Nox4 is a Target for Tuberin Deficiency Syndrome

NADPH oxidase 4 inhibition is a complementary therapeutic strategy for spinal muscular atrophy

Introduction

Spinal muscular atrophy (SMA) is a fatal neurodegenerative disorder, characterized by motor neuron (MN) degeneration and severe muscular atrophy and caused by Survival of Motor Neuron (SMN) depletion. Therapies aimed at increasing SMN in patients have proven their efficiency in alleviating SMA symptoms but not for all patients. Thus, combinational therapies are warranted. Here, we investigated the involvement of NADPH oxidase 4 (NOX4) in SMA-induced spinal MN death and if the modulation of Nox4 activity could be beneficial for SMA patients.

Methods

We analysed in the spinal cord of severe type SMA-like mice before and at the disease onset, the level of oxidative stress and Nox4 expression. Then, we tested the effect of Nox4 inhibition by GKT137831/Setanaxib, a drug presently in clinical development, by intrathecal injection on MN survival and motor behaviour. Finally, we tested if GKT137831/Setanaxib could act synergistically with FDA-validated SMN-upregulating treatment (nusinersen).

Results

We show that NOX4 is overexpressed in SMA and its inhibition by GKT137831/Setanaxib protected spinal MN from SMA-induced degeneration. These improvements were associated with a significant increase in lifespan and motor behaviour of the mice. At the molecular level, GKT137831 activated the pro-survival AKT/CREB signaling pathway, leading to an increase in SMN expression in SMA MNs. Most importantly, we found that the per os administration of GKT137831 acted synergistically with a FDA-validated SMN-upregulating treatment.

Conclusion

The pharmacological inhibition of NOX4 by GKT137831/Setanaxib is neuroprotector and could represent a complementary therapeutic strategy to fight against SMA.

Nanodrugs alleviate acute kidney injury: Manipulate RONS at kidney

Currently, there are no clinical drugs available to treat acute kidney injury (AKI). Given the high prevalence and high mortality rate of AKI, the development of drugs to effectively treat AKI is a huge unmet medical need and a research hotspot. Although existing evidence fully demonstrates that reactive oxygen and nitrogen species (RONS) burst at the AKI site is a major contributor to AKI progression, the heterogeneity, complexity, and unique physiological structure of the kidney make most antioxidant and anti-inflammatory small molecule drugs ineffective because of the lack of kidney targeting and side effects. Recently, nanodrugs with intrinsic kidney targeting through the control of size, shape, and surface properties have opened exciting prospects for the treatment of AKI. Many antioxidant nanodrugs have emerged to address the limitations of current AKI treatments. In this review, we systematically summarized for the first time about the emerging nanodrugs that exploit the pathological and physiological features of the kidney to overcome the limitations of traditional small-molecule drugs to achieve high AKI efficacy. First, we analyzed the pathological structural characteristics of AKI and the main pathological mechanism of AKI: hypoxia, harmful substance accumulation-induced RONS burst at the renal site despite the multifactorial initiation and heterogeneity of AKI. Subsequently, we introduced the strategies used to improve renal targeting and reviewed advances of nanodrugs for AKI: nano-RONS-sacrificial agents, antioxidant nanozymes, and nanocarriers for antioxidants and anti-inflammatory drugs. These nanodrugs have demonstrated excellent therapeutic effects, such as greatly reducing oxidative stress damage, restoring renal function, and low side effects. Finally, we discussed the challenges and future directions for translating nanodrugs into clinical AKI treatment.

•

AKI is a common clinical acute syndrome with high morbidity and mortality but without effective clinical drug available.

•

Hypoxia and accumulation of toxic substances are key pathological features of various heterogeneous AKI.

•

Excessive RONS is the core of the pathological mechanism of AKI.

•

The development of nanodrugs is expected to achieve successful treatment in AKI.

