Berberine Reduces Lipid Accumulation by Promoting Fatty Acid Oxidation in Renal Tubular Epithelial Cells of the Diabetic Kidney

Abnormal lipid metabolism in renal tubular epithelial cells contributes to renal lipid accumulation and disturbed mitochondrial bioenergetics which are important in diabetic kidney disease. Berberine, the major active constituent of Rhizoma coptidis and Cortex phellodendri, is involved in regulating glucose and lipid metabolism. The present study aimed to investigate the protective effects of berberine on lipid accumulation in tubular epithelial cells of diabetic kidney disease. We treated type 2 diabetic db/db mice with berberine (300 mg/kg) for 12 weeks. Berberine treatment improved the physical and biochemical parameters of the db/db mice compared with db/m mice. In addition, berberine decreased intracellular lipid accumulation and increased the expression of fatty acid oxidation enzymes CPT1, ACOX1 and PPAR-α in tubular epithelial cells of db/db mice. The mitochondrial morphology, mitochondrial membrane potential, cytochrome c oxidase activity, mitochondrial reactive oxygen species, and mitochondrial ATP production in db/db mice kidneys were significantly improved by berberine. Berberine intervention activated the AMPK pathway and increased the level of PGC-1α. In vitro berberine suppressed high glucose-induced lipid accumulation and reversed high glucose-induced reduction of fatty acid oxidation enzymes in HK-2 cells. Importantly, in HK-2 cells, berberine treatment blocked the change in metabolism from fatty acid oxidation to glycolysis under high glucose condition. Moreover, berberine restored high glucose-induced dysfunctional mitochondria. These data suggested that berberine alleviates diabetic renal tubulointerstitial injury through improving high glucose-induced reduction of fatty acid oxidation, alleviates lipid deposition, and protect mitochondria in tubular epithelial cells.

miR-3587 Inhibitor Attenuates Ferroptosis Following Renal Ischemia-Reperfusion Through HO-1

Renal ischemia-reperfusion (IR) is frequently observed in patients who are critically ill, yet there are no reliable or effective approaches for the treatment of this condition. Ferroptosis, a form of programmed cell death, is regulated by key genes such as glutathione peroxidase 4 (GPX4) and heme oxygenase-1 (HMOX1) and participates in the injury of renal tubular epithelial cells during IR. This study aimed to investigate the miRNA-mRNA regulatory networks involved in ferroptosis following renal IR. Using bioinformatics analysis, HMOX1 was found to be significantly upregulated during the early stages of renal IR injury, and microRNA-3587 (miR-3587) was identified as a putative regulator of HMOX1. When a miR-3587 inhibitor was applied in a hypoxia-reoxygenation (HR) model system using renal tubular epithelial cells, HO-1 protein (encoded by HMOX1) expression was significantly increased relative to that observed in the HR group, with concomitant increases in GPX4 protein levels, enhanced cell viability, a reduction in malondialdehyde content, decreased Fe2+ level, and the restoration of normal mitochondrial membrane potential. Transmission electron microscopy showed a reduced or absent mitochondrial crest and a damaged mitochondrial outer membrane. Targeting of HMOX1 by miR-3587 was confirmed by luciferase reporter gene assay. In conclusion, these preliminary results indicate that inhibition of miR-3587 promotes HO-1 upregulation, thereby protecting renal tissues from IR-induced ferroptosis.

Inhibitory Effect of Gliquidone on Epithelial-to-Mesenchymal-Transition of Renal Tubular Epithelial Cells Under Diabetic Nephropathy Mouse Model

