Baroreflex control of cardiac contraction (positive inotropy) through sympathetic nerve activation is important for cardiocirculatory homeostasis. Transient receptor potential canonical subfamily (TRPC) channels are responsible for α1-adrenoceptor (α1AR)-stimulated cation entry and their upregulation is associated with pathological cardiac remodeling. Whether TRPC channels participate in physiological pump functions remains unclear. We demonstrate that TRPC6-specific Zn2+ influx potentiates β-adrenoceptor (βAR)-stimulated positive inotropy in rodent cardiomyocytes. Deletion of trpc6 impairs sympathetic nerve–activated positive inotropy but not chronotropy in mice. TRPC6-mediated Zn2+ influx boosts α1AR-stimulated βAR/Gs-dependent signaling in rat cardiomyocytes by inhibiting β-arrestin-mediated βAR internalization. Replacing two TRPC6-specific amino acids in the pore region with TRPC3 residues diminishes the α1AR-stimulated Zn2+ influx and positive inotropic response. Pharmacological enhancement of TRPC6-mediated Zn2+ influx prevents chronic heart failure progression in mice. Our data demonstrate that TRPC6-mediated Zn2+ influx with α1AR stimulation enhances baroreflex-induced positive inotropy, which may be a new therapeutic strategy for chronic heart failure.

Background: Extracellular vesicles (EVs) are important mediators of intercellular communication and can play a key role in the regulation of pathophysiological processes. Particularly, exosome-mediated intercellular crosstalk has been addressed in several disorders such as cancer and lifestyle-related diseases including hypertensive and diabetic vascular diseases. In diabetic kidney disease (DKD), it has been reported that macrophages infiltrate the mesangial region and may play an important role through local inflammation in glomeruli. Design and method:In this study, we focused on exosome as a factor that acts in a paracrine manner in glomeruli and examined the effects of mesangial cellderived exosomes cultured under high-glucose conditions on macrophages. In order to identify new therapeutic agents, we screened a validated compound library that can efficiently inhibit this mechanism and also studied their effects on DKD.Results: Exosomes released from mesangial cells induced inflammation in macrophages, as indicated by the NFkB transcriptional activity and TNFa and IL-1b mRNA expression. In addition, the effect was significantly enhanced in exosomes from mesangial cells cultured under high-glucose conditions compared to lowglucose conditions. We also observed that fluorescent-labeled (DiO) exosomes were endocytosed by macrophages in vitro and in vivo. Next, we conducted drug screening using a validated compound library to find compounds that could specifically and effectively inhibit the inflammation in macrophages induced by exosomes. The screening was divided into four steps, and we succeeded in narrowing down the list to 30 candidate compounds from a total of 1,364 compounds. Finally, an HSP90 inhibitor, alvespimycin, was identified as a compound with a strong inhibitory effect on both exosome uptake and the NFkB transcriptional activity. Treatment of a diabetic rat model with alvespimycin significantly reduced proteinuria, and showed a trend toward suppression of mesangial expansion. Conclusions:We found that mesangial cell-derived exosomes are important for inducing the local inflammation by intercellular crosstalk between mesangial cells and macrophages in DKD. Furthermore, alvespimycin, one of the HSP90 inhibitors obtained by drug screening, can effectively ameliorate the disease progression, suggesting that this mechanism could become a novel therapeutic target for DKD.

smaller in female than in male in SPZF rats, but sex differences were not observed in CP rats. Apelin mRNA levels in female CP rats were the highest among groups. The enhancements of acetylcholine-induced relaxations by PVAT were positively correlated with apelin mRNA levels in PVAT. These results demonstrated that sex difference in enhancing vasorelaxation response by PVAT in renal arteries differs to that in mesenteric arteries in SPZF rats at the same age and to that in another MetS model strain, CP rats, at the same age and arterial sites. This discrepancy observed in female rats between two MetS strains may be associated with the difference in arterial dysfunction mechanism; namely, impairment of only endothelial nitric oxide production in CP rats, and deterioration of re-sponse to nitric oxide in smooth muscle in SPZF rats. Furthermore, apelin levels of PVAT may be involved in the appearance of modulation of PVAT on arterial tone.

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