Vagus nerve stimulation attenuates the systemic inflammatory response to endotoxin

Predictors of response to infliximab in patients with Crohn's disease

BACKGROUND & AIMS

Identifying predictors of response to infliximab in Crohn's disease may lead to better selection of patients for this therapy.

METHODS

One hundred patients with either inflammatory or fistulous Crohn's disease and at least 3 months of follow-up after infliximab infusion were evaluated. Clinical response and duration of response were the primary outcome measures.

RESULTS

For inflammatory disease, 73% of nonsmokers, compared with 22% of smokers, responded to infliximab (P < 0.001). Among patients taking concurrent immunosuppressives, 74% responded to infliximab compared with 39% not taking any immunosuppressives (P = 0.007). Prolonged response (duration >2 months) was achieved in 59% of nonsmokers compared with 6% of smokers (P < 0.001) and in 65% of patients on immunosuppressives compared with 18% not on immunosuppressives (P < 0.001). For fistulous disease, overall response rates were not different between nonsmokers and smokers, but nonsmokers had a longer duration of response (P = 0.046). Concurrent use of immunosuppressive medications had no effect on rate or duration of response. Multivariable logistic regression analysis confirmed the harmful effect of smoking and the beneficial effect of immunosuppressive use on response in patients with inflammatory disease. The same analysis for fistulous disease did not show an association between smoking or concurrent immunosuppressive use and response to infliximab.

CONCLUSIONS

In patients with inflammatory disease, nonsmoking and concurrent immunosuppressive use are associated with higher rates of response and longer duration of response to infliximab. In patients with fistulous Crohn's disease, nonsmoking is associated with longer duration of response to infliximab.

Differential expression of nicotinic acetylcholine receptor subunits in fetal and neonatal mouse thymus

Studies were initiated to identify nicotinic acetylcholine receptor (nAChR) subunits and subtypes expressed in the developing immune system and cell types on which nAChR are expressed. Reported here are reverse transcription-polymerase chain reactions (RT-PCR) studies of nAChR alpha2-alpha7 and beta2-beta4 subunit gene expression using fetal or neonatal regular or scid/scid C57BL/6 mouse thymus. Findings are augmented with studies of murine fetal thymic organ cultures (FOTC) and of human peripheral lymphocytes. Novel partial cDNA sequences were derived for mouse nAChR alpha2, alpha3, beta3 and beta4 subunits, polymorphisms were identified in mouse nAChR alpha4, alpha7 and beta2 subunits, and recently derived sequences for mouse nAChR alpha5 and alpha6 subunits were confirmed. Thymic stromal cells appear to express nAChR alpha2, alpha3, alpha4, alpha7 and beta4 subunits, perhaps in addition to alpha5 and beta2 subunits, in a pattern reminiscent of expression in the developing brain. Immature T cells appear to express alpha3, alpha5, alpha7, beta2 and beta4 subunits, just as do neural crest-derived cells targeted by cholinergic innervation. Peripheral T cells seem to express an unusual profile of alpha2, alpha5 and alpha7 subunits, perhaps indicating that their nAChR express yet-to-be-identified assembly partners or that T cell nicotinic responsiveness occurs through homomeric nAChR composed of alpha7 subunits. Our findings are consistent with published work but show a much wider array of nAChR subunit gene expression in mouse thymic stromal and/or lymphoid cells and evidence for developmental regulation of nAChR subunit expression. These studies suggest important roles for nAChR in immune system development and function and in the neuroimmune network.

A role for abdominal vagal afferents in lipopolysaccharide-induced hypotension

Lipopolysaccharide (LPS) mimics many of the effects of septic shock, including hypotension. LPS-induced hypotension has been attributed to nitric oxide (NO) activation of leukocytes, oxidants, cytokines, and other causes. However, there are some observations inconsistent with these "biochemical" causes. This study investigated a "physiological" mechanism: Are abdominal vagal afferent neurons involved in LPS-induced hypotension? The involvement of NO and leukocytes was also considered. Intravenous LPS (5 mg/kg) was used to induce hypotension in anesthetized rats. Subdiaphragmatic vagal activity was blocked with perivagal lidocaine (2%). Intravenous capsaicin (CAP, 1 mg/kg) or resiniferatoxin (RTX, 1 microg/kg) were used to inhibit afferent neural activity about 30 min before LPS. CAP and RTX have different receptors on different afferent nerves. Blood pressure, plasma nitrate and nitrite (NOx), stable products of NO, and leukocytes were measured over 3 h. LPS-induced hypotension was markedly attenuated by perivagal lidocaine and i.v. RTX, but was not affected by i.v. CAP. LPS caused a marked, transient decrease in leukocytes, mainly neutrophils, which was over within 10 min. This early leukocyte response was not affected by treatments that reduced LPS-induced hypotension. NO increased 3 h after LPS, and the changes in NO were not associated with effects of the pretreatments on blood pressure. It was concluded that abdominal vagal afferents are early mediators of LPS-induced hypotension. Also, NO and leukocytes were not direct mediators of the hypotension.

Is type 2 diabetes mellitus a disorder of the brain?

I propose that type 2 diabetes mellitus is due to damage to neurons in the ventromedial hypothalamus or to a defect in the action or properties of insulin or insulin receptors in the brain. These neuronal abnormalities are probably secondary to a marginal deficiency of long-chain polyunsaturated fatty acids during the critical periods of brain growth and development. Hence, supplementation of adequate amounts of long-chain polyunsaturated fatty acids during the third trimester of pregnancy to 2 y postterm can prevent or postpone the development of diabetes mellitus.

The lipids that matter from infant nutrition to insulin resistance

Breast-fed infants showed decreased incidence of obesity, hypertension, diabetes mellitus, and coronary heart disease in later life and higher cognitive function. Breast milk is rich in long-chain polyunsaturated fatty acids (LCPUFAs) and brain preferentially accumulates LCPUFAs during the last trimester of pregnancy and the first few months of life. Breast-fed infants showed significantly lower plasma glucose levels and higher percentage of docosahexaenoic acid and total percentages of LCPUFAs in their skeletal muscle biopsies compared with formula fed. LCPUFAs suppress the production of pro-inflammatory cytokines, regulate the function of several neurotransmitters, enhance the number of insulin receptors in the brain and other tissues, and decrease insulin resistance. LCPUFAs may enhance the production of bone morphogenetic proteins (BMPs), which participate in neurogenesis. It is proposed that the beneficial effects of breast feeding in later life can be attributed to its rich LCPUFA content. It is likely that inadequate breast feeding results in marginal deficiency of LCPUFAs during the critical stages of development, which can lead to insulin resistance. Hence, promoting prolonged breast feeding and/or supplementing LCPUFAs during the critical stages of development may be beneficial in preventing insulin resistance.

Evidences for vagus nerve in maintenance of immune balance and transmission of immune information from gut to brain in STM-infected rats

AIM: To determine whether Salmonella Typhimurium (STM) in gastrointestinal tract can induce the functional activation of brain, whether the vagus nerve involves in signaling immune information from gastrointestinal tract to brain and how it influences the immune function under natural infection condition.

