Modulation by dantrolene of endotoxin-induced interleukin-10, tumour necrosis factor-alpha and nitric oxide production in vivo and in vitro

Intranasal dantrolene nanoparticles inhibit lipopolysaccharide-induced depression and anxiety behavior in mice

This study investigates the therapeutic effectiveness of intranasal dantrolene nanoparticles pretreatment to inhibit lipopolysaccharide (LPS)-induced pathological inflammation and synapse destruction and depressive and anxiety behavior in mice. Both wild-type (WT) B6SJLF1/J and 5XFAD adult mice (5-10 months old) were pretreated with intranasal dantrolene nanoparticles (dantrolene: 5mg/kg), daily, Monday to Friday, 5 days per week, for 4 weeks. Then, mice were treated with intraperitoneal injection of LPS (5mg/kg) for one time. Behavioral tests for depression, anxiety and side effects were performed 24 hours after a one-time LPS injection. Biomarkers for pyroptosis-related inflammation cytokines (IL-1β and IL-18) in blood and brains were measured using enzyme-linked immunosorbent assay (ELISA) and immunoblotting, respectively. The changes of primary proteins activation inflammatory pyroptosis (NLRP3: NLR family pyrin domain containing 3, Caspase-1, N-GSDMD: N terminal protein gasdermin D) and synapse proteins (PSD-95 and synpatin-1) in brains were measured using immunoblotting. Intranasal dantrolene nanoparticles robustly inhibited LPS-induced depression and anxiety behavior in both WT and 5XFAD mice, without obvious side effects. Intranasal dantrolene nanoparticles significantly inhibited LPS-induced pathological elevation of IL-1β and IL-18 in the blood and synapse loss in the brain. Intranasal dantrolene nanoparticles trended to inhibit LPS-induced elevation of IL1β and IL-18 and the pyroptosis activation proteins in the brain in both type of mice. In conclusion, intranasal dantrolene nanoparticles demonstrated neuroprotection against inflammation mediated depression and anxiety behaviors and should be studied furthermore as a future effective drug treatment of major depression disorder or anxiety psychiatric disorder, especially in AD patients.

Dantrolene and ryanodine receptors in COVID-19: The daunting task and neglected warden

Dantrolene (DTN) is a ryanodine receptor (RyR) antagonist that inhibits Ca²⁺ release from stores in the sarcoplasmic reticulum. DTN is mainly used in the management of malignant hyperthermia. RyRs are highly expressed in immune cells and are involved in different viral infections, including severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2), because Ca²⁺ is necessary for viral replication, maturation and release. DTN can inhibit the proliferation of SARS-CoV-2, indicating its potential role in reducing entry and pathogenesis of SARS-CoV-2. DTN may increase clearance of SARS-CoV-2 and promote coronavirus disease 2019 (COVID-19) recovery by shortening the period of infection. DTN inhibits N-methyl-D-aspartate (NMDA) mediated platelets aggregations and thrombosis. Therefore, DTN may inhibit thrombosis and coagulopathy in COVID-19 through suppression of platelet NMDA receptors. Moreover, DTN has a neuroprotective effect against SARS-CoV-2 infection-induced brain injury through modulation of NMDA receptors, which are involved in excitotoxicity, neuronal injury and the development of neuropsychiatric disorders. In conclusion, DTN by inhibiting RyRs may attenuate inflammatory disorders in SARS-CoV-2 infection and associated cardio-pulmonary complications. Therefore, DNT could be a promising drug therapy against COVID-19. Preclinical and clinical studies are warranted in this regards.

