Ca2+- and protein kinase C-dependent signaling pathway for nuclear factor-kappaB activation, inducible nitric-oxide synthase expression, and tumor necrosis factor-alpha production in lipopolysaccharide-stimulated rat peritoneal macrophages

Nanomaterial-Based Repurposing of Macrophage Metabolism and Its Applications

Macrophage immunotherapy represents an emerging therapeutic approach aimed at modulating the immune response to alleviate disease symptoms. Nanomaterials (NMs) have been engineered to monitor macrophage metabolism, enabling the evaluation of disease progression and the replication of intricate physiological signal patterns. They achieve this either directly or by delivering regulatory signals, thereby mapping phenotype to effector functions through metabolic repurposing to customize macrophage fate for therapy. However, a comprehensive summary regarding NM-mediated macrophage visualization and coordinated metabolic rewiring to maintain phenotypic equilibrium is currently lacking. This review aims to address this gap by outlining recent advancements in NM-based metabolic immunotherapy. We initially explore the relationship between metabolism, polarization, and disease, before delving into recent NM innovations that visualize macrophage activity to elucidate disease onset and fine-tune its fate through metabolic remodeling for macrophage-centered immunotherapy. Finally, we discuss the prospects and challenges of NM-mediated metabolic immunotherapy, aiming to accelerate clinical translation. We anticipate that this review will serve as a valuable reference for researchers seeking to leverage novel metabolic intervention-matched immunomodulators in macrophages or other fields of immune engineering.

Changes in the level of cytokines in the saliva of hypertensive patients with chronic periodontitis after scaling and root planning

INTRODUCTION

Cytokines have a key role in the pathogenesis of both hypertension and periodontitis. Salivary diagnosis is a promising field with numerous clinical applications. Since limited studies have been carried out on how salivary inflammatory cytokines can be determined and how well periodontal disease and hypertension might react to scaling and root planning (SRP). The goal of this study was to identify the pattern of changes in salivary inflammatory cytokines in chronic periodontitis subjects with hypertension after nonsurgical periodontal therapy.

METHODS

It included observational trial recruited 94 chronic periodontitis patients, 44 of whom had hypertension. All subjects have undergone non- surgical periodontal treatment. The clinical periodontal parameters included gingival index (GI), plaque index (PI), and probing of pocket depth (PPD). Unstimulated saliva was collected to determine the inflammatory biomarkers (using a commercial Elisa kit) both before and after SRP RESULTS: In comparison to non-hypertensive participants, the periodontal PPD was significantly higher in hypertensive subjects. All clinical parameters in the first examination, except for PI, were significantly higher in hypertensive than in non-hypertensive subjects. Plaque Index, GI, and PPD parameters at first visit and after finishing treatment positively correlated with salivary IL-1β, excluding pretreatment GI. The current results demonstrate the presence of a positive correlation between diastolic blood pressure and TNF (r = 0.330 and P = 0.029). All patients enrolled in this study showed a significant increase in the salivary levels of IL-4 after SRP.

CONCLUSIONS

The current study offer important and valuable information concerning the practical application of pro-inflammatory and anti-inflammatory cytokines as useful biomarkers and indicators for determining the outcome of SRP and progression of chronic periodontitis in patients with hypertension.

Potential effects of biomaterials on macrophage function and their signalling pathways

The use of biomaterials in biomedicine and healthcare has increased in recent years. Macrophages are the primary immune cells that induce inflammation and tissue repair after implantation of biomaterials. Given that macrophages exhibit high heterogeneity and plasticity, the influence of biomaterials on macrophage phenotype should be considered a crucial evaluation criterion during the development of novel biomaterials. This review provides a comprehensive summary of the physicochemical, biological, and dynamic characteristics of biomaterials that drive the regulation of immune responses in macrophages. The mechanisms involved in the interaction between macrophages and biomaterials, including endocytosis, receptors, signalling pathways, integrins, inflammasomes and long non-coding RNAs, are summarised in this review. In addition, research prospects of the interaction between macrophages and biomaterials are discussed. An in-depth understanding of mechanisms underlying the spatiotemporal changes in macrophage phenotype induced by biomaterials and their impact on macrophage polarization can facilitate the identification and development of novel biomaterials with superior performance. These biomaterials may be used for tissue repair and regeneration, vaccine or drug delivery and immunotherapy.

Lomerizine attenuates LPS-induced acute lung injury by inhibiting the macrophage activation through reducing Ca2+ influx

Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) are life-threatening lung diseases with high mortality rates, predominantly attributable to acute and severe pulmonary inflammation. Lomerizine (LMZ) is a calcium channel blocker previously used in preventing and treating migraine. Here, we found that LMZ inhibited inflammatory responses and lung pathological injury by reducing pulmonary edema, neutrophil infiltration and pro-inflammatory cytokine production in lipopolysaccharide (LPS)-induced ALI mice. In vitro experiments, upon treating with LMZ, the expression of interleukin (IL)-1β, IL-6 and tumor necrosis factor (TNF)-α was attenuated in macrophages. The phosphorylation of p38 MAPK, ERK1/2, JNK, and NF-κB p65 was inhibited after LMZ treatment. Furthermore, LPS-induced Ca2+ influx was reduced by treating with LMZ, which correlated with inhibition of pro-inflammatory cytokine production. And L-type Ca2+ channel agonist Bay K8644 (BK) could restore cytokine generation. In conclusion, our study demonstrated that LMZ alleviates LPS-induced ALI and is a potential agent for treating ALI/ARDS.

In Vivo Immune Adjuvant Effects of CaCO3 Nanoparticles through Intracellular Ca2+ Concentration Regulation

Calcium (Ca) is a vital component of the human body and plays a crucial role in intracellular signaling and regulation as a second messenger. Recent studies have shown that changes in intracellular Ca2+ concentration can influence immune cell function. In this study, we developed calcium carbonate nanoparticles (CaNPs) of various sizes using a Nanosystem Platform to modulate intracellular Ca2+ concentration in vitro and in vivo. Our findings demonstrate that intravenous administration of CaNPs led to changes in the number and ratio of immune cells in the spleen and stimulated the activation of dendritic cells (DCs) and macrophages. Notably, CaNPs exhibited strong adjuvant properties in the absence of antigenic stimuli. These results indicate that CaNPs have the potential to regulate immune cell function by modulating Ca2+ concentrations, offering a novel approach for disease prevention and treatment in combination with antigens or drugs. Overall, our study emphasizes the importance of modulating intracellular Ca2+ concentration as a means of regulating immune cell function.

Role of T CD4+ cells, macrophages, C-low threshold mechanoreceptors and spinal Cav 3.2 channels in inflammation and related pain-like symptoms in murine inflammatory models

BACKGROUND AND PURPOSE

T-type calcium channels, mainly the Ca_v 3.2 subtype, are important contributors to the nociceptive signalling pathway. We investigated their involvement in inflammation and related pain-like symptoms.

EXPERIMENTAL APPROACH

The involvement of Ca_v 3.2 and T-type channels was investigated using genetic and pharmacological inhibition to assess mechanical allodynia/hyperalgesia and oedema development in two murine inflammatory pain models. The location of Ca_v 3.2 channels involved in pain-like symptoms was studied in mice with Ca_v 3.2 knocked out in C-low threshold mechanoreceptors (C-LTMR) and the use of ABT-639, a peripherally restricted T-type channel inhibitor. The anti-oedema effect of Ca_v 3.2 channel inhibition was investigated in chimeric mice with immune cells deleted for Ca_v 3.2. Lymphocytes and macrophages from either green fluorescent protein-targeted Ca_v 3.2 or KO mice were used to determine the expression of Ca_v 3.2 protein and the functional status of the cells.

KEY RESULTS

Ca_v 3.2 channels contributed to the development of pain-like symptoms and oedema in the two murine inflammatory pain models. Our results provided evidence of the involvement of Ca_v 3.2 channels located on C-LTMRs and spinal cord in inflammatory pain. Ca_v 3.2 channels located in T cells and macrophages contribute to the inflammatory process.

