Brain interleukin-1β and tumor necrosis factor-α are involved in lipopolysaccharide-induced delayed rectal allodynia in awake rats

Recently, we have developped a model of delayed (12 h) increase in sensitivity (allodynia) to rectal distension (RD) induced by intraperitoneal lipopolysaccharide (LPS) in awake rats. Thus, we examined whether central interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α) are involved in LPS response. Abdominal contractions (criterion of visceral pain) were recorded in rats equipped with intramuscular electrodes. RDs were performed at various times after pharmacological treatments. RD induced abdominal contractions from a threshold volume of distension of 0.8 ml. At lowest volume (0.4 ml), this number was significantly increased 12 h after LPS. Intracerebroventricular (i.c.v.) injection of IL-1 receptor antagonist, IL-1β converting enzyme inhibitor or recombinant human TNF-α soluble receptor reduced LPS-induced increase of abdominal contractions at 0.4 ml volume of distension. When injected i.c.v., recombinant human IL-1β and recombinant bovine TNF-α reproduced LPS response at 9 and 12 h and at 6 and 9 h, respectively. These data suggest that IL-1β and TNF-α act centrally to induce delayed rectal hypersensitivity and that central release of these cytokines is responsible of LPS-induced delayed (12 h) rectal allodynia.     

Interleukin-10, interleukin-4, and transforming growth factor-beta differentially regulate lipopolysaccharide-induced production of pro-inflammatory cytokines and nitric oxide in co-cultures of rat astroglial and microglial cells

The pro-inflammatory cytokines interleukin-1beta (IL-1beta), IL-6, tumor necrosis factor-alpha (TNF-alpha), and nitric oxide (NO) can be produced by activated glial cells and play a critical role in various neurological diseases. Using primary co-cultures of rat microglial and astroglial cells, we investigated the effects of the anti-inflammatory cytokines transforming growth factor-beta1 (TGF-beta1)/beta2, IL-4, and IL-10 on the production of (pro-) inflammatory mediators after stimulation of the cells with lipopolysaccharide (LPS; 0.1 micrograms/ml, 24 h). IL-10 (10 and 100 ng/ml) and IL-4 (5 and 50 U/ml) suppressed the LPS-induced production of NO, IL-6, and TNF-alpha in a dose-dependent manner, whereas TGF-beta1/beta2 (2 and 20 ng/ml) only suppressed NO production. LPS-induced levels of IL-1beta were suppressed by IL-10, but not by IL-4 and TGF-beta1/beta2. Conversely, co-incubation of the glial cells with LPS and antibodies to TGF-beta1/beta2 selectively enhanced LPS-induced NO production, whereas co-incubation with antibody to IL-10 enhanced LPS-induced production of all pro-inflammatory cytokines and NO. This finding strongly suggests that effective concentrations of TGF-beta1/beta2 and IL-10 are produced by LPS-stimulated glial cell co-cultures. Production of IL-10 in these co-cultures was confirmed by measurement of rat IL-10 by radioimmunoassay. We conclude that anti-inflammatory cytokines affect the production of inflammatory mediators in LPS-activated co-cultures of microglial and astroglial cells differentially.     

Actions of exogenous and endogenous IL-10 on glial responses to bacterial LPS/cytokines

The objective of this study was to investigate the actions of exogenous and endogenous IL-10 on inflammatory responses of glia. Studies were conducted in primary, mixed glial cultures from C57BL/6 (wild-type [WT]) and IL-10-deficient C57BL/6 (IL-10 knockout [KO]) neonatal mice. Activation of cultures from WT mice by bacterial lipopolysaccharide (LPS, 10 ng/ml-10 microg/ml, 24 h), caused dose-dependent increases in nitric oxide (NO) and prostaglandin E(2) (PGE(2)) release. In cultures from IL-10 KO mice, LPS elicited markedly attenuated release of NO (approximately 4-fold) and PGE(2) (approximately 17-fold). In WT cultures, co-incubation with IL-10 (10 or 100 ng/ml, 24 h) inhibited the effects of LPS on release of NO (30%) and PGE(2) (40-50%). In cultures from IL-10 KO mice, the addition of IL-10 (10 or 100 ng/ml, 24 h) completely abolished LPS-induced NO and PGE(2) release. LPS did, however, release of IL-1beta and TNF-alpha in cultures from all animals. Co-incubation of WT cultures with IL-10 (1, 10, or 100 ng/ml, 24 h) dose-dependently reduced the release of IL-1beta (by 0%, 15%, 75%, respectively). In cultures from IL-10 KO mice, co-incubation with IL-10 (1, 10, or 100 ng/ml, 24 h) completely abolished LPS induced release of IL-1beta. Co-incubation with IL-10 (1, 10, 100 ng/ml) reduced, LPS-induced TNF-alpha release dose-dependently in WT cultures (by 15%, 50% and 90%) and abolished LPS-induced TNF-alpha release in cells from IL-10 KO mice. These results indicate that in glia from WT mice, exogenous IL-10 attenuates LPS-induces release of NO, PGE(2), TNF-alpha and IL-1beta. In contrast, mixed glial cultures from IL-10 KO mice showed reduced responses to LPS, but increased sensitivity to exogenous IL-10.     

