Diabetic nephropathy may occur, in part, as a result of intrarenal oxidative stress. NADPH oxidases comprise the only known dedicated reactive oxygen species (ROS)-forming enzyme family. In the ...rodent kidney, three isoforms of the catalytic subunit of NADPH oxidase are expressed (Nox1, Nox2, and Nox4). Here we show that Nox4 is the main source of renal ROS in a mouse model of diabetic nephropathy induced by streptozotocin administration in ApoE(-/-) mice. Deletion of Nox4, but not of Nox1, resulted in renal protection from glomerular injury as evidenced by attenuated albuminuria, preserved structure, reduced glomerular accumulation of extracellular matrix proteins, attenuated glomerular macrophage infiltration, and reduced renal expression of monocyte chemoattractant protein-1 and NF-κB in streptozotocin-induced diabetic ApoE(-/-) mice. Importantly, administration of the most specific Nox1/4 inhibitor, GKT137831, replicated these renoprotective effects of Nox4 deletion. In human podocytes, silencing of the Nox4 gene resulted in reduced production of ROS and downregulation of proinflammatory and profibrotic markers that are implicated in diabetic nephropathy. Collectively, these results identify Nox4 as a key source of ROS responsible for kidney injury in diabetes and provide proof of principle for an innovative small molecule approach to treat and/or prevent chronic kidney failure.
Oxidative stress is considered a hallmark of atherosclerosis. In particular, the superoxide-generating type 1 NADPH oxidase (NOX1) has been shown to be induced and play a pivotal role in early phases ...of mouse models of atherosclerosis and in the context of diabetes mellitus. Here, we investigated the role of the most abundant type 4 isoform (NOX4) in human and mouse advanced atherosclerosis.
Plaques of patients with cardiovascular events or established diabetes mellitus showed a surprising reduction in expression of the most abundant but hydrogen peroxide (H2O2)-generating type 4 isoform (Nox4), whereas Nox1 mRNA was elevated, when compared with respective controls. As these data suggested that NOX4-derived reactive oxygen species may convey a surprisingly protective effect during plaque progression, we examined a mouse model of accelerated and advanced diabetic atherosclerosis, the streptozotocin-treated ApoE(-/-) mouse, with (NOX4(-/-)) and without genetic deletion of Nox4. Similar to the human data, advanced versus early plaques of wild-type mice showed reduced Nox4 mRNA expression. Consistent with a rather protective role of NOX4-derived reactive oxygen species, NOX4(-/-) mice showed increased atherosclerosis when compared with wild-type mice. Deleting NOX4 was associated with reduced H2O2 forming activity and attenuation of the proinflammatory markers, monocyte chemotratic protein-1, interleukin-1β, and tumor necrosis factor-α, as well as vascular macrophage accumulation. Furthermore, there was a greater accumulation of fibrillar collagen fibres within the vascular wall and plaque in diabetic Nox4(-/-)ApoE(-/-) mice, indicative of plaque remodeling. These data could be replicated in human aortic endothelial cells in vitro, where Nox4 overexpression increased H2O2 and reduced the expression of pro-oxidants and profibrotic markers. Interestingly, Nox4 levels inversely correlated with Nox2 gene and protein levels. Although NOX2 is not constitutively active unlike NOX4 and forms rather superoxide, this opens up the possibility that at least some effects of NOX4 deletion are mediated by NOX2 activation.
Thus, the appearance of reactive oxygen species in atherosclerosis is apparently not always a nondesirable oxidative stress, but can also have protective effects. Both in humans and in mouse, the H2O2-forming NOX4, unlike the superoxide-forming NOX1, can act as a negative modulator of inflammation and remodeling and convey atheroprotection. These results have implications on how to judge reactive oxygen species formation in cardiovascular disease and need to be considered in the development of NOX inhibitory drugs.
Diabetic Kidney Disease (DKD) is a significant complication of diabetes and primary cause of end-stage renal disease globally. The exact mechanisms underlying DKD remain poorly understood, but ...multiple factors, including the renin-angiotensin-aldosterone system (RAAS), play a key role in its progression. Aldosterone, a mineralocorticoid steroid hormone, is one of the key components of RAAS and a potential mediator of renal damage and inflammation in DKD. miRNAs, small noncoding RNA molecules, have attracted interest due to their regulatory roles in numerous biological processes. These processes include aldosterone signaling and mineralocorticoid receptor (MR) expression. Numerous miRNAs have been recognized as crucial regulators of aldosterone signaling and MR expression. These miRNAs affect different aspects of the RAAS pathway and subsequent molecular processes, which impact sodium balance, ion transport, and fibrosis regulation. This review investigates the regulatory roles of particular miRNAs in modulating aldosterone signaling and MR activation, focusing on their impact on kidney injury, inflammation, and fibrosis. Understanding the complex interaction between miRNAs and the RAAS could lead to a new strategy to target aldosterone signaling and MR activation using miRNAs. This highlights the potential of miRNA-based interventions for DKD, with the aim of enhancing kidney outcomes in individuals with diabetes.
