Faculty Opinions recommendation of Caspase-11 Requires the Pannexin-1 Channel and the Purinergic P2X7 Pore to Mediate Pyroptosis and Endotoxic Shock.

Abstract Background Inflammation and cytokine release have been implicated in the pathogenesis of chronic heart failure (CHF). Of particular interest, Canakinumab, a monoclonal antibody against interleukin-1b (IL-1β), had provided benefit against cardiovascular events, suggesting that blockade of IL-1β secretion and signaling might be a promising new therapeutic target. Although, recent studies have provided evidence that inflammasome activation is the main contributor to IL-1β maturation, the role of inflammasome activation in CHF remains unknown. Objective Therefore, we aimed to assess inflammasome activation in myocardial samples from end-stage failing hearts. Methods Inflammasome activation was assessed by immunoblotting in left ventricular myocardial specimens harvested from patients with end-stage CHF. Furthermore, immunoblot measurements were also performed on translational animal models of CHF (e.g. rat models of permanent coronary artery ligation and transverse aortic constriction). Left ventricular monocyte and macrophage infiltration was detected by immunohistochemistry. To investigate the molecular background of inflammasome activation, a series of cell culture experiments were performed on AC16 human cardiomyocytes and THP-1 human monocytic cell lines. Results Out of the 4 major inflammasome sensors tested, expression of the inflammasome protein absent in melanoma 2 (AIM2) and NLR family CARD domain-containing protein 4 (NLRC4) increased in human CHF while the NLRP1 and NLRP3 (NLR family, pyrin domain containing 1 and 3) inflammasome showed no change. A similar expression pattern in AIM2 and NLRC4 was also noted in CHF animal models. Furthermore, robust infiltration of Iba1+ monocytes/macrophages was observed in human failing hearts as well as in different animal models of CHF. In vitro AIM2 inflammasome activation, as induced by transfection with double-stranded DNA [poly(deoxyadenylic-deoxythymidylic)] was reduced significantly by the pharmacological blockade of pannexin-1 channels. Conclusions AIM2 and NLRC4 inflammasome activation might contribute to chronic inflammation in CHF. Our findings suggest that pannexin-1 channels might be a promising novel target to reduce inflammasome activation. Funding Acknowledgement Type of funding source: Public grant(s) – National budget only. Main funding source(s): NVKP_16-1-2016-0017

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Deacetylation as a receptor-regulated direct activation switch for pannexin channels

Nature Communications ◽

10.1038/s41467-021-24825-y ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Yu-Hsin Chiu ◽

Christopher B. Medina ◽

Catherine A. Doyle ◽

Ming Zhou ◽

Adishesh K. Narahari ◽

...

Keyword(s):

G Protein Coupled Receptors ◽

Activation Mechanism ◽

Lysine Acetylation ◽

Intercellular Signaling ◽

Histone Deacetylase 6 ◽

Pannexin 1 ◽

Lysine Deacetylase ◽

Channel Opening ◽

Lysine Residues ◽

G Protein Coupled

AbstractActivation of Pannexin 1 (PANX1) ion channels causes release of intercellular signaling molecules in a variety of (patho)physiological contexts. PANX1 can be activated by G protein-coupled receptors (GPCRs), including α1-adrenergic receptors (α1-ARs), but how receptor engagement leads to channel opening remains unclear. Here, we show that GPCR-mediated PANX1 activation can occur via channel deacetylation. We find that α1-AR-mediated activation of PANX1 channels requires Gαq but is independent of phospholipase C or intracellular calcium. Instead, α1-AR-mediated PANX1 activation involves RhoA, mammalian diaphanous (mDia)-related formin, and a cytosolic lysine deacetylase activated by mDia – histone deacetylase 6. HDAC6 associates with PANX1 and activates PANX1 channels, even in excised membrane patches, suggesting direct deacetylation of PANX1. Substitution of basally-acetylated intracellular lysine residues identified on PANX1 by mass spectrometry either prevents HDAC6-mediated activation (K140/409Q) or renders the channels constitutively active (K140R). These data define a non-canonical RhoA-mDia-HDAC6 signaling pathway for GαqPCR activation of PANX1 channels and uncover lysine acetylation-deacetylation as an ion channel silencing-activation mechanism.

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Fisetin inhibits lipopolysaccharide-induced inflammatory response by activating β-catenin, leading to a decrease in endotoxic shock

Scientific Reports ◽

10.1038/s41598-021-87257-0 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Ilandarage Menu Neelaka Molagoda ◽

Jayasingha Arachchige Chathuranga C Jayasingha ◽

Yung Hyun Choi ◽

Rajapaksha Gedara Prasad Tharanga Jayasooriya ◽

Chang-Hee Kang ◽

...

Keyword(s):

Glycogen Synthase ◽

Endotoxic Shock ◽

Inflammatory Activity ◽

Prostaglandin E ◽

Necrosis Factor Alpha ◽

Zebrafish Larvae ◽

Proinflammatory Mediators ◽

Tnf Α ◽

Anti Inflammatory ◽

Gsk 3Β

AbstractFisetin is a naturally occurring flavonoid that possesses several pharmacological benefits including anti-inflammatory activity. However, its precise anti-inflammatory mechanism is not clear. In the present study, we found that fisetin significantly inhibited the expression of proinflammatory mediators, such as nitric oxide (NO) and prostaglandin E2 (PGE2), and cytokines, such as interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-α), in lipopolysaccharide (LPS)-stimulated RAW 264.7 macrophages. Additionally, fisetin attenuated LPS-induced mortality and abnormalities in zebrafish larvae and normalized the heart rate. Fisetin decreased the recruitment of macrophages and neutrophils to the LPS-microinjected inflammatory site in zebrafish larvae, concomitant with a significant downregulation of proinflammatory genes, such as inducible NO synthase (iNOS), cyclooxygenase-2a (COX-2a), IL-6, and TNF-α. Fisetin inhibited the nuclear localization of nuclear factor-kappa B (NF-κB), which reduced the expression of pro-inflammatory genes. Further, fisetin inactivated glycogen synthase kinase 3β (GSK-3β) via phosphorylation at Ser9, and inhibited the degradation of β-catenin, which consequently promoted the localization of β-catenin into the nucleus. The pharmacological inhibition of β-catenin with FH535 reversed the fisetin-induced anti-inflammatory activity and restored NF-κB activity, which indicated that fisetin-mediated activation of β-catenin results in the inhibition of LPS-induced NF-κB activity. In LPS-microinjected zebrafish larvae, FH535 promoted the migration of macrophages to the yolk sac and decreased resident neutrophil counts in the posterior blood island and induced high expression of iNOS and COX-2a, which was accompanied by the inhibition of fisetin-induced anti-inflammatory activity. Altogether, the current study confirmed that the dietary flavonoid, fisetin, inhibited LPS-induced inflammation and endotoxic shock through crosstalk between GSK-3β/β-catenin and the NF-κB signaling pathways.

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