In vivo evidence that activation of tyrosine kinase is a trigger for lipopolysaccharide-induced fever in rats

We measured the rectal temperature of free-moving, conscious rats after intracerebroventricular (i.c.v.) injections of lipopolysaccharide (LPS) and interleukin-1beta (IL-1beta) with or without various antagonists to investigate the mechanisms involved in LPS-induced fever. LPS (3 microg) elicited significant increases in rectal temperature, which lasted from 0.5 h to more than 8 h after administration. This febrile response was inhibited by pretreatment with L-nitro-arginine (LNA), indomethacin (IND), genistein (GEN), tyrphostin 46 and anti-rat IL-1beta antibody (anti-IL-1beta Ab), but was not inhibited by pretreatment with daidzein or chelerythrine (CHE) into the ventricle. LPS (0.3 microg) following orthovanadate (i.c.v.) produced fever, although the small amount of LPS (0.3 microg) or orthovanadate alone showed no effect on rectal temperature. I.c.v. injections of IL-1beta also induced fever of approximately 4-h duration. This effect was inhibited by pretreatment with IND and anti-IL-1beta Ab, but was not inhibited by pretreatment with LNA, GEN or CHE into the ventricle. These findings demonstrate that in the central nervous system, LPS increases IL-1beta production after activation of tyrosine kinase and NO synthase, and IL-1beta promotes prostaglandin production resulting in increased rectal temperature. Activation of tyrosine kinase in the central nervous system is probably a trigger for the febrile response induced by LPS.     

Central injection of interleukin-13 potentiates LPS-induced sickness behavior in rats.

Systemic administration of the bacterial endotoxin lipopolysaccharide (LPS) has profound depressive effects on behavior that are mediated by the inducible expression of proinflammatory cytokines such as interleukin-1 (IL-1), IL-6 and tumor necrosis factor-alpha (TNF-alpha) in the brain. To assess the regulatory effects of the anti-inflammatory cytokine IL-13 on LPS-induced sickness behavior, rats injected i.p. with LPS were administered rat recombinant IL-13 i.c.v. IL-13 (300 ng) potentiated the behavioral effects of LPS (125 microg/kg) when both molecules were co-injected. Administration of IL-13 (300 ng) 12 h prior to LPS (150 microg/kg) did not block the depressing effects of LPS on social exploration. These results indicate that IL-13 acts as a proinflammatory cytokine in the brain.     

Intestinal anti-nociceptive behaviour of NK3 receptor antagonism in conscious rats: evidence to support a peripheral mechanism of action

The involvement of neurokinin receptors in visceral nociception is well documented. However, the role and localization of NK3 receptors is not clearly established. This study was designed to determine whether NK3 receptor antagonists crossing (talnetant) or not (SB-235375) the blood-brain barrier reduce the nociceptive response to colo-rectal distension (CRD) and whether NK3 antagonism reduces inflammation- or stress-induced hypersensitivity to rectal distension. Isobaric CRD and isovolumic rectal distensions were performed in rats equipped with intramuscular electrodes to record abdominal muscle contractions. In controls, CRD induced a pressure-related (15-60 mmHg) increase in the number of abdominal contractions. Both talnetant and SB-235375 [50 mg x kg-1, per oral (p.o.)], which had no effect on colo-rectal tone, reduced the number of contractions associated with CRDs from 30 to 60 mmHg. Three days after rectal instillation of TNBS, abdominal contractions were increased for rectal distension volume of 0.4 mL. This effect was not modified by talnetant (30 mg x kg-1, p.o.). Partial restraint stress increased abdominal contractions at all distension volumes (0-1.2 mL). Talnetant (10 mg kg-1, p.o.) abolished the increase observed for 0.8 and 1.2 mL. These results indicate that peripheral NK3 receptor antagonism reduced nociception associated with CRD and hypersensitivity induced by stress but not inflammation.     