Epigenetic changes are implicated in the persisting vascular effects of hyperglycemia. The precise mechanism whereby chromatin structure and subsequent gene expression are regulated by glucose in ...vascular endothelial cells remain to be fully defined.
We have studied the molecular and functional mechanism whereby the Set7 methyltransferase associates with chromatin formation and histone methylation in vascular cells in response to current and previous exposure to glucose.
To characterize the molecular and functional identity of the Set7 protein, we used vascular cells overexpressing or lacking Set7. Chromatin fractionation for mono-methylation of lysine 4 on histone H3 identified methyltransferase activity. Immunofluorescence experiments strongly suggest that Set7 protein accumulates in the nucleus in response to hyperglycemia. Moreover, activation of proinflammatory genes by high glucose is dependent on Set7 but distinguished by H3K4m1 gene patterns. We show that transient hyperglycemia regulates the expression of proinflammatory genes in vascular endothelial cells in vitro and the persistent increase in glucose-induced gene expression in the aorta of nondiabetic mice.
This study uncovers that the response to hyperglycemia in vascular endothelial cells involves the H3K4 methyltransferase, Set7. This enzyme appears to regulate glucose-induced chromatin changes and gene expression not only by H3K4m1-dependent but also H3K4m1-independent pathways. Furthermore, Set7 appears to be responsible for sustained vascular gene expression in response to prior hyperglycemia and is a potential molecular mechanism for the phenomenon of hyperglycemic memory.
In diabetes mellitus, vascular complications such as atherosclerosis are a major cause of death. The key underlying pathomechanisms are unclear. However, hyperglycemic oxidative stress derived from ...NADPH oxidase (Nox), the only known dedicated enzyme to generate reactive oxygen species appears to play a role. Here we identify the Nox1 isoform as playing a key and pharmacologically targetable role in the accelerated development of diabetic atherosclerosis.
Human aortic endothelial cells exposed to hyperglycemic conditions showed increased expression of Nox1, oxidative stress, and proinflammatory markers in a Nox1-siRNA reversible manner. Similarly, the specific Nox inhibitor, GKT137831, prevented oxidative stress in response to hyperglycemia in human aortic endothelial cells. To examine these observations in vivo, we investigated the role of Nox1 on plaque development in apolipoprotein E-deficient mice 10 weeks after induction of diabetes mellitus. Deletion of Nox1, but not Nox4, had a profound antiatherosclerotic effect correlating with reduced reactive oxygen species formation, attenuation of chemokine expression, vascular adhesion of leukocytes, macrophage infiltration, and reduced expression of proinflammatory and profibrotic markers. Similarly, treatment of diabetic apolipoprotein E-deficient mice with GKT137831 attenuated atherosclerosis development.
These studies identify a major pathological role for Nox1 and suggest that Nox1-dependent oxidative stress is a promising target for diabetic vasculopathies, including atherosclerosis.
Reverse osmosis membranes based on aromatic polyamide (ar-PA) are widely used in desalination of seawater, yet the microscopic mechanism of water diffusion through a polyamide layer remains elusive. ...Here, we study the structure and dynamics of polymer chains and water molecules in ar-PA in comparison to nylon 6 (one of aliphatic polyamides) under various water contents (0.0–15.9 wt%). The infrared (IR) difference spectrum between dry and moist ar-PA shows little change in amide A bands, in contrast to that of nylon 6 which yields a prominent dip. Theoretical analyses using molecular dynamics simulations and quantum electronic and vibrational calculations reveal that the dip in nylon 6 is caused by breaking of hydrogen bonds (HBs) among amide groups. The incoming water molecules that break amide-amide HBs are bound to polyamide chains nearby and diffuse slowly. On the other hand, the amide-amide HBs of ar-PA are kept upon hydration. Such polymer structure facilitates growth of large water clusters with more than 100 water molecules and rapid diffusion of water molecules. The amide A band serves as a fingerprint to characterize the water permeability of polyamide materials.
