The Na/K-ATPase Signaling and SGLT2 Inhibitor-Mediated Cardiorenal Protection: A Crossed Road?

Exploring novel insecticide candidates: Targeting Na+,K+ -ATPase in Drosophila melanogaster through computational and experimental approaches

Pest infestations have been posing a serious and persistent threat to agricultural production. Traditional insecticides are currently confronted with a multitude of problems. The discovery of novel insecticide targets and the screening of active molecules can offer an entirely new direction for surmounting the limitations of traditional insecticides and lay a solid foundation for the development of highly effective insecticides with distinctive mechanisms of action. In this study, the Na+,K+-ATPase of Drosophila melanogaster has been selected as the target. Its three-dimensional structure has been constructed via homology modeling, and the evaluation has indicated that its quality is reliable. Subsequently, techniques including virtual screening, molecular docking, and molecular dynamics simulation have been employed to screen compounds and investigate their mechanisms of action. The analysis of binding modes has demonstrated that hydrogen bonding and hydrophobic interactions have played a crucial role in the binding of ligands. Molecular dynamics simulations and calculations of binding free energies have shown that Compound 1 and Compound 2 have exhibited similar or even stronger affinities in comparison to known inhibitors. Residue decomposition free energy reveals the types of key amino acid residues involved in the interaction between these compounds and NKA. Preliminary bioactivity assays have verified the bioactivities of these compounds. Ouabain, Compound 1, Compound 2, and Compound 4 have shown significant delayed toxic effects, with Compound 4 having a more pronounced delayed effect. Our study has provided certain valuable ideas and insights for the development of new insecticide molecules targeting the Na+,K+-ATPase of Drosophila melanogaster.

Silica Nanoparticles Induce SH-SY5Y Cells Death Via PARP and Caspase Signaling Pathways

A growing stream of research indicates that exposure to Silica nanoparticles (SiNPs) can cause nervous system damage, leading to the occurrence of neurodegenerative diseases such as Alzheimer's disease. However, the specific mechanism by which SiNPs cause neuroblast injury remains unclear and requires further research. This study established an in vitro experimental model of SH-SY5Y cells exposed to SiNPs and observed cell growth through an inverted fluorescence microscope. Cell viability was measured using an MTT assay. The intracellular ROS and Ca2+ levels were detected by flow cytometry. Cell apoptosis was observed using both Hoechst33342 staining and TUNEL staining. The activities of SOD and ATPase and the content of ATP in the cells were tested by biochemical methods. The genes including parp-1, aif, par, ucp2, vdac and prdx3 were explored using quantitative real-time PCR. The expressions of PARP, AIF, PAR, Caspase-3, Caspase-9 and Cyt C proteins were evaluated by Western Blot. The immunofluorescence technique was used to observe the distribution of Parthanatos-related proteins induced by SiNPs. The results showed that SiNPs reduced cell survival rate, induced excessive ROS and Ca2+ overload, decreased SOD activity, ATPase activity, intracellular and mitochondrial ATP content, increased the expression of mitochondrial function and PARP pathway related genes, as well as PARP and Caspase pathway protein expression, ultimately inducing cell apoptosis. As a further test of the roles of PARP and Caspase pathways in SiNPs induced SH-SY5Y cells death, we selected the PARP inhibitor Olaparib and Caspase inhibitor Z-VAD, and the above effects were significantly improved after treatment with the inhibitors. Conclusively, this study confirmed that SiNPs can generate excessive ROS production in SH-SY5Y cells, alter mitochondrial function, and induce cell death through Parthanatos and caspase dependent apoptotic pathways, which can coexist and interact with each other.

The Renoprotective Mechanisms of Sodium-Glucose Cotransporter-2 Inhibitors (SGLT2i)-A Narrative Review

Chronic kidney disease (CKD) is a noncommunicable condition that has become a major healthcare burden across the globe, often underdiagnosed and associated with low awareness. The main cause that leads to the development of renal impairment is diabetes mellitus and, in contrast to other chronic complications such as retinopathy or neuropathy, it has been suggested that intensive glycemic control is not sufficient in preventing the development of diabetic kidney disease. Nevertheless, a novel class of antidiabetic agents, the sodium-glucose cotransporter-2 inhibitors (SGLT2i), have shown multiple renoprotective properties that range from metabolic and hemodynamic to direct renal effects, with a major impact on reducing the risk of occurrence and progression of CKD. Thus, this review aims to summarize current knowledge regarding the renoprotective mechanisms of SGLT2i and to offer a new perspective on this innovative class of antihyperglycemic drugs with proven pleiotropic beneficial effects that, after decades of no significant progress in the prevention and in delaying the decline of renal function, start a new era in the management of patients with CKD.