Lipopolysaccharide (LPS)-induced dopamine cell loss in culture: roles of tumor necrosis factor-alpha, interleukin-1beta, and nitric oxide

Parkinson's disease (PD) is a neurodegenerative disorder characterized by the loss of dopamine (DA) neurons of the substantia nigra pars compacta (SNc). Although the exact mechanisms responsible for this cell loss are unclear, emerging evidence suggests the involvement of inflammatory events. In the present study, we characterized the effects of the proinflammatory bacteriotoxin lipopolysaccharide (LPS) on the number of tyrosine hydroxylase immunoreactive (THir) cells (used as an index for DA neurons) in primary mesencephalic cultures. LPS (10-80 microg/ml) selectively decreased THir cells and increased culture media levels of interleukin-1beta (IL-1beta) and tumor necrosis factor-alpha (TNF-alpha) as well as nitrite (an index of nitric oxide (NO) production). Cultures exposed to both LPS and neutralizing antibodies to IL-1beta or TNF-alpha showed an attenuation of the LPS-induced THir cell loss by at least 50% in both cases. Inhibition of the inducible form of nitric oxide synthase (iNOS) by L-NIL did not affect LPS toxicity, but increased the LPS-induced levels of both TNF-alpha and IL-1beta. These findings suggest that neuroinflammatory stimuli which lead to elevations in cytokines may induce DA neuron cell loss in a NO-independent manner and contribute to PD pathogenesis.     

Involvement of interleukin-1 in glial responses to lipopolysaccharide: endogenous versus exogenous interleukin-1 actions

Interleukin-1beta (IL-1beta) participates in neuroinflammation and neurodegeneration. Its mechanisms of action are not fully understood, but appear to involve complex interactions between neurons and glia. The objective of this study was to determine the involvement of endogenous IL-1beta in inflammatory responses to LPS in cultured mouse glial cells, and compare this to the effects of exogenous IL-1beta. Activation of primary mixed glial cultures by incubation with LPS (1 microgram/ml, 24 h), caused marked (approximately ten-fold) increases in release of NO, twenty-fold increases in PGE(2) and ninety-fold increases of IL-6 release. Incubation with human recombinant IL-1beta (100 ng/ml) also stimulated NO and IL-6 release to a similar extent to LPS, but IL-1beta (1 or 100 ng/ml) caused only modest increases (approximately seven-fold) in PGE(2) release. Co-incubation with IL-1ra inhibited the effects of LPS on NO release (-65%) and IL-6 production (-30%), but failed to reduce PGE(2) release. These results indicate that exogenous IL-1beta induces release of NO, PGE(2) and IL-6 in mixed glial cultures, and that endogenous IL-1beta mediates inflammatory actions of LPS on NO and to a lesser extent IL-6, but not on PGE(2) release in mixed glial cultures. Indeed endogenous IL-1beta appears to inhibit LPS-induced PGE(2) release.     

Acute and chronic stress differently affect visceral sensitivity to rectal distension in female rats

Stressful life events are frequently associated with outward signs of irritable bowel syndrome (IBS). Increasing evidence suggests that acute and chronic stress stimuli implicate different physiological mechanisms and neuroendocrine responses. Therefore, we investigated the influence of acute and chronic stress on visceral nociception in female rats and the involvement of colonic mast cells in this effect. The effect of acute and chronic partial restraint stress (PRS) on visceral sensitivity to rectal distension (RD) was assessed by abdominal muscle electromyography. Colonic mast cell activation was determined by measuring histamine release after in vitro stimulation with substance P (SP) in colonic samples from rats experiencing RD vs. controls. Acute PRS significantly enhanced abdominal response to RD compared with sham PRS for all volumes of distension. In contrast, chronic PRS induced a hyperalgesic response for the highest volumes of distension (0.8 and 1.2 mL), but did not affect the number of abdominal contractions for the lowest volume (0.4 mL) compared with controls. Both acute and chronic PRS increased in vitro SP-induced histamine release without affecting mast cell numbers. RD induced similar in vitro histamine release from colonic samples from both acute and chronic PRS rats; this release, however, was significantly higher than that measured in sham-PRS rats. Acute and chronic PRS differently influence visceral sensitivity in response to RD in female rats. This difference, however, cannot be attributed to a different effect of either stress paradigm on mast cell histamine release.     