Modulation of Ryanodine Receptors Activity Alters the Course of Experimental Autoimmune Encephalomyelitis in Mice

Ryanodine receptors (RyRs), the intracellular Ca²⁺ release channels, are expressed in T lymphocytes and other types of immune cells. Modulation of RyRs has been shown to affect T cell functions in vitro and immune responses in vivo. The effects of modulation of RyRs on the development of autoimmune diseases have not been investigated. Here we studied how modulation of RyRs through administration of RyR inhibitor dantrolene or introducing a gain-of-function RYR1-p.R163C mutation affects clinical progression of experimental autoimmune encephalomyelitis (EAE) in mice, a T cell-mediated autoimmune neuroinflammatory disease. We found that daily intraperitoneal administration of 5 or 10 mg/kg dantrolene beginning at the time of EAE induction significantly reduced the severity of EAE clinical symptoms and dampened inflammation in the spinal cord. The protective effect of dantrolene on EAE was reversible. Dantrolene administration elicited dose-dependent skeletal muscle weakness: mice that received 10 mg/kg dose developed a waddling gait, while 5 mg/kg dantrolene dose administration produced a reduction in four-limb holding impulse values. Mice bearing the gain-of-function RYR1-p.R163C mutation developed the EAE clinical symptoms faster and more severely than wild-type mice. This study demonstrates that RyRs play a significant role in EAE pathogenesis and suggests that inhibition of RyRs with low doses of dantrolene may have a protective effect against autoimmunity and inflammation in humans.

Boron Induces Lymphocyte Proliferation and Modulates the Priming Effects of Lipopolysaccharide on Macrophages

Chemical mediators of inflammation (CMI) are important in host defense against infection. The reduced capacity of host to induce the secretion of these mediators following infection is one of the factors in host susceptibility to infection. Boron, which has been suggested for its role in infection, is reported in this study to increase lymphocyte proliferation and the secretion of CMI by the lipopolysaccharide (LPS)-stimulated peritoneal macrophages in BALB/c mice. Boron was administered to mice orally as borax at different doses for 10 consecutive days, followed by the stimulation of animals with ovalbumin and isolation of splenocytes for proliferation assay. The lymphocyte subsets were determined by flow cytometry in spleen cell suspension. The mediators of inflammation, TNF-α, IL-6, IL-1β and nitric oxide (NO), were measured in culture supernatant of LPS-primed macrophages isolated from borax treated mice. TNF and ILs were measured by ELISA. NO was determined by Griess test. The expression of inducible nitric oxide synthase (iNOS) in macrophages was studied by confocal microscopy. Results showed a significant increase in T and B cell populations, as indicated by an increase in CD4 and CD19, but not CD8, cells. Boron further stimulated the secretion of TNF-α, IL-6, IL-1β, NO and the expression of iNOS by the LPS-primed macrophages. The effect was dose dependent and most significant at a dose level of 4.6 mg/kg b. wt. Taken together, the study concludes that boron at physiological concentration induces lymphocyte proliferation and increases the synthesis and secretion of pro-inflammatory mediators by the LPS-primed macrophages, more specifically the M1 macrophages, possibly acting through Toll-like receptor. The study implicates boron as a regulator of the immune and inflammatory reactions and macrophage polarization, thus playing an important role in augmenting host defense against infection, with possible role in cancer and other diseases.

Pretreatment with apoaequorin protects hippocampal CA1 neurons from oxygen-glucose deprivation

Ischemic stroke affects ∼795,000 people each year in the U.S., which results in an estimated annual cost of $73.7 billion. Calcium is pivotal in a variety of neuronal signaling cascades, however, during ischemia, excess calcium influx can trigger excitotoxic cell death. Calcium binding proteins help neurons regulate/buffer intracellular calcium levels during ischemia. Aequorin is a calcium binding protein isolated from the jellyfish Aequorea victoria, and has been used for years as a calcium indicator, but little is known about its neuroprotective properties. The present study used an in vitro rat brain slice preparation to test the hypothesis that an intra-hippocampal infusion of apoaequorin (the calcium binding component of aequorin) protects neurons from ischemic cell death. Bilaterally cannulated rats received an apoaequorin infusion in one hemisphere and vehicle control in the other. Hippocampal slices were then prepared and subjected to 5 minutes of oxygen-glucose deprivation (OGD), and cell death was assayed by trypan blue exclusion. Apoaequorin dose-dependently protected neurons from OGD--doses of 1% and 4% (but not 0.4%) significantly decreased the number of trypan blue-labeled neurons. This effect was also time dependent, lasting up to 48 hours. This time dependent effect was paralleled by changes in cytokine and chemokine expression, indicating that apoaequorin may protect neurons via a neuroimmunomodulatory mechanism. These data support the hypothesis that pretreatment with apoaequorin protects neurons against ischemic cell death, and may be an effective neurotherapeutic.