This research aimed to study the inhibitory effect of Glurenorm (gliquidone) on epithelial-to-mesenchymal-transition (EMT) of renal tubular epithelial cells based on the diabetic nephropathy (DN) model. In this study, 30 specific pathogen-free (SPF) mice were selected to construct DN model and randomly rolled into groups A, B, and C, with 10 mice in each group. Low-dose, mediumdose, and high-dose Glurenorm were administered intragastrically. The results showed that the serum urea nitrogen content (7.23±0.39 mmol/L, 6.18±0.46 mmol/L) of control and C group was considerably inferior to A group (8.01±0.48 mmol/L), and the content of C group was greatly lower than controls (P < 0.05). The creatinine clearance rate (2.97±0.44 mL/min, 4.02±0.31 mL/min) of mice in control and C group was notably superior to A group (2.18±0.38 mL/min), and that of C group was obviously higher versus controls (P < 0.05). After 5 weeks of intragastric intervention by Glurenorm, the body mass of the mice in control and C group was evidently lower relative to A group, and that of C group was obviously higher versus controls (P < 0.05). Mice in control and C group were remarkably lower in body mass at the 7th week after Glurenorm intervention versus A group, and C group was relatively lower versus controls (P < 0.05). In short, EMT played an important role in promoting the occurrence and progression of renal fibrosis. Glurenorm can reduce the progression of renal fibrosis, inhibit EMT of renal tubular epithelial cells, and effectively protect kidney function.

Effects and Mechanism of Salvianolic Acid B on the Injury of Human Renal Tubular Epithelial Cells Induced by Iopromide

With the increasing application of medical imaging contrast materials, contrast-induced nephropathy (CIN) has become the third major cause of iatrogenic renal insufficiency. CIN is defined as an absolute increase in serum creatinine levels of at least 0.50 mg/dl or an increase &gt;25% of serum creatinine from baseline after exposure to contrast. In this study, the protective effects of salvianolic acid B (Sal B) were detected in human renal tubular epithelial cells (HK-2) exposed to iopromide. The results showed that different concentrations of Sal B counteract the loss of cell viability induced by iopromide, and reduce cell apoptosis, the reactive oxygen species (ROS) levels, and the levels of endoplasmic reticulum stress (ERS)–related and apoptosis-related proteins such as p-IRE-1α, p-eIF-2α/eIF-2α, p-JNK, CHOP, Bax/Bcl-2, and cleaved caspase-3. In addition, Sal B at a concentration of 100 μmol/L inhibited ERS and reduced cell damage to a similar extent as the ERS inhibitor 4-PBA. Importantly, treatment with Sal B could abolish the injury induced by ERS agonist tunicamycin, increasing cell viability and the mitochondrial membrane potential, as well as significantly reducing ROS levels and the expression of Bax/Bcl-2, cleaved-caspase-3, GRP78, p-eIF2α, p-JNK, and CHOP. These results suggested that the protective effect of Sal B against HK-2 cell injury induced by iopromide may be related to the inhibition of ERS.

Hyperosmotic stress induces epithelial-mesenchymal transition through rearrangements of focal adhesions in tubular epithelial cells

Epithelial-mesenchymal transition (EMT) of tubular epithelial cells is a hallmark of renal tubulointerstitial fibrosis and is associated with chronic renal injury as well as acute renal injury. As one of the incidences and risk factors for acute renal injury, increasing the osmolality in the proximal tubular fluid by administration of intravenous mannitol has been reported, but the detailed mechanisms remain unclear. Hyperosmotic conditions caused by mannitol in the tubular tissue may generate not only osmotic but also mechanical stresses, which are known to be able to induce EMT in epithelial cells, thereby contributing to renal injury. Herein, we investigate the effect of hyperosmolarity on EMT in tubular epithelial cells. Normal rat kidney (NRK)-52E cells were exposed to mannitol-induced hyperosmotic stress. Consequently, the hyperosmotic stress led to a reduced expression of the epithelial marker E-cadherin and an enhanced expression of the mesenchymal marker, α-smooth muscle actin (α-SMA), which indicates an initiation of EMT in NKR-52E cells. The hyperosmotic condition also induced time-dependent disassembly and rearrangements of focal adhesions (FAs) concomitant with changes in actin cytoskeleton. Moreover, prevention of FAs rearrangements by cotreatment with Y-27632, a Rho-associated protein kinase inhibitor, could abolish the effects of hyperosmotic mannitol treatment, thus attenuating the expression of α-SMA to the level in nontreated cells. These results suggest that hyperosmotic stress may induce EMT through FAs rearrangement in proximal tubular epithelial cells.