METHODS: Animal model of gastrointestinal tract infection in the rat was established by an intubation of Salmonella Typhimurium (STM) into stomach to mimic the condition of natural bacteria infection. Subdiagphragmatic vagotomy was performed in some of the animals 28 days before infection. The changes of Fos expression visualized with immunohistochemistry technique in hypothalamic paraventricular nucleus (PVN) and superaoptic nucleus (SON) were counted. Meanwhile, the percentage and the Mean Intensities of Fluorescent (MIFs) of CD4+ and CD8+ T cells in peripheral blood were measured by using flow cytometry (FCM), and the pathological changes in ileum and mesenteric lymph node were observed in HE stained sections.

RESULTS: In bacteria-stimulated groups, inflammatory pathological changes were seen in ileum and mesenteric lymph node. The percentages of CD4+ T cells in peripheral blood were decreased from 42% ± 4.5% to 34% ± 4.9% (P < 0.05) and MIFs of CD8+ T cells were also decreased from 2.9 ± 0.39 to 2.1 ± 0.36 (P < 0.05) with STM stimulation. All of them proved that our STM-infection model was reliable. Fos immunoreactive (Fos-ir) cells in PVN and SON increased significantly with STM stimulation, from 189 ± 41 to 467 ± 62 (P < 0.05) and from 64 ± 21 to 282 ± 47 (P < 0.05) individually, which suggested that STM in gastrointestinal tract induced the functional activation of brain. Subdiagphragmatic vagotomy attenuated Fos expression in PVN and SON induced by STM, from 467 ± 62 to 226 ± 45 (P < 0.05) and from 282 ± 47 to 71 ± 19 (P < 0.05) individually, and restored the decreased percentages of CD4+ T cells induced by STM from 34% ± 4.9% to original level 44% ± 6.0% (P < 0.05). In addition, subdiagphragmatic vagotomy itself also decreased the percentages of CD8+ T cells (from 28% ± 3.0% to 21% ± 5.9%, P < 0.05) and MIFs of CD4+ (from 6.6 ± 0.6 to 4.9 ± 1.0, P < 0.05) and CD8+ T cells (from 2.9 ± 0.39 to1.4 ± 0.34, P < 0.05). Both of them manifested the important role of vagus nerve in transmitting immune information from gut to brain and maintaining the immune balance of the organism.

CONCLUSION: Vagus nerve does involve in transmitting abdominal immune information into the brain in STM infection condition and play an important role in maintenance of the immune balance of the organism.

Regulation and function of COX-2 gene expression in isolated gastric parietal cells

We examined expression, function, and regulation of the cyclooxygenase (COX)-2 gene in gastric parietal cells. COX-2-specific mRNA was isolated from purified (>95%) canine gastric parietal cells in primary culture and measured by Northern blots using a human COX-2 cDNA probe. Carbachol was the most potent inducer of COX-2 gene expression. Gastrin and histamine exhibited minor stimulatory effects. Carbachol-stimulated expression was inhibited by intracellular Ca(2+) chelator 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid-AM (90%), protein kinase C (PKC) inhibitor GF-109203X (48%), and p38 kinase inhibitor SB-203580 (48%). Nuclear factor (NF)-kappaB inhibitor 1-pyrrolidinecarbodithioic acid inhibited carbachol-stimulated expression by 80%. Similar results were observed in the presence of adenoviral vector Ad.dom.neg.IkappaB, which expresses a repressor of NF-kappaB. Addition of SB-203580 with Ad.dom.neg.IkappaB almost completely blocked carbachol stimulation of COX-2 gene expression. We examined the effect of carbachol on PGE(2) release by enzyme-linked immunoassay. Carbachol induced PGE(2) release. Ad.dom.neg.IkappaB, alone or with SB-203580, produced, respectively, partial (70%) and almost complete (>80%) inhibition of carbachol-stimulated PGE(2) production. Selective COX-2 inhibitor NS-398 blocked carbachol-stimulated PGE(2) release without affecting basal PGE(2) production. In contrast, indomethacin inhibited both basal and carbachol-stimulated PGE(2) release. Carbachol induces COX-2 gene expression in the parietal cells through signaling pathways that involve intracellular Ca(2+), PKC, p38 kinase, and activation of NF-kappaB. The functional significance of these effects seems to be stimulation of PGE(2) release.

Neural-immune gut-brain communication in the anorexia of disease

Peripheral administration of toxic bacterial products and cytokines have been used to model the immunological, physiological, and behavioral responses to infection, including the anorexia of disease. The vagus nerve is the major neuroanatomic linkage between gut sites exposed to peripheral endotoxins and cytokines and the central nervous system regions that mediate the control of food intake, and thus has been a major research focus of the neurobiological approach to understanding cytokine-induced anorexia. Molecular biological and neurophysiologic evidence demonstrates that peripheral anorectic doses of cytokines and endotoxins elicit significant increases in neural activation at multiple peripheral and central levels of the gut-brain axis and in some cases may modify the neural processing of meal-related gastrointestinal signals that contribute to the negative feedback control of ingestion. However, behavioral studies of the anorectic effects of peripheral cytokines and endotoxins have shown that neither vagal nor splanchnic visceral afferent fibers supplying the gut are necessary for the reduction of food intake in these models. These data do not rule out 1) the potential contribution of supradiaphragmatic vagal afferents or 2) a modulatory role for immune-stimulated gut vagal afferent signals in the expression of cytokine and endotoxin-induced anorexia in the intact organism.

Cannabinoid CB(1) receptor blockade enhances the protective effect of melanocortins in hemorrhagic shock in the rat

Activation of peripheral cannabinoid CB(1) receptors contributes to hemorrhagic hypotension, and endocannabinoids produced by macrophages and platelets may be mediators of this effect. A number of studies have provided evidence that functional links exist in the mechanisms of action of cannabinoids and opioid peptides; and opioids too play an important role in the pathophysiology of hemorrhagic hypotension and shock. On the other hand, melanocortin peptides, which are the main endogenous functional antagonists of opioid peptides, have an antishock effect in animals and humans. Thus, we investigated whether an interaction exists between endocannabinoids and the endogenous opioid/antiopioid system also in a condition of hemorrhagic shock and, particularly, whether the blockade of cannabinoid CB(1) receptors potentiates the antishock effect of melanocortins. Urethane-anesthetized rats were stepwise bled until mean arterial pressure decreased to, and stabilized at, 21-23 mm Hg. In this model of hemorrhagic shock, which caused the death of all control rats within 30 min after vehicle (tween 80, 5% in saline) injection, the intravenous (i.v.) bolus injection of the cannabinoid CB(1) receptor antagonist N-piperidino-5-[4-chlorophenyl]-1-[2,4 dichlorophenyl]-4-methyl-3-pyrazolecarboxamide (SR141716A) increased mean arterial pressure, pulse pressure, respiratory rate and survival rate in a dose-related manner (0.1-3 mg/kg), an almost complete recovery of mean arterial pressure, pulse pressure and respiratory rate, and 100% survival at the end of the observation period (2 h), occurring with the dose of 3 mg/kg. The melanocortin ACTH-(1-24) (adrenocorticotropin) also produced in a dose-related manner (0.02-0.16 mg/kg i.v.) a restoration of cardiovascular and respiratory functions, and increased survival rate, an almost complete recovery and 100% survival at the end of the observation period (2 h) occurring with the dose of 0.16 mg/kg. When a subactive dose of SR141716A (0.2 mg/kg; 30% survival) was associated with a subactive dose of ACTH-(1-24) (0.02 mg/kg; 12% survival), a complete reversal of the shock condition was obtained with 100% survival at the end of the 2-h observation period. The present results show that the concurrent inhibition of both endogenous opioid and cannabinoid systems produces a reversal of hemorrhagic shock more effective than that produced by the inhibition of either of them. These data suggest that functional interactions between endocannabinoids and opioid/antiopioid are at work also in the pathophysiology of hemorrhagic shock.