Biphasic alterations in gastrointestinal transit following endotoxaemia in mice

Lipopolysaccharide (LPS)-induced alterations of gastrointestinal transit were studied in mice using activated charcoal. LPS (10 mg kg-1) induced biphasic alterations of intestinal transit. Increase (acceleration phase) and delay (lag phase) in gastrointestinal transit were observed at 90 and 480 min after LPS injection, respectively. LPS administration induced significant increases in tumour necrosis factor (TNF)-alpha, interleukin (IL)-1beta and nitrate levels in blood serum with maximal levels observed at 1.5, 4, and 8 h after LPS administration, respectively. The effects of recombinant human lzactoferrin (rhLF) on LPS- induced alteration of gastrointestinal transit, and production of TNF-alpha, IL-1beta and nitrate were also studied. Animals were pretreated with rhLF 24 hours before intraperitoneal administration of LPS. RhLF significantly increased gastrointestinal transit during the lag phase. In addition, rhLF decreased the level of TNF-alpha in endotoxaemic animals. The levels of IL-1beta and nitrate were not significantly changed by rhLF. In conclusion, the effect of LPS on gastrointestinal transit is biphasic and the mechanism controlling the second phase most likely depends on TNF-alpha production, while the first phase most likely does not depend on TNF-alpha. On the other hand, it may be regulated by IL-1beta and nitric oxide production.     

Modulation of interleukin-1 receptors followed by endotoxin lipopolysaccharide treatment in the mouse AtT-20 pituitary tumor cell line

OBJECTIVE: We have previously reported the characterization and regulation of interleukin-1 (IL-1) receptors utilizing [125I]IL-1 binding assay in male C57BL/6 mice and the mouse AtT-20 pituitary tumor cells. In the present study, we examine IL-1 receptors using an immunoblotting method to further characterize the mechanisms regulating the interactions of IL-1 receptors with endotoxin, lipopolysaccharide (LPS). METHODS: We established Western blotting for IL-1 receptors using AtT-20 mouse pituitary tumor cells. RESULTS: Several bands were seen; however, only the 105-kD band was neutralized with a 5-fold excess of IL-1 receptor- blocking peptides, suggesting that this band is specific for IL-1 receptors. Next, we investigated the effect of LPS and IL-1beta on IL-1 receptors. Treatment of AtT-20 cells with 0.01 microg/ml of LPS did not affect IL-1 receptors. In contrast, 1 microg/ml of LPS significantly increased IL-1 receptors in AtT-20 cells compared with the control group. In addition, [125I]IL-1beta binding was markedly increased followed by 1 microg/ml of LPS. In contrast, 1 nM recombinant human IL-1beta significantly decreased IL-1 receptors in AtT-20 cells compared with the control group although treatment of AtT-20 cells with 0.01 nM IL-1beta did not affect IL-1 receptors. LPS (0.1 and 1 microg/ml) did not affect IL-1beta concentrations in the medium of AtT-20 cell culture. IL-1beta concentrations in the homogenates from AtT-20 cells were significantly decreased after 1 microg/ml of LPS treatment but not after 0.01 microg/ml LPS. CONCLUSIONS: These data demonstrate that LPS and IL-1beta differentially modulate IL-1 receptors in AtT-20 cells and LPS-induced modulation of IL-1 receptors may provide a novel mechanism for the actions of LPS to alter pituitary function during endotoxemia. Additional in vivo studies are necessary to determine the physiological relevance of this in vitro phenomenon.     

