Ca2+- and Protein Kinase C-dependent Signaling Pathway for Nuclear Factor-κB Activation, Inducible Nitric-oxide Synthase Expression, and Tumor Necrosis Factor-α Production in Lipopolysaccharide-stimulated Rat Peritoneal Macrophages

Gabapentin attenuates cardiac remodeling after myocardial infarction by inhibiting M1 macrophage polarization through the peroxisome proliferator-activated receptor-γ pathway

OBJECTIVES

Inflammation regulates ventricular remodeling after myocardial infarction (MI), and gabapentin exerts anti-inflammatory effects. We investigated the anti-inflammatory role and mechanism of gabapentin after MI.

METHODS

Rats were divided into the sham group (n = 12), MI group (n = 20), and MI + gabapentin group (n = 16). MI was induced by left coronary artery ligation. The effects of gabapentin on THP-1-derived macrophages were examined in vitro.

RESULTS

In vivo, 1 week after MI, gabapentin significantly reduced inducible nitric oxide synthase (iNOS; M1 macrophage marker) expression and decreased pro-inflammatory factors (tumor necrosis factor [TNF]-α and interleukin [IL]-1β). Gabapentin upregulated the M2 macrophage marker arginase-1, as well as CD163 expression, and increased the expression of anti-inflammatory factors, including chitinase-like 3, IL-10, and transforming growth factor-β. Four weeks after MI, cardiac function, infarct size, and cardiac fibrosis improved after gabapentin treatment. Gabapentin inhibited sympathetic nerve activity and decreased ventricular electrical instability in rats after MI. Tyrosine hydroxylase and growth-associated protein 43 were suppressed after gabapentin treatment. Gabapentin downregulated nerve growth factor (NGF) and reduced pro-inflammatory factors (iNOS, TNF-α, and IL-1β). In vitro, gabapentin reduced NGF, iNOS, TNF-α, and IL-1β expression in lipopolysaccharide-stimulated macrophages. Mechanistic studies revealed that the peroxisome proliferator-activated receptor-γ antagonist GW9662 attenuated the effects of gabapentin. Moreover, gabapentin reduced α2δ1 expression in the macrophage plasma membrane and reduced the calcium content of macrophages.

CONCLUSION

Gabapentin attenuates cardiac remodeling by inhibiting inflammation via peroxisome proliferator-activated receptor-γ activation and preventing calcium overload.

Role of Endothelial Kinin B1 Receptor on the Membrane Potential of Transgenic Rat Aorta

The kinin receptors are classically involved in inflammation, pain and sepsis. The effects of the kinin B1 receptor agonist des-Arg9-bradykinin (DBK) and lipopolysaccharide (LPS) were investigated by comparing the membrane potential responses of aortic rings from transgenic rats overexpressing the kinin B1 receptor (B1R) in the endothelium (TGR(Tie2B1)) and Sprague Dawley (SD) rats. No difference in the resting membrane potential in the aorta’s smooth muscle from the transgenic and SD rats was observed. The aorta rings from SD rats hyperpolarized only to LPS but not to DBK, whereas the aorta rings from TGR(Tie2B1) responded by the administration of both drugs. DBK and LPS responses were inhibited by the B1 receptor antagonist R715 and by iberiotoxin in both cases. Thapsigargin induced a hyperpolarization in the smooth muscle of SD rats that was not reversed by R715, but was reversed by iberiotoxin and this hyperpolarization was further augmented by DBK administration. These results show that the model of overexpression of vascular B1 receptors in the TGR(Tie2B1) rats represent a good model to study the role of functional B1 receptors in the absence of any pathological stimulus. The data also show that KCa channels are the final mediators of the hyperpolarizing responses to DBK and LPS. In addition, we suggest an interaction between the B1R and TLR4, since the hyperpolarization induced by LPS could be abolished in the presence of R715.

The dominant-negative mitochondrial calcium uniporter subunit MCUb drives macrophage polarization during skeletal muscle regeneration

[Figure: see text].