Angiotensin II inhibits interleukin-6 mRNA expression of LPS-stimulated macrophages through down-regulating calcium signaling

BACKGROUND

The renin-angiotensin system plays a key role in the regulation of blood pressure following hemorrhage and shock. Recent studies also suggest renin-angiotensin system regulates inflammatory mediator production although the amechanism is largely unknown. This purpose of the study was to examine the effect of angiotensin II on macrophage (MØ) IL-6 messenger RNA (mRNA) expression induced by lipopolysaccharide (LPS) and on the alterations in the calcium influx.

METHODS

J774A.1 cells, a mouse MØ cell line, were exposed to E. coli LPS (1 or 10 μg/ml) in the presence of angiotensin II (10 nM to 1 μM). IL-6 mRNA expression was determined by the reverse transcription polymerase chain reaction technique. IL-6 protein production was measured by ELISA. To examine the involvement of calcium signaling in IL-6 mRNA expression, MØ were exposed to various calcium agonists and antagonists in the presence of LPS stimulation. Changes of intracellular [Ca(2+)] by LPS stimulation and angiotensin II treatment were determined by a fura-2 fluorescence ratio method.

RESULTS

LPS stimulation increased MØ IL-6 mRNA expression, which was inhibited by Angiotensin II in a dose-dependent fashion. Both thapsigargin and A23187 augmented the IL-6 mRNA levels induced by LPS stimulation, but only thapsigargin was able to induce IL-6 mRNA directly. TMB-8 but not verapamil inhibited LPS-stimulated MØ IL-6 mRNA. Finally, angiotensin II significantly altered the changes in intracellular [Ca(2+)] levels induced by LPS stimulation by reducing both the peak and slope of calcium spikes.

CONCLUSIONS

Our data show that calcium signaling is closely related to IL-6 mRNA expression. Angiotensin II inhibits IL-6 mRNA expression of LPS-stimulated MØ. The inhibitory effects of angiotensin II appear, at least in part, to be mediated through down regulating calcium dependent pathways.

Review article: bacterial translocation in the critically ill--evidence and methods of prevention

BACKGROUND

Delayed sepsis, systemic inflammatory response syndrome (SIRS) and multiorgan failure remain major causes of morbidity and mortality on intensive care units. One factor thought to be important in the aetiology of SIRS is failure of the intestinal barrier resulting in bacterial translocation and subsequent sepsis.

AIM

This review summarizes the current knowledge about bacterial translocation and methods to prevent it.

METHODS

Relevant studies during 1966-2006 were identified from a literature search. Factors, which detrimentally affect intestinal barrier function, are discussed, as are methods that may attenuate bacterial translocation in the critically ill patient.

RESULTS

Methodological problems in confirming bacterial translocation have restricted investigations to patients undergoing laparotomy. There are only limited data available relating to specific interventions that might preserve intestinal barrier function or limit bacterial translocation in the intensive care setting. These can be categorized broadly into pre-epithelial, epithelial and post-epithelial interventions.

CONCLUSIONS

A better understanding of factors that influence translocation could result in the implementation of interventions which contribute to improved patient outcomes. Glutamine supplementation, targeted nutritional intervention, maintaining splanchnic flow, the judicious use of antibiotics and directed selective gut decontamination regimens hold some promise of limiting bacterial translocation. Further research is required.

