Beyond proteinuria: VDR activation reduces renal inflammation in experimental diabetic nephropathy

Local inflammation is thought to contribute to the progression of diabetic nephropathy. The vitamin D receptor (VDR) activator paricalcitol has an antiproteinuric effect in human diabetic nephropathy at high doses. We have explored potential anti-inflammatory effects of VDR activator doses that do not modulate proteinuria in an experimental model of diabetic nephropathy to gain insights into potential benefits of VDR activators in those patients whose proteinuria is not decreased by this therapy. The effect of calcitriol and paricalcitol on renal function, albuminuria, and renal inflammation was explored in a rat experimental model of diabetes induced by streptozotocin. Modulation of the expression of mediators of inflammation by these drugs was explored in cultured podocytes. At the doses used, neither calcitriol nor paricalcitol significantly modified renal function or reduced albuminuria in experimental diabetes. However, both drugs reduced the total kidney mRNA expression of IL-6, monocyte chemoattractant protein (MCP)-1, and IL-18. Immunohistochemistry showed that calcitriol and paricalcitol reduced MCP-1 and IL-6 in podocytes and tubular cells as well as glomerular infiltration by macrophages, glomerular cell NF-κB activation, apoptosis, and extracellular matrix deposition. In cultured podocytes, paricalcitol and calcitriol at concentrations in the physiological and clinically significant range prevented the increase in MCP-1, IL-6, renin, and fibronectin mRNA expression and the secretion of MCP-1 to the culture media induced by high glucose. In conclusion, in experimental diabetic nephropathy VDR activation has local renal anti-inflammatory effects that can be observed even when proteinuria is not decreased. This may be ascribed to decreased inflammatory responses of intrinsic renal cells, including podocytes, to high glucose.     

Molecular mechanism underlying 1,25-dihydroxyvitamin D regulation of nephrin gene expression

Nephrin plays a key role in maintaining the structure of the slit diaphragm in the glomerular filtration barrier. Our previous studies have demonstrated potent renoprotective activity for 1,25-dihydroxyvitamin D (1,25(OH)(2)D(3)). Here we showed that in podocytes 1,25(OH)(2)D(3) markedly stimulated nephrin mRNA and protein expression. ChIP scan of the 6-kb 5' upstream region of the mouse nephrin gene identified several putative vitamin D response elements (VDREs), and EMSA confirmed that the VDRE at -312 (a DR4-type VDRE) could be bound by vitamin D receptor (VDR)/retinoid X receptor. Luciferase reporter assays of the proximal nephrin promoter fragment (-427 to +173) showed strong induction of luciferase activity upon 1,25(OH)(2)D(3) treatment, and the induction was abolished by mutations within -312VDRE. ChIP assays showed that, upon 1,25(OH)(2)D(3) activation, VDR bound to this VDRE leading to recruitment of DRIP205 and RNA polymerase II and histone 4 acetylation. Treatment of mice with a vitamin D analog induced nephrin mRNA and protein in the kidney, accompanied by increased VDR binding to the -312VDRE and histone 4 acetylation. 1,25(OH)(2)D(3) reversed high glucose-induced nephrin reduction in podocytes, and vitamin D analogs prevented nephrin decline in both type 1 and 2 diabetic mice. Together these data demonstrate that 1,25(OH)(2)D(3) stimulates nephrin expression in podocytes by acting on a VDRE in the proximal nephrin promoter. Nephrin up-regulation likely accounts for part of the renoprotective activity of vitamin D.     

