Effect of 1,25(OH)2D3 on transdifferentiation of rat renal tubular epithelial cells induced by high glucose

VDR Regulates BNP Promoting Neurite Growth and Survival of Cochlear Spiral Ganglion Neurons through cGMP-PKG Signaling Pathway

Spiral ganglion neurons (SGNs) are important for hearing, and their peripheral and central processes connect sensory cells of the Corti organ to the central nervous system. The resulting network forms a point-to-point auditory conduction. As a cardiac hormone, brain natriuretic peptide (BNP) binds to natriuretic peptide receptor type A leading to diuresis, vasodilatation, inhibition of renin and aldosterone production, and cardiac and vascular myocyte growth. This study primarily aimed to explore the expression and function of BNP in the rat's inner ear and elucidate its regulatory mechanism. We determined the expression and function of BNP and found that the vitamin D receptor (VDR) could upregulate the expression of BNP and enhance its function. In SGNs of the rat inner ear, BNP promotes neuron survival and prolongs neurite length through the cGMP-PKG signaling pathway, which could be regulated by VDR and provide a novel approach for neuronal regeneration therapy. To the best of our knowledge, this is the first study to report this potential transcriptional regulatory relationship and will act as a reference for research on neuronal regeneration therapy for SGNs injury.

Protective Role of Vitamin D in Renal Tubulopathies

Vitamin D is tightly linked with renal tubular homeostasis: the mitochondria of proximal convoluted tubule cells are the production site of 1α,25-dihydroxyvitamin D3. Patients with renal impairment or tubular injury often suffer from chronic inflammation. This alteration comes from oxidative stress, acidosis, decreased clearance of inflammatory cytokines and stimulation of inflammatory factors. The challenge is to find the right formula for each patient to correctly modulate the landscape of treatment and preserve the essential functions of the organism without perturbating its homeostasis. The complexity of the counter-regulation mechanisms and the different axis involved in the Vitamin D equilibrium pose a major issue on Vitamin D as a potential effective anti-inflammatory drug. The therapeutic use of this compound should be able to inhibit the development of inflammation without interfering with normal homeostasis. Megalin-Cubilin-Amnionless and the FGF23-Klotho axis represent two Vitamin D-linked mechanisms that could modulate and ameliorate the damage response at the renal tubular level, balancing Vitamin D therapy with an effect potent enough to contrast the inflammatory cascades, but which avoids potential severe side effects.

Tanshinone IIA improves diabetes mellitus via the NF-κB-induced AMPK signal pathway

Diabetes mellitus (DM) is a systemic metabolic disease. Tanshinone IIA (Tan-IIA) presents potential benefits for DM. The purpose of this study was to investigate the efficacy of Tan-IIA in type 2 DM rats and explore its potential mechanism in renal cells. A type 2 DM rat model was established and administered with Tan-IIA or PBS. It was demonstrated that Tan-IIA treatment significantly reduced levels of total cholesterol, non-esterified fatty acids, total triglyceride and low-density lipoprotein cholesterol in experimental DM rats compared with the control group. The results indicated that Tan-IIA treatment significantly decreased levels of interleukin (IL)-8, tumor necrosis factor-α, C-reactive protein and IL-6. It was identified that Tan-IIA treatment significantly decreased nuclear factor-κB levels and significantly elevated 5' adenosine monophosphate-activated protein kinase levels. Western blot analysis indicated that Tan-IIA elevated immunocyte precipitation in renal cells. Furthermore, Tan-IIA treatment improved lipid metabolism, glucose metabolism, insulin resistance and body weight of type 2 DM rats. In conclusion, Tan-IIA administration may inhibit inflammatory cytokines and alleviate type 2 DM symptoms in experimental rats.

1,25(OH)2D3 promotes chondrocyte apoptosis and restores physical function in rheumatoid arthritis through the NF-κB signal pathway

We explored the modulatory effect of 1,25(OH)₂D₃ on chondrocytes and physical function in rats with RA and its mechanism underlying the regulation of NF-κB signal pathway. RA patients and healthy volunteers were selected. Sprague-Dawley (SD) rats were used to establish RA models. The paw volume of rats was estimated. Chondrocytes were isolated from RA rats. The protein levels in both cartilage tissues and chondrocytes were determined using western blotting. Apoptosis was evaluated using TUNEL assay. Serum levels of IL-1β, IL-6, IL-10 and IL-17 were measured by enzyme-linked immunosorbent assay (ELISA). Serum levels of 1,25(OH)₂D₃ were lower in RA patients than in healthy volunteers. Rats in the RA + VD₃ group were lighter than those in normal and PBS groups, with an increased paw volume, severer joint swelling, higher expression levels of p-IκBα, p-p65, IL-1β, IL-6, and IL-17, and lower expression level of IL-10, while those in RA and RA + VD₃ + NF-κB group differed more significantly. In addition, by comparing RA rats and RA + NF-κB rats, we found that TNF-α stimulation exacerbated RA, increased expression levels of p-IκBα, p-p65, IL-1β, IL-6, and IL-17, and decreased the expression level of IL-10. Compared with RA chondrocytes, chondrocytes from RA + VD₃ rats exhibited lower expression levels of p-IκBα and p-p65, and had more apoptotic cells, while those from RA + NF-κB rats showed an opposite trend. Taken together, 1,25(OH)₂D₃ accelerates chondrocyte apoptosis and improve physical function in rats with RA by the inhibition of NF-κB signal pathway.