The Effects of Spironolactone on Inflammation in a Rodent Model of Pulmonary Arterial Hypertension

肺动脉高压（PAH）是一组罕见但致命的疾病，其特征是小肺动脉进行性狭窄和闭塞，心脏右侧受压，最终死于右心衰竭。迫切需要新的治疗方法，因为目前的治疗方法不能逆转这种进行性疾病，50%的患者在诊断后7年内死亡。炎症最近被认为是PAH患者肺动脉异常的重要组成部分，因此假设阻断炎症的药物可能对PAH患者有益。 虽然螺内酯（SPL）的盐皮质激素受体（MR）非依赖性抗炎作用已被认识了几十年，但其机制知之甚少，并且SPL对PAH炎症的影响之前尚未研究过。我们的小组已经发现了一个非MR依赖的机制，SPL抑制肺动脉内皮细胞在体外炎症。我们确定XPB降解是SPL抑制NF-κ B和AP-1炎症信号传导的一种共享的、MR独立的机制。与SPL不同，依普利酮（EPL）不会引起XPB降解，并且在体外无法抑制炎症信号传导（Elinoff JM et al. Atriovasc Res. 2018）。 在PAH临床前模型中，在疾病开始时或之后早期开始盐皮质激素受体（MR）拮抗剂治疗可预防肺血管重塑。然而，MR阻滞在已确诊疾病（一种临床相关性更高的疾病）中的疗效仍然未知。因此，我们研究了两种MR拮抗剂EPL和SPL在大鼠SU 5416缺氧（SuHx）PAH模型中严重右心室（RV）功能障碍后的有效性。 本研究已完成，描述MR拮抗剂对PAH大鼠SuHx模型中心室相互依赖性影响的手稿于2022财年发表，总结如下。 在研究治疗前第5周结束时，SuHx大鼠的心脏磁共振成像（MRI）证实了已确立疾病的特征，包括RV射血分数降低、RV肥大、明显的间隔扁平伴左心室充盈受损和心脏指数降低。与安慰剂相比，用EPL或SPL治疗5周可改善左心室充盈，并防止心脏指数进一步下降。EPL减少室间隔位移，SPL效果相似，但不显著。虽然MR拮抗剂没有显着降低肺动脉压或血管重塑的SuHx大鼠建立的疾病，动物与较高的药物水平有较低的肺动脉压。与对心脏功能的影响一致，EPL治疗倾向于抑制RV中的MR和促炎基因诱导。SPL代谢产物不能诱导XPB降解，体内检测到的相对较低的血清药物浓度以及Su/Hx大鼠在药物消耗间隔期间XPB蛋白水平的潜在恢复可能解释了保留的RV和肺XPB蛋白表达以及SPL治疗动物中通过该机制缺乏抗炎作用。总之，在SuHx PAH模型中，在发生显著RV功能障碍后，MR拮抗剂治疗对室间依赖性产生了适度但一致的有益作用。这些结果表明，RV结构和/或功能的测量可能是PAH患者MR拮抗剂临床试验的有用终点。

Pulmonary arterial hypertension (PAH) encompasses a group of rare but lethal diseases characterized by progressive narrowing and occlusion of the small pulmonary arteries, stress on the right-side of the heart and eventually death from right-heart failure. New treatments are urgently needed because current therapy does not reverse this progressive disease and 50% of patients die within 7 years of their diagnosis. Inflammation has recently been recognized as an important part of the abnormal pulmonary arteries in patients with PAH, and therefore it has been hypothesized that drugs that block inflammation may have benefits in patients with PAH. While mineralocorticoid receptor (MR) independent anti-inflammatory effects of spironolactone (SPL) have been recognized for decades, the mechanism was poorly understood and the effects of SPL on inflammation in PAH have not been previously studied. Our group has uncovered an MR-independent mechanism whereby SPL suppresses inflammation in pulmonary artery endothelial cells in vitro. We identified XPB degradation as a shared, MR-independent mechanism by which SPL inhibits both NF-kB and AP-1 inflammatory signaling. Unlike SPL, eplerenone (EPL) did not cause XPB degradation and failed to suppress inflammatory signaling in vitro (Elinoff JM et al. Cardiovasc Res. 2018). Treatment with mineralocorticoid receptor (MR) antagonists beginning at the outset of disease, or early thereafter, prevents pulmonary vascular remodeling in pre-clinical models of PAH. However, the efficacy of MR blockade in established disease, a more clinically relevant condition, remains unknown. Therefore, we investigated the effectiveness of two MR antagonists, EPL and SPL, after development of severe right ventricular (RV) dysfunction in the rat SU5416-hypoxia (SuHx) PAH model. This study is completed and a manuscript describing the effects of MR antagonists on ventricular interdependence in the rat SuHx model of PAH was published in FY22 and summarized below. Cardiac magnetic resonance imaging (MRI) in SuHx rats at the end of week 5, prior to study treatment, confirmed features of established disease including reduced RV ejection fraction, RV hypertrophy, pronounced septal flattening with impaired left ventricular filling and reduced cardiac index. Five weeks of treatment with either EPL or SPL improved left ventricular filling and prevented the further decline in cardiac index compared to placebo. Interventricular septal displacement was reduced by EPL while SPL effects were similar, but not significant. Although MR antagonists did not significantly reduce pulmonary artery pressure or vessel remodeling in SuHx rats with established disease, animals with higher drug levels had lower pulmonary pressures. Consistent with effects on cardiac function, EPL treatment tended to suppress MR and proinflammatory gene induction in the RV. The inability of SPL metabolites to induce XPB-degradation, the relatively lower serum drug concentrations detected in vivo and the potential recovery of XPB protein levels during the intervals between drug consumption by Su/Hx rats may explain preserved RV and lung XPB protein expression and the lack of anti-inflammatory effects through this mechanism in SPL-treated animals. In conclusion, MR antagonist treatment led to modest, but consistent beneficial effects on interventricular dependence after the onset of significant RV dysfunction in the SuHx PAH model. These results suggest that measures of RV structure and/or function may be useful endpoints in clinical trials of MR antagonists in PAH patients.