CONCLUSION AND IMPLICATIONS

Ca_v 3.2 channels play crucial roles in inflammation and related pain, implying that targeting of Ca_v 3.2 channels with pharmacological agents could be an attractive and readily evaluable strategy in clinical trials, to relieve chronic inflammatory pain in patients.

Mitochondrial Calcium Nanoregulators Reverse the Macrophage Proinflammatory Phenotype Through Restoring Mitochondrial Calcium Homeostasis for the Treatment of Osteoarthritis

Introduction

Osteoarthritis (OA) is a chronic degenerative joint disease accompanied by an elevated macrophage proinflammatory phenotype, which is triggered by persistent pathologically elevated calcium ion levels in mitochondria. However, existing pharmacological compounds targeting the inhibition of mitochondrial calcium ion (m[Ca²⁺]) influx are currently limited in terms of plasma membrane permeability and low specificity for ion channels and transporters. In the present study, we synthesized mesoporous silica nanoparticle-amidated (MSN)-ethylenebis (oxyethylenenitrilo)tetraacetic acid (EGTA)/triphenylphosphine (TPP)-polyethylene glycol (PEG) [METP] nanoparticles (NPs), which specifically target mitochondria and block excess calcium ion influx.

Methods

m[Ca²⁺] overload in OA mouse bone marrow-derived macrophages (BMDMs) was detected by a fluorescence probe. A tissue in situ fluorescence colocalization assay was used to evaluate METP NP uptake by macrophages. BMDMs from healthy mice were pretreated with a concentration gradient of METP NPs followed by lipopolysaccharide (LPS) stimulation and detection of m[Ca²⁺] levels in vitro. The optimal METP NP concentration was further applied, and the endoplasmic reticulum (ER) and cytoplasm calcium levels were detected. The inflammatory phenotype was measured by surface markers, cytokine secretion and intracellular inflammatory gene/protein expression. A Seahorse cell energy metabolism assay was performed to elucidate the mechanism by which METP NPs reverse the BMDM proinflammatory phenotype.

Results

The present study identified calcium overload in BMDM mitochondria of OA mice. We demonstrated that METP NPs reversed the increased m[Ca²⁺] levels in mitochondria and the proinflammatory phenotype of BMDMs, with both in vivo and in vitro experiments, via the inhibition of the mitochondrial aspartate-arginosuccinate shunt and ROS production.

Conclusion

We demonstrated that METP NPs are effective and highly specific regulators of m[Ca²⁺] overload. In addition, we demonstrated that these METP NPs reverse the macrophage proinflammatory phenotype by restoring m[Ca²⁺] homeostasis, thereby inhibiting the tissue inflammatory response and achieving a therapeutic effect for OA.

Hydrogen Sulfide Regulates Macrophage Function in Cardiovascular Diseases

Significance: Hydrogen sulfide (H₂S) is an endogenous gasotransmitter that plays a vital role in immune system regulation. Recently, the regulation of macrophage function by H₂S has been extensively and actively recognized. Recent Advances: The mechanisms by which endogenous H₂S controls macrophage function have attracted increasing attention. The generation of endogenous H₂S from macrophages is mainly catalyzed by cystathionine-γ-lyase. H₂S is involved in the macrophage activation and inflammasome formation, which contributes to macrophage apoptosis, adhesion, chemotaxis, and polarization. In addition, H₂S has redox ability and interacts with reactive oxygen species to prevent oxidative stress. Moreover, H₂S epigenetically regulates gene expression. Critical Issues: In this article, the generation of endogenous H₂S in macrophages and its regulatory effect on macrophage function are reviewed. In addition, the signal transduction targeting macrophages by H₂S is also addressed. Finally, the potential therapeutic effect of H₂S on macrophages is discussed. Future Directions: Further experiments are required to explore the involvement of endogenous H₂S in the regulation of macrophage function in various physiological and pathophysiological processes and elucidate the mechanisms involved. Regarding the clinical translation of H₂S, further exploration of the application of H₂S in inflammation-related diseases is needed. Antioxid. Redox Signal. 38, 45-56.

Molecular Mechanisms of Lipopolysaccharide (LPS) Induced Inflammation in an Immortalized Ovine Luteal Endothelial Cell Line (OLENDO)

Escherichia coli (E. coli) is the most common Gram-negative bacterium causing infection of the uterus or mammary gland and is one of the major causes of infertility in livestock. In those animals affected by E. coli driven LPS-mediated infections, fertility problems occur in part due to disrupted follicular and luteal functionality. However, the molecular mechanisms by which LPS induces inflammation, and specifically, the role of LPS in the disruption of capillary morphogenesis and endothelial barrier function remain unclear. Here, we hypothesized that LPS may lead to alterations in luteal angiogenesis and vascular function by inducing inflammatory reactions in endothelial cells. Accordingly, OLENDO cells were treated with LPS followed by evaluation of the expression of selected representative proinflammatory cytokines: NF-kB, IL6, IL8, TNFα, and ICAM 1. While TNFα was not affected by treatment with LPS, transcripts of NF-kB, IL6, and IL8 were affected in a dosage-dependent manner. Additionally, the activity of TLR2 and TLR4 was blocked, resulting in suppression of the LPS-induced expression of ICAM 1, NF-kB, IL6, and IL8. Inhibition of the PKA or MAPK/ERK pathways suppressed the LPS-stimulated expression of NF-kB, IL6, and IL8, whereas blocking the PKC pathway had the opposite effect. Furthermore, LPS-induced phosphorylation of Erk1 and Erk2 was inhibited when the TLR4 or MAPK/ERK pathways were blocked. Finally, LPS seems to induce inflammatory processes in OLENDO cells via TLR2 and TLR4, utilizing different signaling pathways.

Cubic multi-ions-doped Na2TiO3 nanorod-like coatings: Structure-stable, highly efficient platform for ions-exchanged release to immunomodulatory promotion on vascularized bone apposition

The dissolution-derived release of bioactive ions from ceramic coatings on metallic implants, despite improving osseointegration, renders a concern on the interfacial breakdown of the metal/coating/bone system during long-term service. Consequently, persistent efforts to seek alternative strategies instead of dissolution-derived activation are pressingly carrying out. Inspired by bone mineral containing ions as Ca²⁺, Mg²⁺, Sr²⁺ and Zn²⁺, here we hydrothermally grew the quadruple ions co-doped Na₂TiO₃ nanorod-like coatings. The co-doped ions partially substitute Na⁺ in Na₂TiO₃, and can be efficiently released from cubic lattice via exchange with Na⁺ in fluid rather than dissolution, endowing the coatings superior long-term stability of structure and bond strength. Regulated by the coatings-conditioned extracellular ions, TLR4-NFκB signalling is enhanced to act primarily in macrophages (MΦs) at 6 h while CaSR-PI3K-Akt1 signalling is potentiated to act predominately since 24 h, triggering MΦs in a M1 response early and then in a M2 response to sequentially secrete diverse cytokines. Acting on endothelial and mesenchymal stem cells with the released ions and cytokines, the immunomodulatory coatings greatly promote Type-H (CD31^hiEmcn^hi) angiogenesis and osteogenesis in vitro and in vivo, providing new insights into orchestrating insoluble ceramics-coated implants for early vascularized osseointegration in combination with long-term fixation to bone.

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Co-doped Ca²⁺, Mg²⁺, Sr²⁺ and Zn²⁺ in Na₂TiO₃ efficiently release via ion exchange.

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QID elevates extracellular concentrations of the ions and MΦ intracellular [Ca²⁺].

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Co-doped Na₂TiO₃ coatings promote immunomodulatory apposition of vascularized bone.