Effect of prophylactic intracerebroventricular injection of methylprednisolone on nitrogen and catecholamine excretion in the urine after laparotomy in rats

BACKGROUND

This study was carried out to determine whether the prophylactic injection of glucocorticoid into the intracerebroventricular (i.c.v.) space reduced TNF-alpha and IL-1beta mRNA synthesis in the brain after laparotomy, resulting in a reduction of nitrogen excretion in the urine.

PATIENTS AND METHODS

Male SD rats (body wt., 225-250 g, n = 114) were catheterized into the i.c.v. space on day 0. On day 4, the rats were assigned to four groups: (1) Control, (2) laparotomy (Trauma), (3) intraperitoneal (i.p.) injection of methylprednisolone (MP) plus laparotomy (IPMP), and (4) i.c.v. injection of MP plus laparotomy (ICVMP). Either 3 or 24 h after surgery, the animals were sacrificed. TNF-alpha and IL-1beta mRNA levels in tissues, including the brain cortex and hypothalamus, were measured by RT-PCR. The amounts of nitrogen and catecholamine excretion in the 24-h urine were determined.

RESULTS

The i.p. injection of MP reduced TNF-alpha and IL-1beta mRNA levels in all the tissues 3 h after laparotomy compared with those of the Trauma group. The icv injection of MP prevented elevation of the TNF-alpha and IL-1beta mRNA levels in the brain (cortex, TNF-alpha, ICVMP 0.43 +/- 0.06, P < 0.05, vs Trauma; cortex, IL-1beta, ICVMP 0.25 +/- 0.09, P < 0.05, vs. Trauma; hypothalamus, TNF-alpha, ICVMP 0.31 +/- 0.04, P < 0.05, vs. Trauma; hypothalamus, IL-1beta, ICVMP 0.25 +/- 0.14, P < 0.05, vs. Trauma), but did not inhibit an increase in TNF-alpha and IL-1beta mRNA levels in the liver and skeletal muscle. Both nitrogen and catecholamine excretions in the urine were decreased by ip and by i.c.v. injection of MP compared to those of the Trauma group (nitrogen, ICVMP 559.3 +/- 52.0 mg/day, P < 0.05, vs. Trauma; catecholamine, ICVMP 13.8 +/- 1.8 microg/day, P < 0.05, vs. Trauma).

CONCLUSION

A reduction in TNF-alpha and IL-1beta mRNA synthesis in the brain due to prophylactic injection of MP into the icv space reduced the catabolic response after laparotomy.

Pharmacological stimulation of the cholinergic antiinflammatory pathway

Efferent activity in the vagus nerve can prevent endotoxin-induced shock by attenuating tumor necrosis factor (TNF) synthesis. Termed the "cholinergic antiinflammatory pathway," inhibition of TNF synthesis is dependent on nicotinic alpha-bungarotoxin-sensitive acetylcholine receptors on macrophages. Vagus nerve firing is also stimulated by CNI-1493, a tetravalent guanylhydrazone molecule that inhibits systemic inflammation. Here, we studied the effects of pharmacological and electrical stimulation of the intact vagus nerve in adult male Lewis rats subjected to endotoxin-induced shock to determine whether intact vagus nerve signaling is required for the antiinflammatory action of CNI-1493. CNI-1493 administered via the intracerebroventricular route was 100,000-fold more effective in suppressing endotoxin-induced TNF release and shock as compared with intravenous dosing. Surgical or chemical vagotomy rendered animals sensitive to TNF release and shock, despite treatment with CNI-1493, indicating that an intact cholinergic antiinflammatory pathway is required for antiinflammatory efficacy in vivo. Electrical stimulation of either the right or left intact vagus nerve conferred significant protection against endotoxin-induced shock, and specifically attenuated serum and myocardial TNF, but not pulmonary TNF synthesis, as compared with sham-operated animals. Together, these results indicate that stimulation of the cholinergic antiinflammatory pathway by either pharmacological or electrical methods can attenuate the systemic inflammatory response to endotoxin-induced shock.

Nicotine reduces the incidence of type I diabetes in mice

Nicotine has been previously shown to have immunosuppressive actions. Type I diabetes is an autoimmune disease resulting from the specific destruction of the insulin-producing pancreatic beta-cells. Thus, we hypothesized that nicotine may exert protective effects against type I diabetes. The multiple low-dose streptozotocin (MLDS)-induced model and spontaneous nonobese diabetic (NOD) mouse model of type I diabetes were used to assess whether nicotine could prevent this autoimmune disease. Blood glucose levels, diabetes incidence, pancreas insulin content, and cytokine levels were measured in both models of diabetes, both to asses the level of protection exerted by nicotine and to further investigate its mechanism of action. Nicotine treatment reduced the hyperglycemia and incidence of disease in both the MLDS and NOD mouse models of diabetes. Nicotine also protected against the diabetes-induced decrease in pancreatic insulin content observed in both animal models. The pancreatic levels of the Th1 cytokines interleukin (IL)-12, IL-1, tumor necrosis factor (TNF)-alpha, and interferon (IFN)-gamma were increased in both MLDS-induced and spontaneous NOD diabetes, an effect prevented by nicotine treatment. Nicotine treatment increased the pancreatic levels of the Th2 cytokines IL-4 and IL-10. Nicotine treatment reduces the incidence of type I diabetes in two animal models by changing the profile of pancreatic cytokine expression from Th1 to Th2.

Lipopolysaccharide induces rapid production of IL-10 by monocytes in the presence of apoptotic neutrophils

There is growing evidence that apoptotic neutrophils have an active role to play in the regulation and resolution of inflammation following phagocytosis by macrophages and dendritic cells. However, their influence on activated blood monocytes, freshly recruited to sites of inflammation, has not been defined. In this work, we examined the effect of apoptotic neutrophils on cytokine production by LPS-activated monocytes. Monocytes stimulated with LPS in the presence of apoptotic neutrophils for 18 h elicited an immunosuppressive cytokine response, with enhanced IL-10 and TGF-beta production and only minimal TNF-alpha and IL-1beta cytokine production. Time-kinetic studies demonstrated that IL-10 production was markedly accelerated in the presence of apoptotic neutrophils, whereas there was a sustained reduction in the production of TNF-alpha and IL-1beta. This suppression of proinflammatory production was not reversible by depletion of IL-10 or TGF-beta or by addition of exogenous IFN-gamma. It was demonstrated, using Transwell experiments, that monocyte-apoptotic cell contact was required for induction of the immunosuppressive monocyte response. The response of monocytes contrasted with that of human monocyte-derived macrophages in which there was a reduction in IL-10 production. We conclude from these data that interaction between activated monocytes and apoptotic neutrophils creates a unique response, which changes an activated monocyte from being a promoter of the inflammatory cascade into a cell primed to deactivate itself and other cells.