NLRP3 inflammasome negatively regulates podocyte autophagy in diabetic nephropathy

Inflammasome mechanisms are recognized as a key pathophysiology of diabetic nephropathy (DN). The nucleotide-oligomerization domain-like receptor 3 (NLRP3) inflammasome has attracted the most attention. Autophagy as a conserved intracellular catabolic pathway plays essential roles in the maintenance of podocytes. Although autophagy was involved in preventing excessive inflammatory responses in kidney diseases, a clear understanding of the regulation of NLRP3 inflammasome on autophagy in glomerular damage in DN is still lacking. In this study, we focused on the effect of the activation of NLRP3 inflammasome on the suppression of podocyte autophagy and aimed to investigate the role of autophagy in podocyte injury in DN. Podocyte autophagy has been confirmed to be inhibited in high-fat diet/streptozotocin (HFD/STZ)-induced DN mice, and NLRP3 has been found to be upregulated in both mice and human DN biopsies and in vitro. Activation of NLRP3 inflammasome exacerbated podocyte autophagy and reduced podocyte nephrin expression, while silencing of NLRP3 efficiently restored podocyte autophagy and ameliorated podocyte injury induced by high glucose. The results showed that NLRP3 was a negative regulator of autophagy and suggested that restoration of podocyte autophagy by inactivation of NLRP3 under high glucose could reduce podocyte injury. Proper modification of autophagy and inflammasome has the potential to benefit the kidney in DN.     

MAD2B promotes podocyte injury through regulating Numb-dependent Notch 1 pathway in diabetic nephropathy

Rationale: Recent studies have demonstrated that the loss of podocyte is a critical event in diabetic nephropathy (DN). Previously, our group have found that the mitotic arrest deficient protein MAD2B was involved in high glucose (HG)-induced podocyte injury by regulating APC/C activity. However, the exact mechanism of MAD2B implicated in podocyte injury is still lacking.Methods: The experiments were conducted by using kidney tissues from streptozotocin (STZ) induced diabetic mice with or without podocyte-specific deletion of MAD2B and the cultured podocytes exposed to different treatments. Glomerular pathological injury was evaluated by periodic acid-Schiff staining and transmission electron microscopy. The endogenous interaction between MAD2B and Numb was discovered by yeast two-hybrid analysis and co-immunoprecipitation assay. The expressions of MAD2B, Numb and related pathway were detected by western blot, immunochemistry and immunofluorescence.Results: The present study revealed that MAD2B was upregulated in diabetic glomeruli and cultured podocytes under hyperglycemic conditions. Podocyte-specific deletion of MAD2B alleviated podocyte injury and renal function deterioration in mice of diabetic nephropathy. Afterwards, MAD2B was found to interact with Numb, which was downregulated in diabetic glomeruli and HG-stimulated cultured podocytes. Interestingly, MAD2B genetic deletion could partly reverse the decline of Numb in podocytes exposed to HG and in diabetic mice, and the expressions of Numb downstream molecules such as NICD and Hes-1 were decreased accordingly. In addition, overexpression of Numb ameliorated HG-induced podocyte injury.Conclusions: The present findings suggest that upregulated MAD2B expression contributes to Numb depletion and activation of Notch 1 signaling pathway, which ultimately leads to podocyte injury during DN progression.     

MDM2 is implicated in high‐glucose‐induced podocyte mitotic catastrophe via Notch1 signalling

Podocyte injury and depletion are essential events involved in the pathogenesis of diabetic nephropathy (DN). As a terminally differentiated cell, podocyte is restricted in ‘post‐mitosis’ state and unable to regenerate. Re‐entering mitotic phase will cause podocyte disastrous death which is defined as mitotic catastrophe (MC). Murine double minute 2 (MDM2), a cell cycle regulator, is widely expressed in renal resident cells including podocytes. Here, we explore whether MDM2 is involved in podocyte MC during hyperglycaemia. We found aberrant mitotic podocytes with multi‐nucleation in DN patients. In vitro, cultured podocytes treated by high glucose (HG) also showed an up‐regulation of mitotic markers and abnormal mitotic status, accompanied by elevated expression of MDM2. HG exposure forced podocytes to enter into S phase and bypass G2/M checkpoint with enhanced expression of Ki67, cyclin B1, Aurora B and p‐H3. Genetic deletion of MDM2 partly reversed HG‐induced mitotic phase re‐entering of podocytes. Moreover, HG‐induced podocyte injury was alleviated by MDM2 knocking down but not by nutlin‐3a, an inhibitor of MDM2‐p53 interaction. Interestingly, knocking down MDM2 or MDM2 overexpression showed inhibition or activation of Notch1 signalling, respectively. In addition, genetic silencing of Notch1 prevented HG‐mediated podocyte MC. In conclusion, high glucose up‐regulates MDM2 expression and leads to podocyte MC. Notch1 signalling is an essential downstream pathway of MDM2 in mediating HG‐induced MC in podocytes.     

