Intermedin1-53 Protects Cardiac Fibroblasts by Inhibiting NLRP3 Inflammasome Activation During Sepsis

[Recent research on pyroptosis in sepsis-induced myocardial depression]

Sepsis-induced myocardial depression (SIMD), a common complication of sepsis, is one of the main causes of death in patients with sepsis. The pathogenesis of SIMD is complicated, and the process of SIMD remains incompletely understood, with no single or definitive mechanism fully elucidated. Notably, pyroptosis, as a pro-inflammatory programmed cell death, is characterized by Gasdermin-mediated formation of pores on the cell membrane, cell swelling, and cell rupture accompanied by the release of large amounts of inflammatory factors and other cellular contents. Mechanistically, pyroptosis is mainly divided into the canonical pathway mediated by caspase-1 and the non-canonical pathway mediated by caspase-4/5/11. Pyroptosis has been confirmed to participate in various inflammation-associated diseases. In recent years, more and more studies have shown that pyroptosis is also involved in the occurrence and development of SIMD. This article reviews the molecular mechanisms of pyroptosis and its research progress in SIMD, aiming to provide novel strategies and targets for the treatment of SIMD.

Mechanism of sodium butyrate, a metabolite of gut microbiota, regulating cardiac fibroblast transdifferentiation via the NLRP3/Caspase-1 pyroptosis pathway

BACKGROUND

Cardiac fibroblasts (CFs) are activated after initial injury, and then differentiate into myofibroblasts (MFs), which play a pivotal role as the primary mediator cells in pathological remodeling. Sodium butyrate (NaB), being a metabolite of gut microbiota, exhibits anti-inflammatory property in local therapies on sites other than the intestine. Thus, this study aimed to probe the mechanism by which NaB regulates CFs transdifferentiation through the NLRP3/Caspase-1 pyroptosis pathway.

METHODS

CFs were cultured in vitro and induced into MFs by TGFβ1. CFs were identified by immunofluorescence labelling technique of vimentin and α-SMA, followed by treatment with NaB or NLRP3 inflammasome inhibitor (CY-09) and its activator [nigericin sodium salt (NSS)]. The expression levels of α-SMA, GSDMD-N/NLRP3/cleaved Caspase-1 proteins, and inflammatory factors IL-1β/IL-18/IL-6/IL-10 were determined using immunofluorescence, Western blot and ELISA. Cell proliferation and migration were evaluated using the CCK-8 assay and the cell scratch test, respectively.

RESULTS

Following the induction of TGFβ1, CFs exhibited increased expression levels of α-SMA proteins and IL-6/IL-10, as well as cell proliferative and migratory abilities. TGFβ1 induced CFs to differentiate into MFs, while NaB inhibited this differentiation. NaB inactivated the NLRP3/Caspase-1 pyroptosis pathway. CY-09 demonstrated inhibitory effects on the NLRP3/Caspase-1 pyroptosis pathway, leading to a reduction in TGFβ1-induced CFs transdifferentiation. NSS activated the NLRP3/Caspase-1 pyroptosis pathway, and thus partially counteracting the inhibitory effect of intestinal microbiota metabolite NaB on CFs transdifferentiation.

CONCLUSION

NaB, a metabolite of the gut microbiota, inhibited the activation of the NLRP3/Caspase-1 pyroptosis pathway in TGFβ1-induced CFs, repressed the transdifferentiation of CFs into MFs.

Ameliorative effect of anisodamine (654-1/654-2) against myocardial dysfunction induced by septic shock via the NF-κB/NLRP-3 or the PI3K-AKT/NF-κB pathway

BACKGROUND

Septic shock, an extremely dangerous condition that causes impairment of organ function, always largely contributes to mortality in intensive care units. The impact of septic shock-induced organ damage on morbidity and mortality is substantially influenced by myocardial dysfunction. However, it remains unclear whether and in what manner anisodamine (654-1/654-2) ameliorates myocardial dysfunction caused by septic shock.

PURPOSE

This study is the pioneering investigation and validation about the protective efficacy of anisodamine (654-1/654-2) against LPS-induced myocardial dysfunction in septic shock rats. It also aims to explore the differences in the underlying molecular mechanisms of both drugs.

