High-dose vitamin D3 supplementation ameliorates renal fibrosis by vitamin D receptor activation and inhibiting TGF-β1/Smad3 signaling pathway in 5/6 nephrectomized rats

Antifibrotic effects of vitamin D3 on human lung fibroblasts derived from patients with idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a progressive and fatal interstitial lung disease. Up to now, no treatment can stop the progression of IPF. Vitamin D3 (VD) reduces experimental lung fibrosis in murine models and depletion of vitamin D3 might be associated with the reduced survival of patients with IPF. In this context, we determined if VD can prevent the pro-fibrotic functions of human lung fibroblasts (HLFs) isolated from patients with IPF. IPF and control HLFs were derived from surgical lung biopsies collected from patients with IPF or with primary lung cancer, respectively. VD (3-100 nM) markedly reduced the basal and PDGF-induced proliferation of HLFs. VD also altered cell cycle by increasing the percentage of IPF HLFs arrested in the G0/G1 phase, and by downregulating the expression of various cell cycle regulatory proteins. In addition, VD barely prevented the TGF-β1-induced differentiation in HLFs. At 100 nM, VD slightly reduced the expression of the pro-fibrotic marker α-smooth muscle actin, and had no effect on fibronectin and collagen-1 expression. In contrast, 100 nM VD strongly inhibited the aerobic glycolytic metabolism induced by TGF- β1. Finally, VD reduced both the secretion of lactate, the levels of lactate deshydrogenase mRNA and the activity of intracellular LDH in IPF HLFs. In conclusion, our study shows that VD reduced pro-fibrotic functions of HLFs. These findings suggest that it might be interesting to assess the potential clinical benefits of vitamin D supplementation in patients with IPF, especially on lung function decline.

Differential effect of basal vitamin D status in monocrotaline induced pulmonary arterial hypertension in normal and vitamin D deficient rats: Possible involvement of eNOS/TGF-β/α-SMA signaling pathways

Vitamin D deficiency is common and linked to poor prognosis in pulmonary arterial hypertension (PAH). We investigated the differential effect of basal vitamin D levels in monocrotaline (MCT) induced PAH in normal and vitamin D deficient (VDD) rats. Rats were fed a VDD diet and exposed to filtered fluorescent light to deplete vitamin D. Normal rats were pretreated with vitamin D 100 IU/d and treated with vitamin D 100 and 200 IU/d, while VDD rats received vitamin D 100 IU/d. Vitamin D receptor (VDR) silencing was done in human umbilical vein endothelial cells (HUVECs) using VDR siRNA. Calcitriol (50 nM/mL) was added to human pulmonary artery smooth muscle cells (HPASMCs) and HUVECs before and after the exposure to TGF-β (10 ng/mL). Vitamin D 100 IU/d pretreatment in normal rats up-regulated the expression of eNOS and inhibited endothelial to mesenchymal transition significantly and maximally. Vitamin D 100 IU/d treatment in VDD rats was comparable to vitamin D 200 IU/d treated normal rats. These effects were significantly attenuated by L-NAME (20 mg/kg), a potent eNOS inhibitor. Exposure to TGF- β significantly reduced the expression of eNOS and increased the mesenchymal marker expression in normal and VDR-silenced HUVECs and HPASMCs, which were averted by treatment and maximally inhibited by pretreatment with calcitriol (50 nM). To conclude, this study provided novel evidence suggesting the beneficial role of higher basal vitamin D levels, which are inversely linked with PAH severity.

Oral Administration of Vitamin D3 Prevents Corneal Damage in a Knock-Out Mouse Model of Sjögren's Syndrome

BACKGROUND

Vitamin D deficiency has been associated with dry eye development during Sjögren's syndrome (SS). Here, we investigated whether repeated oral vitamin D3 supplementation could prevent the corneal epithelium damage in an SS mouse model.

METHODS

30 female mouse knock-out for the thrombospondin 1 gene were randomized (six per group) in untreated mice euthanized at 6 weeks as negative control (C-) or at 12 weeks as the positive control for dry eye (C+). Other mice were sacrificed after 6 weeks of oral vitamin D3 supplementation in the drinking water (1000, 8000, and 20,000 IU/kg/week, respectively).

RESULTS

The C+ mice showed alterations in their corneal epithelial morphologies and thicknesses (p < 0.01 vs. C-), while the mice receiving 8000 (M) and 20,000 (H) IU/kg/week of vitamin D3 showed preservation of the corneal epithelium morphology and thickness (p < 0.01 vs. C+). Moreover, while the C+ mice exhibited high levels and activity of corneal tumor necrosis factor alpha converting enzyme (TACE), neovascularization and fibrosis markers; these were all reduced in the M and H mice.

CONCLUSIONS

Oral vitamin D3 supplementation appeared to counteract the negative effect of TACE on corneal epithelium in a mouse model of SS-associated dry eye.