Peripheral cholinergic pathway modulates hyperthermia induced by stress in rats exposed to open-field stress

Exposure to an open field is psychologically stressful and leads to an elevation in core temperature (T(c)). Methyl scopolamine (MS), a muscarinic antagonist, and pyridostigmine (PYR), a carbamate that inhibits acetylcholinesterase, do not cross the blood-brain barrier and have little effect on T(c) in resting, nonstressed animals. However, we have found that MS has an antipyretic effect on T(c) that is caused by handling and cage-switch stress. PYR should act pharmacologically to reverse the effects of MS. To this end, we assessed the effects of MS and PYR on stress-induced hyperthermia. Male Sprague-Dawley rats at 90 days of age were housed individually at an ambient temperature of 22 degrees C. T(c) and motor activity were monitored by radiotelemetry in an open-field chamber. Rats were dosed intraperitoneally at 1200 with 1.0 mg/kg MS, 0.1 mg/kg PYR, a combination of MS and PYR, or saline and placed immediately inside the open-field chamber for 60 min. Stress-induced hyperthermia was suppressed immediately by MS and enhanced by PYR. T(c) only increased by 0.3 degrees C in the MS-treated animals. The hyperthermic response in the PYR group was nearly 0.6 degrees C above that of rats dosed with saline. Coadministration of PYR and MS led to a stress-induced hyperthermia response nearly identical to that of rats injected with saline. Overall, open-field stress exacerbated the effects of MS and PYR on body T(c) and provides support for a peripheral cholinergic mechanism that mediates stress-induced hyperthermia.

Estrogen, statins, and polyunsaturated fatty acids: similarities in their actions and benefits-is there a common link?

OBJECTIVES

To investigate whether there is any common link between estrogen, statins, and polyunsaturated fatty acids (PUFAs), which have similar actions and benefits.

METHODS

To critically review the literature pertaining to the actions of estrogen, statins, and various PUFAs.

RESULTS

Estrogen, statins, and PUFAs enhance nitric oxide synthesis, suppress the production of proinflammatory cytokines such as tumor necrosis factor(alpha), interleukin-1, interleukin-2, and interleukin-6, show antioxidant-like and antiatherosclerotic properties, have neuroprotective actions, and by themselves or their products inhibit tumor cell proliferation and improve osteoporosis. Estrogen, statins, and PUFAs not only have similar actions but also appear to interact with each other. For instance, the binding of estrogen to its receptor on the cell membrane may be determined by its lipid content, statins and PUFAs inhibit 3-hydroxy-3-methylglutaryl coenzyme A reductase activity, statins influence the metabolism of PUFAs, and PUFA deficiency enhances 3-hydroxy-3-methylglutaryl coenzyme A reductase activity. Statins and PUFAs inhibit tumor cell proliferation, suppress ras activity, and may prevent neurodegeneration and improve cognitive functions such as learning and memory. This suggests that PUFAs might be mediators of the actions of statins. Estrogen boosts cognitive performance in women after menopause and may protect against Alzheimer's disease.

CONCLUSIONS

The common link between estrogen, statins, and PUFAs may be nitric oxide. Hence, a combination(s) of estrogen or its derivatives, statins, and various PUFAs may form a novel approach in the management of various conditions such as hyperlipidemias, coronary heart disease, atherosclerosis, osteoporosis, cancer, neurodegenerative conditions, and to improve memory.

Bacterial lipopolysaccharides and innate immunity

Bacterial lipopolysaccharides (LPS) are the major outer surface membrane components present in almost all Gram-negative bacteria and act as extremely strong stimulators of innate or natural immunity in diverse eukaryotic species ranging from insects to humans. LPS consist of a poly- or oligosaccharide region that is anchored in the outer bacterial membrane by a specific carbohydrate lipid moiety termed lipid A. The lipid A component is the primary immunostimulatory centre of LPS. With respect to immunoactivation in mammalian systems, the classical group of strongly agonistic (highly endotoxic) forms of LPS has been shown to be comprised of a rather similar set of lipid A types. In addition, several natural or derivatised lipid A structures have been identified that display comparatively low or even no immunostimulation for a given mammalian species. Some members of the latter more heterogeneous group are capable of antagonizing the effects of strongly stimulatory LPS/lipid A forms. Agonistic forms of LPS or lipid A trigger numerous physiological immunostimulatory effects in mammalian organisms, but--in higher doses--can also lead to pathological reactions such as the induction of septic shock. Cells of the myeloid lineage have been shown to be the primary cellular sensors for LPS in the mammalian immune system. During the past decade, enormous progress has been obtained in the elucidation of the central LPS/lipid A recognition and signaling system in mammalian phagocytes. According to the current model, the specific cellular recognition of agonistic LPS/lipid A is initialized by the combined extracellular actions of LPS binding protein (LBP), the membrane-bound or soluble forms of CD14 and the newly identified Toll-like receptor 4 (TLR4)*MD-2 complex, leading to the rapid activation of an intracellular signaling network that is highly homologous to the signaling systems of IL-1 and IL-18. The elucidation of structure-activity correlations in LPS and lipid A has not only contributed to a molecular understanding of both immunostimulatory and toxic septic processes, but has also re-animated the development of new pharmacological and immunostimulatory strategies for the prevention and therapy of infectious and malignant diseases.

Is insulin an antiinflammatory molecule?

I suggest that insulin suppresses the secretion and antagonizes the harmful effects of tumor necrosis factor-alpha, macrophage migration-inhibitory factor, and superoxide anion. Therefore, the glucose-insulin-potassium regimen might be beneficial in acute myocardial infarction and useful in the management of patients with septicemia, septic shock, and other inflammatory diseases in which tumor necrosis factor-alpha and macrophage migration-inhibitory factor have important roles.

Involvement of the central nervous system in the protective effect of melanocortins in myocardial ischaemia/reperfusion injury

Melanocortin peptides exert, in rats, a protective effect in myocardial ischaemia followed by reperfusion, or permanent occlusion of a coronary artery. Moreover, melanocortins have an anti-shock effect. Since the mechanism of the life-saving effect of these peptides in haemorrhagic shock includes an essential brain loop, we aimed to determine whether the central nervous system (CNS) is also involved in the protective effect against the outcome of short-term myocardial ischaemia followed by reperfusion. Ischaemia was produced in anaesthetized rats by ligature of the left anterior descending coronary artery for 5 min. Reperfusion-induced ventricular tachycardia (VT), ventricular fibrillation (VF) and lethality, and the time-course of arterial blood pressure over 5 min following reperfusion were evaluated. Groups of 8-14 rats were used. Intravenous (i.v.) injection of ACTH-(1-24) (0.16-0.48 mg/kg) during the ischaemic period dose dependently reduced the incidence of VT, VF and of lethality. In saline-treated rats, coronary reperfusion caused VT in 100% animals, VF in 86%, and death in 86%. The highest dose of ACTH-(1-24) (0.48 mg/kg) completely prevented the occurrence of VT, VF and death in all rats (P<0.005). Moreover, the melanocortin peptide prevented the fall in mean arterial pressure (MAP) occurring during reperfusion. Treatment with ACTH-(1-24) by the intracerebroventricular (i.c.v.) route also reduced the incidence of VT, VF and lethality, and prevented the fall in MAP in a dose dependent manner. Complete (100%) protection occurred with an i.c.v. dose (0.048 mg/kg) 10 times less than that needed by the i.v. route. The present data show that in the protective effect of melanocortin peptides against the injury after myocardial ischaemia/reperfusion, the i.c.v. route of administration is more effective than the i.v. route. They suggest that a CNS mechanism, not yet identified, may be involved.