METHODS

A septic shock model was established in SD rats by after tail vein administration of LPS. 64 rats were distributed into eight groups, such as LPS group, control group, LPS+654-1 group (1.25, 2.5, and 5 mg/kg), and LPS+654-2 group (1.25, 2.5, and 5 mg/kg). The hemodynamics, echocardiography, immunohistochemical analysis, TEM, TUNEL assay, and H&E staining were utilized to assess the septic shock model and myocardial function. Lactic acid, inflammatory markers (IL-1β, IL-6, and TNF-α), endothelial injure markers (SDC-1, HS and TM) and myocardial injury markers (CK, c-TNT and NT-pro BNP) were assessed using ELISA or biochemical kits. Additionally, the mechanisms of 654-1/654-2 were analyzed using RNA-seq and bioinformatics, and validated using western blotting and RT-PCR.

RESULTS

Administration of 654-1/654-2 significantly restored hemodynamics and improved myocardial and endothelial glycocalyx injury in septic shock rats. Furthermore, 654-1/654-2 dose-dependently reduced plasma levels of lactic acid, inflammatory cytokines, and markers of endothelial and myocardial injury. Analyses using RNA-seq, WB and RT-PCR techniques indicated that 654-1/654-2 could mitigate myocardial and endothelial injury by inhibiting the NF-κB and NLRP-3 pathways, and activating the PI3K-AKT pathway.

CONCLUSIONS

These findings demonstrated that 654-1/654-2 could alleviate myocardial damage in septic shock rats. Specifically, 654-1 inhibited the NF-κB/NLRP-3 pathway, whereas 654-2 promoted the PI3K-AKT pathway and inhibited the NF-κB pathway, effectively mitigating the inflammatory response and cell apoptosis.

NLRP3 inflammasome involves in the pathophysiology of sepsis-induced myocardial dysfunction by multiple mechanisms

Sepsis-induced myocardial dysfunction (SIMD) is one of the serious health-affecting problems worldwide. At present, the mechanisms of SIMD are still not clearly elucidated. The NOD-like receptor protein 3 (NLRP3) inflammasome has been assumed to be involved in the pathophysiology of SIMD by regulating multiple biological processes. NLRP3 inflammasome and its related signaling pathways might affect the regulation of inflammation, autophagy, apoptosis, and pyroptosis in SIMD. A few molecular specific inhibitors of NLRP3 inflammasome (e.g., Melatonin, Ulinastatin, Irisin, Nifuroxazide, and Ginsenoside Rg1, etc.) have been developed, which showed a promising anti-inflammatory effect in a cellular or animal model of SIMD. These experimental findings indicated that NLRP3 inflammasome could be a promising therapeutic target for SIMD treatment. However, the clinical translation of NLRP3 inhibitors for treating SIMD still requires robust in vivo and preclinical trials.

Research progress on the activation mechanism of NLRP3 inflammasome in septic cardiomyopathy

Sepsis is an uncontrolled host response to infection, resulting in a clinical syndrome involving multiple organ dysfunctions. Cardiac damage is the most common organ damage in sepsis. Uncontrolled inflammatory response is an important mechanism in the pathogenesis of septic cardiomyopathy (SCM). NLRP3 inflammasome promotes inflammatory response by controlling the activation of caspase-1 and the release of pro-inflammatory cytokines interleukin IL-1β and IL-18. The role of NLRP3 inflammasome has received increasing attention, but its activation mechanism and regulation of inflammation in SCM remain to be investigated.

Myo-inositol oxygenase (MIOX) accelerated inflammation in the model of infection-induced cardiac dysfunction by NLRP3 inflammasome

BACKGROUND

Cardiac dysfunction is an important component of multiple organ failure caused by sepsis, and an important cause of high mortality in patients with sepsis. Herein, we attempted to determine whether myo-inositol oxygenase (MIOX) has proinflammation enzyme in infection-induced cardiac dysfunction (IICD) and its underlying mechanism.

METHODS

Patients with IICD were collected by our hospital. A mouse model of IICD was induced into male db/db mice by cecal ligation and puncture (CLP). All mice were injected with 20 μL of LV-MIOX or LV-control short hairpin RNA using a 0.5-mL insulin syringe. On the second day, all mice were induced by CLP. H9C2 cell was also induced with lipopolysaccharide and adenosine triphosphate. Quantitative analysis of messenger RNAs (mRNAs) and gene microarray hybridization was used to analyze the mRNA expression levels. Enzyme-linked immunosorbent assay, immunofluorescence, and Western blot analysis were used to analyze the protein expression levels.

RESULTS

The serum expressions of MIOX mRNA level in patients with IICD were upregulated compared to normal healthy volunteers. MIOX promoted inflammation levels in the in vitro model of IICD. Si-MIOX inhibited inflammation levels in the in vitro model of IICD. MIOX accelerated inflammation and cardiac dysfunction in infection-induced mice. MIOX interacted with NLR family pyrin domain containing 3 (NLRP3) protein to reduce the degradation of NLRP3. The inhibition of MIOX reversed the effects of NLRP3 in the in vitro model of cardiac dysfunction.