Cigarette Smoke Promotes Interleukin-8 Production in Alveolar Macrophages Through the Reactive Oxygen Species/Stromal Interaction Molecule 1/Ca2+ Axis

Chronic obstructive pulmonary disease (COPD), primarily attributed to cigarette smoke (CS), is characterized by multiple pathophysiological changes, including oxidative stress and inflammation. Stromal interaction molecule 1 (STIM1) is a Ca²⁺ sensor that regulates Ca²⁺ entry in different types of cells. The present study aimed to explore the relationship between CS-induced oxidative stress and inflammation, as well as the functional role of STIM1 thereinto. Our results showed that the reactive oxygen species (ROS)/STIM1/Ca²⁺ axis played a critical role in CS-induced secretion of interleukin (IL)-8 in human alveolar macrophages. Specifically, smokers with COPD (SC) showed higher levels of ROS in the lung tissues compared with healthy non-smokers (HN). STIM1 was upregulated in the lung tissues of COPD patients. The expression of STIM1 was positively associated with ROS levels and negatively correlated with pulmonary function. The expression of STIM1 was also increased in the bronchoalveolar lavage fluid (BALF) macrophages of COPD patients and PMA-differentiated THP-1 macrophages stimulated by cigarette smoke extract (CSE). Additionally, CSE-induced upregulation of STIM1 in PMA-differentiated THP-1 macrophages was inhibited by pretreatment with N-acetylcysteine (NAC), a ROS scavenger. Transfection with small interfering RNA (siRNA) targeting STIM1 and pretreatment with NAC alleviated CSE-induced increase in intracellular Ca²⁺ levels and IL-8 expression. Furthermore, pretreatment with SKF-96365 and 2-APB, the inhibitors of Ca²⁺ influx, suppressed CSE-induced secretion of IL-8. In conclusion, our study demonstrates that CSE-induced ROS production may increase the expression of STIM1 in macrophages, which further promotes the release of IL-8 by regulating Ca²⁺ entry. These data suggest that STIM1 may play a crucial role in CSE-induced ROS production and inflammation, and participate in the pathogenesis of COPD.

Receptor-specific Ca2+ oscillation patterns mediated by differential regulation of P2Y purinergic receptors in rat hepatocytes

Extracellular agonists linked to inositol-1,4,5-trisphosphate (IP₃) formation elicit cytosolic Ca²⁺ oscillations in many cell types, but despite a common signaling pathway, distinct agonist-specific Ca²⁺ spike patterns are observed. Using qPCR, we show that rat hepatocytes express multiple purinergic P2Y and P2X receptors (R). ADP acting through P2Y1R elicits narrow Ca²⁺ oscillations, whereas UTP acting through P2Y2R elicits broad Ca²⁺ oscillations, with composite patterns observed for ATP. P2XRs do not play a role at physiological agonist levels. The discrete Ca²⁺ signatures reflect differential effects of protein kinase C (PKC), which selectively modifies the falling phase of the Ca²⁺ spikes. Negative feedback by PKC limits the duration of P2Y1R-induced Ca²⁺ spikes in a manner that requires extracellular Ca²⁺. By contrast, P2Y2R is resistant to PKC negative feedback. Thus, the PKC leg of the bifurcated IP₃ signaling pathway shapes unique Ca²⁺ oscillation patterns that allows for distinct cellular responses to different agonists.

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Distinct stereotypic Ca²⁺ oscillations are elicited by P2Y1 and P2Y2 receptors

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P2X receptors do not contribute to the generation of Ca²⁺ oscillations

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Agonist-specific Ca²⁺ spike shapes reflect discrete modes of PKC negative feedback

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Bifurcation of IP₃/PKC signaling yields unique Ca²⁺ oscillation signatures

Prediction of Re-positivity for Coronavirus Nucleic Acid Among COVID-19 Patients in the Recovery Phase

Background and Objectives: Although the pathogenesis and treatment of coronavirus disease 2019 (COVID-19) have been gradually revealed, the risk for re-emergence of coronavirus nucleic acids in recovered patients remains poorly understood. Hence, this study evaluated the risk predictors associated with re-positivity for virus nucleic acid. Methods: Between February 1 and March 20, 2020, we retrospectively reviewed the clinical epidemiological data of 129 COVID-19 patients who were treated at Zhongxiang People's Hospital of Hubei Province in China. Subsequently, a risk prediction model for the re-positivity of virus nucleic acid was developed, and a receiver operating characteristic (ROC) curve was drawn for further validation. Results: In this study, the rate of re-positivity for virus nucleic acid was 17.8% (23/129) where all re-positivity cases were asymptomatic. The median time interval from discharge to nucleic acid re-positivity to discharge after being cured again was 11.5 days (range: 7-23 days). Multivariate logistic regression analysis showed that leukocytopenia [odds ratio (OR) 7.316, 95% confidence interval (CI) 2.319-23.080, p = 0.001], prealbumin < 150 mg/L (OR 4.199, 95% CI 1.461-12.071, p = 0.008), and hyperpyrexia (body temperature >39°C, OR 4.643, 95% CI 1.426-15.117, p = 0.011) were independent risk factors associated with re-positivity. The area under the ROC curve was 0.815 (95% CI, 0.729-0.902). Conclusion: COVID-19 patients with leukocytopenia, low prealbumin level, and hyperpyrexia are more likely to test positive for virus nucleic acid after discharge. Timely and effective treatment and appropriate extension of hospital stays and quarantine periods may be feasible strategies for managing such patients.

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.

PKC downregulation upon rapamycin treatment attenuates mitochondrial disease

Leigh syndrome is a fatal neurometabolic disorder caused by defects in mitochondrial function. Mechanistic target of rapamycin (mTOR) inhibition with rapamycin attenuates disease progression in a mouse model of Leigh syndrome (Ndufs4 knock-out (KO) mouse); however, the mechanism of rescue is unknown. Here we identify protein kinase C (PKC) downregulation as a key event mediating the beneficial effects of rapamycin treatment of Ndufs4 KO mice. Assessing the impact of rapamycin on the brain proteome and phosphoproteome of Ndufs4 KO mice, we find that rapamycin restores mitochondrial protein levels, inhibits signalling through both mTOR complexes and reduces the abundance and activity of multiple PKC isoforms. Administration of PKC inhibitors increases survival, delays neurological deficits, prevents hair loss and decreases inflammation in Ndufs4 KO mice. Thus, PKC may be a viable therapeutic target for treating severe mitochondrial disease.

PKCβ/NF-κB pathway in diabetic atrial remodeling

Atrial remodeling in diabetes is partially attributed to NF-κB/TGF-β signal transduction pathway activation. We examined whether the hyperglycemia-induced increased expression of NF-κB/TGF-β was dependent upon protein kinase C-β (PKCβ) and tested the hypothesis that selective inhibition of PKCβ using ruboxistaurin (RBX) can reduce NF-κB/TGF-β expression and inhibit abnormal atrial remodeling in streptozotocin (STZ)-induced diabetic rats. The effects of PKCβ inhibition on NF-κB/TGF-β signal transduction pathway-mediated atrial remodeling were investigated in STZ-induced diabetic rats. Mouse atrial cardiomyocytes (HL-1 cells) were cultured in low- or high-glucose or mannitol conditions in the presence or absence of small interference RNA that targeted PKCβ. PKCβ inhibition using ruboxistaurin (RBX, 1 mg/kg/day) decreased the expression of NF-κBp65, p-IκB, P38MARK, TNF-α, TGF-β, Cav1.2, and NCX proteins and inducibility of atrial fibrillation (AF) in STZ-induced diabetic rats. Exposure of cardiomyocytes to high-glucose condition activated PKCβ and increased NF-κB/TGF-β expression. Suppression of PKCβ expression by small interference RNA decreased high-glucose-induced NF-κB and extracellular signal-related kinase activation in HL-1 cells. Pharmacological inhibition of PKCβ is an effective method to reduce AF incidence in diabetic rat models by preventing NF-κB/TGF-β-mediated atrial remodeling.