Zaprinast, an inhibitor of cGMP-selective phosphodiesterases, enhances the secretion of TNF-alpha and IL-1beta and the expression of iNOS and MHC class II molecules in rat microglial cells

Proinflammatory cytokines produced by activated glial cells may in turn augment the immune/inflammatory reactions of glial cells through autocrine and paracrine routes. The NO/cGMP signaling represents one of the reactions of activated glial cells. We investigated whether the production of proinflammatory cytokines by glial cells is affected by NO-dependent downstream cGMP signaling. In primary cultures of mixed astrocytes and microglial cells, zaprinast (0.1 mM), an inhibitor of cGMP-selective phosphodiesterases, enhanced the basal and LPS (1.0 microg/ml)-induced secretion of TNF-alpha and IL-1beta. Zaprinast also enhanced NO production induced by LPS or IFN-gamma (100 U/ml), and in microglial cell cultures, but not in astrocyte cultures, zaprinast enhanced the basal and the IFN-gamma-induced production of the cytokines, TNF-alpha and IL-1beta, and of NO. This upregulation by zaprinast was partially inhibited by KT5823 (1.0 microM), an inhibitor of protein kinase G. The LPS-induced production of TNF-alpha, IL-1beta, and NO was inhibited by ODQ (50 microM), an inhibitor of soluble guanylyl cyclase, and by KT5823. Immunohistochemical analysis of mixed glial cell cultures showed that LPS/IFN-gamma-induced iNOS expression and the enhanced expression of iNOS by zaprinast were restricted to microglial cells. Zaprinast enhanced the IFN-gamma (200 U/ml)-induced expression of MHC Class II molecules in astrocytes and microglial cells in mixed cultures, but did not enhance this IFN-gamma-induced expression in pure astrocytes, which lacked paracrine TNF-alpha from microglial cells. Summarizing, zaprinast, which is associated with cGMP/protein kinase G signaling, may augment central immune/inflammatory reactions, possibly via the increased production of TNF-alpha and IL-1beta by activated microglial cells.     

Chronic administration of tianeptine balances lipopolysaccharide-induced expression of cytokines in the spleen and hypothalamus of rats

The antidepressant tianeptine has been shown to protect the hippocampus against the deleterious consequences of stress and to attenuate the behavioral and neuroendocrine effects of the cytokine inducer lipopolysaccharide (LPS). Since sickness symptoms are linked to peripheral and brain production of cytokines and pro-inflammatory cytokines can promote neurotoxicity, the present study was undertaken to test the possibility that tianeptine attenuates production of pro-inflammatory cytokines. This hypothesis has been tested by studying the effects of a chronic intraperitoneal (i.p.) administration of tianeptine (10 mg/kg twice a day for 21 days) to rats on the induction by LPS (250 microg/kg, i.p.) of the production of pro- and anti-inflammatory cytokines, at the periphery (spleen, pituitary) and in the brain (hypothalamus, hippocampus). The expression of mRNAs coding for IL-1 beta, TNF-alpha, IL-6 or IL-10 (RT-PCR) and plasma levels of IL-1 beta, TNF-alpha and IL-10 (ELISA) were measured at various time intervals following LPS. Chronic tianeptine treatment attenuated LPS-induced expression of TNF-alpha in the spleen as well as plasma levels of this cytokine and altered the central balance between pro- and anti-inflammatory cytokines (IL-1 beta/IL-10). These results open new vistas in the pharmacological activity of tianeptine and provide further insights on the possible mechanisms of action involved in its neuroprotective properties.     

LPS-dependent suppression of social exploration is augmented in type 1 diabetic mice

We have previously shown that type 2 diabetes (T2D) in the mouse is associated with increased responsivity to innate immune challenge. Here we demonstrate that in a mouse model of type 1 diabetes (T1D) LPS-dependent suppression of social exploration (SE) is augmented and dependent on hyperglycemia. T1D was induced in mice with intraperitoneal (i.p.) streptozotocin (STZ). After 4d, STZ treated mice had blood glucose levels of 417+/-34mg/dl compared to 160+/-11mg/dl in non-STZ treated mice. When these diabetic mice were challenged with i.p. lipopolysaccharide (LPS), LPS-induced depression of SE was nearly 2.7-fold greater in diabetic mice at 2h than in non-diabetic mice. Examination of peritoneal proinflammatory cytokine levels 2h after LPS administration showed that diabetic mice had 4-, 2.5- and 3.6-fold greater concentrations of IL-1beta, IL-6 and TNF-alpha, respectively, when compared to non-diabetic mice. Control of blood glucose levels with injected insulin in diabetic mice improved 2h post LPS-induced loss of SE by 3.9-fold. Interestingly, insulin given intracerebroventricularly to diabetic mice did not impact LPS-induced loss of SE but did increase basal SE 8, 12 and 24h later. Finally, administration of STZ to hyperglycemic/hyperinsulinemic db/db mice did not alter LPS-induced loss of SE. Taken together these findings indicate that mice with T1D have augmented loss of SE in response to LPS and this is due to hyperglycemia and not to insulin.     

