal complex after systemic endotoxin is not dependent on the vagus nerve

The present study used activation of the c-Fos oncogene protein within neurons in the dorsal vagal complex (DVC) as a marker of neuronal excitation in response to systemic endotoxin challenge [i.e. , lipopolysaccharide (LPS)]. Specifically, we investigated whether vagal connections with the brain stem are necessary for LPS cytokine- induced activation of DVC neurons. Systemic exposure to LPS elicited a significant activation of c-Fos in neurons in the nucleus of the solitary tract (NST) and area postrema of all thiobutabarbital-anesthetized rats examined, regardless of the integrity of their vagal nerves. That is, rats with both vagi cervically transected were still able to respond with c-Fos activation of neurons in the DVC. Unilateral cervical vagotomy produced a consistent but small reduction in c-Fos activation in the ipsilateral NST of all animals within this experimental group. Given that afferent input to the NST is exclusively excitatory, it is not surprising that unilateral elimination of all vagal afferents would diminish NST responsiveness (on the vagotomized side). These data lead us to conclude that the NST itself is a primary central nervous system detector of cytokines.     

Ketamine does not affect intestinal microcirculation in pentobarbital-anaesthetized rats during experimental endotoxaemia

The objective of the study was to evaluate the effects of ketamine on intestinal microcirculation in pentobarbital-anaesthetized rats during experimental endotoxaemia. A prospective, randomized, controlled study was carried out using 32 male Lewis rats. The animals were divided into four groups (n = 8 each). All animals were initially anaesthetized with 60 mg/kg pentobarbital (i.p.). Group 1 served as a control (18.5 mg/kg/h pentobarbital i.v.). Groups 2 and 4 received an endotoxin intravenous infusion of 15 mg/kg lipopolysaccharide (LPS) from Escherichia coli. Groups 3 and 4 also received 10 mg/kg/h ketamine (i.v.). After 2 h of observation, the animals were examined for intestinal functional capillary density (FCD) and leukocyte adherence to the venular endothelium by means of intravital fluorescence microscopy (IVM). Subsequent to this examination, blood samples were collected to determine release of the cytokines tumour necrosis factor (TNF)-alpha, interleukin (IL)-1beta, IL-6 and IL-10. Endotoxaemia tended to decrease intestinal FCD (mucosa: -10.1%, muscularis longitudinalis: -2%, muscularis circularis: -9.8%) and significantly increase leukocyte adherence within submucosal venules (collecting venules: +133%, postcapillary venules: +207%; P<0.05). TNF-alpha, IL-1beta, IL-6 and IL-10 levels were significantly elevated following endotoxin challenge. The addition of ketamine to pentobarbital anaesthesia did not significantly affect FCD, leukocyte behaviour or cytokine levels. In conclusion, intravenous pentobarbital anaesthesia with the additional administration of ketamine did not cause alterations within the microcirculation or changes in cytokine release during endotoxaemia. In rats, the combination of pentobarbital and ketamine is suitable for use during the study of intestinal microcirculation in experimental endotoxaemia.     

Endotoxemia in newborn rats attenuates acute pancreatitis at adult age.

