Metformin suppresses hypoxia-induced stabilization of HIF-1α through reprogramming of oxygen metabolism in hepatocellular carcinoma Metformin suppresses hypoxia-induced stabilization of HIF-1α through reprogramming of oxygen metabolism in hepatocellular carcinoma

Emerging studies have reported the mechanosensitive Piezo1 (piezo type mechanosensitive ion channel component 1) plays essential roles in regulating the vascular tone through mechanistic actions on intracellular calcium homeostasis. However, the specific roles of Piezo1 in pulmonary vessels remain incompletely understood. We aim to investigate whether and how Piezo1 regulates the intracellular calcium homeostasis in human pulmonary arterial smooth muscle cells (PASMCs) under normal and pulmonary arterial hypertension (PAH) conditions. Cultured human PASMCs isolated from both control donors and idiopathic PAH patients were used as cell models. Fura-2 based intracellular calcium imaging was performed to measure the intracellular free calcium concentration ([Ca ²⁺ ] _i ). Results showed that activation of Piezo1 by Yoda1 increases [Ca ²⁺ ] _i by inducing both intracellular calcium release from internal calcium stores through the intracellular (intra-) Piezo1 localized at the subcellular organelles, including endoplasmic reticulum/sarcoplasmic reticulum, mitochondria, and nucleus; as well as extracellular calcium influx through the plasma membrane-localized Piezo1 in a mechanism independent of the store-operated calcium entry. Moreover, the Piezo1-mediated increase of [Ca ²⁺ ] _i is linked to increased contraction and proliferation of PASMCs. Yoda1 induces dose-dependent vasocontraction in endothelium-denuded rat intrapulmonary arteries. Significant upregulation and increased activity of Piezo1 were observed in idiopathic PAH-PASMCs versus donor-PASMCs, contributing to the increased [Ca ²⁺ ] _i and excessive proliferation of idiopathic PAH-PASMCs. In summary, Piezo1 mediates the increase of [Ca ²⁺ ] _i by triggering both intracellular calcium release and extracellular influx. The enhanced Piezo1 expression and activity accounts, at least partially, for the abnormally elevated [Ca ²⁺ ] _i and proliferation in idiopathic PAH-PASMCs.

In pulmonary arterial smooth muscle cells (PASMCs), voltage-gated K⁺ (K_v) channels play an important role in regulating membrane potential, cytoplasmic free Ca²⁺ concentration, and pulmonary vasomotor tone. Previous studies demonstrated that exposure of rats to chronic hypoxia decreased K_v channel function in PASMCs from distal pulmonary arteries (dPA). To determine whether this decrease in function was due to decreased expression of K_v channel proteins and which K_v proteins might be involved, we analyzed K_v channel gene expression in intact, endothelium-denuded dPAs obtained from rats exposed to 10% O₂ for 3 wk. K_v1.1, K_v1.2, K_v1.4, K_v1.5, K_v1.6, K_v2.1, K_v3.1, K_v4.3, and K_v9.3 channel α-subunits and K_v1, K_v2, and K_v3 β-subunits were expressed in rat dPAs. Exposure to chronic hypoxia decreased mRNA and protein levels of K_v1.1, K_v1.5, K_v1.6, K_v2.1, and K_v4.3 α-subunits in dPAs but did not alter gene or protein expression of these channels in aorta. Furthermore, chronic hypoxia did not alter the mRNA levels of β-subunits in dPAs. These results suggest that diminished transcription of K_v α-subunits may reduce the number of functional K_v channels in dPAs during prolonged hypoxia, causing the decreased K_v current previously observed in PASMCs and leading to pulmonary artery vasoconstriction.

Animal model of cigarette smoke (CS) –induced chronic obstructive pulmonary disease (COPD) is the primary testing methodology for drug therapies and studies on pathogenic mechanisms of disease. However, researchers have rarely run simultaneous or side-by-side tests of whole-body and nose-only CS exposure in building their mouse models of COPD. We compared and evaluated these two different methods of CS exposure, plus airway Lipopolysaccharides (LPS) inhalation, in building our COPD mouse model. Compared with the control group, CS exposed mice showed significant increased inspiratory resistance, functional residual capacity, right ventricular hypertrophy index, and total cell count in BALF. Moreover, histological staining exhibited goblet cell hyperplasia, lung inflammation, thickening of smooth muscle layer on bronchia, and lung angiogenesis in both methods of CS exposure. Our data indicated that a viable mouse model of COPD can be established by combining the results from whole-body CS exposure, nose-only CS exposure, and airway LPS inhalation testing. However, in our study, we also found that, given the same amount of particulate intake, changes in right ventricular pressure and intimal thickening of pulmonary small artery are a little more serious in nose-only CS exposure method than changes in the whole-body CS exposure method.

Rationale: Vascular remodeling, including smooth muscle cell hypertrophy and proliferation, is the key pathological feature of pulmonary arterial hypertension (PAH). Prostaglandin I2 analogs (beraprost, iloprost, and treprostinil) are effective in the treatment of PAH. Of note, the clinically favorable effects of treprostinil in severe PAH may be attributable to concomitant activation of DP1 (D prostanoid receptor subtype 1). Objectives: To study the role of DP1 in the progression of PAH and its underlying mechanism. Methods: DP1 levels were examined in pulmonary arteries of patients and animals with PAH. Multiple genetic and pharmacologic approaches were used to investigate DP1-mediated signaling in PAH. Measurements and Main Results: DP1 expression was downregulated in hypoxia-treated pulmonary artery smooth muscle cells and in pulmonary arteries from rodent PAH models and patients with idiopathic PAH. DP1 deletion exacerbated pulmonary artery remodeling in hypoxia-induced PAH, whereas pharmacological activation or forced expression of the DP1 receptor had the opposite effect in different rodent models. DP1 deficiency promoted pulmonary artery smooth muscle cell hypertrophy and proliferation in response to hypoxia via induction of mTORC1 (mammalian target of rapamycin complex 1) activity. Rapamycin, an inhibitor of mTORC1, alleviated the hypoxia-induced exacerbation of PAH in DP1-knockout mice. DP1 activation facilitated raptor dissociation from mTORC1 and suppressed mTORC1 activity through PKA (protein kinase A)-dependent phosphorylation of raptor at Ser791. Moreover, treprostinil treatment blocked the progression of hypoxia-induced PAH in mice in part by targeting the DP1 receptor. Conclusions: DP1 activation attenuates hypoxia-induced pulmonary artery remodeling and PAH through PKA-mediated dissociation of raptor from mTORC1. These results suggest that the DP1 receptor may serve as a therapeutic target for the management of PAH.

Airway mucus dysfunction and impaired immunological defenses are hallmarks of several lung diseases, including asthma, cystic fibrosis, and chronic obstructive pulmonary diseases, and are mostly causative factors in bacterial-biofilm-associated respiratory tract infections. Bacteria residing within the biofilm architecture pose a complex challenge in clinical settings due to their increased tolerance to currently available antibiotics and host immune responses, resulting in chronic infections with high recalcitrance and high rates of morbidity and mortality. To address these unmet clinical needs, potential anti-biofilm therapeutic strategies are being developed to effectively control bacterial biofilm. This review focuses on recent advances in the development and application of nanoparticulate drug delivery systems for the treatment of biofilm-associated respiratory tract infections, especially addressing the respiratory barriers of concern for biofilm accessibility and the various types of nanoparticles used to combat biofilms. Understanding the obstacles facing pulmonary drug delivery to bacterial biofilms and nanoparticle-based approaches to combatting biofilm may encourage researchers to explore promising treatment modalities for bacterial-biofilm-associated chronic lung infections.