Modulating Repolarization of Tumor-Associated Macrophages with Targeted Therapeutic Nanoparticles as a Potential Strategy for Cancer Therapy

There are always some components in the tumor microenvironment (TME), such as tumor-associated macrophages (TAMs), that help tumor cells escape the body's immune surveillance. Therefore, this situation can lead to tumor growth, progression, and metastasis, resulting in low response rates for cancer therapy. Macrophages play an important role with strong plasticity and functional diversity. Facing different microenvironmental stimulations, macrophages undergo a dynamic change in phenotype and function into two major macrophage subpopulations, namely classical activation/inflammation (M1) and alternative activation/regeneration (M2) type. Through various signaling pathways, macrophages polarize into complex groups, which can perform different immune functions. In this review, we emphasize the use of nanopreparations for macrophage related immunotherapy based on the pathological knowledge of TAMs phenotype. These macrophages targeted nanoparticles re-edit and re-educate macrophages by attenuating M2 macrophages and reducing aggregation to the TME, thereby relieving or alleviating immunosuppression. Among them, we describe in detail the cellular mechanisms and regulators of several major signaling pathways involved in the plasticity and polarization functions of macrophages. The advantages and challenges of those nanotherapeutics for these pathways have been elucidated, providing the basis and insights for the diagnosis and treatment strategies of various diseases centered on macrophages.

KCa3.1 Inhibition of Macrophages Suppresses Inflammatory Response Leading to Endothelial Damage in a Cell Model of Kawasaki Disease

Purpose

Macrophages-mediated inflammation is linked with endothelial damage of Kawasaki disease (KD). KCa3.1, a calcium-activated potassium channel, modulates inflammation of macrophages. However, little is known about the role of KCa3.1 in inflammation by macrophages involved in KD. Hence, this study is aimed to explore the potential role of KCa3.1 in regulating inflammatory response by macrophages and subsequent vascular injury in an in vitro model of KD.

Methods

RAW264.7 cells were stimulated with Lactobacillus casei cell wall extract (LCWE) with or without TRAM-34 or PDTC or AG490. Subsequently, mouse coronary artery endothelial cells (MCAECs) were incubated with RAW264.7 cells-conditioned medium to mimic local inflammatory lesions in KD. CCKi8 assay was used to evaluate cell viability. The mRNA levels of inflammatory mediators were detected by qRT-PCR. Expressions of KCa3.1, MCAECs injury-associated molecules, proteins involved in signal pathways of nuclear factor-κB (NF-κB), signal transducers and activators of transcription (STAT) 3 and p38 were evaluated by Western blot.

Results

Our study showed that LCWE increased KCa3.1 protein level in RAW264.7 macrophages and KCa3.1 inhibition by TRAM-34 notably suppressed the expression of pro-inflammatory molecules in LCWE-treated macrophages via blocking the activation of NF-κB and STAT3 pathways. Besides, the inflammation and damage of MCAECs were attenuated in the TRAM-34-treated group compared with the KD model group. This vascular protective role was dependent on the down-regulation of NF-κB and STAT3 signal pathways, which was confirmed by using inhibitors of NF-κB and STAT3.

Conclusion

This study demonstrates that KCa3.1 blockade of macrophages suppresses inflammatory reaction leading to mouse coronary artery endothelial cell injury in a cell model of KD by hampering the activation of NF-κB and STAT3 signaling pathway. These findings imply that KCa3.1 may be a potential therapeutic target for KD.

Signal Transduction in Immune Cells and Protein Kinases

Immune response relies upon several intracellular signaling events. Among the protein kinases involved in these pathways, members of the protein kinase C (PKC) family are prominent molecules because they have the capacity to acutely and reversibly modulate effector protein functions, controlling both spatial distribution and dynamic properties of the signals. Different PKC isoforms are involved in distinct signaling pathways, with selective functions in a cell-specific manner.In innate system, Toll-like receptor signaling is the main molecular event triggering effector functions. Various isoforms of PKC can be common to different TLRs, while some of them are specific for a certain type of TLR. Protein kinases involvement in innate immune cells are presented within the chapter emphasizing their coordination in many aspects of immune cell function and, as important players in immune regulation.In adaptive immunity T-cell receptor and B-cell receptor signaling are the main intracellular pathways involved in seminal immune specific cellular events. Activation through TCR and BCR can have common intracellular pathways while others can be specific for the type of receptor involved or for the specific function triggered. Various PKC isoforms involvement in TCR and BCR Intracellular signaling will be presented as positive and negative regulators of the immune response events triggered in adaptive immunity.

Role of Pericytes in the Development of the Renin/Angiotensin System: Induction of Functional Renin in Cultures of Pericytes

Renal pericytes have a critical importance for angiogenesis and vascular remodeling, medullary blood flow regulation, and development of fibrosis. An emerging role for kidney pericytes is their ability to induce renin expression and synthesis. Here, we present methods for purification of human renal pericytes, their primary culture, and differentiation into renin-producing cells. Possible applications of these protocols include investigations into (1) renin cell recruitment mechanisms, (2) modulation of renin expression/secretion by small molecules, and (3) renin expression/secretion in nonrenal pericytes. A potential therapeutic application of this work is the identification of new players regulating the renin-angiotensin system.