Mammary adipocytes bioactivate 25‐hydroxyvitamin D3 and signal via vitamin D3 receptor,modulating mammary epithelial cell growth

The vitamin D₃ receptor (VDR) is present in all microenvironments of the breast, yet it is hypothesized to signal through the epithelium to regulate hormone induced growth and differentiation. However, the influence or contribution of the other microenvironments within the breast that express VDR, like the breast adipose tissue, are yet to be investigated. We hypothesized that the breast adipocytes express the signaling components necessary to participate in vitamin D₃ synthesis and signaling via VDR, modulating ductal epithelial cell growth and differentiation. We utilized human primary breast adipocytes and VDR wild type (WT) and knockout (KO) mice to address whether breast adipocytes participate in vitamin D₃‐induced growth regulation of the ductal epithelium. We report in this study that breast primary adipocytes express VDR, CYP27B1 (1α‐hydroxylase, 1α‐OHase), the enzyme that generates the biologically active VDR ligand, 1α,25‐dihydroxyvitamin D₃ (1,25D₃), and CYP24 (24‐hydroxylase, 24‐OHase), a VDR‐1,25D₃ induced target gene. Furthermore, the breast adipocytes participate in bioactivating 25‐hydroxyvitamin D₃ (25D₃) to the active ligand, 1,25D₃, and secreting it to the surrounding microenvironment. In support of this concept, we report that purified mammary ductal epithelial fragments (organoids) from VDR KO mice, co‐cultured with WT breast adipocytes, were growth inhibited upon treatment with 25D₃ or 1,25D₃ compared to vehicle alone. Collectively, these results demonstrate that breast adipocytes bioactivate 25D₃ to 1,25D₃, signal via VDR within the adipocytes, and release an inhibitory factor that regulates ductal epithelial cell growth, suggesting that breast adipose tissue contributes to vitamin D₃‐induced growth regulation of ductal epithelium. J. Cell. Biochem. 112: 3393–3405, 2011. © 2011 Wiley Periodicals, Inc.     

Apelin promotes diabetic nephropathy by inducing podocyte dysfunction via inhibiting proteasome activities

Podocyte injuries are associated with progression of diabetic nephropathy (DN). Apelin, an adipocyte‐derived peptide, has been reported to be a promoting factor for DN. In this study, we aim to determine whether apelin promotes progression of DN by inducing podocyte dysfunction. kk‐Ay mice were used as models for DN. Apelin and its antagonist, F13A were intraperitoneally administered for 4 weeks, respectively. Renal function and foot process proteins were analysed to evaluate the effects of apelin on kk‐Ay mice and podocytes. Apelin increased albuminuria and decreased podocyte foot process proteins expression in kk‐Ay mice, which is consistent with the results that apelin receptor (APLNR) levels increased in glomeruli of patients or mice with DN. In cultured podocytes, high glucose increased APLNR expression and apelin administration was associated with increased permeability and decreased foot process proteins levels. All these dysfunctions were associated with decreased 26S proteasome activities and increased polyubiquitinated proteins in both kk‐Ay mice and cultured podocytes, as demonstrated by 26S proteasome activation with cyclic adenosine monophosphate (cAMP) or oleuropein. These effects seemed to be related to endoplasmic reticulum (ER) stress, as apelin increased C/EBP homologous protein (CHOP) and peiFα levels while cAMP or oleuropein reduced it in high glucose and apelin treated podocytes. These results suggest that apelin induces podocyte dysfunction in DN through ER stress which was induced by decreased proteasome activities in podocytes.     