LASSBio-468: a new achiral thalidomide analogue which modulates TNF-alpha and NO production and inhibits endotoxic shock and arthritis in an animal model

As part of a program researching the synthesis and immunopharmacological evaluation of novel synthetic compounds, we have described the immune modulatory profile of the new achiral thalidomide analogue LASSBio-468 in the present work. This compound was planned as an N-substituted phthalimide derivate, structurally designed as a hybrid of thalidomide and aryl sulfonamides, which were previously described as tumor necrosis factor-alpha (TNF-alpha) and PDE4 inhibitors. LASSBio-468 was recently demonstrated to inhibit the TNF-alpha production induced by lipopolysaccharide (LPS), in vivo. Here, we investigated whether this compound would affect chronic inflammation processes associated with the production of this pro-inflammatory cytokine. Treatment with LASSBio-468 before a lethal dose injection of LPS in animals greatly inhibited endotoxic shock. This effect seems to be mediated by a specific down regulation of TNF-alpha and nitric oxide production, regulated mainly at the RNA level. In another model, histopathological analysis indicated that this compound also inhibited adjuvant-induced arthritis in rats. Taken together, our data demonstrated a potent anti-inflammatory effect of LASSBio-468, suggesting its use as a potential drug against chronic inflammatory diseases.

Imidocarb, a potent anti-protozoan drug, up-regulates interleukin-10 production by murine macrophages

Interleukin-10 (IL-10), a potent antiinflammatory and immunosuppressive cytokine, plays an important role in the regulation of immune responses. To discover small molecules that stimulate IL-10 production, a cell-based screening assay was performed using a murine macrophage cell line, RAW264.7. Imidocarb, (3,3'-bis-2-imidazolin-2-yl)-carbanilide, which has been used as an anti-protozoan drug for the prevention and treatment of babesiosis in cattle, was thus identified. Imidocarb markedly enhanced LPS-induced IL-10 production not only by RAW264.7 cells but also by murine peritoneal macrophages in a concentration-dependent manner. It also augmented IL-10 production in the presence of zymosan, a yeast cell wall component. In contrast, imidocarb inhibited LPS-induced tumor necrosis factor (TNF)-alpha production by peritoneal macrophages. In mice, intraperitoneal administration of imidocarb significantly increased serum IL-10 levels and lowered TNF-alpha levels. Our results suggest that a novel anti-inflammatory property of imidocarb could lead to new therapeutic approaches in inflammatory conditions.

Flupentixol and trifluperidol reduce secretion of tumor necrosis factor-alpha and nitric oxide by rat microglial cells

Tumor necrosis factor-alpha (TNF-alpha) and nitric oxide (NO), both of which are produced by activated microglial cells, are involved in the neuropathogenesis of many diseases affecting the central nervous system (CNS). There is a need to develop drugs that inhibit neurotoxic processes in neurodegenerative diseases. The aim of this study was to evaluate the effect of two neuroleptics, flupentixol and trifluperidol, on the release of pro-apoptotic TNF-alpha and NO by LPS-activated rat microglial cells. Flupentixol and trifluperidol reduced the TNF-alpha and NO release by cultured microglia exposed to LPS for 6 and 24h. The results suggest that flupentixol and trifluperidol, which are well-known antipsychotic drugs, may be used in the treatment of CNS diseases associated with excessive TNF-alpha and NO release.

LAAE-14, a new in vitro inhibitor of intracellular calcium mobilization, modulates acute and chronic inflammation

A new lipidic acid-amido ether derivative (LAAE-14) able to reduce dose-dependently the calcium increases mediated either by calcium ionophore ionomycin, by the endoplasmic reticular Ca(2+)-ATPase inhibitor thapsigargin, or by the chemotactic tripeptide N-formyl-L-methionyl-L-leucyl-L-phenylalanine (fMLP), in human neutrophils as well as in murine peritoneal macrophages, but not ATP, has been evaluated as a potential anti-inflammatory drug. This compound attenuated leukocyte activation by means of its inhibitory effect on the respiratory burst elicited in both types of cells by 12-O-tetradecanoyl phorbol 13-acetate, by inhibition of the degranulation process induced by cytochalasin B+fMLP or cytochalasin B+platelet activating factor, as well as by reduction of leukotriene B(4) synthesis induced by the calcium ionophore A23187. In addition, in zymosan-stimulated mouse peritoneal macrophages LAAE-14 caused a potent inhibition of nitrite and prostaglandin E(2) production. This compound exerted acute and chronic anti-inflammatory effects by oral route, that may be related with several mechanisms such as attenuation of leukocyte activation, inhibition of inducible nitric oxide synthase, cyclo-oxygenase-2 and cytosolic phospholipase A(2) expression as well as reduction in tumour necrosis factor-alpha production. Its anti-inflammatory profile is clearly correlated with its behavior as inhibitor of intracellular calcium mobilization. The profile and potency of this compound may have relevance for the inhibition of the inflammatory response at different levels and may represent a new approach to the development of new anti-inflammatory drugs.