Paeoniflorin suppresses IL-33 production by macrophages

Objective: Interleukin (IL)-33 has been attracting more and more attention as a new member of theIL-1 cytokine family in recent years. However, the underlying mechanisms referred to the regulation of endogenous IL-33 production are not fully illustrated. Paeoniflorin (PF) has been reported to possess multiple pharmacological activities, including anti-inflammation and anti-allergy. In this study, we aimed to investigate the effect of PF on IL-33 production by macrophages and explore the underlying mechanisms.Methods: In vivo, IL-33 production in mice after lipopolysaccharide (LPS) injection together with PF application was detected by enzyme-linked immunosorbent assay (ELISA). In vitro, MTT, Real-time PCR, ELISA, Calcium (Ca²⁺) imaging and Western blot were used to assess the cytotoxicity of PF, IL-33 expression at mRNA and protein levels, Ca²⁺ influx, protein kinase C (PKC) activity, nuclear factor-kappa B (NF-κB), and mitogen-activated protein kinase (MAPK) activation in LPS-stimulated RAW264.7 macrophages with PF administration.Results: Our results indicated that PF (5 and 25 mg/kg) significantly reduced the production of TNF-a, IL-1β, and IL-33 in the peritoneal exudate of LPS-treated mice. In vitro assay, upregulation of PF concentration (≥ 20 μM) showed an increased cytotoxicity in RAW264.7 cells during the 24-h cell culture. PF (10 μM) inhibited IL-33 production, Ca²⁺ influx, PKC activity, NF-κB (p65) activation, and P38MAPK phosphorylation in LPS-treated macrophages. Notably, NF-κB inhibitor (BAY 11-7085), P38MAPK inhibitor (SB203580), and Ca²⁺ blocker (NiCl₂) also curbed LPS-induced IL-33 production, respectively.Conclusions: PF suppresses IL-33 production by macrophages via inhibiting NF-κB and P38MAPK activation associated with the regulation of Ca²⁺ mobilization.

Paeoniflorin relieves LPS-induced inflammatory pain in mice by inhibiting NLRP3 inflammasome activation via transient receptor potential vanilloid 1

LPS has been widely used to induce inflammatory pain, attributing to production of inflammatory cytokines and sensitization of nociceptors. Paeoniflorin (PF) possesses anti-nociceptive property, but its effect on LPS-induced inflammatory pain has not been investigated. In this study, we aimed to investigate the analgesic effect of PF on an inflammatory pain mouse model and explore the underlying mechanisms. LPS-induced inflammatory pain model was established in C57BL/6J mice after PF treatment. Then, thermal hyperalgesia, neutrophil infiltration, inflammatory cytokine production, intracellular Ca²⁺ levels, PKC activity, transient receptor potential vanilloid 1 (TRPV-1) expression, NF-κB transcription, and NLPR3 inflammasome activation were assessed by thermal withdrawal latency, histopathology, ELISA, intracellular Ca²⁺ concentration, immunohistochemistry, and Western blot, separately. PF significantly relieved inflammatory pain and paw edema in mice with LPS-induced inflammatory pain. Additionally, PF inhibited neutrophil infiltration, inflammatory cytokine production (IL-1β, TNF-α, and IL-6), intracellular Ca²⁺ levels, and PKC activity as well as suppressed TRPV-1 expression, NF-κB transcription, and NLPR3 inflammasome activation in the footpad tissue samples. Importantly, capsaicin (TRPV-1 agonists) obviously reversed the pain-relieving effect of PF, suggesting the involvement of TRPV-1 in the analgesic activity of PF. Our results indicated PF ameliorated LPS-induced inflammation and pain in mice by inhibiting TRPV-1-mediated NLRP3 inflammasome activation. These findings suggest that PF can be as a potential pharmacological agent for inflammatory pain and thus deserves more attention and further investigation.

Inducible nitric oxide synthase: Regulation, structure, and inhibition

A considerable number of human diseases have an inflammatory component, and a key mediator of immune activation and inflammation is inducible nitric oxide synthase (iNOS), which produces nitric oxide (NO) from l-arginine. Overexpressed or dysregulated iNOS has been implicated in numerous pathologies including sepsis, cancer, neurodegeneration, and various types of pain. Extensive knowledge has been accumulated about the roles iNOS plays in different tissues and organs. Additionally, X-ray crystal and cryogenic electron microscopy structures have shed new insights on the structure and regulation of this enzyme. Many potent iNOS inhibitors with high selectivity over related NOS isoforms, neuronal NOS, and endothelial NOS, have been discovered, and these drugs have shown promise in animal models of endotoxemia, inflammatory and neuropathic pain, arthritis, and other disorders. A major issue in iNOS inhibitor development is that promising results in animal studies have not translated to humans; there are no iNOS inhibitors approved for human use. In addition to assay limitations, both the dual modalities of iNOS and NO in disease states (ie, protective vs harmful effects) and the different roles and localizations of NOS isoforms create challenges for therapeutic intervention. This review summarizes the structure, function, and regulation of iNOS, with focus on the development of iNOS inhibitors (historical and recent). A better understanding of iNOS' complex functions is necessary before specific drug candidates can be identified for classical indications such as sepsis, heart failure, and pain; however, newer promising indications for iNOS inhibition, such as depression, neurodegenerative disorders, and epilepsy, have been discovered.

Hydrogen Sulfide, Adipose Tissue and Diabetes Mellitus

Hydrogen sulfide (H₂S) is now increasingly considered to be the third gasotransmitter alongside other gaseous signaling molecules, nitric oxide (NO) and carbon monoxide (CO). H₂S is produced by a variety of endogenous enzymatic and non-enzymatic pathways and acts as a modulator of the physiological and pathological events of the body. Adipocytes express the cystathionine γ lyase (CSE)/H₂S system, which modulates a variety of biological activities in adipose tissue (AT), including inflammation, apoptosis, insulin resistance, adipokine secretion and adipocyte differentiation. Abnormalities in the physiological functions of AT play an important role in the process of diabetes mellitus. Therefore, this review provides an overview of the general aspects of H₂S biochemistry, the effect of H₂S on AT function and diabetes mellitus and its molecular signalling mechanisms as well as the potential application of H₂S in pharmacotherapy.

Mitochondrial Calcium Uptake Is Instrumental to Alternative Macrophage Polarization and Phagocytic Activity

Macrophages are highly plastic and dynamic cells that exert much of their function through phagocytosis. Phagocytosis depends on a coordinated, finely tuned, and compartmentalized regulation of calcium concentrations. We examined the role of mitochondrial calcium uptake and mitochondrial calcium uniporter (MCU) in macrophage polarization and function. In primary cultures of human monocyte-derived macrophages, calcium uptake in mitochondria was instrumental for alternative (M2) macrophage polarization. Mitochondrial calcium uniporter inhibition with KB-R7943 or MCU knockdown, which prevented mitochondrial calcium uptake, reduced M2 polarization, while not affecting classical (M1) polarization. Challenging macrophages with E. coli fragments induced spikes of mitochondrial calcium concentrations, which were prevented by MCU inhibition or silencing. In addition, mitochondria remodelled in M2 macrophages during phagocytosis, especially close to sites of E. coli internalization. Remarkably, inhibition or knockdown of MCU significantly reduced the phagocytic capacity of M2 macrophages. KB-R7943, which also inhibits the membrane sodium/calcium exchanger and Complex I, reduced mitochondria energization and cellular ATP levels, but such effects were not observed with MCU silencing. Therefore, phagocytosis inhibition by MCU knockdown depended on the impaired mitochondrial calcium buffering rather than changes in mitochondrial and cellular energy status. These data uncover a new role for MCU in alternative macrophage polarization and phagocytic activity.

Effects of Baicalin on piglet monocytes involving PKC-MAPK signaling pathways induced by Haemophilus parasuis

Background

Haemophilus parasuis (HPS) is the causative agent of Glässer’s disease, characterized by arthritis, fibrinous polyserositis and meningitis, and resulting in worldwide economic losses in the swine industry. Baicalin (BA), a commonly used traditional Chinese medication, has been shown to possess a series of activities, such as anti-bacterial, anti-viral, anti-tumor, anti-oxidant and anti-inflammatory activities. However, whether BA has anti-apoptotic effects following HPS infection is unclear. Here, we investigated the anti-apoptotic effects and mechanisms of BA in HPS-induced apoptosis via the protein kinase C (PKC)–mitogen-activated protein kinase (MAPK) pathway in piglet’s mononuclear phagocytes (PMNP).

