Excess amount of cytokine produced by inflammatory stimuli contributes to the progression of myocardial damage in myocarditis. Some angiotensin II receptor type 1 antagonists are reported to inhibit proinflammatory cytokine production in vitro and in vivo. We tested the hypothesis that olmesartan, a novel angiotensin II receptor type 1 antagonist, ameliorated experimental autoimmune myocarditis (EAM) in rats attributing to the suppression of inflammatory cytokines in the heart. We orally administered olmesartan 1, 3, and 10mg/kg/day to rats with EAM for 3 weeks. The results showed that olmesartan decreased blood pressure significantly compared with the untreated group, but markedly reduced the severity of myocarditis by comparing the heart weight/body weight ratio, pericardial effusion scores, macroscopic scores and microscopic scores. Myocardial interleukin (IL)-1β expression by western blotting and IL-1β-positive staining cells by immunohistochemistry were significantly lower in rats with EAM given olmesartan treatment compared with those of rats given vehicle. We conclude that Olmesartan ameliorates acute EAM in rats. The cardioprotection of olmesartan may be due to suppression of inflammatory cytokines dependent of the hemodynamic modifications.

Objective: Recent evidence has suggested that peroxisome proliferator-activated receptor-(PPAR- ) serves as a negative regulator in the immune system. In the present study, we investigated the expression of PPAR-and the effect of PPAR-ligands on experimental autoimmune myocarditis (EAM).Methods and Results: Experimental autoimmune myocarditis was induced in Lewis rats by immunization with porcine cardiac myosin. PPAR-γ ligands 15-deoxy- 12,14-PGJ2 200μg·kg−1·d−1 by ip and pioglitazone 10mg·kg−1·d−1 by oral were administered for 3 weeks. PPAR-γexpression was upregulated in myocarditis and the enhanced PPAR-γ expression was prominently stained in the nuclear and perinuclear regions of the positive-stained cells in the inflammatory lesions. Administration of PPAR-γ ligands markedly reduced the severity of myocarditis, as indicated by the heart weight/body weight ratio, pericardial effusion scores, macroscopic scores, and microscopic scores. The upregulated PPAR- expression was also reduced by PPAR-γ ligands treatment. In addition, PPAR-ligands suppressed the proliferative response and interferon-production of T cell-enriched splenocytes from rats with EAM. Furthermore, the cytotoxic activity and myocarditogenic potential of these T cells were inhibited by PPAR-γ ligands treatment. Conclusions: PPAR-γ ligands ameliorate EAM associated with inhibition of expansion and activation of the self-sensitive T cells. These results suggest that PPAR-ligands may have the potential to modulate human inflammatory heart diseases as myocarditis.

目的探讨过氧化物酶体增殖因子活化受体（PPARγ）在急性心肌炎发病中的作用；PPARγ配体治疗对急性心肌炎的影响及其可能的作用机制。方法6周龄Lewis大鼠注射猪心肌球蛋白诱导自身免疫性心肌炎（EAM）大鼠36只。分为正常对照、阳性对照、15d2PGJ2治疗组及比格列酮治疗组，每组9只。22天后大鼠麻醉状态下开胸，用免疫组化法观察PPARγ在炎症心肌中的表达及PPARγ配体15d2PGJ2注射（200μg·kg- 1·d - 1）和比格列酮口服（10mg·kg- 1·d-1）治疗对心肌炎症程度，及对致敏T细胞的增殖、活化和致心肌炎能力的影响。结果PPARγ在炎症心肌组织中表达增强，主要定位在炎性浸润细胞的核和核周围区；15d2PGJ2和比格列酮治疗使心肌炎症得到减轻，心重P体重、炎症分级严重程度明显减轻；免疫组化分析招募入炎性病灶内的CD4+、CD8+细胞和巨噬细胞数目，15d2PGJ2和比格列酮治疗明显减少病灶内炎性细胞浸润：与阳性对照组相比，病灶内巨噬细胞（22±4、26±6 vs 45±8，分别P<0101）、CD4+ 细胞（8±2、10±3 vs 18±5，P<0101）和CD8+细胞（3±1、4±2 vs 7±2，分别P<0101和<0105） 数目明显减少。体外实验证实PPARγ配体抑制富含T细胞的脾和淋巴结细胞增殖反应及γ干扰素产生；致敏T淋巴结细胞对其特异的抗原（心肌细胞）的细胞毒分析表明，免疫诱导后给予15d2PGJ2治疗组和比格列酮治疗组与阳性对照组相比其淋巴结细胞的细胞毒活性被显著抑制。心肌炎大鼠致敏T淋巴细胞过继转染注射后，受体鼠均被诱发心肌炎，PPARγ配体治疗抑制EAM大鼠致敏T细胞的致心肌炎能力。结论PPARγ配体治疗减轻实验性自身免疫性心肌炎，其机制与抑制T细胞增殖反应及活化和抑制自身反应性T细胞的致心肌毒作用有关。

Objective: To test the hypothesis that activation of peroxisome proliferator activated receptor c (PPAR-c) reduces experimental autoimmune myocarditis (EAM) associated with inhibitor kB (IkB) a induction, blockade of nuclear factor kB (NF-kB), and inhibition of inflammatory cytokine expression. Methods: EAM was induced in Lewis rats by immunisation with porcine cardiac myosin. PPAR-c activators 15-deoxy-D12, 14-prostaglandin J2 (15d-PGJ2) and pioglitazone (PIO) were administrated to rats with EAM. Results: Enhanced PPAR-c expression was prominently stained in the nuclear and perinuclear regions of infiltrating inflammatory cells. Administration of 15d-PGJ2 and PIO greatly reduced the severity of myocarditis and suppressed myocardial mRNA and protein expression of inflammatory cytokines in rats with EAM. In addition, treatment with PPAR-c activators enhanced IkB concentrations in the cytoplasmic fractions and nuclear fractions from inflammatory myocardium. Concurrently, NF-kB was greatly activated in myocarditis; this activation was blocked in the 15d-PGJ2 treated and PIO treated groups. Conclusions: PPAR-cmay have a role in the pathophysiology of EAM. Because an increase in IkB expression and inhibition of translocation of the NF-kB subunit p65 to the nucleus in inflammatory cells correlated with the protective effects of PPAR-c activators, these results suggest that PPAR-c activators act sequentially through PPAR-c activation, IkB induction, blockade of NF-kB activation, and inhibition of inflammatory cytokine expression. These results suggest that PPAR-c activators such as 15d-PGJ2 and PIO may have the potential to modulate human inflammatory heart diseases such as myocarditis.

We investigated whether carvedilol protects against experimental autoimmune myocarditis (EAM) attributing to antioxidant properties. Acute EAM was induced by porcine cardiac myosin in Lewis rats. We orally administered a vehicle, various dosages of carvedilol, metoprolol, or propranolol to rats with EAM for 3 weeks. Three β-blockers decreased heart rates to the same extent. Carvedilol, but not metoprolol or propranolol, markedly reduced the severity of myocarditis at the two different dosages. Only carvedilol decreased the myocardial protein carbonyl contents, and also decreased the myocardial thiobarbituric acid reactive substance products in rats with EAM. Accordingly, carvedilol protects against acute EAM in rats, and this superior cardioprotective effect of carvedilol to metoprolol and propranolol may be due to the antioxidant properties in addition to the hemodynamic modifications.