CONCLUSIONS

Taken together, these findings demonstrate that MIOX accelerates inflammation in the model of IICD, which may be, at least in part, attributable to NLRP3 activity by the suppression of NLRP3 degradation in IICD.

Celastrol Treatment Ameliorated Acute Ischemic Stroke-Induced Brain Injury by Microglial Injury Inhibition and Nrf2/HO-1 Pathway Activations

Background

Stroke is the third main reason of mortality, which is the leading reason for adult disability in the globe. Poststroke inflammation is well known to cause acute ischemic stroke- (AIS-) induced brain injury (BI) exacerbation. Celastrol (CL) has exhibited anti-inflammatory activities in various inflammatory traits though underlying mechanisms remain unknown. So, the present investigation is aimed at studying CL protective mechanism against AIS-induced BI.

Methods

A mouse model regarding middle cerebral artery occlusion and an oxygen-glucose deprivation (OGD) cell model with or not CL treatment were constructed to study CL protective effects. NF-E2-related factor 2 (Nrf2) was then silenced in BV2 microglia cells (BV2) to study Nrf2 role regarding CL-mediated neuroprotection.

Results

The results showed that CL treatment suppressed AIS-induced BI by inhibiting NLRP3/caspase-1 pathway activations and induction of apoptosis and pyroptosis in vivo and in vitro. NLRP3/caspase-1 pathway blocking activation suppressed OGD-induced cell pyroptosis and apoptosis. Also, CL treatment reversed OGD-induced microglial injury by promoting Nrf2/heme oxygenase-1 (HO-1) pathway activations. Nrf2 downregulation reversed CL protective effects against OGD-induced microglial injury, pyroptosis, and apoptosis.

Conclusion

The findings advise that CL treatment ameliorated AIS-induced BI by inhibiting microglial injury and activating the Nrf2/HO-1 pathway.

The cardioprotective effects of perindopril in a model of polymicrobial sepsis: The role of radical oxygen species and the inflammation pathway

Mortality rates associated with myocardial dysfunction due to sepsis and septic shock are generally high across the world. The present study focused on the antioxidant and anti-inflammatory effects of perindopril (PER) for the purpose of preventing the adverse effects of sepsis on the myocardium and developing new alternatives in treatment. The control group received only saline solution via the oral route for 4 days. The second group underwent cecal ligation puncture (CLP), and the third underwent CLP and received PER (2 mg/kg). Rats in the third group received 2 mg/kg PER per oral (p.o.) from 4 days before induction of sepsis. Thiobarbituric acid reactive species (TBARS), total thiol (-SH), interleukin-1 beta (IL-1β), IL-6, 8-hydroxy-2'-deoxyguanosine (8-OHdG), and nuclear factor kappa B (NF-κB/p65) levels increased in the CLP groups. In contrast, PER (2 mg/kg) decreased the levels of biochemical parameters other than total-SH and decreased 8-OHdG, NF-κB/p65 immunopositivity in rat heart tissues. The data from this study show that impairment of the oxidant/antioxidant balance and inflammatory cytokine levels in favor of inflammation in heart tissue under septic conditions results in severe tissue damage. PER administration before sepsis was shown to exhibit antioxidant and anti-inflammatory properties by reducing these effects. This in turn increased the importance of PER as new evidence of its protective effects in heart tissue.

Intermedin1-53 Inhibits NLRP3 Inflammasome Activation by Targeting IRE1α in Cardiac Fibrosis

Intermedin (IMD), a paracrine/autocrine peptide, protects against cardiac fibrosis. However, the underlying mechanism remains poorly understood. Previous study reports that activation of nucleotide-binding oligomerization domain (NOD)-like receptor family pyrin domain containing 3 (NLRP3) inflammasome contributes to cardiac fibrosis. In this study, we aimed to investigate whether IMD mitigated cardiac fibrosis by inhibiting NLRP3. Cardiac fibrosis was induced by angiotensin II (Ang II) infusion for 2 weeks in rats. Western blot, real-time PCR, histological staining, immunofluorescence assay, RNA sequencing, echocardiography, and hemodynamics were used to detect the role and the mechanism of IMD in cardiac fibrosis. Ang II infusion resulted in rat cardiac fibrosis, shown as over-deposition of myocardial interstitial collagen and cardiac dysfunction. Importantly, NLRP3 activation and endoplasmic reticulum stress (ERS) were found in Ang II-treated rat myocardium. Ang II infusion decreased the expression of IMD and increased the expression of the receptor system of IMD in the fibrotic rat myocardium. IMD treatment attenuated the cardiac fibrosis and improved cardiac function. In addition, IMD inhibited the upregulation of NLRP3 markers and ERS markers induced by Ang II. In vitro, IMD knockdown by small interfering RNA significantly promoted the Ang II-induced cardiac fibroblast and NLRP3 activation. Moreover, silencing of inositol requiring enzyme 1 α (IRE1α) blocked the effects of IMD inhibiting fibroblast and NLRP3 activation. Pre-incubation with PKA pathway inhibitor H89 blocked the effects of IMD on the anti-ERS, anti-NLRP3, and anti-fibrotic response. In conclusion, IMD alleviated cardiac fibrosis by inhibiting NLRP3 inflammasome activation through suppressing IRE1α via the cAMP/PKA pathway.