Bacterial endotoxin (lipopolysaccharide, LPS), at high concentration is responsible for sepsis, and neonatal mortality, however low concentration of LPS protected the pancreas against acute damage. The aim of this study was to investigate the effect of exposition of suckling rats to LPS on the course of acute pancreatitis at adult age. Suckling rat (30-40g) received intraperitoneal (i.p.) injection of saline (control) or LPS from Escherichia coli or Salmonella typhi (5, 10 or 15 mg/kg-day) during 5 consecutive days. Two months later these rats have been subjected to i.p. cearulein infusion (25 microg/kg) to produce caerulein-induced pancreatitis (CIP). The following parameters were tested: pancreatic weight and morphology, plasma amylase and lipase activities, interleukin 1beta (IL-1 beta), interleukin 6 (IL-6), and interleukin 10 (IL-10) plasma concentrations. Pancreatic concentration of superoxide dismutase (SOD) and lipid peroxidation products; malondialdehyde (MDA) and 4-hydroxynonenal (4-HNE) have been also measured. Caerulein infusion produced CIP in all animals tested, that was confirmed by histological examination. In the rats, which have been subjected in the neonatal period of life to LPS at doses 10 or 15 mg/kg-day x 5 days, all manifestations of CIP have been reduced. In these animals acute inflammatory infiltration of pancreatic tissue and pancreatic cell vacuolization have been significantly diminished. Also pancreatic weight, plasma lipase and alpha-amylase activities, as well as plasma concentrations of IL-1beta and IL-6 have been markedly decreased, whereas plasma anti-inflammatory IL-10 concentration was significantly increased in these animals as compared to the control rats, subjected in the infancy to saline injection instead of LPS. Caerulein-induced fall in pancreatic SOD concentration was reversed and accompanied by significant reduction of MDA + 4 HNE in the pancreatic tissue. The effects of LPS derived from E. coli or S. typhi were similar. Pretreatment of suckling rats with LPS at dose of 10 mg/kg-day x 5 days resulted in the most prominent attenuation of acute pancreatitis at adult age, whereas LPS at dose of 5 mg/kg-day x 5 days given to the neonatal rats failed to affect significantly acute pancreatitis induced in these animals 2 months later. We conclude that: 1/ Prolonged exposition of suckling rats to bacterial endotoxin attenuated acute pancreatitis induced in these animals at adult age. 2/ This effect could be related to the increased concentration of antioxidative enzyme SO in the pancreatic tissue and to the modulation of cytokines production in these animals.     

Effects of vagotomy on serum endotoxin, cytokines, and corticosterone after intraperitoneal lipopolysaccharide

The vagus nerve appears to play a role in communicating cytokine signals to the central nervous system, but the exact extent of its involvement in cytokine-to-brain communication remains controversial. Recently, subdiaphragmatic vagotomy was shown to increase bacterial translocation across the gut barrier and thus may cause endotoxin tolerance. The current experiment tested whether or not vagotomized animals have similar systemic responses to endotoxin challenge as do sham-operated animals. Subdiaphragmatically vagotomized and sham-operated animals were injected intraperitoneally with one of three doses (10, 50, 100 microg/kg) of lipopolysaccharide (LPS) or vehicle, and blood samples were taken at 15, 30, 60, 90, and 120 min after the injection. The intraperitoneal injection of LPS increased circulating LPS levels at all time points examined. In addition, all three doses of LPS significantly increased serum interleukin (IL)-1beta, IL-6, and corticosterone in both control and vagotomized rats. In conclusion, vagotomy itself has no marked effect on circulating endotoxin levels or the production of IL-1beta, IL-6, or corticosterone in blood after an intraperitoneal injection of LPS.     

Cytokines in the Hypophysis: A Comparative Look at Interleukin-6 in the Porcine Anterior Pituitary Gland

Interleukin-6 (IL-6) is a multifunctional cytokine produced by a variety of cell types in tissues of both the immune and endocrine systems. Among the major functions described for IL-6 are its role in the maturation of B cells to high-output antibody-producing cells and its contribution to the acute physiological responses to infection and inflammation, notably production of hepatic acute phase proteins and activation of the hypothalamic-pituitary-adrenal axis. In addition to these better known functions, IL-6 recently has been found within the pituitary of laboratory rats and also in the human pituitary. In rats, pituitary IL-6 mRNA is upregulated by peripheral exposure to bacterial endotoxin. However, the role of anterior pituitary IL-6 in host responses to infection and inflammation remains uncertain, although it may regulate pituitary hormone secretion. The following brief review summarizes the information available concerning cytokine production within the anterior pituitary of species of domestic livestock. To our knowledge, experiments conducted in our laboratory evaluating regulation of IL-6 mRNA expression and secretion from the porcine anterior pituitary provide most of the data in domestic species confirming the presence of IL-6 in the pituitary. Our data indicate that IL-6 mRNA is present in cultured porcine anterior pituitary cells and that the pituitary directly responds to stimulation with bacterial endotoxin by increasing secretion of IL-6. Furthermore, endotoxin-induced upregulation of IL-6 mRNA expression and secretion appears to be dependent upon production of cyclooxygenase products of arachidonic acid metabolism.