The Novel Lysosomal Autophagy Inhibitor (ROC-325) Ameliorates Experimental Pulmonary Hypertension

Background: Autophagy plays an important role in the pathogenesis of pulmonary hypertension (PH). ROC-325 is a novel small molecule lysosomal autophagy inhibitor that has more potent anticancer activity than the antimalarial drug hydroxychloroquine, the latter has been prevalently used to inhibit autophagy. Here, we sought to determine the therapeutic benefit and mechanism of action of ROC-325 in experimental PH models.

Methods and results: Hemodynamics, echocardiography, and histology measurement showed that ROC-325 treatment prevented the development of PH, right ventricular hypertrophy, fibrosis, dysfunction, and vascular remodeling after monocrotaline and Sugen5416/hypoxia administration. ROC-325 attenuated high K+ or alveolar hypoxia-induced pulmonary vasoconstriction and enhanced endothelial-dependent relaxation in isolated pulmonary artery rings. ROC-325 treatment inhibited autophagy and enhanced endothelial nitric oxide synthase activity in lung tissues of monocrotaline-PH rats. In cultured human and rat pulmonary arterial smooth muscle cell and pulmonary arterial endothelial cell under hypoxia exposure, ROC-325 increased LC3B (light chain 3 beta) and p62 accumulation, endothelial cell nitric oxide production via phosphorylation of endothelial nitric oxide synthase (Ser1177) and dephosphorylation of endothelial nitric oxide synthase (Thr495) as well as decreased HIF (hypoxia-inducible factor)-1α and HIF-2α stabilization.

Conclusions: These data indicate that ROC-325 is a promising novel agent for the treatment of PH that inhibits autophagy, downregulates HIF levels, and increases nitric oxide production.

 

Comments:

The passage you provided describes a study conducted to investigate the therapeutic potential of a small molecule called ROC-325 in experimental models of pulmonary hypertension (PH). The researchers aimed to determine the effects of ROC-325 on PH development and understand its mechanism of action.

The study utilized different experimental models of PH, induced by monocrotaline administration or a combination of Sugen5416 and hypoxia. Hemodynamic measurements, echocardiography, and histological analysis were performed to evaluate the impact of ROC-325 treatment. The results showed that treatment with ROC-325 prevented the development of PH, right ventricular hypertrophy (enlargement of the right side of the heart), fibrosis, dysfunction, and vascular remodeling in these models.

Additionally, the researchers investigated the effect of ROC-325 on pulmonary blood vessels. They found that ROC-325 attenuated pulmonary vasoconstriction induced by high potassium levels or alveolar hypoxia (low oxygen levels in the air sacs of the lungs). Furthermore, ROC-325 enhanced endothelial-dependent relaxation, a process important for maintaining normal blood vessel function, in isolated pulmonary artery rings.

The study also explored the impact of ROC-325 on autophagy, a cellular process involved in the degradation and recycling of cellular components. ROC-325 treatment inhibited autophagy in lung tissues of rats with monocrotaline-induced PH. Moreover, it increased the activity of endothelial nitric oxide synthase (eNOS), an enzyme that produces nitric oxide, in the lung tissues of these rats. Nitric oxide is a molecule important for regulating blood vessel tone and function.

In cell culture experiments using human and rat pulmonary arterial smooth muscle cells and pulmonary arterial endothelial cells exposed to hypoxia, ROC-325 treatment resulted in the accumulation of LC3B and p62, two proteins associated with autophagy. It also increased nitric oxide production by promoting the phosphorylation of eNOS at Ser1177 and dephosphorylation at Thr495. Additionally, ROC-325 decreased the stabilization of HIF-1α and HIF-2α, which are proteins involved in the response to low oxygen levels (hypoxia).

Based on these findings, the study concludes that ROC-325 shows promise as a novel therapeutic agent for the treatment of pulmonary hypertension. Its beneficial effects appear to be mediated through the inhibition of autophagy, downregulation of HIF levels, and increased nitric oxide production, which collectively contribute to the prevention of PH development and associated pathological changes.