Recombinant Human Annexin A5 Can Repair the Disrupted Cardiomyocyte Adherens Junctions in Endotoxemia

Recombinant human annexin A5 (Anx5) is known to protect cardiac function during endotoxemia, although the underlying mechanisms have yet to be elucidated. In this study, we demonstrated that Anx5 could repair the disrupted cardiomyocyte adherens junctions and improve the myocardial contractile function in lipopolysaccharide (LPS)-induced endotoxemia. Mechanistic studies revealed that Anx5 could antagonize the disassociation between p120-catenin (p120) and N-cadherin as well as the dephosphorylation of p120 in LPS-treated cardiomyocytes. Small interference RNA and specific inhibitors experiment demonstrated that Anx5 regulated p120 functions by inhibition of p21-activated kinase 5 in a protein kinase Cα-dependent way. Moreover, Anx5 could inhibit nuclear factor κB activation and downregulate the level of inflammatory cytokines, such as tumor necrosis factor α and interleukin 1β, which contributed to improving tissue pathological damage in LPS-induced mouse endotoxemia model. Taken together, Anx5 could protect cardiomyocytes adherens junctions and improve myocardial contractile function via regulation of p120 and anti-inflammation in LPS-induced endotoxemia. This study provided novel insights in the prevention and treatment of septic shock.

Depletion of H2S during obesity enhances store-operated Ca2+ entry in adipose tissue macrophages to increase cytokine production

The increased production of proinflammatory cytokines by adipose tissue macrophages (ATMs) contributes to chronic, low-level inflammation during obesity. We found that obesity in mice reduced the bioavailability of the gaseous signaling molecule hydrogen sulfide (H2S). Steady-state, intracellular concentrations of H2S were lower in ATMs isolated from mice with diet-induced obesity than in ATMs from lean mice. In addition, the intracellular concentration of H2S in the macrophage cell line RAW264.7 was reduced during an acute inflammatory response evoked by the microbial product lipopolysaccharide (LPS). Reduced intracellular concentrations of H2S led to increased Ca(2+) influx through the store-operated Ca(2+) entry (SOCE) pathway, which was prevented by the exogenous H2S donor GYY4137. Furthermore, GYY4137 inhibited the Orai3 channel, a key component of the SOCE machinery. The enhanced production of proinflammatory cytokines by RAW264.7 cells and ATMs from obese mice was reduced by exogenous H2S or by inhibition of SOCE. Together, these data suggest that the depletion of macrophage H2S that occurs during acute (LPS-induced) or chronic (obesity) inflammation increases SOCE through disinhibition of Orai3 and promotes the production of proinflammatory cytokines.

Transient receptor potential vanilloid 1 gene deficiency ameliorates hepatic injury in a mouse model of chronic binge alcohol-induced alcoholic liver disease

Experimental alcohol-induced liver injury is exacerbated by a high polyunsaturated fat diet rich in linoleic acid. We postulated that bioactive oxidized linoleic acid metabolites (OXLAMs) play a critical role in the development/progression of alcohol-mediated hepatic inflammation and injury. OXLAMs are endogenous ligands for transient receptor potential vanilloid 1 (TRPV1). Herein, we evaluated the role of signaling through TRPV1 in an experimental animal model of alcoholic liver disease (ALD). Chronic binge alcohol administration increased plasma OXLAM levels, specifically 9- and 13-hydroxy-octadecadienoic acids. This effect was associated with up-regulation of hepatic TRPV1. Exposure of hepatocytes to these OXLAMs in vitro resulted in activation of TRPV1 signal transduction with increased intracellular Ca(2+) levels. Genetic depletion of TRPV1 did not blunt hepatic steatosis caused by ethanol, but prevented hepatic injury. TRPV1 deficiency protected from hepatocyte death and prevented the increase in proinflammatory cytokine and chemokine expression, including tumor necrosis factor-α, IL-6, macrophage inflammatory protein-2, and monocyte chemotactic protein 1. TRPV1 depletion markedly blunted ethanol-mediated induction of plasminogen activator inhibitor-1, an important alcohol-induced hepatic inflammation mediator, via fibrin accumulation. This study indicates, for the first time, that TRPV1 receptor pathway may be involved in hepatic inflammatory response in an experimental animal model of ALD. TRPV1-OXLAM interactions appear to play a significant role in hepatic inflammation/injury, further supporting an important role for dietary lipids in ALD.