Physiological significance of the interleukin 1 receptor accessory protein

Interleukin 1 receptor accessory protein (IL-1RAcP) is an essential signal-transducing component of the IL-1 receptor type I. The recent availability of IL-1RAcP-deficient (KO) mice allows to study the in vivo function of IL-1RAcP. Animals were injected intraperitoneally with rat recombinant IL-1beta (200 ng/mouse), lipopolysaccharide (LPS, 5 microg/mouse), or subjected to 1-hour restraint stress. Neuroendocrine and immune parameters were measured 2 h after IL-1 or LPS injection or just after restraint. In wild-type controls, IL-1 and LPS activated the hypothalamic-pituitary-adrenal axis and increased plasma IL-6. In KO mice, the plasma levels of corticosterone and IL-6 increased after LPS, but not after rat recombinant IL-1beta. The LPS-induced depression of the lymphoproliferation was similar in wild-type and KO mice. Finally, the 1-hour restraint was able to increase the plasma levels of corticosterone in KO mice. These results show that IL-1RAcP is essential for physiological activities of peripheral IL-1, as it was previously demonstrated for those of brain IL-1. However, using IL-1RAcP KO mice, we were unable to demonstrate a specific role of endogenous IL-1 during LPS-induced inflammation. Moreover, stress-induced activation of the hypothalamic-pituitary-adrenal axis may occur in the absence of the IL-1-transducing receptor, IL-1RAcP.     

Stress-induced visceral hypersensitivity to rectal distension in rats: role of CRF and mast cells

Background: psychological factors have long been implicated in the aetiology of irritable bowel syndrome often associated with abdominal pain. This work was designed to study, in rats, the influence of partial restraint stress on the abdominal cramps induced by rectal distension and to determine the role of corticotropin releasing factor (CRF) and mast cells degranulation in this response. Methods: abdominal contractions were electromyographically recorded. Thirty minutes after stress or intracerebroventricular CRF, rectal distension was performed by inflation of a balloon (0.4–1.2 mL). α-helical CRF_9–41 or doxantrazole were administered centrally (15 min) and intraperitoneally (30 min), respectively, before stress. Histamine release and the number of mast cells were determined in colonic pieces from stressed and control rats. Results: stress and CRF enhanced the number of abdominal cramps evoked by rectal distension without affecting rectal compliance. α-helical CRF_9–41 and doxantrazole antagonized the stress and CRF-induced enhancement of abdominal cramps. Stress increased the colonic histamine content whereas the number of colonic mast cells was unchanged. Conclusions: stress enhances abdominal contractions in response to rectal distension in rats via pathways involving central CRF and intestinal mast cells.     

IL-10 and glucocorticoids inhibit Abeta(1-42)- and lipopolysaccharide-induced pro-inflammatory cytokine and chemokine induction in the central nervous system

Alzheimer's disease (AD) is characterized by neuropil threads composed of structurally abnormal neurites, neurons containing paired helical filaments of tau protein, and extracellular deposits of amyloid-beta (Abeta) peptide, a protein fragment having neurotoxic and glial immune response activating potential. In the present study, we demonstrate that an acute intracerebroventricular (icv) injection of Abeta(1-42) in the mouse induces a time- and dose-dependent production of IL-1alpha, IL-1beta, IL-6 and MCP-1 in the hippocampus and cortex as measured by ELISA. Cytokine and chemokine levels were maximal at 9 h, with MCP-1 and IL-1alpha remaining elevated over a 24 h period and IL-1beta remaining elevated over a 48 h period. The temporal profile of Abeta-induced cytokine induction differed from that observed for LPS. Following an icv injection of LPS, maximal levels of IL-1alpha, IL-1beta, IL-6 and MCP-1 were attained by 9 h and, except for MCP-1, returned to levels indistinguishable from control at 24 h. MCP-1 remained elevated at 24 h and returned to basal levels at 48 h. In contrast, little production of TNF-alpha was observed under either Abeta or LPS acute stimulus conditions. Treatment with anti-inflammatory agents such as prednisolone, dexamethasone, or IL-10 inhibited both Abeta- and LPS-induced cytokine and chemokine production in the brain. In summary, icv administration of Abeta and LPS induced elevated brain levels of pro-inflammatory cytokines that could be inhibited by immune suppressing drugs and anti-inflammatory proteins, thus providing support for the utility of anti-inflammatory therapeutics in modulating the immunopathology observed in brain inflammatory diseases such as AD.     

