Alcoholic and nonalcoholic fatty liver disease (ALD and NAFLD) are the predominant causes of liver-related mortality in Western countries. We have shown that limiting classical (M1) Kupffer cell (KC) polarization reduces alcohol-induced liver injury. Herein, we investigated whether favoring alternatively activated M2 KCs may protect against ALD and NAFLD. Ongoing alcohol drinkers and morbidly obese patients, with minimal hepatic injury and steatosis, displayed higher hepatic expression of M2 genes, as compared to patients with more severe liver lesions; individuals with limited liver lesions showed negligible hepatocyte apoptosis but significant macrophage apoptosis. Experiments in mouse models of ALD or NAFLD further showed that BALB/c or resveratrol-treated mice fed alcohol or a high-fat diet displayed preponderant M2 KC polarization, M1 KC apoptosis, and resistance to hepatocyte steatosis and apoptosis, as compared to control C57BL6/J mice. In vitro experiments in isolated KC, peritoneal, and Raw264.7 macrophages demonstrated that M1 macrophage apoptosis was promoted by conditioned medium from macrophages polarized into an M2 phenotype by either interleukin (IL)4, resveratrol, or adiponectin. Mechanistically, IL10 released from M2 cells promoted M1 death, and anti-IL10 antibodies blunted the proapoptic effects of M2-conditioned media. IL10 secreted by M2 KCs promoted selective M1 death by a mechanism involving activation of arginase in high inducible nitric oxide synthase-expressing M1 KCs. In alcohol-exposed mice, neutralization of IL10 impaired M1 apoptosis. Conclusion : These data uncover a novel mechanism regulating the M1/M2 balance that relies on apoptotic effects of M2 KCs towards their M1 counterparts. They suggest that promoting M2-induced M1 KC apoptosis might prove a relevant strategy to limit alcohol- and high fat-induced inflammation and hepatocyte injury.

Sphingomyelinases (SMases) hydrolyse sphingomyelin, releasing ceramide and creating a cascade of bioactive lipids. These lipids include sphingosine and sphingosine-1-phosphate, all of which have a specific signalling capacity. Sphingomyelinase activation occurs in different cardiovascular system cell types, namely cardiac myocytes, endothelial and vascular smooth muscle cells, mediating cell proliferation, cell death, and contraction of cardiac and vascular myocytes. Three main types of SMases contribute to cardiovascular physiology: the lysosomal and secreted acidic SMases (L- and S-ASMases, respectively) and the membrane neutral SMase (NSMase). These three enzymes have common activators, including ischaemia/reperfusion stress and proinflammatory cytokines, but they differ in their enzymatic properties and subcellular locations that determine the final effect of enzyme activation. This review focuses on the recent advances in the understanding of ASMase and NSMase pathways and their specific contribution to cardiovascular pathophysiology. Current knowledge indicates that the inhibitors of the different SMase types are potential tools for the treatment of cardiovascular diseases. Acid SMase inhibitors could be tools against post-ischaemia reperfusion injury and in the treatment of atherosclerosis. Neutral SMase inhibitors could be tools for the treatment of atherosclerosis, heart failure, and age-related decline in vasomotion. However, the design of bioavailable and more specific SMase-type inhibitors remains a challenge.

Post‐myocardial infarction (MI) heart failure is a major public health problem in Western countries and results from ischemia/reperfusion (IR)‐induced cell death, remodeling, and contractile dysfunction. Ex vivo studies have demonstrated the cardioprotective anti‐inflammatory effect of the cannabinoid type 2 (CB2) receptor agonists within hours after IR. Herein, we evaluated the in vivo effect of CB2 receptors on IR‐induced cell death, fibrosis, and cardiac dysfunction and investigated the target role of cardiac myocytes and fibroblasts. The infarct size was increased 24 h after IR in CB2 ^/_ vs . wild‐type (WT) hearts and decreased when WT hearts were injected with the CB2 agonist JWH133 (3 mg/kg) at reperfusion. Compared with WT hearts, CB2 ^–/– hearts showed widespread injury 3 d after IR, with enhanced apoptosis and remodeling affecting the remote myocardium. Finally, CB2 ^–/– hearts exhibited exacerbated fibrosis, associated with left ventricular dysfunction 4 wk after IR, whereas their WT counterparts recovered normal function. Cardiac myocytes and fibroblasts isolated from CB2 ^–/– hearts displayed a higher H ₂ O ₂ ‐ induced death than WT cells, whereas 1 μM JWH133 triggered survival effects. Furthermore, H ₂ O ₂ ‐induced myofibroblast activation was increased in CB2 ^–/– fibroblasts but decreased in 1 μM JWH133‐treated WT fibroblasts, compared with that in WT cells. Therefore, CB2 receptor activation may protect against post‐IR heart failure through direct inhibition of cardiac myocyte and fibroblast death and prevention of myofibroblast activation.—Defer, N.,Wan, J., Souktani, R., Escoubet, B., Perier, M., Caramelle, P., Manin, S., Deveaux, V., Bourin, M.‐C., Zimmer, A., Lotersztajn, S., Pecker, F., Pavoine, C. The cannabinoid receptor type 2 promotes cardiac myocyte and fibroblast survival and protects against ischemia/reperfusion‐induced cardiomyopathy. FASEB J. 23, 2120–2130 (2009)

Background—: Stromal interaction molecule 1 (STIM1) is a dynamic calcium signal transducer implicated in hypertrophic growth of cardiomyocytes. STIM1 is thought to act as an initiator of cardiac hypertrophic response at the level of the sarcolemma, but the pathways underpinning this effect have not been examined. Methods and Results—: To determine the mechanistic role of STIM1 in cardiac hypertrophy and during the transition to heart failure, we manipulated STIM1 expression in mice cardiomyocytes by using in vivo gene delivery of specific short hairpin RNAs. In 3 different models, we found that Stim1 silencing prevents the development of pressure overload–induced hypertrophy but also reverses preestablished cardiac hypertrophy. Reduction in STIM1 expression promoted a rapid transition to heart failure. We further showed that Stim1 silencing resulted in enhanced activity of the antihypertrophic and proapoptotic GSK-3β molecule. Pharmacological inhibition of glycogen synthase kinase-3 was sufficient to reverse the cardiac phenotype observed after Stim1 silencing. At the level of ventricular myocytes, Stim1 silencing or inhibition abrogated the capacity for phosphorylation of Akt ^S473 , a hydrophobic motif of Akt that is directly phosphorylated by mTOR complex 2. We found that Stim1 silencing directly impaired mTOR complex 2 kinase activity, which was supported by a direct interaction between STIM1 and Rictor, a specific component of mTOR complex 2. Conclusions—: These data support a model whereby STIM1 is critical to deactivate a key negative regulator of cardiac hypertrophy. In cardiomyocytes, STIM1 acts by tuning Akt kinase activity through activation of mTOR complex 2, which further results in repression of GSK-3β activity.