Inhibition of the NLRP3/IL-1β axis protects against sepsis-induced cardiomyopathy

BACKGROUND

Septic cardiomyopathy worsens the prognosis of critically ill patients. Clinical data suggest that interleukin-1β (IL-1β), activated by the NLRP3 inflammasome, compromises cardiac function. Whether or not deleting Nlrp3 would prevent cardiac atrophy and improve diastolic cardiac function in sepsis was unclear. Here, we investigated the role of NLRP3/IL-1β in sepsis-induced cardiomyopathy and cardiac atrophy.

METHODS

Male Nlrp3 knockout (KO) and wild-type (WT) mice were exposed to polymicrobial sepsis by caecal ligation and puncture (CLP) surgery (KO, n = 27; WT, n = 33) to induce septic cardiomyopathy. Sham-treated mice served as controls (KO, n = 11; WT, n = 16). Heart weights and morphology, echocardiography and analyses of gene and protein expression were used to evaluate septic cardiomyopathy and cardiac atrophy. IL-1β effects on primary and immortalized cardiomyocytes were investigated by morphological and molecular analyses. IonOptix and real-time deformability cytometry (RT-DC) analysis were used to investigate functional and mechanical effects of IL-1β on cardiomyocytes.

RESULTS

Heart morphology and echocardiography revealed preserved systolic (stroke volume: WT sham vs. WT CLP: 33.1 ± 7.2 μL vs. 24.6 ± 8.7 μL, P < 0.05; KO sham vs. KO CLP: 28.3 ± 8.1 μL vs. 29.9 ± 9.9 μL, n.s.; P < 0.05 vs. WT CLP) and diastolic (peak E wave velocity: WT sham vs. WT CLP: 750 ± 132 vs. 522 ± 200 mm/s, P < 0.001; KO sham vs. KO CLP: 709 ± 152 vs. 639 ± 165 mm/s, n.s.; P < 0.05 vs. WT CLP) cardiac function and attenuated cardiac (heart weight-tibia length ratio: WT CLP vs. WT sham: -26.6%, P < 0.05; KO CLP vs. KO sham: -3.3%, n.s.; P < 0.05 vs. WT CLP) and cardiomyocyte atrophy in KO mice during sepsis. IonOptix measurements showed that IL-1β decreased contractility (cell shortening: IL-1β: -15.4 ± 2.3%, P < 0.001 vs. vehicle, IL-1RA: -6.1 ± 3.3%, P < 0.05 vs. IL-1β) and relaxation of adult rat ventricular cardiomyocytes (time-to-50% relengthening: IL-1β: 2071 ± 225 ms, P < 0.001 vs. vehicle, IL-1RA: 564 ± 247 ms, P < 0.001 vs. IL-1β), which was attenuated by an IL-1 receptor antagonist (IL-1RA). RT-DC analysis indicated that IL-1β reduced cardiomyocyte size (P < 0.001) and deformation (P < 0.05). RNA sequencing showed that genes involved in NF-κB signalling, autophagy and lysosomal protein degradation were enriched in hearts of septic WT but not in septic KO mice. Western blotting and qPCR disclosed that IL-1β activated NF-κB and its target genes, caused atrophy and decreased myosin protein in myocytes, which was accompanied by an increased autophagy gene expression. These effects were attenuated by IL-1RA.

CONCLUSIONS

IL-1β causes atrophy, impairs contractility and relaxation and decreases deformation of cardiomyocytes. Because NLRP3/IL-1β pathway inhibition attenuates cardiac atrophy and cardiomyopathy in sepsis, it could be useful to prevent septic cardiomyopathy.

