Skeletal Muscle SIRT3 Deficiency Contributes to Pulmonary Vascular Remodeling in Pulmonary Hypertension Due to Heart Failure With Preserved Ejection Fraction.

BACKGROUND: Pulmonary hypertension (PH) is a major complication linked to adverse outcomes in heart failure with preserved ejection fraction (HFpEF), yet no specific therapies exist for PH associated with HFpEF (PH-HFpEF). We have recently reported on the role of skeletal muscle SIRT3 (sirtuin-3) in modulation of PH-HFpEF, suggesting a novel endocrine signaling pathway for skeletal muscle modulation of pulmonary vascular remodeling. In this study, we attempted to define the processes by which skeletal muscle SIRT3 defects affect pulmonary vascular health in PH-HFpEF. METHODS AND RESULTS: Skeletal muscle-specific Sirt3 knockout mice (Sirt3skm-/-) exhibited reduced pulmonary vascular density accompanied by pulmonary vascular proliferative remodeling and elevated pulmonary pressures. Using mass spectrometry-based comparative secretome analysis, we demonstrated elevated secretion of LOXL2 (lysyl oxidase homolog 2) in SIRT3-deficient skeletal muscle cells. Elevated circulation and protein expression levels of LOXL2 were also observed in plasma and skeletal muscle of Sirt3skm-/- mice, a rat model of PH-HFpEF, and humans with PH-HFpEF. In addition, expression levels of CNPY2 (canopy fibroblast growth factor signaling regulator 2), a known proliferative and angiogenic factor, were increased in pulmonary artery endothelial cells and pulmonary artery smooth muscle cells of Sirt3skm-/- mice and animal models of PH-HFpEF. CNPY2 levels were also higher in pulmonary artery smooth muscle cells of subjects with obesity compared with nonobese subjects. Moreover, treatment with recombinant LOXL2 protein promoted pulmonary artery endothelial cell migration/proliferation and pulmonary artery smooth muscle cell proliferation through regulation of CNPY2-p53 signaling. Last, skeletal muscle-specific Loxl2 deletion decreased pulmonary artery endothelial cell and pulmonary artery smooth muscle cell expression of CNPY2 and improved pulmonary pressures in mice with high-fat diet-induced PH-HFpEF. CONCLUSIONS: This study demonstrates a systemic pathogenic impact of skeletal muscle SIRT3 deficiency in remote pulmonary vascular remodeling and PH-HFpEF. This study suggests a new endocrine signaling axis that links skeletal muscle health and SIRT3 deficiency to remote CNPY2 regulation in the pulmonary vasculature through myokine LOXL2. Our data also identify skeletal muscle SIRT3, myokine LOXL2, and CNPY2 as potential targets for the treatment of PH-HFpEF.

Deficiency of the Deubiquitinase UCHL1 Attenuates Pulmonary Arterial Hypertension.

BACKGROUND: The ubiquitin-proteasome system regulates protein degradation and the development of pulmonary arterial hypertension (PAH), but knowledge about the role of deubiquitinating enzymes in this process is limited. UCHL1 (ubiquitin carboxyl-terminal hydrolase 1), a deubiquitinase, has been shown to reduce AKT1 (AKT serine/threonine kinase 1) degradation, resulting in higher levels. Given that AKT1 is pathological in pulmonary hypertension, we hypothesized that UCHL1 deficiency attenuates PAH development by means of reductions in AKT1. METHODS: Tissues from animal pulmonary hypertension models as well as human pulmonary artery endothelial cells from patients with PAH exhibited increased vascular UCHL1 staining and protein expression. Exposure to LDN57444, a UCHL1-specific inhibitor, reduced human pulmonary artery endothelial cell and smooth muscle cell proliferation. Across 3 preclinical PAH models, LDN57444-exposed animals, Uchl1 knockout rats (Uchl1-/-), and conditional Uchl1 knockout mice (Tie2Cre-Uchl1fl/fl) demonstrated reduced right ventricular hypertrophy, right ventricular systolic pressures, and obliterative vascular remodeling. Lungs and pulmonary artery endothelial cells isolated from Uchl1-/- animals exhibited reduced total and activated Akt with increased ubiquitinated Akt levels. UCHL1-silenced human pulmonary artery endothelial cells displayed reduced lysine(K)63-linked and increased K48-linked AKT1 levels. RESULTS: Supporting experimental data, we found that rs9321, a variant in a GC-enriched region of the UCHL1 gene, is associated with reduced methylation (n=5133), increased UCHL1 gene expression in lungs (n=815), and reduced cardiac index in patients (n=796). In addition, Gadd45α (an established demethylating gene) knockout mice (Gadd45α-/-) exhibited reduced lung vascular UCHL1 and AKT1 expression along with attenuated hypoxic pulmonary hypertension. CONCLUSIONS: Our findings suggest that UCHL1 deficiency results in PAH attenuation by means of reduced AKT1, highlighting a novel therapeutic pathway in PAH.