Immunodepression in the surgical patient and increased susceptibility to infection

Multiple organ failure is the major problem in intensive care patients. The failure of the organ 'immune system' is frequently overlooked, however. In this issue the article by Angele and Faist provides an excellent review of the topic. Deactivation of monocyte and lymphocyte functions seems to play a key role in post-traumatic immunodepression. To accompany that review we summarize our knowledge of the mechanisms of deactivation. Stress response, lipopolysaccharide translocalization and tissue injury contribute to 'immunoparalysis'. Recently developed, well standardized assays now allow us to monitor the immune system like other organ functions and opens new approaches for therapeutic interventions.

Nutritional factors in the pathobiology of human essential hypertension

Endothelial cells produce vasodilator and vasoconstrictor substances. Dietary factors such as sodium, potassium, calcium, magnesium, zinc, selenium, vitamins A, C, and E, and essential fatty acids and their products such as eicosanoids can influence blood pressure, cardio- and cerebrovascular diseases, and concentrations of blood lipids and atherosclerosis. There might be a close interaction between these dietary factors, sympathetic and parasympathetic nervous systems, the metabolism of essential fatty acids, nitric oxide, prostacyclin, and endothelium in human essential hypertension. A deficiency in any one factor, dietary or endogenous, or alterations in their interactions with each other, can lead to endothelial dysfunction and development of hypertension. Therefore, alterations in the metabolism of essential fatty acids might be a predisposing factor to the development of essential hypertension and insulin resistance.

Is obesity an inflammatory condition?

Obesity may be a low-grade systemic inflammatory disease. Overweight and obese children and adults have elevated serum levels of C-reactive protein, interleukin-6, tumor necrosis factor-alpha, and leptin, which are known markers of inflammation and closely associated with cardiovascular risk factors and cardiovascular and non-cardiovascular causes of death. This may explain the increased risk of diabetes, heart disease, and many other chronic diseases in the obese. The complex interaction between several neurotransmitters such as dopamine, serotonin, neuropeptide Y, leptin, acetylcholine, melanin-concentrating hormone, ghrelin, nitric oxide, and cytokines and insulin and insulin receptors in the brain ultimately determines and regulates food intake. Breast-feeding of more than 12 mo is associated with decreased incidence of obesity. Breast milk is a rich source of long-chain polyunsaturated fatty acids (LCPUFAs) and brain is especially rich in these fatty acids. LCPUFAs inhibit the production of proinflammatory cytokines and enhance the number of insulin receptors in various tissues and the actions of insulin and several neurotransmitters. LCPUFAs may enhance the production of bone morphogenetic proteins, which participate in neurogenesis, so these fatty acids might play an important role in brain development and function. It is proposed that obesity is a result of inadequate breast feeding, which results in marginal deficiency of LCPUFAs during the critical stages of brain development. This results in an imbalance in the structure, function, and feedback loops among various neurotransmitters and their receptors, which ultimately leads to a decrease in the number of dopamine and insulin receptors in the brain. Hence, promoting prolonged breast feeding may decrease the prevalence of obesity. Exercise enhances parasympathetic tone, promotes antiinflammation, and augments brain acetylcholine and dopamine levels, events that suppress appetite. Acetylcholine and insulin inhibit the production of proinflammatory cytokines and provide a negative feedback loop for postprandial inhibition of food intake, in part, by regulating leptin action. Statins, peroxisome proliferator-activated receptor-gamma binding agents, non-steroidal antiinflammatory drugs, and infant formulas supplemented with LCPUFAs, and LCPUFAs themselves, which suppress inflammation, may be beneficial in obesity.

Gamma(2)-melanocyte-stimulating hormone suppression of systemic inflammatory responses to endotoxin is associated with modulation of central autonomic and neuroendocrine activities

Central autonomic and neuroendocrine activities are important components of the host response to bacterial inflammation. We demonstrate that intravenous infusion of gamma(2)-melanocyte-stimulating hormone (gamma(2)-MSH), a potent autonomic regulating peptide, prevents lipopolysaccharide (LPS)-induced hypotension and tachycardia, and modulates the ACTH response to endotoxin. In the hypothalamic paraventricular nucleus, a major neuroendocrine and autonomic center, gamma(2)-MSH inhibits LPS-induced increases in CRF mRNA levels, but does not suppress LPS-augmented arginine vasopressin heteronuclear RNA expression. In the locus coeruleus, a brainstem noradrenergic center, gamma(2)-MSH inhibits LPS-induced increases in tyrosine hydroxylase mRNA levels. Gamma(2)-MSH inhibits LPS-induced IL-1beta gene expression in the brain, pituitary and thymus, and prevents increases in plasma NO levels. These findings reveal that gamma(2)-MSH attenuates systemic inflammatory responses to endotoxin and suggest that modulation of central autonomic and neuroendocrine activities by gamma(2)-MSH contributes to its anti-inflammatory effects.

Nitric oxide: does it play a role in the heart of the critically ill?

Nitric oxide regulates many aspects of myocardial function, not only in the normal heart but also in ischemic and nonischemic heart failure, septic cardiomyopathy, cardiac allograft rejection, and myocarditis. Accumulating evidence implicates the endogenous production of nitric oxide in the regulation of myocardial contractility, distensibility, heart rate, coronary vasodilation, myocardial oxygen consumption, mitochondrial respiration, and apoptosis. The effects of nitric oxide promote left ventricular mechanical efficiency, ie, appropriate matching between cardiac work and myocardial oxygen consumption. Most of these beneficial effects are attributed to the low physiologic concentrations generated by the constitutive endothelial or neuronal nitric oxide synthase. By contrast, inducible nitric oxide synthase generates larger concentrations of nitric oxide over longer periods of time, leading to mostly detrimental effects. In addition, the recently identified beta3-adrenoceptor mediates a negative inotropic effect through coupling to endothelial nitric oxide synthase and is overexpressed in heart failure. An imbalance between beta 1 and beta2-adrenoceptor and beta3-adrenoceptor, with a prevailing influence of beta3-adrenoceptor, may play a causal role in the pathogenesis of cardiac diseases such as terminal heart failure. Likewise, changes in the expression of endothelial nitric oxide synthase or inducible nitric oxide synthase within the myocardium may alter the delicate balance between the effects of nitric oxide produced by either of these isoforms. New treatments such as selective inducible nitric oxide synthase blockade, endothelial nitric oxide synthase promoting therapies, and selective beta3-adrenoceptor modulators may offer promising new therapeutic approaches to optimize the care of critically ill patients according to their stage and specific underlying disease process.