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•A dip of amide A, present in nylon 6, disappears in RO (aromatic polyamides).•The absence indicates that amide-amide hydrogen bonds (HBs) are kept upon hydration.•The HB structure facilitates growth of water clusters and rapid water diffusion.•The amide A band is a fingerprint to probe the water permeability.
Trained immunity confers a sustained augmented response of innate immune cells to a secondary challenge, via a process dependent on metabolic and transcriptional reprogramming. Because of its ...previous associations with metabolic and transcriptional memory, as well as the importance of H3 histone lysine 4 monomethylation (H3K4me1) to innate immune memory, we hypothesize that the Set7 methyltransferase has an important role in trained immunity induced by β-glucan. Using pharmacological studies of human primary monocytes, we identify trained immunity-specific immunometabolic pathways regulated by Set7, including a previously unreported H3K4me1-dependent plasticity in the induction of oxidative phosphorylation. Recapitulation of β-glucan training in vivo additionally identifies Set7-dependent changes in gene expression previously associated with the modulation of myelopoiesis progenitors in trained immunity. By revealing Set7 as a key regulator of trained immunity, these findings provide mechanistic insight into sustained metabolic changes and underscore the importance of characterizing regulatory circuits of innate immune memory.
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•Set7 regulates enhanced cytokine production in trained immunity in vitro•Set7 knockout mice are unable to mount trained immunity against endotoxin challenge•Set7 modulates cellular respiration in β-glucan-trained macrophages•Set7-dependent histone methylation regulates MDH2 and SDHB in trained cells
Using a combination of pharmacological and genetic approaches, Keating et al. show that the Set7 methyltransferase is a regulator of trained immunity induced by β-glucan. Activation of Set7 increases oxidative phosphorylation in trained cells via histone lysine methylation at gene enhancers of key enzymes of the TCA cycle.
Macrophages are innate immune cells that contribute to classical immune functions and tissue homeostasis. Ubiquitin-specific protease 2 (USP2) controls cytokine production in macrophages, but its ...organ-specific roles are still unknown. In this study, we generated myeloid-selective
Usp2
knockout (ms
Usp2
KO) mice and specifically explored the roles of testicular macrophage-derived USP2 in reproduction. The ms
Usp2
KO mice exhibited normal macrophage characteristics in various tissues. In the testis, macrophage
Usp
2 deficiency negligibly affected testicular macrophage subpopulations, spermatogenesis, and testicular organogenesis. However, frozen–thawed sperm derived from ms
Usp2
KO mice exhibited reduced motility, capacitation, and hyperactivation. In addition, macrophage
Usp2
ablation led to a decrease in the sperm population exhibiting high intracellular pH, calcium influx, and mitochondrial membrane potential. Interrupted pronuclei formation in eggs was observed when using frozen–thawed sperm from ms
Usp2
KO mice for in vitro fertilization. Administration of granulocyte macrophage-colony stimulating factor (GM-CSF), whose expression was decreased in testicular macrophages derived from ms
Usp2
KO mice, restored mitochondrial membrane potential and total sperm motility. Our observations demonstrate a distinct role of the deubiquitinating enzyme in organ-specific macrophages that directly affect sperm function.
Excessive production of renal reactive oxygen species (ROS) plays a major role in diabetic kidney disease (DKD). Here, we provide key findings demonstrating the predominant pathological role of the ...pro-oxidant enzyme NADPH oxidase 5 (NOX5) in DKD, independent of the previously characterized NOX4 pathway. In patients with diabetes, we found increased expression of renal NOX5 in association with enhanced ROS formation and upregulation of ROS-sensitive factors early growth response 1 (EGR-1), protein kinase C-α (PKC-α), and a key metabolic gene involved in redox balance, thioredoxin-interacting protein (TXNIP). In preclinical models of DKD, overexpression of NOX5 in Nox4-deficient mice enhances kidney damage by increasing albuminuria and augmenting renal fibrosis and inflammation via enhanced ROS formation and the modulation of EGR1, TXNIP, ERK1/2, PKC-α, and PKC-ε. In addition, the only first-in-class NOX inhibitor, GKT137831, appears to be ineffective in the presence of NOX5 expression in diabetes. In vitro, silencing of NOX5 in human mesangial cells attenuated upregulation of EGR1, PKC-α, and TXNIP induced by high glucose levels, as well as markers of inflammation (TLR4 and MCP-1) and fibrosis (CTGF and collagens I and III) via reduction in ROS formation. Collectively, these findings identify NOX5 as a superior target in human DKD compared with other NOX isoforms such as NOX4, which may have been overinterpreted in previous rodent studies.
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