Protein kinase C and acute respiratory distress syndrome

The acute respiratory distress syndrome (ARDS) is a major public health problem and a leading source of morbidity in intensive care units. Lung tissue in patients with ARDS is characterized by inflammation, with exuberant neutrophil infiltration, activation, and degranulation that is thought to initiate tissue injury through the release of proteases and oxygen radicals. Treatment of ARDS is supportive primarily because the underlying pathophysiology is poorly understood. This gap in knowledge must be addressed to identify urgently needed therapies. Recent research efforts in anti-inflammatory drug development have focused on identifying common control points in multiple signaling pathways. The protein kinase C (PKC) serine-threonine kinases are master regulators of proinflammatory signaling hubs, making them attractive therapeutic targets. Pharmacological inhibition of broad-spectrum PKC activity and, more importantly, of specific PKC isoforms (as well as deletion of PKCs in mice) exerts protective effects in various experimental models of lung injury. Furthermore, PKC isoforms have been implicated in inflammatory processes that may be involved in the pathophysiologic changes that result in ARDS, including activation of innate immune and endothelial cells, neutrophil trafficking to the lung, regulation of alveolar epithelial barrier functions, and control of neutrophil proinflammatory and prosurvival signaling. This review focuses on the mechanistic involvement of PKC isoforms in the pathogenesis of ARDS and highlights the potential of developing new therapeutic paradigms based on the selective inhibition (or activation) of specific PKC isoforms.

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.

Magnesium sulfate mitigates acute lung injury in endotoxemia rats

BACKGROUND

Magnesium sulfate (MgSO4) possesses potent anti-inflammation capacity. We sought to elucidate the effects of MgSO4 on mitigating acute lung injury induced by endotoxemia. MgSO4 is an antagonist of the L-type calcium channels and the N-methyl-D-aspartate (NMDA) receptor. The roles of the L-type calcium channels and NMDA receptor in this regard were also elucidated.

METHODS

Ninety-six adult male rats were randomized to receive normal saline, MgSO4 (100 mg/kg), lipopolysaccharide (LPS), LPS plus MgSO4 (10, 50, or 100 mg/kg), LPS plus MgSO4 (100 mg/kg) plus the L-type calcium channel activator BAY-K8644, or LPS plus MgSO4 (100 mg/kg) plus exogenous NMDA (n=12 in each group). Between-group differences in lung injury were evaluated.

RESULTS

Histologic findings, in concert with assays of leukocyte infiltration (polymorphonuclear leukocytes/alveoli ratio and myeloperoxidase activity) and lung water content (wet/dry weight ratio), confirmed that LPS induced acute lung injury. LPS also caused significant inflammatory response (increases in chemokine, cytokine, and prostaglandin E2 concentrations) and imposed significant oxidative stress (increases in nitric oxide and malondialdehyde concentrations) in rat lungs. MgSO4 at the dosages of 50 mg/kg and 100 mg/kg, but not at 10 mg/kg, significantly mitigated the acute lung injury, lung inflammatory response, and oxidative stress caused by endotoxemia. Moreover, the protective effects of MgSO4 were counteracted by BAY-K8644 and exogenous NMDA.

CONCLUSIONS

MgSO4 mitigates lung inflammatory response, oxidative stress, and acute lung injury in endotoxemia rats in a dose-dependent manner. The mechanisms may involve antagonizing the L-type calcium channels and the NMDA receptor.

Inhibition of ATP-induced macrophage death by emodin via antagonizing P2X7 receptor

Emodin (1,3,8-trihydroxy-6-methylanthraquinone), an anthraquinone derivative from Rheum officinale Baill, exhibits anti-inflammatory and immunosuppressive activities, however, the underlying mechanisms are not fully understood. This study examined the effects of emodin on ATP-evoked responses in rat peritoneal macrophages and in human embryonic kidney 293 cells (HEK293) heterologously expressing the cloned rat P2X7 receptor. Emodin reduced macrophage death induced by millimolar ATP in a concentration-dependent manner with the half of maximal inhibition values (IC50) of 0.2 microM. It also strongly inhibited ATP-induced dye uptake or pore formation, a hallmark property associated with P2X7 receptor activation, and 2',3'-O-(benzoyl-4-benzoyl)-ATP (BzATP) induced increases in intracellular Ca2+ concentrations in macrophages with an IC50 of 0.5 microM. Furthermore, emodin significantly suppressed BzATP-evoked currents in P2X7 receptor expressing HEK293 cells with an IC50 of 3.4 microM. Taken together, these results provide compelling evidence for a novel action of emodin as a P2X7 receptor antagonist, which may underlie its anti-inflammatory and immunosuppressive activities.