Hemodynamic interactions of propofol and dantrolene in chronically instrumented dogs

The hemodynamic interaction of dantrolene, a specific drug for malignant hyperthermia, and propofol which appears to be safe in malignant hyperthermia-susceptible patients, has not been investigated. We performed this study to examine the hemodynamic actions of dantrolene at a therapeutic dose during propofol anesthesia. Ten dogs were chronically instrumented for the measurements of systemic and coronary hemodynamics. The dogs were assigned to receive propofol with vehicle or dantrolene in a random manner on separate experimental days. Propofol significantly decreased mean arterial blood pressure, left ventricular systolic and end-diastolic pressure, the maximal rate of increase in left ventricular pressure, and left ventricular regional segment shortening. Coronary blood flow (CBF) was unchanged but coronary vascular resistance (CVR) decreased. Dantrolene reversed the decrease in mean arterial blood pressure and left ventricular systolic pressure caused by propofol, and significantly increased heart rate. However, left ventricular end-diastolic pressure, cardiac output, maximal rate of increase in left ventricular pressure, and segment shortening were unchanged. CBF was significantly increased with a decrease in CVR. These results suggest that dantrolene reverses the hypotensive action produced by propofol and causes an increase in CBF with a decrease in CVR, but does not significantly change the negative inotropic effects. Thus, dantrolene exerts favorable hemodynamic effects during propofol anesthesia.

IMPLICATIONS

Our study suggests that dantrolene reverses the hypotensive action produced by propofol and causes an increase in coronary blood flow with a decrease in coronary vascular resistance, but does not significantly change the negative inotropic effects.

Myotropic effect of helicokinins, tachykinin-related peptides and Manduca sexta allatotropin on the gut of Heliothis virescens (Lepidoptera: Noctuidae)

Different insect neuropeptides (helicokinins, tachykinin-related and allatoregulating peptides) were investigated with regard to their myostimulatory effects using whole-gut preparations isolated from fifth instar Heliothis virescens larvae. The experiments demonstrated that representatives of all three peptide families are able to induce and amplify gut contractions in this species in a dose-dependent manner. Structure-activity studies (alanine scan, D-amino acid scan and truncated analogues) with the helicokinin Hez-K1 supported the finding, that the core sequence for biological activity of kinins is the amidated C-terminal pentapeptide (FSPWG-amide). Similar investigations with insect tachykinin isolated from Leucophaea madera (Lem-TRP1) revealed that the minimum sequence evoking a physiological gut response in H. virescens is the amidated hexapeptide (GFLGVR-amide), which represents the conserved amino acid sequence for Leucophaea TRPs in general. The peptide concentration causing a half-maximal gut contraction (EC(50)) for Lem-TRP1 was about 26 nM. Although the potency of Lem-TRP1 was 9-fold lower compared with Hez-KI (EC(50): 3 nM), the maximal tension of the gut obtained with Lem-TRP1 was 1.7-fold higher compared with Hez-KI. The EC(50) of Manduca sexta allatotropin (Mas-AT; 79 nM) was of lowest potency among all three peptides tested. In a pharmacological study, co-incubation experiments with Lem-TRP1, Hez-KI or Mas-AT and compounds interfering with signal transduction pathways were employed to investigate the mode of action of the myotropic effects of these peptides. Cadmium and the protein kinase C (PKC) inhibitor tamoxifen attenuated the contractile effects of all three peptides tested. The data suggest that in the gut muscle of H. virescens the myotropic peptides bind to G-protein-coupled receptors that cause contraction by promoting the entry of extracellular calcium mediated by a PKC involved pathway.

