The NADPH oxidase (Nox) family of proteins is comprised of seven members, including Noxes1–5 and the Duoxes 1 and 2. Nox4 is readily distinguished from the other Nox isoforms by its high level of expression in cardiovascular tissues and unique enzymatic properties. Nox4 is constitutively active and the amount of reactive oxygen species (ROS) contributed by Nox4 is primarily regulated at the transcriptional level although there is recent evidence for post-translational control. Nox4 emits a different pattern of ROS and its subcellular localizations, tissue distribution and influence over signaling pathways is different from the other Nox enzymes. Previous investigations have revealed that Nox4 is involved in oxygen sensing, vasomotor control, cellular proliferation, differentiation, migration, apoptosis, senescence, fibrosis, and angiogenesis. Elevated expression of Nox4 has been reported in a number of cardiovascular diseases, including atherosclerosis, pulmonary fibrosis, and hypertension, cardiac failure and ischemic stroke. However, many important questions remain regarding the functional significance of Nox4 in health and disease, including the role of Nox4 subcellular localization and its downstream targets. The goal of this review is to summarize the recent literature on the genetic and enzymatic regulation, subcellular localization, signaling pathways, and the role of Nox4 in cardiovascular disease states.

Rationale: Posttranscriptional modifications are implicated in vascular remodeling of pulmonary hypertension (PH). N⁶-methyladenosine (m⁶A) is an abundant RNA modification that is involved in various biological processes. Whether m⁶A RNA modification and m⁶A effector proteins play a role in pulmonary vascular remodeling and PH have not been demonstrated. Objectives: To determine whether m⁶A modification and m⁶A effectors contribute to the pathogenesis of PH. Methods: m⁶A modification and YTHDF1 expression were measured in human and experimental PH samples. RIP analysis and m⁶A-sequencing were employed to screen m⁶A-marked transcripts. Genetic approaches were employed to assess the respective roles of YTHDF1 and MAGED1 in PH. Primary cells isolation and cultivation were utilized for function analysis of pulmonary artery smooth muscle cells (PASMCs). Measurements and Main Results: Elevated m⁶A levels and increased YTHDF1 protein expression were found in human and rodent PH samples as well as in hypoxic PASMCs. Deletion of YTHDF1 ameliorated PASMCs proliferation, phenotype switch and PH development both in vivo and in vitro. m⁶A RIP analysis identified MAGED1 as an m⁶A-regulated gene in PH and genetic ablation of MAGED1 improved vascular remodeling and hemodynamic parameters in SU5416/Hypoxia mice. YTHDF1 recognized and promoted translation of MAGED1 in an m⁶A dependent manner which was absent in METTL3 deficient PASMCs. In addition, MAGED1 silencing inhibited hypoxia-induced proliferation of PASMCs through downregulating PCNA. Conclusions: YTHDF1 promotes PASMCs proliferation and PH by enhancing MAGED1 translation. This study identifies the m⁶A RNA modification as a novel mediator of pathological changes in PASMCs and PH.

Objective—: Pulmonary hypertension (PH) is a progressive disease arising from remodeling and narrowing of pulmonary arteries (PAs) resulting in high pulmonary blood pressure and ultimately right ventricular failure. Elevated production of reactive oxygen species by NADPH oxidase 4 (Nox4) is associated with increased pressure in PH. However, the cellular location of Nox4 and its contribution to aberrant vascular remodeling in PH remains poorly understood. Therefore, we sought to identify the vascular cells expressing Nox4 in PAs and determine the functional relevance of Nox4 in PH. Approach and Results—: Elevated expression of Nox4 was detected in hypertensive PAs from 3 rat PH models and human PH using qualititative real-time reverse transcription polymerase chain reaction, Western blot, and immunofluorescence. In the vascular wall, Nox4 was detected in both endothelium and adventitia, and perivascular staining was prominently increased in hypertensive lung sections, colocalizing with cells expressing fibroblast and monocyte markers and matching the adventitial location of reactive oxygen species production. Small-molecule inhibitors of Nox4 reduced adventitial reactive oxygen species generation and vascular remodeling as well as ameliorating right ventricular hypertrophy and noninvasive indices of PA stiffness in monocrotaline-treated rats as determined by morphometric analysis and high-resolution digital ultrasound. Nox4 inhibitors improved PH in both prevention and reversal protocols and reduced the expression of fibroblast markers in isolated PAs. In fibroblasts, Nox4 overexpression stimulated migration and proliferation and was necessary for matrix gene expression. Conclusion—: These findings indicate that Nox4 is prominently expressed in the adventitia and contributes to altered fibroblast behavior, hypertensive vascular remodeling, and development of PH.

Plicated as a mediator of chronic inflammatory diseases, but recent studies dispute these findings and suggest that IL-17A can favorably modulate inflammation. Here, we examined the role of IL-17A in diabetic nephropathy. We observed that IL-17A levels in plasma and urine were reduced in patients with advanced diabetic nephropathy. Type 1 diabetic mice that are genetically deficient in IL-17A developed more severe nephropathy, whereas administration of low-dose IL-17A prevented diabetic nephropathy in models of type 1 and type 2 diabetes. Moreover, IL-17A administration effectively treated, prevented, and reversed established nephropathy in genetic models of diabetes. Protective effects were also observed after administration of IL-17F but not IL-17C or IL-17E. Notably, tubular epithelial cell-specific overexpression of IL-17A was sufficient to suppress diabetic nephropathy. Mechanistically, IL-17A administration suppressed phosphorylation of signal transducer and activator of transcription 3, a central mediator of fibrosis, upregulated anti-inflammatory microglia/macrophage WAP domain protein in an AMP-activated protein kinase–dependent manner and favorably modulated renal oxidative stress and AMP-activated protein kinase activation. Administration of recombinant microglia/macrophage WAP domain protein suppressed diabetes-induced albuminuria and enhanced M2 marker expression. These observations suggest that the beneficial effects of IL-17 are isoform-specific and identify low-dose IL-17A administration as a promising therapeutic approach in diabetic kidney disease....