Hsp22 ameliorates lipopolysaccharide-induced myocardial injury by inhibiting inflammation, oxidative stress, and apoptosis

Sepsis-induced myocardial dysfunction (SIMD) is ubiquitous in septic shock patients and is associated with high morbidity and mortality rates. Heat shock protein 22 (Hsp22), which belongs to the small HSP family of proteins, is involved in several biological functions. However, the function of Hsp22 in lipopolysaccharide (LPS)-induced myocardial injury is not yet established. This study was aimed at investigating the underlying mechanistic aspects of Hsp22 in myocardial injury induced by LPS. In this study, following the random assignment of male C57BL/6 mice into control, LPS-treated, and LPS + Hsp22 treated groups, relevant echocardiograms and staining were performed to scrutinize the cardiac pathology. Plausible mechanisms were proposed based on the findings of the enzyme-linked immunosorbent assay and Western blotting assay. A protective role of Hsp22 against LPS-induced myocardial injury emerged, as evidenced from decreased levels of creatinine kinase-MB (CK-MB), lactate dehydrogenase (LDH), and enhanced cardiac function. The post-LPS administration-caused spike in inflammatory cytokines (IL-1β, IL-6, TNF-α and NLRP3) was attenuated by the Hsp22 pre-treatment. In addition, superoxide dismutase (SOD) activity and B-cell lymphoma-2 (Bcl2) levels were augmented by Hsp22 treatment resulting in lowering of LPS-induced oxidative stress and cardiomyocyte apoptosis. In summary, the suppression of LPS-induced myocardial injury by Hsp22 overexpression via targeting of inflammation, oxidative stress, and apoptosis in cardiomyocytes paves the way for this protein to be employed in the therapy of SIMD.

Emodin alleviates LPS-induced myocardial injury through inhibition of NLRP3 inflammasome activation

Myocardial injury and cardiovascular dysfunction are serious consequences of sepsis and contribute to high mortality. Currently, the pathogenesis of myocardial injury in sepsis is still unclear, and therapeutic approaches are limited. In this study, we investigated the protective effect of emodin on septic myocardial injury and the underlying mechanism. Lipopolysaccharide (LPS)-induced C57BL/6 mice and cardiomyocytes were used as models of sepsis in vivo and in vitro, respectively. The results showed that emodin alleviated cardiac dysfunction, myocardial injury and improved survival rate in LPS-induced septic mice. Emodin attenuated the levels of inflammatory cytokines and cardiac inflammation induced by LPS. Emodin reduced NOD-like receptor protein 3 (NLRP3) and Gasdermin D (GSDMD) expression in the heart tissue of LPS-induced septic mice. In vitro, emodin alleviated LPS-induced cell injury and inflammation in cardiomyocytes by inhibiting NLRP3 inflammasome activation. In addition, an NLRP3 inhibitor was used to further confirm the function of the NLRP3 inflammasome in LPS-induced myocardial injury. Taken together, our findings suggest that emodin improves LPS-induced myocardial injury and cardiac dysfunction by alleviating the inflammatory response and cardiomyocyte pyroptosis by inhibiting NLRP3 inflammasome activation, which provides a feasible strategy for preventing and treating myocardial injury in sepsis.

Adrenomedullin 2 attenuates LPS-induced inflammation in microglia cells by receptor-mediated cAMP-PKA pathway

Inflammation plays a critical role in the development of neurodegenerative diseases. Adrenomedullin 2 (AM2), a member of the calcitonin gene-related peptide family, has been known to have anti-inflammatory effects. Here, we evaluated the anti-inflammatory effects of AM2 in LPS-activated microglia and BV2 cells. The endogenous mRNA and protein expressions of AM2, calcitonin receptor-like receptor (CLR), receptor activity-modifying proteins (RAMPs) including RAMP1, RAMP2 and RAMP3 and the production of inflammatory mediators including tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS) were detected by RT-PCR and Western blot. Our results revealed that LPS (1 μg/mL) significantly stimulated CLR, RAMP1, RAMP2 and RAMP3 protein expressions in BV2 microglia cells, but AM2 had a significant decrease. However, the mRNA levels of AM2, CLR, and RAMP1/2/3 were all markedly increased. LPS also induced obvious increases in mRNA and protein levels of the inflammatory mediators (TNF-α, IL-1β, COX2 and iNOS). More importantly, AM2 (10 nM) administration effectively inhibited the mRNA and protein expressions of these mediators induced by LPS and increased the cAMP content in LPS-stimulated BV2 cells. Furthermore, the antagonism with AM2 receptor antagonist IMD17-47, adrenomedullin (AM) receptor antagonist by AM22-52 or the inhibition of protein kinase A (PKA) activation by P1195 effectively prevented the inhibitory role of AM2 in LPS-induced production of the above inflammatory mediators. In conclusion, AM2 inhibits LPS-induced inflammation in BV2 microglia cells that may be mainly through AM receptor-mediated cAMP-PKA pathway. Our results indicate AM2 plays an important protective role in microglia inflammation, suggesting therapeutic potential for AM2 in neuroinflammation diseases caused by activated microglia.