B-lymphocytes from malignant hyperthermia-susceptible patients have an increased sensitivity to skeletal muscle ryanodine receptor activators

Malignant hyperthermia (MH) is a pharmacogenetic disease triggered by volatile anesthetics and succinylcholine in genetically predisposed individuals. The underlying feature of MH is a hypersensitivity of the calcium release machinery of the sarcoplasmic reticulum, and in many cases this is a result of point mutations in the skeletal muscle ryanodine receptor calcium release channel (RYR1). RYR1 is mainly expressed in skeletal muscle, but a recent report demonstrated the existence of this isoform in human B-lymphocytes. As B-cells can produce a number of cytokines, including endogenous pyrogens, we investigated whether some of the symptoms seen during MH could be related to the involvement of the immune system. Our results show that (i) Epstein-Barr virus-immortalized B-cells from MH-susceptible individuals carrying the V2168M RYR1 gene mutation were more sensitive to the RYR activator 4-chloro-m-cresol and (ii) their peripheral blood leukocytes produce more interleukin (IL)-1beta after treatment with the RYR activators caffeine and 4-chloro-m-cresol, compared with cells from healthy controls. Our result demonstrate that RYR1-mediated calcium signaling is involved in release of IL-1beta from B-lymphocytes and suggest that some of the symptoms seen during an MH episode may be due to IL-1beta production.

Platelet-activating factor evokes Ca2+ transients after the blockade of ryanodine receptor by dantrolene in RAW 264.7 macrophages

In the present study we studied platelet-activating factor (PAF)-, and ATP-induced increases in intracellular Ca2+ concentration ([Ca2+]i) using RAW 264.7 macrophages filled with fura-2/AM and imaged with fluorescence video microscopy. We found that the prevalence of detectable [Ca2+]i responses to PAF application was significantly higher in the presence of dantrolene. Dantrolene itself significantly decreased basal [Ca2+]i of macrophages compared to control cases after a 20-min incubation period. In the dantrolene-treated cells even the peak [Ca2+]i in response to PAF (as an average of all cells) was below the baseline of control suggesting that decreased [Ca2+]i plays a permissive role in the Ca2+ rise induced by PAF in macrophages. In contrast to the effect of PAF, neither the amplitude of response to ATP nor the frequency of responding cells changed significantly during dantrolene treatment in our experiments. These cells were able to respond to a standard immune stimulus as well: lipopolysaccharide (LPS) was able to increase [Ca2+]i. Our data indicate that the effectiveness of PAF to increase [Ca2+]i in RAW 264.7 macrophages depends on the resting [Ca2+]i. It has also been shown in this study that PAF and ATP differently regulate Ca2+ homeostasis in macrophages during inflammatory response and therefore they possibly differently modulate cytokine production by macrophages.

Regulation of murine airway responsiveness by endothelial nitric oxide synthase

Nitric oxide (NO) is a potent vasodilator, but it can also modulate contractile responses of the airway smooth muscle. Whether or not endothelial (e) NO synthase (NOS) contributes to the regulation of bronchial tone is unknown at present. Experiments were designed to investigate the isoforms of NOS that are expressed in murine airways and to determine whether or not the endogenous release of NO modulates bronchial tone in wild-type mice and in mice with targeted deletion of eNOS [eNOS(-/-)]. The presence of neuronal NOS (nNOS), inducible NOS (iNOS), and eNOS in murine trachea and lung parenchyma was assessed by RT-PCR, immunoblotting, and immunohistochemistry. Airway resistance was measured in conscious unrestrained mice by means of a whole body plethysmography chamber. The three isoforms of NOS were constitutively present in lungs of wild-type mice, whereas only iNOS and nNOS were present in eNOS(-/-) mice. Labeling of nNOS was localized in submucosal airway nerves but was not consistently detected, and iNOS immunoreactivity was observed in tracheal and bronchiolar epithelial cells, whereas eNOS was expressed in endothelial cells. In wild-type mice, treatment with N-nitro-L-arginine methyl ester, but not with aminoguanidine, potentiated the increase in airway resistance produced by inhalation of methacholine. eNOS(-/-) mice were hyperresponsive to inhaled methacholine and markedly less sensitive to N-nitro-L-arginine methyl ester. These results demonstrate that the three NOS isoforms are expressed constitutively in murine lung and that NO derived from eNOS plays a physiological role in controlling bronchial airway reactivity.