SGLT2-independent effects of canagliflozin on NHE3 and mitochondrial complex I activity inhibit proximal tubule fluid transport and albumin uptake

Beyond glycemic control, SGLT2 inhibitors (SGLT2is) have protective effects on cardiorenal function. Renoprotection has been suggested to involve inhibition of NHE3 leading to reduced ATP-dependent tubular workload and mitochondrial oxygen consumption. NHE3 activity is also important for regulation of endosomal pH, but the effects of SGLT2i on endocytosis are unknown. We used a highly differentiated cell culture model of proximal tubule (PT) cells to determine the direct effects of SGLT2i on Na+-dependent fluid transport and endocytic uptake in this nephron segment. Strikingly, canagliflozin but not empagliflozin reduced fluid transport across cell monolayers and dramatically inhibited endocytic uptake of albumin. These effects were independent of glucose and occurred at clinically relevant concentrations of drug. Canagliflozin acutely inhibited surface NHE3 activity, consistent with a direct effect, but did not affect endosomal pH or NHE3 phosphorylation. In addition, canagliflozin rapidly and selectively inhibited mitochondrial complex I activity. Inhibition of mitochondrial complex I by metformin recapitulated the effects of canagliflozin on endocytosis and fluid transport, whereas modulation of downstream effectors AMPK and mTOR did not. Mice given a single dose of canagliflozin excreted twice as much urine over 24 h compared with empagliflozin-treated mice despite similar water intake. We conclude that canagliflozin selectively suppresses Na+-dependent fluid transport and albumin uptake in PT cells via direct inhibition of NHE3 and of mitochondrial function upstream of the AMPK/mTOR axis. These additional targets of canagliflozin contribute significantly to reduced PT Na+-dependent fluid transport in vivo.NEW & NOTEWORTHY Reduced NHE3-mediated Na+ transport has been suggested to underlie the cardiorenal protection provided by SGLT2 inhibitors. We found that canagliflozin, but not empagliflozin, reduced NHE3-dependent fluid transport and endocytic uptake in cultured proximal tubule cells. These effects were independent of SGLT2 activity and resulted from inhibition of mitochondrial complex I and NHE3. Studies in mice are consistent with greater effects of canagliflozin versus empagliflozin on fluid transport. Our data suggest that these selective effects of canagliflozin contribute to reduced Na+-dependent transport in proximal tubule cells.

Hypoxic Stress-Dependent Regulation of Na,K-ATPase in Ischemic Heart Disease

In cardiomyocytes, regular activity of the Na,K-ATPase (NKA) and its Na/K pump activity is essential for maintaining ion gradients, excitability, propagation of action potentials, electro-mechanical coupling, trans-membrane Na⁺ and Ca²⁺ gradients and, thus, contractility. The activity of NKA is impaired in ischemic heart disease and heart failure, which has been attributed to decreased expression of the NKA subunits. Decreased NKA activity leads to intracellular Na⁺ and Ca²⁺ overload, diastolic dysfunction and arrhythmias. One signal likely related to these events is hypoxia, where hypoxia-inducible factors (HIF) play a critical role in the adaptation of cells to low oxygen tension. HIF activity increases in ischemic heart, hypertension, heart failure and cardiac fibrosis; thus, it might contribute to the impaired function of NKA. This review will mainly focus on the regulation of NKA in ischemic heart disease in the context of stressed myocardium and the hypoxia-HIF axis and argue on possible consequences of treatment.

SGLT2 inhibitors in the treatment of type 2 cardiorenal syndrome: Focus on renal tubules

The pathogenesis of type 2 cardiorenal syndrome (CRS) is mostly associated with reduced cardiac output, increased central venous pressure (CVP), activation of the renin-angiotensin-aldosterone system (RAAS), inflammation, and oxidative stress. As a drug to treat diabetes, sodium-glucose transporter 2 inhibitor (SGLT2i) has been gradually found to have a protective effect on the heart and kidney and has a certain therapeutic effect on CRS. In the process of chronic heart failure (CHF) leading to chronic renal insufficiency, the renal tubular system, as the main functional part of the kidney, is the first to be damaged, but this damage can be reversed. In this review, we focus on the protective mechanisms of SGLT2i targeting renal tubular in the treatment of CRS, including natriuresis and diuresis to relieve renal congestion, attenuate renal tubular fibrosis, improve energy metabolism of renal tubular, and slow tubular inflammation and oxidative stress. This may have beneficial effects on the treatment of CRS and is a direction for future research.

New insights into cellular links between sodium-glucose cotransporter-2 inhibitors and ketogenesis

Sodium-glucose cotransporter-2 inhibitors (SGLT2is) are a newly developed class of highly effective antidiabetic therapies that normalize hyperglycemia via urinary glucose excretion. However, they may be accompanied by certain side effects that negatively impact their therapeutic benefits. SGLT2is induce a metabolic shift from glucose to fatty acids and thus increase lipolysis which, in turn, induces ketogenesis. The complete pathways linking SGLT2is to ketoacidosis have not yet been fully elucidated, though much is now known. Therefore, in this mechanistic study, we present the current knowledge and shed light upon the possible cellular pathways involved. A deeper understanding of the possible links between SGLT2is and ketogenesis could help to prevent adverse side effects in diabetic patients treated with these drugs.