Results

Our data demonstrated that HPS could induce reactive oxygen species (ROS) production, arrest the cell cycle and promote apoptosis via the PKC–MAPK signaling pathway in PMNP. Moreover, when BA was administered, we observed a reduction in ROS production, suppression of cleavage of caspase-3 in inducing apoptosis, and inhibition of activation of the PKC–MAPK signaling pathway for down-regulating p-JNK, p-p38, p-ERK, p-PKC-α and PKC-δ in PMNP triggered by HPS.

Conclusions

Our data strongly suggest that BA can reverse the apoptosis initiated by HPS through regulating the PKC–MAPK signaling pathway, which represents a promising therapeutic agent in the treatment of HPS infection.

Selenoprotein SELENOK Enhances the Migration and Phagocytosis of Microglial Cells by Increasing the Cytosolic Free Ca2+ Level Resulted from the Up-Regulation of IP3R

Enhancing the migration and phagocytosis of microglial cells is of great significance for the reducing of the risk of the neurodegenerative diseases, such as Alzheimer's disease (AD) and Parkinson's disease (PD). The effect of mouse selenoprotein K (mSELENOK) on the migration and phagocytosis of BV2 microglial cells and its mechanism were studied. The results showed that the over-expression of mSELENOK can increase the migratory and phagocytic abilities of the microglial cells, while the knockdown of mSELENOK can decrease the migratory and phagocytic abilities of the cells. The cytosolic free Ca²⁺ level and inositol trisphosphate receptor (IP₃R) mRNA transcript and protein expression were also increased significantly as the consequence of the over-expression of mSELENOK in the microglial cells. On the contrary, the level of cytosolic free Ca²⁺ and the mRNA transcript and protein expression of IP₃R in mSELENOK knockdown cells were decreased significantly. 2-aminoethoxydiphenyl borate (2-APB), an antagonist of IP₃R, could prevent the increased migration, phagocytosis, and cytosolic free Ca²⁺ level of mSELENOK over-expressed microglial cells, and knockdown of IP₃R₃ could reduce the increased cytosolic Ca²⁺ level in mSELENOK over-expressed microglial cells. Further studies revealed that selenium supplement (Na₂SeO₃) can increase the expression of mSELENOK in microglial cells significantly. In summary, these data suggest that mSELENOK can increase cytosolic free Ca²⁺ level of microglial cells by up-regulating the expression of IP₃R, thus enhancing the migration and phagocytosis of microglial cells. Our results indicated that mSELENOK is an important selenoprotein, which plays a role in trace element selenium's functions and can enhance the migration and phagocytosis of microglial cells.

LPS Induces mTORC1 and mTORC2 Activation During Monocyte Adhesion

Monocyte adhesion is a crucial step in transmigration and can be induced by lipopolysaccharide (LPS). Here, we studied the role of mammalian target of rapamycin (mTOR) complexes, mTORC1 and mTORC2, and PKC in this process. We used THP-1 cells, a human monocytic cell line, to investigate monocyte adhesion under static and flow conditions. We observed that 1.0 μg/mL LPS increased PI3K/mTORC2 pathway and PKC activity after 1 h of incubation. WYE-354 10⁻⁶ M (mTORC2/mTORC1 inhibitor) and 10⁻⁶ M wortmannin avoided monocyte adhesion in culture plates. In addition, WYE also blocked LPS-induced CD11a expression. Interestingly, rapamycin and WYE-354 blocked both LPS-induced monocyte adhesion in a cell monolayer and actin cytoskeleton rearrangement, confirming mTORC1 involvement in this process. Once activated, PKC activates mTORC1/S6K pathway in a similar effect observed to LPS. Activation of the mTORC1/S6K pathway was attenuated by 10⁻⁶ M U0126, an MEK/ERK inhibitor, and 10⁻⁶ M calphostin C, a PKC inhibitor, indicating that the MEK/ERK/TSC2 axis acts as a mediator. In agreement, 80 nM PMA (a PKC activator) mimicked the effect of LPS on the activation of the MEK/ERK/TSC2/mTORC1/S6K pathway, monocyte adhesion to ECV cells and actin cytoskeleton rearrangement. Our findings show that LPS induces activation of mTOR complexes. This signaling pathway led to integrin expression and cytoskeleton rearrangement resulting in monocyte adhesion. These results describe a new molecular mechanism involved in monocyte adhesion in immune-based diseases.

Choline transport links macrophage phospholipid metabolism and inflammation

Choline is an essential nutrient that is required for synthesis of the main eukaryote phospholipid, phosphatidylcholine. Macrophages are innate immune cells that survey and respond to danger and damage signals. Although it is well-known that energy metabolism can dictate macrophage function, little is known as to the importance of choline homeostasis in macrophage biology. We hypothesized that the uptake and metabolism of choline are important for macrophage inflammation. Polarization of primary bone marrow macrophages with lipopolysaccharide (LPS) resulted in an increased rate of choline uptake and higher levels of PC synthesis. This was attributed to a substantial increase in the transcript and protein expression of the choline transporter-like protein-1 (CTL1) in polarized cells. We next sought to determine the importance of choline uptake and CTL1 for macrophage immune responsiveness. Chronic pharmacological or CTL1 antibody-mediated inhibition of choline uptake resulted in altered cytokine secretion in response to LPS, which was associated with increased levels of diacylglycerol and activation of protein kinase C. These experiments establish a previously unappreciated link between choline phospholipid metabolism and macrophage immune responsiveness, highlighting a critical and regulatory role for macrophage choline uptake via the CTL1 transporter.

PKCα in colon cancer cells promotes M1 macrophage polarization via MKK3/6-P38 MAPK pathway

Tumor associated macrophages are potential targets of the immune therapy for patients with colon cancer. PKCα acts as a tumor suppressor in the intestine. However, the correlation between PKCα expressed in colon cancer cells and tumor associated macrophages polarization has never been detected. In the present study, the correlation between PKCα expression and level of M1 macrophages was evaluated in human colon cancer tissues. A xenograft mouse model of colon cancer cells with different PKCα expression level was constructed to evaluate the effect of PKCα on M1 macrophages polarization in vivo. Co-culture of colon cancer cells and differentiated macrophages was used to detect the potential interplay in vitro. PKCα regulated production of cytokines which correlated with macrophage polarization and the underlying mechanism was further explored. Our study showed that high PKCα expression in human colon cancer tissues correlated with better prognosis and high M1 macrophage content. PKCα expressed in colon cancer cells inhibited the growth of colon cancer in mice model. PKCα induced macrophages polarized to the M1-like phenotype both in vitro and in vivo. Mechanistically, PKCα targeted P38 via MKK3/6 to promote IL12 and GM-CSF expression which further enhanced M1-like macrophages polarization. In conclusion, this study provided evidence for the first time that PKCα in colon cancer cells play an anticancer action by inducing the polarization of tumor associated macrophages to M1-like phenotype in the tumor microenvironment. PKCα promoted IL12/GM-CSF-mediated M1 polarization through MKK3/6-P38 signaling pathway. Our investigation suggested that modulation of the PKCα signaling pathway might serve as a novel strategy for colon cancer therapy.