Inhibition of the Na(+)/H(+) antiporter suppresses IL-12 p40 production by mouse macrophages

The amiloride-inhibitable Na(+)/H(+) antiporter plays an important role in macrophage activation. The intracellular pathways leading to interleukin (IL)-12 p40 production by activated macrophages are incompletely understood. In the present study, we examined the contribution of the Na(+)/H(+) antiporter to the production of IL-12 p40. Amiloride or its analogs decreased the production of IL-12 p40 in macrophages stimulated with bacterial lipopolysaccharide and interferon-gamma. The order of potency of amiloride analogs was consistent with the proposition that the effect of amiloride is mediated by the inhibition of the Na(+)/H(+) antiporter. The effect of amiloride was post-transcriptional, as IL-12 p40 mRNA levels induced by lipopolysaccharide and interferon-gamma were not affected by this inhibitor. Furthermore, the inhibitory effect of amiloride on IL-12 p40 production was not a result of interference with the activation of the p38 and p42/44 mitogen-activated protein kinases or c-Jun kinase. In summary, the production of IL-12 p40 requires a functional Na(+)/H(+) antiporter.

Lipopolysaccharide enhances bradykinin-induced signal transduction via activation of Ras/Raf/MEK/MAPK in canine tracheal smooth muscle cells

Bacterial lipopolysaccharide (LPS) was found to induce inflammatory responses and to enhance bronchial hyperreactivity to several contractile agonists. However, the implication of LPS in the pathogenesis of bronchial hyperreactivity was not completely understood. Therefore, in this study, we investigated the effect of LPS on mitogen-activated protein kinase (MAPK) activation associated with potentiation of bradykinin (BK)-induced inositol phosphates (IPs) accumulation and Ca(2+) mobilization in canine cultured tracheal smooth muscle cells (TSMCs). LPS stimulated phosphorylation of p42/p44 MAPK in a time- and concentration-dependent manner using a Western blot analysis against a specific phosphorylated form of MAPK antibody. Maximal stimulation of the p42 and p44 MAPK isoforms occurred after 7 min-incubation and the maximal effect was achieved with 100 microg ml(-1) LPS. Pretreatment of TSMCs with LPS potentiated BK-induced IPs accumulation and Ca(2+) mobilization. However, there was no effect on the IPs response induced by endothelin-1, 5-hydroxytryptamine, and carbachol. In addition, pretreatment with PDGF-BB enhanced BK-induced IPs response. These enhancements by LPS and PDGF-BB might be due to an increase in BK B(2) receptor density (B(max)) in TSMCs, characterized by competitive inhibition of [(3)H]-BK binding using B(1) and B(2) receptor-selective reagents. The enhancing effects of LPS and PDGF-BB were attenuated by PD98059, an inhibitor of MAPK kinase (MEK), suggesting that the effect of LPS may share a common signalling pathway with PDGF-BB in TSMCs. Furthermore, overexpression of dominant negative mutants, H-Ras-15A and Raf-N4, significantly suppressed p42/p44 MAPK activation induced by LPS and PDGF-BB, indicating that Ras and Raf may be required for activation of these kinases. These results suggest that the augmentation of BK-induced responses produced by LPS might be, at least in part, mediated through activation of Ras/Raf/MEK/MAPK pathway in TSMCs.

