TRPC channels blockade abolishes endotoxemic cardiac dysfunction by hampering intracellular inflammation and Ca2+ leakage.

Intracellular Ca2+ dysregulation is a key marker in septic cardiac dysfunction; however, regulation of the classic Ca2+ regulatory modules cannot successfully abolish this symptom. Here we show that the knockout of transient receptor potential canonical (TRPC) channel isoforms TRPC1 and TRPC6 can ameliorate LPS-challenged heart failure and prolong survival in mice. The LPS-triggered Ca2+ release from the endoplasmic reticulum both in cardiomyocytes and macrophages is significantly inhibited by Trpc1 or Trpc6 knockout. Meanwhile, TRPC's molecular partner - calmodulin - is uncoupled during Trpc1 or Trpc6 deficiency and binds to TLR4's Pococurante site and atypical isoleucine-glutamine-like motif to block the inflammation cascade. Blocking the C-terminal CaM/IP3R binding domain in TRPC with chemical inhibitor could obstruct the Ca2+ leak and TLR4-mediated inflammation burst, demonstrating a cardioprotective effect in endotoxemia and polymicrobial sepsis. Our findings provide insight into the pathogenesis of endotoxemic cardiac dysfunction and suggest a novel approach for its treatment.

PFKFB3 promotes endotoxemia-induced myocardial dysfunction through inflammatory signaling and apoptotic induction.

Cardiac dysfunction is a vital complication during endotoxemia (ETM). Accumulating evidence suggests that enhanced glycolytic metabolism promotes inflammatory and myocardial diseases. In this study, we performed deep mRNA sequencing analysis on the hearts of control and lipopolysaccharide (LPS)-challenged mice (40 mg/kg, i.p.) and identified that the glycolytic enzyme, 6-phosphofructo-2-kinase (PFK-2)/fructose-2,6-bisphosphatase 3 (PFKFB3) might play an indispensable role in ETM-induced cardiac damage. Quantitative real-time PCR validated the transcriptional upregulation of PFKFB3 in the myocardium of LPS-challenged mice and immunoblotting and immunostaining assays confirmed that LPS stimulation markedly increased the expression of PFKFB3 at the protein level both in vivo and in vitro. The potent antagonist 3-(3pyridinyl)-1-(4-pyridinyl)-2-propen-1-one (3PO) was used to block PFKFB3 activity in vivo (50 mg/kg, i.p.) and in vitro (10 µM). Echocardiographic analysis and TUNEL staining showed that 3PO significantly alleviated LPS-induced cardiac dysfunction and apoptotic injury in vivo. 3PO also suppressed the LPS-induced secretion of tumor necrosis factor-α, interleukin (IL)-1ß, IL-6 and lactate in the serum, in addition to lactate in the myocardium. PFKFB3 inhibition also diminished the nuclear translocation and phosphorylation of transcription factor nuclear factor-κB (NF-κB) in both adult cardiomyocytes and HL-1 cells. Furthermore, immunoblotting analysis showed that 3PO inhibited LPS-induced apoptotic induction in cardiomyocytes. Taken together, these findings demonstrate that PFKFB3 participates in LPS-induced cardiac dysfunction via mediating inflammatory and apoptotic signaling pathway.