NADPH oxidase family proteins: signaling dynamics to disease management

Reactive oxygen species (ROS) are pervasive signaling molecules in biological systems. In humans, a lack of ROS causes chronic and extreme bacterial infections, while uncontrolled release of these factors causes pathologies due to excessive inflammation. Professional phagocytes such as neutrophils (PMNs), eosinophils, monocytes, and macrophages use superoxide-generating NADPH oxidase (NOX) as part of their arsenal of antimicrobial mechanisms to produce high levels of ROS. NOX is a multisubunit enzyme complex composed of five essential subunits, two of which are localized in the membrane, while three are localized in the cytosol. In resting phagocytes, the oxidase complex is unassembled and inactive; however, it becomes activated after cytosolic components translocate to the membrane and are assembled into a functional oxidase. The NOX isoforms play a variety of roles in cellular differentiation, development, proliferation, apoptosis, cytoskeletal control, migration, and contraction. Recent studies have identified NOX as a major contributor to disease pathologies, resulting in a shift in focus on inhibiting the formation of potentially harmful free radicals. Therefore, a better understanding of the molecular mechanisms and the transduction pathways involved in NOX-mediated signaling is essential for the development of new therapeutic agents that minimize the hyperproduction of ROS. The current review provides a thorough overview of the various NOX enzymes and their roles in disease pathophysiology, highlights pharmacological strategies, and discusses the importance of computational modeling for future NOX-related studies.

Interplay between RNA-binding protein HuR and Nox4 as a novel therapeutic target in diabetic kidney disease

Objective

Glomerular injury is a prominent pathological feature of diabetic kidney disease (DKD). Constitutively active NADPH oxidase 4 (Nox4) is a major source of reactive oxygen species that mediates hyperglycemia-induced mesangial cell (MC) fibrotic injury. However, the mechanism that Nox4 utilizes to achieve its biological outcome remains elusive, and the signaling pathways that regulate this isoform oxidase are not well understood. Here, our goal is to study the detailed mechanism by which NAPDH oxidase 4 (Nox4) is post-transcriptionally regulated in MC during diabetic pathology.

Methods

We studied the protein expression of HuR, Nox4 and matrix proteins by western blotting, while we assessed the mRNA stability of Nox4 by RT-PCR and polysomal assay, examined in vitro cultured glomerular mesangial cells treated by high glucose (HG) and diabetic animal induced by STZ. The binding assay between HuR and the Nox4 promoter was done by immuno-precipiating with HuR antibody and detecting the presence of Nox4 mRNA, or by pull-down by using biotinlyated labeled Nox4 promoter RNA and detecting the presence of the HuR protein. The binding was also confirmed in MCs where Nox4 promoter-containing luciferage constructs were transfected. ROS levels were measured with DHE/DCF dyes in cells, or lucigenin chemiluminescence for Nox enzymatic levels, or HPLC assay for superoxide. HuR protein was inhibited by antisense oligo that utilized osmotic pumps for continuous delivery in animal models. The H1bAc1 ratio was measured by an ELISA kit for mice.

Results

We demonstrate that in MCs, high glucose (HG) elicits a rapid upregulation of Nox4 protein via translational mechanisms. Nox4 mRNA 3′ untranslated region (3′-UTR) contains numerous AU-rich elements (AREs) that are potential binding sites for the RNA-binding protein human antigen R (HuR). We show that HG promotes HuR activation/expression and that HuR is required for HG-induced Nox4 protein expression/mRNA translation, ROS generation, and subsequent MC fibrotic injury. Through a series of invitro RNA-binding assays, we demonstrate that HuR acts via binding to AREs in Nox4 3′-UTR in response to HG. The invivo relevance of these observations is confirmed by the findings that increased Nox4 is accompanied by the binding of HuR to Nox4 mRNA in kidneys from type 1 diabetic animals, and further suppressing HuR expression showed a reno-protective role in a type 1 diabetic mouse model via reducing MC injury, along with the improvement of hyperglycemia and renal function.

Conclusions

We established for the first time that HuR-mediated translational regulation of Nox4 contributes to the pathogenesis of fibrosis of the glomerular microvascular bed. Thus therapeutic interventions affecting the interplay between Nox4 and HuR could be exploited as valuable tools in designing treatments for DKD.

•

Increased HuR protein activation/expression responding to HG treatment and in diabetic animals.

•

HuR binds to 3′UTR of Nox4 and promotes its translation during HG treatment.

•

An inhibitor for HuR could be a potential treatment for diabetic kidney disease.

Reactive oxygen species and cancer: A complex interaction

Elevated levels of Reactive Oxygen Species (ROS), increased antioxidant ability and the maintenance of redox homeostasis can cumulatively contribute to tumor progression and metastasis. The sources and the role of ROS in a heterogeneous tumor microenvironment can vary at different stages of tumor: initiation, development, and progression, thus making it a complex subject. In this review, we have summarized the sources of ROS generation in cancer cells, its role in the tumor microenvironment, the possible functions of ROS and its important scavenger systems in tumor progression with special emphasis on solid tumors.