Differential effect of a single high dose of the tricyclic antidepressant imipramine on interleukin-1beta and tumor necrosis factor-alpha secretion following an in vivo lipopolysaccharide challenge in rats

Tricyclic antidepressants (TCAs) of which imipramine is one, are commonly used in the treatment of depressive disorders and other forms of psychiatric illness. There have been many reports regarding the suppressive effects of TCAs on immune function. However, information is still limited regarding the effects of TCAs on the immune system, as many of the studies conducted to date have concentrated on in vitro exposure to such drugs, or ex vivo measures of immunity following drug administration. Thus in the present investigation, an in vivo challenge with bacterial lipopolysaccharide (LPS) (100 microg/kg; i.p.) was used to assess immunocompetence following administration of a single high dose of the TCA, imipramine (100 mg/kg, p.o.). The results demonstrated that imipramine pretreatment inhibits LPS-induced increases in serum concentrations of the proinflammatory cytokine, tumor necrosis factor (TNF)-alpha both 3 and 6 h, following administration. However, LPS-induced interleukin (IL)-1beta secretion was not significantly altered following imipramine treatment at either of the timepoints examined. In addition, serum concentrations of corticosterone and the antiinflammatory cytokine IL-10 were measured, and imipramine treatment failed to alter either basal, or LPS-induced increases in these immunosuppressive agents. In conclusion, although IL-1beta and TNF-alpha are both macrophage-derived proinflammatory cytokines, the present study demonstrates a differential sensitivity of these cytokines to the suppressive effects of the TCA imipramine. Furthermore, the suppressive effects of imipramine on LPS-induced TNF-alpha secretion could not be attributed to either increased glucocorticoid levels, or increased secretion of the antiinflammatory cytokine IL-10. The relevance of these findings to antidepressant-induced immunotoxicity are discussed.

Antiinflammatory properties of mycophenolate mofetil in murine endotoxemia: inhibition of TNF-alpha and upregulation of IL-10 release

Mycophenolate mofetil (MMF) is a new immunosuppressive agent currently used in organ transplantation and under evaluation in immune-mediated inflammatory disorders such as rheumatoid arthritis. Although MMF was shown to inhibit purine nucleotide synthesis in lymphocytes, it is still unclear whether it might also exert direct antiinflammatory actions in vivo. To address this question, we evaluated the effects of MMF administration on the responses of mice to a single challenge with bacterial lipopolysaccharide (LPS). We observed that MMF treatment inhibits the release of tumor necrosis factor-alpha (TNF-alpha) and nitric oxide (NO) upon LPS injection whereas it promotes IL-10 production. In parallel, MMF was found to protect mice from LPS-induced lethality. Inhibition of TNF-alpha release was also observed in IL-10-deficient mice indicating that it does not exclusively depend on the upregulation of IL-10 endogenous synthesis. In view of the differential effects of MMF on the LPS-induced production of TNF-alpha and NO on one hand and that of IL-10 on the other hand, we conclude that beside its immunosuppressive action at the lymphocyte level, MMF is also endowed with antiinflammatory properties.

IL-12 as a therapeutic target for pharmacological modulation in immune-mediated and inflammatory diseases: regulation of T helper 1/T helper 2 responses

Interleukin-12 (IL-12) is a pivotal cytokine in driving the immune system towards a T helper (Th)1 type response and preventing a Th2 type immune profile. Therefore, IL-12 is indispensable in the defense against certain, mainly intracellular pathogens, but overproduction of this cytokine is crucially involved in the etiology of several inflammatory and autoimmune diseases. Hence, IL-12 is an ideal target for pharmacological intervention in the therapy of autoimmune and inflammatory diseases. The production of IL-12 and a resultant Th1 type immune response can be suppressed with several pharmacological approaches including modulation of intracellular cyclic AMP levels, glucocorticoids and nuclear factor-kappaB inhibition. IL-12 responsiveness may be inhibited using anti-IL-12 antibodies, soluble IL-12 receptors or the IL-12 p40 homodimer. Exploitation of these approaches may provide novel means for the experimental therapy of a variety of pathophysiological states.