Near-infrared light-controlled regulation of intracellular calcium to modulate macrophage polarization

Macrophages are multifunctional immune cells with diverse physiological functions such as fighting against infection, influencing progression of pathologies, maintaining homeostasis, and regenerating tissues. Macrophages can be induced to adopt distinct polarized phenotypes, such as classically activated pro-inflammatory (M1) phenotypes or alternatively activated anti-inflammatory and pro-healing (M2), to execute diverse and dynamic immune functions. However, unbalanced polarizations of macrophage can lead to various pathologies, such as atherosclerosis, obesity, tumor, and asthma. Thus, the capability to remotely control macrophage phenotypes is important to the success of treating many pathological conditions involving macrophages. In this study, we developed an upconversion nanoparticle (UCNP)-based photoresponsive nanocarrier for near-infrared (NIR) light-mediated control of intracellular calcium levels to regulate macrophage polarization. UCNP was coated with mesoporous silica (UCNP@mSiO₂), into which loaded calcium regulators that can either supply or deplete calcium ions. UCNP@mSiO₂ was chemically modified through serial coupling of photocleavable linker and Arg-Gly-Asp (RGD) peptide-bearing molecular cap via cyclodextrin-adamantine host-guest complexation. The RGD-bearing cap functioned as the photolabile gating structure to control the release of calcium regulators and facilitated the cellular uptake of UCNP@mSiO₂ nanocarrier. The upconverted UV light emission from the UCNP@mSiO₂ under NIR light excitation triggered the cleavage of cap and intracellular release of calcium regulators, thereby allowing temporal regulation on the intracellular calcium levels. Application of NIR light through skin tissue promoted M1 or M2 polarization of macrophages, by elevating or depleting intracellular calcium levels, respectively. To the best of our knowledge, this is the first demonstration of NIR light-mediated remote control on macrophage polarization. This photoresponsive nanocarrier offers the potential to remotely manipulate in vivo immune functions, such as inflammation or tissue regeneration, via NIR light-controlled macrophage polarization.

Magnesium enhances the chondrogenic differentiation of mesenchymal stem cells by inhibiting activated macrophage-induced inflammation

Magnesium deficiency increases the generation of pro-inflammatory cytokines, which is consistently accompanied by the sensitization of cells such as neutrophils, macrophages and endothelial cells. We investigated the potential of magnesium to regulate macrophage polarization and macrophage-induced inflammation with or without lipopolysaccharide (LPS) and interferon-γ (IFN-γ) activation and further elucidated whether these effects impact the inhibitory functions of activated macrophage-induced inflammation on cartilage regeneration. The results showed that magnesium inhibited the activation of macrophages, as indicated by a significant reduction in the percentage of CCR7-positive cells, while the percentage of CD206-positive cells decreased to a lesser degree. After activation, both pro-inflammatory and anti-inflammatory cytokines were down-regulated at the mRNA level and certain cytokines (IL-1β, IL-6 and IL-10) were decreased in the cell supernatant with the addition of magnesium. Moreover, magnesium decreased the nuclear translocation and phosphorylation of nuclear factor-κB (NF-κB) to impede its activation. A modified micromass culture system was applied to assess the effects of activated macrophage-conditioned medium with or without magnesium treatment on the chondrogenic differentiation of human bone marrow mesenchymal stem cells (hBMSCs). Magnesium enhanced the chondrogenic differentiation of hBMSCs by reversing the adverse effects of activated macrophage-induced inflammation.

Lipopolysaccharide stimulates endogenous β-glucuronidase via PKC/NF-κB/c-myc signaling cascade: a possible factor in hepatolithiasis formation

Hepatolithiasis is commonly encountered in Southeastern and Eastern Asian countries, but the pathogenesis mechanism of stone formation is still not well understood. Now, the role of endogenous β-glucuronidase in pigment stones formation is being gradually recognized. In this study, the mechanism of increased expression and secretion of endogenous β-glucuronidase during hepatolithiasis formation was investigated. We assessed the endogenous β-glucuronidase, c-myc, p-p65, and p-PKC expression in liver specimens with hepatolithiasis by immunohistochemical staining, and found that compared with that in normal liver samples, the expression of endogenous β-glucuronidase, c-myc, p-p65, and p-PKC in liver specimens with hepatolithiasis significantly increased, and their expressions were positively correlated with each other. Lipopolysaccharide (LPS) induced increased expression of endogenous β-glucuronidase and c-myc in hepatocytes and intrahepatic biliary epithelial cells in a dose- and time-dependent manner, and endogenous β-glucuronidase secretion increased, correspondingly. C-myc siRNA transfection effectively inhibited the LPS-induced expression of endogenous β-glucuronidase. Furthermore, NF-κB inhibitor pyrrolidine dithiocarbamate or PKC inhibitor chelerythrine could effectively inhibit the LPS-induced expression of c-myc and endogenous β-glucuronidase, and the expression of p-p65 was also partly inhibited by chelerythrine. Our clinical observations and experimental data indicate that LPS could induce the increased expression and secretion of endogenous β-glucuronidase via a signaling cascade of PKC/NF-κB/c-myc in hepatocytes and intrahepatic biliary epithelial cells, and endogenous β-glucuronidase might play a possible role in the formation of hepatolithiasis.

Aeromonas hydrophila-induced alterations in cytosolic calcium activate pro-apoptotic cPKC-MEK1/2-TNFα axis in infected headkidney macrophages of Clarias gariepinus

Alterations in intracellular-calcium (Ca²⁺)_i homeostasis is critical to Aeromonas hydrophila-induced headkidney macrophages (HKM) apoptosis of Clarias gariepinus, though the implications are poorly understood. Here, we describe the role of intermediate molecules of Ca^2+-signaling pathway that are involved in HKM apoptosis. We observed phosphoinositide-3-kinase/phospholipase C is critical for (Ca²⁺)_i release in infected HKM. Heightened protein kinase-C (PKC) activity and phosphorylation of MEK1/2-ERK1/2 was noted which declined in presence of 2-APB, Go6976 and PD98059, inhibitors to IP3-receptor, conventional PKC isoforms (cPKC) and MEK1/2 respectively implicating Ca²⁺/cPKC/MEK-ERK1/2 axis imperative in A. hydrophila-induced HKM apoptosis. Significant tumor necrosis factor-α (TNFα) production and its subsequent reduction in presence of MEK-ERK1/2 inhibitor U0126 suggested TNFα production downstream to cPKC-mediated signaling via MEK1/2-ERK1/2 pathway. RNAi and inhibitor studies established the role of TNFα in inducing caspase-8-mediated apoptosis of infected HKM. We conclude, alterations in A. hydrophila-induced (Ca²⁺)i alterations activate cPKC-MEK1/2-ERK1/2-TNFα signaling cascade triggering HKM apoptosis.

Inhibition of immune responses and related proteins in Rhamdia quelen exposed to diclofenac

Nonsteroidal anti-inflammatory drugs are among the most widely detected pharmaceuticals in surface water worldwide. The nonsteroidal anti-inflammatory drug diclofenac is used to treat many types of pain and inflammation. Diclofenac's potential to cause adverse effects in exposed wildlife is a growing concern. To evaluate the effects of waterborne diclofenac on the immune response in Rhamdia quelen (South American catfish), fish were exposed to 3 concentrations of diclofenac (0.2, 2.0, and 20.0 μg/L) for 14 d. Some of the exposed fish were also given an intraperitoneal injection on day 14 of 1 mg/kg of carrageenan to evaluate cell migration to the peritoneum. Total blood leukocyte count and carrageenan-induced leukocyte migration to the peritoneal cavity, particularly of polymorphonuclear cells, were significantly affected for all diclofenac exposure groups. Nitric oxide production was significantly reduced in the diclofenac-treated fish. Plasma and kidney proteins were analyzed by means of liquid chromatography-tandem mass spectrometry in a shotgun proteomic approach. In both plasma and kidney of diclofenac-exposed R. quelen, the expression of 20 proteins related to the inflammatory process, nitric oxide production, leukocyte migration, and the complement cascade was significantly altered. In addition, class I major histocompatibility complex was significantly decreased in plasma of diclofenac-treated fish. Thus, waterborne exposure to diclofenac could lead to suppression of the innate immune system in R. quelen. Environ Toxicol Chem 2017;36:2092-2107. © 2017 SETAC.

Structure of the Toll/Interleukin-1 Receptor (TIR) Domain of the B-cell Adaptor That Links Phosphoinositide Metabolism with the Negative Regulation of the Toll-like Receptor (TLR) Signalosome

Ligand binding to Toll-like receptors (TLRs) results in dimerization of their cytosolic Toll/interleukin-1 receptor (TIR) domains and recruitment of post-receptor signal transducers into a complex signalosome. TLR activation leads to the production of transcription factors and pro-inflammatory molecules and the activation of phosphoinositide 3-kinases (PI3K) in a process that requires the multimodular B-cell adaptor for phosphoinositide 3-kinase (BCAP). BCAP has a sequence previously proposed as a "cryptic" TIR domain. Here, we present the structure of the N-terminal region of human BCAP and show that it possesses a canonical TIR fold. Dimeric BCAP associates with the TIR domains of TLR2/4 and MAL/TIRAP, suggesting that it is recruited to the TLR signalosome by multitypic TIR-TIR interactions. BCAP also interacts with the p85 subunit of PI3K and phospholipase Cγ, enzymes that deplete plasma membrane phosphatidylinositol 4,5-bisphosphate (PIP2), and these interactions provide a molecular explanation for BCAP-mediated down-regulation of inflammatory signaling.