Shikonin Ameliorates LPS-Induced Cardiac Dysfunction by SIRT1-Dependent Inhibition of NLRP3 Inflammasome

Shikonin (SHI) is an anti-inflammatory agent extracted from natural herbs. It is still unknown whether SHI ameliorates lipopolysaccharide (LPS)-induced cardiac dysfunction. This study aims to explore the protective effects of SHI on LPS-induced myocardial injury and its mechanism. The LPS-induced cardiac dysfunction mouse model was employed to investigate the protective effects of SHI. In the present study, we found that SHI treatment improved the survival rate and cardiac function and remarkably ameliorated the release of inflammatory cytokines and macrophage infiltration in heart tissue of LPS-treated mice. SHI also reduced lactate dehydrogenase (LDH) and cardiac troponin (cTn) release, cell inflammation, and apoptosis in LPS plus adenosine triphosphate (ATP)-treated H9c2 cells. In addition, SHI significantly upregulated silent information regulator 1 (SIRT1) expression and suppressed the upregulation of NOD-like receptor protein 3 (NLRP3), cleaved caspase-1, and caspase-1 activity in heart tissues induced by LPS. Meanwhile, we got the same results in LPS plus ATP-treated H9c2 cells in vitro. Further, SIRT1 inhibitor or siRNA partially blocked SHI-mediated upregulation of SIRT1 expression and downregulation of NLRP3, cleaved caspase-1, and caspase-1 activity in heart tissues induced by LPS. Therefore, we conclude that SHI ameliorates LPS-induced cardiac dysfunction by inhibiting SIRT1-dependent activation of NLRP3 inflammasomes and might be a promising therapeutic strategy for the treatment of LPS-induced cardiac dysfunction.

Inhibition of Sphingosine Kinase 1 Attenuates Sepsis-induced Microvascular Leakage via Inhibiting Macrophage NLRP3 Inflammasome Activation in Mice

BACKGROUND

Sepsis is the overwhelming inflammatory response to infection, in which nucleotide-binding oligomerization domain-like receptor containing pyrin domain 3 (NLRP3) inflammasome plays a crucial role. Shingosine-1-phosphate is reported to evoke NLRP3 inflammasome activation. Sphingosine kinase 1 (SphK1) is the major kinase that catalyzes bioactive lipid shingosine-1-phosphate formation and its role in sepsis remains uncertain. The authors hypothesize that SphK1 elicits NLRP3 inflammasome activation and exacerbates sepsis.

METHODS

Peripheral blood mononuclear cells were isolated from septic patients and healthy volunteers to measure messenger RNA (mRNA) expression. In mice, sepsis was induced by cecal ligation and puncture. Bone marrow-derived macrophages were prepared from C57BL/6J wild-type, Casp1, Nlrp3 and SphK1 mice. PF-543 was used as the specific inhibitor of SphK1. Mortality, peripheral perfusion, lung Evan's blue dye index, lung wet/dry ratio, lung injury score, lung myeloperoxidase activity, NLRP3 activation, and function of endothelial adherens junction were measured.

RESULTS

SphK1 mRNA expression was higher in cells from septic patients versus healthy volunteers (septic patients vs. healthy volunteers: 50.9 ± 57.0 fold change vs. 1.2 ± 0.1 fold change, P < 0.0001) and was positively correlated with IL-1β mRNA expression in these cells (r = 0.537, P = 0.012) and negatively correlated with PaO2/FIO2 ratios (r = 0.516, P = 0.017). In mice that had undergone cecal ligation and puncture, the 5-day mortality was 30% in PF-543-treated group and 80% in control group (n = 10 per group, P = 0.028). Compared with controls, PF-543-treated mice demonstrated improved peripheral perfusion and alleviated extravascular Evan's blue dye effusion (control vs. PF-543: 25.5 ± 3.2 ng/g vs. 18.2 ± 1.4 ng/g, P < 0.001), lower lung wet/dry ratio (control vs. PF-543: 8.0 ± 0.2 vs. 7.1 ± 0.4, P < 0.0001), descending lung injury score, and weaker lung myeloperoxidase activity. Inhibition of SphK1 suppressed caspase-1 maturation and interleukin-1β release through repressing NLRP3 inflammasome activation, and subsequently stabilized vascular endothelial cadherin through suppressing interleukin-1β-evoked Src-mediated phosphorylation of vascular endothelial cadherin.

