-Atrial fibrillation (AF) is frequently associated with enhanced inflammatory response. The "NACHT, LRR and PYD domain containing protein 3" (NLRP3)-inflammasome mediates caspase-1 activation and interleukin-1β release in immune cells, but is not known to play a role in cardiomyocytes (CMs). Here, we assessed the role of CM NLRP3-inflammasome in AF. -NLRP3-inflammasome activation was assessed by immunoblot in atrial whole-tissue lysates and CMs from patients with paroxysmal (pAF) or long-standing persistent (chronic) AF (cAF). To determine whether CM-specific activation of NLPR3 is sufficient to promote AF, a CM-specific knock-in mouse model expressing constitutively active NLRP3 (CM-KI) was established. In vivo electrophysiology was used to assess atrial arrhythmia vulnerability. To evaluate the mechanism of AF, electrical activation pattern, Ca spark frequency (CaSF), atrial effective refractory period (AERP), and morphology of atria were evaluated in CM-KI mice and WT littermates. -NLRP3-inflammasome activity was increased in atrial CMs of pAF and cAF patients. CM-KI mice developed spontaneous premature atrial contractions and inducible AF, which was attenuated by a specific NLRP3-inflammasome inhibitor, MCC950. CM-KI mice exhibited ectopic activity, abnormal sarcoplasmic-reticulum Ca-release, AERP shortening and atrial hypertrophy. Adeno-associated virus subtype-9 mediated CM-specific knockdown of suppressed AF development in CM-KI mice. Finally, genetic inhibition of prevented AF development in CREM transgenic mice, a well-characterized mouse model of spontaneous AF. -Our study establishes a novel pathophysiological role for CM NLRP3-inflammasome signaling with a mechanistic link to the pathogenesis of AF, and establishes inhibition of NLRP3 as a potential novel AF-therapy approach.

Diabetic cardiomyopathy is a common complication in patients with diabetes and is associated with underlying chronic inflammation and cardiac cell death, subsequently leading to heart failure (HF). ELAV-like protein 1 (ELAVL1) plays a critical role in the progression of inflammation and HF. However the role of ELAVL-1 in inflammation induced cardiac cell death (pyroptosis) under hyper glycemic condition remains elusive. Our data demonstrates that ELAVL1 expression augmented with a concomitant increase in caspase-1 and IL-1 beta expression in human hearts and human ventricular cardiomyocytes under hyperglycemic condition. Furthermore, ELAVL1 knockdown abrogates TNF-α induced canonical pyroptosis via NLRP3, caspase-1 and IL-1beta suppression. Bioinformatics analysis and target validation assays showed that miR-9 directly targets ELAVL1. Interestingly, miRNA-9 expression significantly reduced in high glucose treated cardiomyocytes and in human diabetic hearts. Inhibition of miR-9 upregulates ELAVL1 expression and activates caspase-1. Alternatively, treatment with miR-9 mimics attenuates hyperglycemia-induced ELAVL1 and inhibits cardiomyocyte pyroptosis. Taken together our study highlights the potential therapeutic implications of targeting miR-9/ELAVL1 in preventing cardiomyocyte cell loss during HF in diabetics.

Translation is a fundamental cellular process, and its dysregulation can contribute to human diseases such as cancer. During translation initiation the eukaryotic initiation factor 2 (eIF2) forms a ternary complex (TC) with GTP and the initiator methionyl-tRNA (tRNAi), mediating ribosomal recruitment of tRNAi. Limiting TC availability is a central mechanism for triggering the integrated stress response (ISR), which suppresses global translation in response to various cellular stresses, but induces specific proteins such as ATF4. This study shows that OLA1, a member of the ancient Obg family of GTPases, is an eIF2-regulatory protein that inhibits protein synthesis and promotes ISR by binding eIF2, hydrolyzing GTP, and interfering with TC formation. OLA1 thus represents a novel mechanism of translational control affecting de novo TC formation, different from the traditional model in which phosphorylation of eIF2α blocks the regeneration of TC. Depletion of OLA1 caused a hypoactive ISR and greater survival in stressed cells. In vivo, OLA1-knockdown rendered cancer cells deficient in ISR and the downstream proapoptotic effector, CHOP, promoting tumor growth and metastasis. Our work suggests that OLA1 is a novel translational GTPase and plays a suppressive role in translation and cell survival, as well as cancer growth and progression.

Abstract4-Hydroxynonenal (4-HNE) has been suggested to be involved in stress-induced signaling for apoptosis. In present studies, we have examined the effects of 4-HNE on the intrinsic apoptotic pathway associated with p53 in human retinal pigment epithelial (RPE and ARPE-19) cells. Our results show that 4-HNE causes induction, phosphorylation, and nuclear accumulation of p53 which is accompanied with down regulation of MDM2, activation of the pro-apoptotic p53 target genes viz. p21 and Bax, JNK, caspase3, and onset of apoptosis in treated RPE cells. Reduced expression of p53 by an efficient silencing of the p53 gene resulted in a significant resistance of these cells to 4-HNE-induced cell death. The effects of 4-HNE on the expression and functions of p53 are blocked in GSTA4-4 over expressing cells indicating that 4-HNE-induced, p53-mediated signaling for apoptosis is regulated by GSTs. Our results also show that the induction of p53 in tissues of mGsta4 (-/-) mice correlate with elevated levels of 4-HNE due to its impaired metabolism. Together, these studies suggest that 4-HNE is involved in p53-mediated signaling in in vitro cell cultures as well as in vivo that can be regulated by GSTs.