Selenoprotein SelK increases the secretion of insulin from MIN6 β cells

The expression of selenoprotein SelK triggers the secretion of insulin from MIN6 β cells by increasing the cytosolic free Ca²⁺ level, resulting from the up-regulated IP3R3 expression.

Alpha-1-antitrypsin interacts with gp41 to block HIV-1 entry into CD4+ T lymphocytes

Background

Study of a clinic case reveals that alpha-1-antitrypsin (AAT) deficiency is related to CD4+ T cell count decline and AIDS progression, suggesting that AAT might be an endogenous inhibitor of HIV/AIDS. Previous study shows that AAT inhibits HIV-1 replication in infected host cells and the C-terminus fragment of AAT, VIRIP, interferes with HIV-1 infection. However, it is still unclear whether and how intact AAT inhibits HIV-1 infection. It is also unknown what the mechanism of AAT is and which critical step(s) are involved.

Results

In the present study, the C-terminus of AAT (C) was synthesized. C terminus-truncated AAT (ΔAAT) was also prepared by digesting AAT with metalloproteinase. Primary CD4+ T cells were then co-cultured with HIV-1 with the presence or absence of AAT/C/ΔAAT to detect cis-infection of HIV-1. The interaction between AAT/C/ΔAAT and gp120/gp41 was also measured. Meanwhile, HIV-1 reverse transcriptase activity and viral DNA integration were also detected in these lymphocytes. The results demonstrated that AAT and C, not ΔAAT, inhibited HIV-1 entry by directly interacting with gp41. Meanwhile, AAT, C and ΔAAT could not directly interfere with the steps of viral RNA reverse transcription and viral DNA integration.

Conclusion

AAT inhibits HIV-1 entry by directly interacting with gp41 through its C-terminus and thereby inhibits HIV-1 infection.

Electronic supplementary material

The online version of this article (doi:10.1186/s12866-016-0751-2) contains supplementary material, which is available to authorized users.

Human lung-resident macrophages express CB1 and CB2 receptors whose activation inhibits the release of angiogenic and lymphangiogenic factors

Macrophages are pivotal effector cells in immune responses and tissue remodeling by producing a wide spectrum of mediators, including angiogenic and lymphangiogenic factors. Activation of cannabinoid receptor types 1 and 2 has been suggested as a new strategy to modulate angiogenesis in vitro and in vivo. We investigated whether human lung-resident macrophages express a complete endocannabinoid system by assessing their production of endocannabinoids and expression of cannabinoid receptors. Unstimulated human lung macrophage produce 2-arachidonoylglycerol,N-arachidonoyl-ethanolamine,N-palmitoyl-ethanolamine, and N-oleoyl-ethanolamine. On LPS stimulation, human lung macrophages selectively synthesize 2-arachidonoylglycerol in a calcium-dependent manner. Human lung macrophages express cannabinoid receptor types 1 and 2, and their activation induces ERK1/2 phosphorylation and reactive oxygen species generation. Cannabinoid receptor activation by the specific synthetic agonists ACEA and JWH-133 (but not the endogenous agonist 2-arachidonoylglycerol) markedly inhibits LPS-induced production of vascular endothelial growth factor-A, vascular endothelial growth factor-C, and angiopoietins and modestly affects IL-6 secretion. No significant modulation of TNF-α or IL-8/CXCL8 release was observed. The production of vascular endothelial growth factor-A by human monocyte-derived macrophages is not modulated by activation of cannabinoid receptor types 1 and 2. Given the prominent role of macrophage-assisted vascular remodeling in many tumors, we identified the expression of cannabinoid receptors in lung cancer-associated macrophages. Our results demonstrate that cannabinoid receptor activation selectively inhibits the release of angiogenic and lymphangiogenic factors from human lung macrophage but not from monocyte-derived macrophages. Activation of cannabinoid receptors on tissue-resident macrophages might be a novel strategy to modulate macrophage-assisted vascular remodeling in cancer and chronic inflammation.

HDAC6 regulates cellular viral RNA sensing by deacetylation of RIG-I

RIG-I is a key cytosolic sensor that detects RNA viruses through its C-terminal region and activates the production of antiviral interferons (IFNs) and proinflammatory cytokines. While posttranslational modification has been demonstrated to regulate RIG-I signaling activity, its significance for the sensing of viral RNAs remains unclear. Here, we first show that the RIG-I C-terminal region undergoes deacetylation to regulate its viral RNA-sensing activity and that the HDAC6-mediated deacetylation of RIG-I is critical for viral RNA detection. HDAC6 transiently bound to RIG-I and removed the lysine 909 acetylation in the presence of viral RNAs, promoting RIG-I sensing of viral RNAs. Depletion of HDAC6 expression led to impaired antiviral responses against RNA viruses, but not against DNA viruses. Consequently, HDAC6 knockout mice were highly susceptible to RNA virus infections compared to wild-type mice. These findings underscore the critical role of HDAC6 in the modulation of the RIG-I-mediated antiviral sensing pathway.

Bioelectric modulation of macrophage polarization

Macrophages play a critical role in regulating wound healing and tissue regeneration by changing their polarization state in response to local microenvironmental stimuli. The native roles of polarized macrophages encompass biomaterials and tissue remodeling needs, yet harnessing or directing the polarization response has been largely absent as a potential strategy to exploit in regenerative medicine to date. Recent data have revealed that specific alteration of cells' resting potential (Vmem) is a powerful tool to direct proliferation and differentiation in a number of complex tissues, such as limb regeneration, craniofacial patterning and tumorigenesis. In this study, we explored the bioelectric modulation of macrophage polarization by targeting ATP sensitive potassium channels (KATP). Glibenclamide (KATP blocker) and pinacidil (KATP opener) treatment not only affect macrophage polarization, but also influence the phenotype of prepolarized macrophages. Furthermore, modulation of cell membrane electrical properties can fine-tune macrophage plasticity. Glibenclamide decreased the secretion and gene expression of selected M1 markers, while pinacidil augmented M1 markers. More interestingly, glibencalmide promoted macrophage alternative activation by enhancing certain M2 markers during M2 polarization. These findings suggest that control of bioelectric properties of macrophages could offer a promising approach to regulate macrophage phenotype as a useful tool in regenerative medicine.

Calcium and Superoxide-Mediated Pathways Converge to Induce Nitric Oxide-Dependent Apoptosis in Mycobacterium fortuitum-Infected Fish Macrophages

Mycobacterium fortuitum causes ‘mycobacteriosis’ in wide range of hosts although the mechanisms remain largely unknown. Here we demonstrate the role of calcium (Ca⁺²)-signalling cascade on M. fortuitum-induced apoptosis in headkidney macrophages (HKM) of Clarias sp. M. fortuitum could trigger intracellular-Ca⁺² influx leading to the activation of calmodulin (CaM), protein kinase C alpha (PKCα) and Calmodulin kinase II gamma (CaMKIIg). Gene silencing and inhibitor studies established the role of CaM in M. fortuitum pathogenesis. We noted that CaMKIIg activation is regulated by CaM as well as PKCα-dependent superoxide anions. This is altogether first report of oxidised CaMKIIg in mycobacterial infections. Our studies with targeted-siRNA and pharmacological inhibitors implicate CaMKIIg to be pro-apoptotic and critical for the activation of extra-cellular signal regulated kinase 1/2 (ERK1/2). Inhibiting the ERK1/2 pathway attenuated nitric oxide synthase 2 (NOS2)-induced nitric oxide (NO) production. Conversely, inhibiting the NOS2-NO axis by specific-siRNA and inhibitors down-regulated ERK1/2 activation suggesting the crosstalk between ERK1/2 and NO is essential for pathogenesis induced by the bacterium. Silencing the NOS2-NO axis enhanced intracellular bacterial survival and attenuated caspase-8 mediated activation of caspase-3 in the infected HKM. Our findings unveil hitherto unknown mechanism of M. fortuitum pathogenesis. We propose that M. fortuitum triggers intracellular Ca⁺² elevations resulting in CaM activation and PKCα-mediated superoxide generation. The cascade converges in common pathway mediated by CaMKIIg resulting in the activation of ERK1/2-NOS2 axis. The crosstalk between ERK1/2 and NO shifts the balance in favour of caspase dependent apoptosis of M. fortuitum-infected HKM.