Can perinatal supplementation of long-chain polyunsaturated fatty acids prevent hypertension in adult life?

It is suggested that adequate provision of long-chain polyunsaturated fatty acids during the critical periods of brain growth prevents the development of hypertension in later life.

Interleukin-18 regulates both Th1 and Th2 responses

Although interleukin-18 is structurally homologous to IL-1 and its receptor belongs to the IL-1R/Toll-like receptor (TLR) superfamily, its function is quite different from that of IL-1. IL-18 is produced not only by types of immune cells but also by non-immune cells. In collaboration with IL-12, IL-18 stimulates Th1-mediated immune responses, which play a critical role in the host defense against infection with intracellular microbes through the induction of IFN-gamma. However, the overproduction of IL-12 and IL-18 induces severe inflammatory disorders, suggesting that IL-18 is a potent proinflammatory cytokine that has pathophysiological roles in several inflammatory conditions. IL-18 mRNA is expressed in a wide range of cells including Kupffer cells, macrophages, T cells, B cells, dendritic cells, osteoblasts, keratinocytes, astrocytes, and microglia. Thus, the pathophysiological role of IL-18 has been extensively tested in the organs that contain these cells. Somewhat surprisingly, IL-18 alone can stimulate Th2 cytokine production as well as allergic inflammation. Therefore, the functions of IL-18 in vivo are very heterogeneous and complicated. In principle, IL-18 enhances the IL-12-driven Th1 immune responses, but it can also stimulate Th2 immune responses in the absence of IL-12.

Endotoxin-stimulated innate immunity: A contributing factor for asthma

Exposure to airborne endotoxin in infancy may protect against asthma by promoting enhanced T(H)1 response and tolerance to allergens. On the other hand, later in life, it adversely affects patients with asthma. Endotoxin binding to receptors on macrophages and other cells generates IL-12, which inhibits IgE responses. It also generates cytokines like IL-1, TNF-alpha, and IL-8, which cause inflammation. These signal transduction pathways resemble those leading to the generation of cytokines, such as IL-4, IL-13, and IL-5, which are responsible for the inflammation of IgE-mediated allergic disease. The main difference seems to be that endotoxin recruits neutrophils, but IgE recruits eosinophils, and the details of the tissue injury from these granulocytes differ. Sources of airborne endotoxin include many agricultural dusts, aerosols from contaminated water in many industrial plants, contaminated heating and air-conditioning systems, mist-generating humidifiers, and damp or water-damaged homes. Acute inhalation of high concentrations of endotoxin can cause fever, cough, and dyspnea. Chronic inhalation of lesser amounts causes chronic bronchitis and emphysema and is associated with airway hyperresponsiveness. Airborne endotoxin adversely affects patients with asthma in 3 ways: (1) by increasing the severity of the airway inflammation; (2) by increasing the susceptibility to rhinovirus-induced colds; and (3) by causing chronic bronchitis and emphysema with development of irreversible airway obstruction after chronic exposure of adults. The most effective management is mitigating exposure. The potential of drug treatments requires further clinical investigation.

The role of Kupffer cell alpha(2)-adrenoceptors in norepinephrine-induced TNF-alpha production

Although previous studies have demonstrated that plasma levels of the proinflammatory cytokine tumor necrosis factor-alpha (TNF-alpha) increase during early sepsis, the precise mechanism responsible for its upregulation remains to be elucidated. Since recent studies have shown that the gut is an important source of norepinephrine (NE) release during early sepsis and enterectomy prior to the onset of sepsis attenuates TNF-alpha production, we hypothesized that gut-derived NE plays a major role in upregulating TNF-alpha via the activation of alpha(2)-adrenoceptors on Kupffer cells. To confirm that NE increases TNF-alpha synthesis and release, Kupffer cells were isolated from normal rats and incubated with NE (20 or 50 nM) or another alpha(2)-adrenergic agonist clonidine (50 nM) without addition of Escherichia coli endotoxin. Supernatant levels of TNF-alpha were then measured. In additional animals, intraportal infusion of NE (20 microM) with or without the specific alpha(2)-adrenergic antagonist yohimbine (1 mM) at a rate of 13 microl/min was carried out for 2 h. Plasma and Kupffer cell levels of TNF-alpha were assayed thereafter. Moreover, the effects of NE and yohimbine on TNF-alpha production was further examined using an isolated perfused liver preparation. The results indicate that both NE and clonidine increased TNF-alpha release by approximately 4-7-fold in the isolated cultured Kupffer cells. Similarly, intraportal infusion of NE in vivo or in isolated livers increased TNF-alpha synthesis and release which was inhibited by co-infusion of yohimbine. Furthermore, the increased cellular levels of TNF-alpha in Kupffer cells after in vivo administration of NE was also blocked by yohimbine. These results, taken together, suggest that gut-derived NE upregulates TNF-alpha production in Kupffer cells through an alpha(2)-adrenergic pathway, which appears to be responsible at least in part for the increased levels of circulating TNF-alpha observed during early sepsis as well as other pathophysiologic conditions such as trauma, hemorrhagic shock, or gut ischemia/reperfusion.

Cardiac variability in critically ill adults: influence of sepsis

OBJECTIVE

To evaluate, in critically ill adults, factors associated with impaired sympathovagal balance.

DESIGN

One-month inception cohort study.

SETTING

Twenty-six-bed medical intensive care unit of a teaching hospital.

PATIENTS

Critically ill adults with an expected duration of intensive care unit stay of > or =48 hrs were enrolled. Patients with permanent arrhythmia or cardiac pacing were not included.

INTERVENTIONS

None.

MEASUREMENT AND MAIN RESULTS

Sympathovagal balance was assessed on the day after intensive care unit admission by the low-frequency/high-frequency ratio obtained from spectral components of heart rate signal: overall variability, low frequency, and high frequency.

RESULTS

Forty-one patients, 13 with sepsis and 28 without sepsis, were assessed. Predictors of low-frequency/high-frequency ratio with the automatic interaction detection method were sepsis and age. Binary logit analysis adjusted for age showed that sepsis remained a strong and independent factor of a low-frequency/high-frequency ratio of <1.50, with an odds ratio of 3.63 (95% confidence interval, 1.47-9.01, p =.005). Use of mechanical ventilation, catecholamines, or sedation did not add any information. The use of the low-frequency/high-frequency ratio in diagnosing sepsis may be supported by a likelihood ratio for low frequency/high frequency <1 at 6.47.

CONCLUSIONS

This work suggests that impaired cardiac variability and notably sympathovagal balance (i.e., a low-frequency/high-frequency ratio <1.0) may be a diagnostic test for sepsis.

Mind over immunity

The central nervous system regulates the innate immune system by elaborating anti-inflammatory hormone cascades in response to bacterial products and immune mediators. We recently discovered that the central nervous system also responds via acetylcholine-mediated efferent signals carried through the vagus nerve. Nicotinic cholinergic receptors expressed on macrophages detect these signals and respond with a dampened cytokine response. Vagus nerve stimulators can mimic this response and can prevent lethal endotoxemia. This newly appreciated cholinergic anti-inflammatory pathway provides a neural substrate to study brain-immune interactions and might be harnessed for therapy of cytokine-mediated disease.