CONCLUSIONS

SphK1 plays a crucial role in NLRP3 inflammasome activation and contributes to lung injury and mortality in mice polymicrobial sepsis.

Interleukin-35 pretreatment attenuates lipopolysaccharide-induced heart injury by inhibition of inflammation, apoptosis and fibrotic reactions

Previous studies have demonstrated that targeting inflammation is a promising strategy for treating lipopolysaccharide (LPS)-induced sepsis and related heart injury. Interleukin-35 (IL-35), which consists of two subunits, Epstein-Barr virus-induced gene 3 (EBI3) and p35, is an immunosuppressive cytokine of the IL-12 family and exhibits strong anti-inflammatory activity. However, the role of IL-35 in LPS-induced heart injury reains obscure. In this study, we explored the role of IL-35 in heart injury induced by LPS and its potential mechanisms. Mice were treated with a plasmid encoding IL-35 (pIL-35) and then injected intraperitoneally (ip) with LPS (10 mg/kg). Cardiac function was assessed by echocardiography 12 h later. LPS apparently decreased the expression of EBI3 and p35 and caused cardiac dysfunction and pathological changes, which were significantly improved by pIL-35 pretreatment. Moreover, pIL-35 pretreatment significantly decreased the levels of cardiac proinflammatory cytokines including TNF-α, IL-6, and IL-1β, and the NLRP3 inflammasome. Furthermore, decreased number of apoptotic myocardial cells, increased BCL-2 levels and decreased BAX levels inhibited apoptosis, and LPS-induced upregulation of the expression of cardiac pro-fibrotic genes (MMP2 and MMP9) and fibrotic factor (Collagen type I) was inhibited. Further investigation indicated that pIL-35 pretreatment might suppressed the activation of the cardiac NF-κBp65 and TGF-β1/Smad2/3 signaling pathways in LPS-treated mice. Similar cardioprotective effects of IL-35 pretreatment were observed in mouse myocardial fibroblasts challenged with LPS in vitro. In summary, IL-35 pretreatment can attenuate cardiac inflammation, apoptosis, and fibrotic reactions induced by LPS, implicating IL-35 as a promising therapeutic target in sepsis-related cardiac injury.

Intermedin alleviates pathological cardiac remodeling by upregulating klotho

Cardiac remodeling is accompanied by cardiac hypertrophy, fibrosis, dysfunction, and eventually leading to heart failure. Intermedin (IMD), as a paracrine/autocrine peptide, has a protective effect in cardiovascular diseases. In this study, we elucidated the role and the underlying mechanism of IMD in pathological remodeling. Pathological remodeling mouse models were induced by abdominal aorta constriction for 4 weeks or angiotensin II (Ang II) infusion for 2 weeks in wildtype, IMD-overexpression, IMD-knockout and klotho-knockdown mice. Western blot, real-time PCR, histological staining, echocardiography and hemodynamics were used to detect the role of IMD in cardiac remodeling. Cardiac hypertrophy, fibrosis and dysfunction were significantly aggravated in IMD-knockout mice versus wildtype mice, and the expression of klotho was downregulated. Conversely, cardiac remodeling was alleviated in IMD-overexpression mice, and the expression of klotho was upregulated. Hypertension induced by Ang II infusion rather than abdominal aorta constriction was mitigated by IMD. However, the cardioprotective effect of IMD was blocked in klotho-knockdown mice. Similar results were found in cultured neonatal rat cardiomyocytes, which was pretreated with IMD before Ang II stimulation. Mechanistically, IMD inhibited the phosphorylation of Ca²⁺/calmodulin-dependent protein kinase II (CaMKII) and the activity of calcineurin to protect against cardiac hypertrophy through upregulating klotho in vivo and in vitro. Furthermore, peroxisome proliferator-activated receptor γ (PPARγ) might mediate IMD upregulating klotho. In conclusion, pathological remodeling may be alleviated by endogenous IMD, which inhibits the expression of calcineurin and p-CaMKII by upregulating klotho via the PPARγ pathway. It suggested that IMD might be a therapeutic target for heart disease.