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.

Low-density lipoprotein receptor-related protein 1 mediates α1-antitrypsin internalization in CD4+ T lymphocytes

In α1-antitrypsin-deficient HIV patients, an accelerated decline of CD4(+) T cell numbers is observed, suggesting that α1-antitrypsin is a potential endogenous HIV inhibitor. In infected T lymphocytes, α1-antitrypsin potently blocks NF-κB activation and HIV-1 replication by directly interacting with IκBα in the cytosol, thereby altering its ubiquitination pattern. However, the mechanism of α1-antitrypsin entry into the cytosol, where IκBα locates, remains unclear. In the present study, we investigated the mechanism of α1-antitrypsin internalization in CD4(+) T cells. Thus, primary CD4(+) T cells were infected with HIV-1 and then incubated with α1-antitrypsin to detect its internalization. We found that CD4(+) T cells internalized α1-antitrypsin through a clathrin-dependent endocytosis process. Next, intracellular α1-antitrypsin exerted the inhibitory effect on NF-κB activation and HIV-1 replication. On primary CD4(+) T cells, α1-antitrypsin interacted with low-density lipoprotein receptor-related protein 1 to initiate the internalization. Inside CD4(+) T lymphocytes, α1-antitrypsin was transported from the endosome to the lysosome and then released into the cytosol, where it is possible for α1-antitrypsin to directly interact with IκBα. These results together suggest that α1-antitrypsin internalization is a clathrin-dependent and low-density lipoprotein receptor-related protein 1-mediated endocytosis process. Internalized α1-antitrypsin is transported through the endosome-lysosome-cytosol routine to interact with cytosolic IκBα and block NF-κB activation and HIV-1 replication.

SjCa8, a calcium-binding protein from Schistosoma japonicum, inhibits cell migration and suppresses nitric oxide release of RAW264.7 macrophages

Background

Schistosomiasis is considered second only to malaria as the most devastating parasitic disease in tropical countries. Schistosome cercariae invade the host by penetrating the skin and migrate though the lungs and portal circulation to their final destination in the hepatic portal system and eventually the mesenteric veins. Previous studies have shown that the cytotoxic pathways that target schistosomulum in the lung-stage involve nitric oxide (NO) produced by macrophages. By contrast, skin-stage schistosomulas can evade clearance, indicating that they might be freed from macrophage NO-mediated cytotoxicity to achieve immune evasion; however, the critical molecules and mechanisms involved remain unknown.

Methods

Recombinant SjCa8 (rSjCa8), an 8-kDa calcium-binding protein that is stage-specifically expressed in cercaria and early skin-stage schistosomulas of Schistosoma japonicum, was incubated with mouse RAW264.7 macrophages. Effects on macrophage proliferation were determined using Cell Counting Kit-8. Next, transwell assay was carried out to further investigate the role of rSjCa8 in macrophage migration. The effects of rSjCa8 on macrophage apoptosis were evaluated using confocal microscopy and flow cytometry. Additional impacts of rSjCa8 on NO release by lipopolysaccharide (LPS)-stimulated macrophages as well as the underlying mechanisms were explored using fluorescent probe, nitric oxide signaling pathway microarray, quantitative real-time PCR, mutagenesis, and neutralizing antibody approaches.

Results

rSjCa8 exhibited a striking inhibitory effect on macrophage migration, but did not markedly increase cell proliferation or apoptosis. Additionally, rSjCa8 potently inhibited NO release by LPS-stimulated macrophages in a dose- and time-dependent manner, and the inhibitory mechanism was closely associated with intracellular Ca²⁺ levels, the up-regulation of catalase expression, and the down-regulation of the expression of 47 genes, including Myc, Gadd45a, Txnip, Fas, Sod2, Nos2, and Hmgb1. Vaccination with rSjCa8 increased NO concentration in the challenging skin area of infected mice and reduced the number of migrated schistosomula after skin penetration by cercariae.

Conclusions

Our findings indicate that SjCa8 might be a novel molecule that plays a critical role in immune evasion by S. japonicum cercaria during the process of skin penetration. The inhibitory impacts of rSjCa8 on macrophage migration and [Ca²⁺]_i-dependent NO release suggest it might represent a novel vaccine candidate and chemotherapeutic target for the prevention and treatment of schistosomiasis.

Electronic supplementary material

The online version of this article (doi:10.1186/s13071-015-1119-4) contains supplementary material, which is available to authorized users.

Kv1.3 channel blockade enhances the phagocytic function of RAW264.7 macrophages

This study aimed to comprehend the largely unknown role of voltage-gated potassium channel 1.3 (Kv1.3) in the phagocytic function of macrophages. We found that blocking of the Kv1.3 channel with 100 pmol L(-1) Stichodactyla helianthus neurotoxin (ShK) enhanced the phagocytic capacities of both resting and lipopolysaccharide (LPS)-stimulated RAW264.7 macrophages in the chicken erythrocyte system. In the fluorescein isothiocyanate (FITC)-labeled Escherichia coli k-12 system, ShK increased the phagocytic capacities of resting RAW264.7 cells, but not of the LPS-stimulated cells, as LPS alone stimulated almost saturated phagocytosis of the macrophages. ShK increased the nitric oxide (NO) production in LPS-activated cells, but not in resting RAW264.7 cells. There was no effect of ShK alone on the cytokine secretions in resting RAW264.7 cells, but it suppressed IL-1β secretion in LPS-stimulated RAW264.7 cells. At a concentration of 100 pmol L(-1), ShK did not affect the viability of the tested cells. Kv1.3 was expressed in RAW264.7 cells; this expression was downregulated by LPS, but significantly upregulated by disrupting caveolin-dependent endocytosis with filipin III. In addition, cytochalasin D, an inhibitor of actin polymerization, did not affect the Kv1.3 expression. Thus, blocking of the Kv1.3 channel enhances the phagocytic capacity and NO production of this cell line. Our results suggest that Kv1.3 channel serves as a negative regulator of phagocytosis in macrophages and can therefore be a potential target in the treatment of macrophage dysfunction.

Suppression of Propionibacterium acnes Infection and the Associated Inflammatory Response by the Antimicrobial Peptide P5 in Mice

The cutaneous inflammation associated with acne vulgaris is caused by the anaerobic bacterium Propionibacterium acnes through activation of the innate immune system in the skin. Current standard treatments for acne have limitations that include adverse effects and poor efficacy in many patients, making development of a more effective therapy highly desirable. In the present study, we demonstrate the protective effects of a novel customized α-helical cationic peptide, P5, against P. acnes-induced inflammatory responses in vitro and in vivo. Application of P5 significantly reduced expression of two inflammatory cytokines IL-8 and TNF-α in P. acnes-treated primary human keratinocytes, where P5 appeared to act in part by binding to bacterial lipoteichoic acid, thereby suppressing TLR2-to-NF-κB signaling. In addition, in a mouse model of acne vulgaris, P5 exerted both anti-inflammatory and antimicrobial effects against P. acnes, but exerted no cytotoxic effects against skin cells. These results demonstrate that P5, and perhaps other cationic antimicrobial peptides, offer the unique ability to reduce numbers P. acnes cells in the skin and to inhibit the inflammation they trigger. This suggests these peptides could potentially be used to effectively treat acne without adversely affecting the skin.