IL-4, IL-10 and IL-13 modulate A beta(1--42)-induced cytokine and chemokine production in primary murine microglia and a human monocyte cell line

A hallmark of the immunopathology associated with Alzheimer's disease (AD) is the presence of activated microglia surrounding senile plaque deposits of beta-amyloid (A beta) peptides. A beta peptides have been shown to be potent activators of microglia and macrophages, but little is known about endogenous factors that may modulate their responses to amyloid. We investigated whether the 'anti-inflammatory' cytokines IL-4, IL-10 and IL-13 could regulate A beta-induced production of the inflammatory cytokines IL-1 alpha, IL-1 beta, TNF-alpha, IL-6 and the chemokine MCP-1. A beta(1-42) time- and dose-dependently induced the production and secretion of these inflammatory proteins in the human THP-1 monocyte cell line and in primary murine microglia, similar to what was observed for lipopolysaccharide (LPS) stimulated cells. IL-10 was found to suppress all A beta and LPS-induced inflammatory proteins measured (IL-1 alpha, IL-1 beta, IL-6, TNF-alpha and MCP-1) in both cell types with the exception of LPS-induced MCP-1 in THP-1 cells where no change was observed. In contrast to the inhibition observed for IL-10, both IL-4 and IL-13 enhanced MCP-1 secretion. IL-4 and IL-13 reduced IL-6 secretion, but effects on IL-1 alpha, IL-1 beta or TNF-alpha were dependent on cell type and stimulus conditions. Additional experiments using RT-PCR showed that IL-4, IL-10 and IL-13 mRNA is found to be present in human brain tissue. These results show that IL-4, IL-10, and IL-13 differentially regulate microglial responses to A beta and may play a role in the inflammation pathology observed surrounding senile plaques.     

Disturbance of oligodendrocyte development,hypomyelination and white matter injury in the neonatal rat brain after intracerebral injection of lipopolysaccharide

Increasing data provide support for the hypothesis that brain inflammation plays an important role in injury to developing white matter. In the present study, inflammatory responses in the neonatal rat brain were investigated following lipopolysaccharide (LPS) administration at postnatal day 5. LPS-induced brain injury was examined in brain sections 24 h, 3 and 9 days after LPS injection. White matter rarefaction was observed in 50% of the rat brains (three out of six) 24 h after LPS injection. Lateral ventricle enlargement was found in 100% (four out of four) and 89% (eight out of nine) of rat brains 3 and 9 days after LPS administration, respectively. White matter necrosis was found in three out of nine brains injected with LPS on P14. None of these injuries was observed in any control rat brains. No histological changes in gray matter were noted in the LPS-injected rat brain. Proinflammatory cytokines, tumor necrosis factor-alpha (TNFalpha), interleukin-1beta (IL-1beta) and interleukin-6 (IL-6), and inducible nitric oxide synthase (iNOS) in the rat brain were greatly induced after LPS administration. Activated astrocytes and microglia/macrophages were found in the affected rat brains. Double-labeling showed that IL-1beta and iNOS expressing cells were microglia/macrophages. Injury to or delayed development of immature oligodendrocytes (OLs) was evident by decreased immunostaining for both O4 and O1 antibodies, markers for developing immature OLs, in the LPS-injected as compared to the control rat brain. LPS also resulted in hypomyelination, as indicated by reduced myelin basic protein (MBP) immunostaining in the P8 rat brain. Co-administration of IL-1 receptor antagonist (IL-1Ra) with LPS reduced brain injury by improving myelination and subsequent reduction of lateral ventricle enlargement. These results indicate that developing OLs may be the target cells for LPS-induced brain injury and inflammatory cytokines are possible mediators of LPS-induced brain injury.