Plasma and cerebrospinal fluid interleukin-6 concentrations in posttraumatic stress disorder

BACKGROUND

Interleukin-6 (IL-6) secretion is suppressed by glucocorticoids and stimulated by catecholamines. Patients with posttraumatic stress disorder (PTSD) have decreased cortisol and increased catecholamine secretion. The purpose of this study was to assess the relation of IL-6 levels and hypothalamic-pituitary-adrenal and noradrenergic activity in patients with well-characterized PTSD.

METHODS

Cerebrospinal fluid (CSF) was withdrawn via a lumbar subarachnoid catheter over 6 h from 11 combat veterans with PTSD and 8 age- and sex-matched healthy controls. Blood was withdrawn concurrently. We measured IL-6, CRH and norepinephrine concentrations in the CSF and IL-6, ACTH, cortisol and norepinephrine in plasma.

RESULTS

Mean and median CSF IL-6 concentrations were higher in PTSD than in controls (mean = 24.0 vs. 14.6, p = 0.05; median = 26.7 vs. 14.3, p < 0.03): plasma IL-6 concentrations, however, were not different between the two groups. Plasma IL-6 and norepinephrine were positively correlated in the PTSD group (r = +0.74, p < 0.04), but not in normals (r = -0.55, p = 0.20).

CONCLUSIONS

PTSD patients have increased CSF concentrations of IL-6. Their plasma IL-6 is not elevated but is more tightly associated with noradrenergic output in these patients than in normals. Both findings might be explained by the low cortisol secretion previously reported in PTSD as a result of lowered glucocorticoid suppression of IL-6 secretion. High levels of CSF IL-6 may reflect neurodegeneration or compensatory neuroprotection.

The biological role of non-neuronal acetylcholine in plants and humans

Acetylcholine, one of the most exemplary neurotransmitters, has been detected in bacteria, algae, protozoa, tubellariae and primitive plants, suggesting an extremely early appearance in the evolutionary process and a wide expression in non-neuronal cells. In plants (Urtica dioica), acetylcholine is involved in the regulation of water resorption and photosynthesis. In humans, acetylcholine and/or the synthesizing enzyme, choline acetyltransferase, have been demonstrated in epithelial (airways, alimentary tract, urogenital tract, epidermis), mesothelial (pleura, pericardium), endothelial, muscle and immune cells (granulocytes, lymphocytes, macrophages, mast cells). The widespread expression of non-neuronal acetylcholine is accompanied by the ubiquitous expression of cholinesterase and acetylcholine sensitive receptors (nicotinic, muscarinic). Both receptor populations interact with more or less all cellular signalling pathways. Thus, non-neuronal acetylcholine can be involved in the regulation of basic cell functions like gene expression, proliferation, differentiation, cytoskeletal organization, cell-cell contact (tight and gap junctions, desmosomes), locomotion, migration, ciliary activity, electrical activity, secretion and absorption. Non-neuronal acetylcholine also plays a role in the control of unspecific and specific immune functions. Future experiments should be designed to analyze the cellular effects of acetylcholine in greater detail and to illuminate the involvement of the non-neuronal cholinergic system in the pathogenesis of diseases such as acute and chronic inflammation, local and systemic infection, dementia, atherosclerosis, and finally cancer.

Roles of muscarinic acetylcholine receptors in interleukin-2 synthesis in lymphocytes

Receptors for many neurotransmitters including catecholamines and acetylcholine (ACh) have been detected on the cell surface of lymphocytes. It has been demonstrated that a human T cell line synthesizes ACh and suggested that ACh may be an autacoid modulating T cell-dependent immune responses. However, the biochemical interactions of the ACh system with the immune system have not been elucidated in detail. We have shown that m1 and m2 muscarinic receptor mRNAs are expressed in human peripheral blood lymphocytes and in human T cell line Jurkat cells and that pretreatment of these cells with a muscarinic receptor agonist enhances interleukin-2 (IL-2) production. We also postulated possible intracellular signaling pathways via which muscarinic receptors regulate IL-2 production in Jurkat cells. The findings suggest that M1 muscarinic receptors are involved in muscarinic receptor-mediated enhancement of IL-2 production in Jurkat cells and that the transcription factor AP-1 and pathways via mitogen-activated protein kinase (MAPK)/extracellular signal regulated protein kinase and c-Jun N-terminal kinase, but not via p38 MAPK, may be involved in the muscarinic receptor-mediated enhancement of IL-2 production. Our findings demonstrate a neuro-immune interaction through muscarinic receptor signaling in immune cells.

The key-role of vagal nerve and adrenals in the cytoprotection and general gastric mucosal integrity

BACKGROUND

Our laboratory group observed earlier that the gastric mucosal cytoprotective effect of prostacyclin (PGI(2)) disappeared after surgical vagotomy in rats. Similarly to this, the beta-carotene induced gastric cytoprotection disappeared in adrenalectomized rats too.

AIMS

In these studies we aimed to investigate the possible role of vagal nerve and adrenals in the development of gastric mucosal lesions induced by exogenously administered chemicals (ethanol, HCl, NaOH, NaCl and indomethacin), and on the effects of cytoprotective and antisecretory drugs (atropine, cimetidine), and scavengers (vitamin A and beta-carotene).

METHODS

The observations were carried out in fasted CFY strain rats. The gastric mucosal lesions were produced by intragastric (i.g.) administration of narcotising agents (96% ethanol; 0.6 M HCl; 0.2 M NaOH; 25% NaCl) or subcutaneously (s.c.) administered indomethacin (20 mg/kg) in intact, surgically bilaterally vagatomized, and adrenalectomized rats without or with glucocorticoid supplementation (Oradexon, 0.6 mg/kg given i.m. for 1 week). The gastric mucosal protective effect of antisecretory doses of atropine (0.1-0.5-1.0 mg/kg i.g.) and cimetidine (10-25-50 mg/kg i.g.), and vitamin A and beta-carotene (0.01-0.1-1.0-10 mg/kg i.g.) was studied. The number and severity of mucosal gastric lesions was numerically or semiquantitatively measured. In other series of observations the gastric acid secretion and mucosal damage were studied in 24 h pylorus-ligated rats without and with acute bilateral surgical vagotomy.

RESULTS

It was found that: (1) the chemical-induced gastric mucosal damage was enhanced in vagotomized and adrenalectomized rats, meanwhile the endogenous secretion of gastric acid, and the development of mucosal damage can be prevented by surgical vagotomy; (2) the gastric cyto- and general protection produced by the drugs and scavengers disappeared in vagotomized and adrenalectomized rats; (3) the gastric mucosal protective effects of drugs and of scavengers returned after sufficient glucocorticoid supplementation of the rats.

CONCLUSION

It has been concluded that the intact vagal nerve and adrenals have a key role in the gastric mucosal integrity, and in drugs- and scavengers-induced gastric cyto- and general mucosal protection.