Plasma Proteomics Identifies B2M as a Regulator of Pulmonary Hypertension in Heart Failure With Preserved Ejection Fraction.

BACKGROUND: Pulmonary hypertension (PH) represents an important phenotype in heart failure with preserved ejection fraction (HFpEF). However, management of PH-HFpEF is challenging because mechanisms involved in the regulation of PH-HFpEF remain unclear. METHODS: We used a mass spectrometry-based comparative plasma proteomics approach as a sensitive and comprehensive hypothesis-generating discovery technique to profile proteins in patients with PH-HFpEF and control subjects. We then validated and investigated the role of one of the identified proteins using in vitro cell cultures, in vivo animal models, and independent cohort of human samples. RESULTS: Plasma proteomics identified high protein abundance levels of B2M (ß2-microglobulin) in patients with PH-HFpEF. Interestingly, both circulating and skeletal muscle levels of B2M were increased in mice with skeletal muscle SIRT3 (sirtuin-3) deficiency or high-fat diet-induced PH-HFpEF. Plasma and muscle biopsies from a validation cohort of PH-HFpEF patients were found to have increased B2M levels, which positively correlated with disease severity, especially pulmonary capillary wedge pressure and right atrial pressure at rest. Not only did the administration of exogenous B2M promote migration/proliferation in pulmonary arterial vascular endothelial cells but it also increased PCNA (proliferating cell nuclear antigen) expression and cell proliferation in pulmonary arterial vascular smooth muscle cells. Finally, B2m deletion improved glucose intolerance, reduced pulmonary vascular remodeling, lowered PH, and attenuated RV hypertrophy in mice with high-fat diet-induced PH-HFpEF. CONCLUSIONS: Patients with PH-HFpEF display higher circulating and skeletal muscle expression levels of B2M, the magnitude of which correlates with disease severity. Our findings also reveal a previously unknown pathogenic role of B2M in the regulation of pulmonary vascular proliferative remodeling and PH-HFpEF. These data suggest that circulating and skeletal muscle B2M can be promising targets for the management of PH-HFpEF.

BPR3P0128, a non-nucleoside RNA-dependent RNA polymerase inhibitor, inhibits SARS-CoV-2 variants of concern and exerts synergistic antiviral activity in combination with remdesivir.

Viral RNA-dependent RNA polymerase (RdRp), a highly conserved molecule in RNA viruses, has recently emerged as a promising drug target for broad-acting inhibitors. Through a Vero E6-based anti-cytopathic effect assay, we found that BPR3P0128, which incorporates a quinoline core similar to hydroxychloroquine, outperformed the adenosine analog remdesivir in inhibiting RdRp activity (EC50 = 0.66 µM and 3 µM, respectively). BPR3P0128 demonstrated broad-spectrum activity against various severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants of concern. When introduced after viral adsorption, BPR3P0128 significantly decreased SARS-CoV-2 replication; however, it did not affect the early entry stage, as evidenced by a time-of-drug-addition assay. This suggests that BPR3P0128's primary action takes place during viral replication. We also found that BPR3P0128 effectively reduced the expression of proinflammatory cytokines in human lung epithelial Calu-3 cells infected with SARS-CoV-2. Molecular docking analysis showed that BPR3P0128 targets the RdRp channel, inhibiting substrate entry, which implies it operates differently-but complementary-with remdesivir. Utilizing an optimized cell-based minigenome RdRp reporter assay, we confirmed that BPR3P0128 exhibited potent inhibitory activity. However, an enzyme-based RdRp assay employing purified recombinant nsp12/nsp7/nsp8 failed to corroborate this inhibitory activity. This suggests that BPR3P0128 may inhibit activity by targeting host-related RdRp-associated factors. Moreover, we discovered that a combination of BPR3P0128 and remdesivir had a synergistic effect-a result likely due to both drugs interacting with separate domains of the RdRp. This novel synergy between the two drugs reinforces the potential clinical value of the BPR3P0128-remdesivir combination in combating various SARS-CoV-2 variants of concern.