Role of TXNIP/NLRP3 in sepsis-induced myocardial dysfunction

Myocardial injury is one of the main symptoms of sepsis. However, the mechanisms underlying sepsis-induced myocardial dysfunction remain unclear. In the present study, the concentration of cardiac troponin T (CTnT) in serum was measured using an enzyme-linked immunosorbent assay kit. The levels of interleukin (IL)-1β and IL-18 were assessed by reverse transcription-quantitative polymerase chain reaction (RT-qPCR) analysis and the level of malondialdehyde (MDA) was determined using a corresponding kit. Myocardial pathology was analyzed via hematoxylin and eosin staining. RT-qPCR analysis and western blotting and/or immunohistochemistry were used to quantify the expression levels of thioredoxin-interacting protein (TNXIP), NOD-like receptor pyrin domain containing 3 (NLRP3), cleaved caspase-1, caspase-1, catalase and manganese-superoxide dismutase (MnSOD). The viability of cells was determined using a cell counting kit-8. Apoptosis and reactive oxygen species (ROS) were examined using flow cytometry. Models of sepsis-induced myocardial injury were successfully established; evidence included increases in the levels of CTnT, IL-1β, IL-18 and MDA and myocardial tissue damage in vivo, and decreased cell viability and improvements in IL-1β and IL-18 in vitro. The levels of TXNIP, NLRP3 and cleaved caspase-1 were upregulated in the sepsis models. Small interfering RNA targeting TNXNIP (siTXNIP) increased cell viability, reduced the apoptotic rate and attenuated the release of IL-1β and IL-18. The levels of TXNIP, NLRP3 and cleaved caspase-1 and production of ROS were suppressed by siTXNIP, accompanied by increases in catalase and MnSOD. TXNIP/NLRP3 serves an important role in the development of sepsis-induced myocardial damage.

α-Mangostin suppresses NLRP3 inflammasome activation via promoting autophagy in LPS-stimulated murine macrophages and protects against CLP-induced sepsis in mice

BACKGROUND

The major mechanism of sepsis is immunosuppression caused by host response dysfunction. It has been found that α-Mangostin (α-M) is a potential candidate as a treatment for multiple inflammatory and immune disorders. To date, the role of α-M in host response during sepsis remains unexplored.

METHODS AND RESULTS

Herein, we examined the effect of α-M on macrophages-mediated host response in the presence of lipopolysaccharide (LPS), and the vital organ function, inflammatory response, and survival rate in septic mice. In murine peritoneal macrophages, α-M induced autophagy and then inhibited LPS-stimulated NLRP3 inflammasome activation, as well as interleukin-1β (IL-1β) production. Moreover, α-M improved phagocytosis and killing of macrophages, and increased M2 macrophages numbers after LPS stimulation. Furthermore, in vivo experiment suggested that α-M reduced serum levels of tumor necrosis factor-α (TNF-α), interferon-γ (IFN-γ), IL-1β, alanine transaminase (ALT), aspartate transaminase (AST), and creatinine (Cr), whilst increased that of interleukin-10 (IL-10) in caecal ligation and puncture (CLP) mice.

CONCLUSION

Taken together, these findings showed that α-M-mediated macrophages autophagy contributed to NLRP3 inflammasome inactivation and α-M exerted organ protection in septic mice.

NLRP3 deficiency accelerates pressure overload-induced cardiac remodeling via increased TLR4 expression

NLRP3, a member of the nucleotide-binding oligomerization domain (NOD)-like receptor family, is involved in cardiac inflammation. However, the functional role of NLRP3 in cardiac remodeling is not clear. To investigate the roles of NLRP3 in pressure overload-induced cardiac remodeling, NLRP3 knockout and wild-type mice were subjected to aortic banding to induce cardiac remodeling. The data showed that NLRP3 expression was downregulated in the remodeling process. NLRP3 deficiency accelerated cardiac hypertrophy, fibrosis, and inflammation responses with deteriorating cardiac dysfunction in the pressure overload-induced cardiac remodeling mouse model. Neonatal rat cardiomyocytes were isolated and stimulated with phenylephrine (PE). We identified NLRP3 as a negative regulator of cardiomyocyte remodeling in PE-stimulated cardiomyocyte remodeling using adenovirus-NLRP3 and NLRP3 siRNA. Mechanistically, we found that the expression of Toll-like receptor (TLR) 4 was upregulated in NLRP3-deficient mouse hearts and PE-stimulated cardiomyocytes. NLRP3 knockout mice subjected to a TLR4 inhibitor revealed a relieved cardiac remodeling response with improved cardiac dysfunction. Our data suggested that NLRP3 could be a therapeutic target for cardiac remodeling and heart failure. KEY MESSAGES: NLRP3 expression was downregulated in the remodeling process. NLRP3 deficiency accelerated pressure overload-induced cardiac remodeling. NLRP3 acted as a negative regulator of cardiomyocyte remodeling via downregulating TLR4.