Thermoregulatory manifestations of systemic inflammation: lessons from vagotomy

The multiple effects of vagotomy on the thermoregulatory response to systemic inflammation are reviewed (primarily, for the model of intravenous lipopolysaccharide administration in the rat). The following conclusions are drawn. (1) Vagotomy-associated thermoeffector insufficiency is likely to account for the attenuation of the fever response observed in some--but not all--studies; such an insufficiency is, however, preventable by postoperative care, including the use of a liquid diet. (2) The febrile response to low doses of lipopolysaccharide (monophasic fever) is mediated by the hepatic (but not gastric or celiac) vagal fibers, presumably afferent; the same fibers are likely to be involved in the development of tolerance to low doses of circulating endotoxins. (3) Phase 1 of the polyphasic febrile response to moderate doses of lipopolysaccharide involves capsaicin-sensitive afferents (either nonvagal only or both nonvagal and vagal), does not involve cholecystokinin A-receptors, and may involve peripheral prostaglandins. (4) Febrile phase 2 does not require the integrity of abdominal nerve fibers, either vagal or nonvagal, at least in the rat. (5) Phase 3 of the febrile response to intravenous lipopolysaccharide (and perhaps the response to intraperitoneal lipopolysaccharide) involves capsaicin-insensitive vagal fibers, presumably efferent; the involvement of these fibers in febrigenic mechanisms is strongly modulated by an unknown factor. (6) A hepatoceliac vagal, presumably efferent, mechanism ('an anti-inflammatory pathway') counteracts the development of lipopolysaccharide-induced hypothermia and shock.

Multiple neural mechanisms of fever

In rats, fevers induced by moderate-to-high doses of intravenous lipopolysaccharide consist of three phases (phases 1, 2 and 3) with body temperature peaks at approximately 1, 2, and 5 h postinjection, respectively. In this study, the effects of bilateral truncal subdiaphragmatic vagotomy and intraperitoneal capsaicin desensitization on febrile phases 1-3 were assessed in adult Wistar rats. Surgical vagotomy was performed approximately 30 d before the experiment; this procedure interrupts both afferent and efferent vagal fibers. Capsaicin was administered intraperitoneally in two consecutive injections (2 and 3 mg/kg, 3 h apart) 1 week prior to the experiment; this procedure desensitizes afferent fibers, primarily within the abdominal cavity, and does not lead to the known thermal effects of systemic capsaicin desensitization. At a neutral ambient temperature, the rats were given Escherichia coli lipopolysaccharide (10 microg/kg) through a preimplanted jugular catheter, and their colonic temperature wes measured by thermocouples for 7 h. The control rats exhibited the typical triphasic febrile responses. Confirming our earlier studies, subdiaphragmatic vagotomy did not affect phases 1 and 2; it did, however, result in a 2.5-fold reduction of phase 3. Capsaicin desensitization modified the febrile response differently: phases 2 and 3 were unaffected, but phase 1 disappeared. We suggest that neural afferent fibers (nonvagal but perhaps vagal as well) play an important role in the early febrile response (phase 1) by transducing peripheral pyrogenic signals to the brain. We also suggest that vagal efferent fibers are likely to participate in the later febrile response (phase 3) via an unknown mechanism.

Role of vagus nerve signaling in CNI-1493-mediated suppression of acute inflammation

CNI-1493 is a potent anti-inflammatory agent, which deactivates macrophages and inhibits the synthesis of proinflammatory mediators. The objective of the present study was to identify the role of the central nervous system (CNS) and efferent vagus nerve signaling in CNI-1493-mediated modulation of acute inflammation in the periphery. CNI-1493 was administered either intracerebroventricularly (i.c.v., 0.1-1,000 ng/kg) or intravenously (i.v., 5 mg/kg) in anesthetized rats subjected to a standard model of acute inflammation (subcutaneous (s.c.) injection of carrageenan). I.c.v. CNI-1493 significantly suppressed carrageenan-induced paw edema, even in doses at least 6-logs lower than those required for a systemic effect. Bilateral cervical vagotomy or atropine blockade (1 mg/kg/h) abrogated the anti-inflammatory effects of CNI-1493 (1 microg/kg, i.c.v. or 5 mg/kg, i.v.), indicating that the intact vagus nerve is required for CNI-1493 activity. Recording of the efferent vagus nerve activity revealed an increase in discharge rate starting at 3-4 min after CNI-1493 administration (5 mg/kg, i.v.) and lasting for 10-14 min (control activity=87+/-5.4 impulses/s versus CNI-1493-induced activity= 229+/-6.7 impulses/s). Modulation of efferent vagus nerve activity by electrical stimulation (5 V, 2 ms, 1 Hz) of the transected peripheral vagus nerve for 20 min (10 min before carrageenan administration and 10 min after) also prevented the development of acute inflammation. Local administration of the vagus nerve neurotransmitter, acetylcholine (4 microg/kg, s.c.), or cholinergic agonists into the site of carrageenan-injection also inhibited acute inflammation. These results now identify a previously unrecognized role of efferent vagus nerve activity in mediating the central action of an anti-inflammatory agent.

Beneficial effect(s) of n-3 fatty acids in cardiovascular diseases: but, why and how?

Low rates of coronary heart disease was found in Greenland Eskimos and Japanese who are exposed to a diet rich in fish oil. Suggested mechanisms for this cardio-protective effect focused on the effects of n-3 fatty acids on eicosanoid metabolism, inflammation, beta oxidation, endothelial dysfunction, cytokine growth factors, and gene expression of adhesion molecules; But, none of these mechanisms could adequately explain the beneficial actions of n-3 fatty acids. One attractive suggestion is a direct cardiac effect of n-3 fatty acids on arrhythmogenesis. N-3 fatty acids can modify Na+ channels by directly binding to the channel proteins and thus, prevent ischemia-induced ventricular fibrillation and sudden cardiac death. Though this is an attractive explanation, there could be other actions as well. N-3 fatty acids can inhibit the synthesis and release of pro-inflammatory cytokines such as tumor necrosis factoralpha (TNFalpha) and interleukin-1 (IL-1) and IL-2 that are released during the early course of ischemic heart disease. These cytokines decrease myocardial contractility and induce myocardial damage, enhance the production of free radicals, which can also suppress myocardial function. Further, n-3 fatty acids can increase parasympathetic tone leading to an increase in heart rate variability and thus, protect the myocardium against ventricular arrhythmias. Increased parasympathetic tone and acetylcholine, the principle vagal neurotransmitter, significantly attenuate the release of TNF, IL-1beta, IL-6 and IL-18. Exercise enhances parasympathetic tone, and the production of anti-inflammatory cytokine IL-10 which may explain the beneficial action of exercise in the prevention of cardiovascular diseases and diabetes mellitus. TNFalpha has neurotoxic actions, where as n-3 fatty acids are potent neuroprotectors and brain is rich in these fatty acids. Based on this, it is suggested that the principle mechanism of cardioprotective and neuroprotective action(s) of n-3 fatty acids can be due to the suppression of TNFalpha and IL synthesis and release, modulation of hypothalamic-pituitary-adrenal anti-inflammatory responses, and an increase in acetylcholine release, the vagal neurotransmitter. Thus, there appears to be a close interaction between the central nervous system, endocrine organs, cytokines, exercise, and dietary n-3 fatty acids. This may explain why these fatty acids could be of benefit in the management of conditions such as septicemia and septic shock, Alzheimer's disease, Parkinson's disease, inflammatory bowel diseases, diabetes mellitus, essential hypertension and atherosclerosis.