Vitamin D3 attenuates cisplatin-induced intestinal injury by inhibiting ferroptosis, oxidative stress, and ROS-mediated excessive mitochondrial fission

Intestinal injury is one of the main side-effects of cisplatin (CP) chemotherapy, severely limiting the clinical application of CP. Vitamin D₃ is an essential nutrient for mammals and exists in a wide range of foods; it regulates immune function and reduces oxidative stress. However, the effect of vitamin D₃ on CP-induced intestinal injury is not elucidated. This is the first study to investigate the relationship between ferroptosis and the protective effect of vitamin D₃ on CP-induced intestinal injury. An animal model of CP-induced intestinal injury was established to evaluate the effect of vitamin D₃ on CP-induced intestinal injury and elucidate the underlying mechanisms. We found that vitamin D₃ alleviated intestinal barrier injury and the abnormal morphological structure in CP-induced intestinal injury mice. Vitamin D₃ suppressed oxidative stress by increasing the antioxidant capacity, inhibiting the accumulation of ROS and MDA, and reducing intestinal inflammatory responses. Vitamin D₃ also decreased excessive mitochondrial fission and increased mitochondrial ATPase activity by inhibiting ROS production, which further alleviated the accumulation of ROS. We also confirmed the involvement of ferroptosis in CP-induced intestinal injury in our animal model using ferrostatin-1 (Fer-1) intervention. Vitamin D₃ decreased iron accumulation and reversed GPX4 and DHODH down-regulation. In conclusion, vitamin D₃ protected against CP-induced intestinal injury by inhibiting ferroptosis and alleviating oxidative stress and ROS-mediated excessive mitochondrial fission, suggesting that it may be a novel and promising candidate to prevent CP-induced intestinal injury.

The Protective Effect of Ursolic Acid on Unilateral Ureteral Obstruction in Rats by Activating the Nrf2/HO-1 Antioxidant Signaling Pathway

Renal interstitial fibrosis is a common pathological feature of a variety of kidney diseases that progress to end-stage renal disease. The excessive deposition of extracellular matrix (ECM) is a typical pathological change of renal interstitial fibrosis. The production of reactive oxygen species in renal tubules is an important factor leading to the development of renal interstitial fibrosis. Ursolic acid (UA) is a natural pentacyclic triterpene carboxylic acid compound widely found in plants. It has anti-inflammatory, antioxidant, and antitumor cell proliferation effects. It can reduce the development of fibrosis by inhibiting the oxidative stress response of the liver; there is currently no relevant research on whether UA can protect the renal interstitial fibrosis by resisting oxidative stress in the kidneys. In this study, our purpose is to investigate the effect of ursolic acid on renal interstitial fibrosis after unilateral ureteral obstruction (UUO) in rats and its related mechanisms. We established a UUO model by surgically ligating the right ureter of the rat and instilling UA preparation (40 mg/kg/d) through the stomach after the operation, once a day for 7 days. We found that UUO caused impaired renal function, increased pathological damage, increased renal interstitial fibrosis, increased apoptosis, increased oxidative stress damage, and decreased antioxidants. However, after UA preparations were given, the abovementioned damage was significantly improved. At the same time, we also found that UA preparations can significantly increase the relative expression of Nrf2/HO-1 signaling pathway in kidney tissue after UUO. In order to further verify whether the Nrf2/HO-1 signaling pathway is involved in the development of renal interstitial fibrosis, we injected zinc protoporphyrin (ZnPP, 45 umol/kg), a specific blocker of the Nrf2/HO-1 signaling pathway, into the intraperitoneal cavity after UUO in rats and before the gastric perfusion of ursolic acid preparations. Subsequently, we observed that the protective effect of UA on renal interstitial fibrosis after UUO in rats was reversed. Combining all the research results, we proved that UA has a protective effect on renal interstitial fibrosis after UUO in rats, which may be achieved by activating the Nrf2/HO-1 signaling pathway.

Effect of a high vs. standard dose of vitamin D3 supplementation on bone metabolism and kidney function in children with chronic kidney disease

We investigated the effects of high- vs. standard-dose vitamin D supplementation on kidney function and bone metabolism in children with chronic kidney disease (CKD). Children were randomized to receive one of two formulations: 75 participants received 2,000 IU/D of oral supplementation of vitamin D, while 75 participants received 400 IU/d for a minimum of 4 months. We investigated the effects of vitamin D supplementation on kidney-related indicators and bone metabolism-related indicators at different doses. A total of 158 participants were screened, among whom 150 met the inclusion criteria. The indicators of chronic kidney disease such as eGFR and serum uric acid were negatively correlated with the 25(OH)D level and BMD. Serum 25(OH)D and osteocalcin levels were positively correlated with spine BMD. The standard dose of vitamin D can improve the serum uric acid level, but high doses of vitamin D supplementation had no significant effect on the serum uric acid level. High doses of vitamin D supplementation can also improve the alkaline phosphatase level. When comparing the results of different doses of vitamin D supplementation, it was found that high-dose vitamin D supplementation did not improve bone density in the spine and femur neck relative to the standard dose of vitamin D but improved hypocalcemia and N-terminal propeptide of the human procollagen type I (PINP) level. Among the children with clinical kidney disease, high-dose vitamin D treatment for 4 months resulted in statistically significant improvement in kidney function but no significant difference in bone metabolism compared with the standard-dose vitamin D treatment.