The importance of nuclear import in protection of the vitamin D receptor from polyubiquitination and proteasome‐mediated degradation

Others and we previously showed that the vitamin D receptor (VDR) is subject to degradation by the 26S proteasome and that treatment with 1,25‐dihydroxyvitamin D₃ (1,25D₃) inhibited this degradation. In the present study, we found that in osteoblasts, but not in intestinal epithelial cells, the VDR was susceptible to degradation by the 26S proteasome. The subcellular site for degradation of the VDR in osteoblasts is the cytoplasm and the site for ligand‐dependent protection of the VDR from the 26S proteasome is the chromatin. These direct relationships between nuclear localization and protection of the VDR from 26S proteasome degradation led us to hypothesize that the unoccupied cytoplasmic VDR is a substrate for polyubiquitination, which targets VDR for degradation by the 26S proteasome, and that nuclear localization has the ability to protect the VDR from polyubiquitination and degradation. To test these hypotheses, we used Cos‐1 cells transfected with human VDR and histidine‐tagged ubiquitin expression vectors. We found that unoccupied VDR was polyubiquitinated and that 1,25D₃ inhibited this modification. Mutations in the nuclear localization signal of VDR (R49W/R50G and K53Q/R54G/K55E) or in the dimerization interface of VDR with retinoid X receptor (M383G/Q385A) abolished the ability of 1,25D₃ to protect the VDR from polyubiquitination, although these mutations had no effect on the ligand‐binding activity of VDR. Therefore, we concluded that in some cellular environments unoccupied cytoplasmic VDR is susceptible to polyubiquitination and proteasome degradation and that ligand‐dependent heterodimerization and nuclear localization protect the VDR from these modifications. J. Cell. Biochem. 110: 926–934, 2010. © 2010 Wiley‐Liss, Inc.     

Increased SHP-1 Protein Expression by High Glucose Levels Reduces Nephrin Phosphorylation in Podocytes

Nephrin, a critical podocyte membrane component that is reduced in diabetic nephropathy, has been shown to activate phosphotyrosine signaling pathways in human podocytes. Nephrin signaling is important to reduce cell death induced by apoptotic stimuli. We have shown previously that high glucose level exposure and diabetes increased the expression of SHP-1, causing podocyte apoptosis. SHP-1 possesses two Src homology 2 domains that serve as docking elements to dephosphorylate tyrosine residues of target proteins. However, it remains unknown whether SHP-1 interacts with nephrin and whether its elevated expression affects the nephrin phosphorylation state in diabetes. Here we show that human podocytes exposed to high glucose levels exhibited elevated expression of SHP-1, which was associated with nephrin. Coexpression of nephrin-CD16 and SHP-1 reduced nephrin tyrosine phosphorylation in transfected human embryonic kidney 293 cells. A single tyrosine-to-phenylalanine mutation revealed that rat nephrin Tyr¹¹²⁷ and Tyr¹¹⁵² are required to allow SHP-1 interaction with nephrin. Overexpression of dominant negative SHP-1 in human podocytes prevented high glucose-induced reduction of nephrin phosphorylation. In vivo, immunoblot analysis demonstrated that nephrin expression and phosphorylation were decreased in glomeruli of type 1 diabetic Akita mice (Ins2^+/C96Y) compared with control littermate mice (Ins2^+/+), and this was associated with elevated SHP-1 and cleaved caspase-3 expression. Furthermore, immunofluorescence analysis indicated increased colocalization of SHP-1 with nephrin in diabetic mice compared with control littermates. In conclusion, our results demonstrate that high glucose exposure increases SHP-1 interaction with nephrin, causing decreased nephrin phosphorylation, which may, in turn, contribute to diabetic nephropathy.     

Characterization of Vitamin D insensitive prostate cancer cells

The antitumor effects of 1,25-dihydroxyvitamin D₃ (calcitriol) are being exploited for prevention and treatment of prostate cancer (CaP). These studies examined the antiproliferative effects of calcitriol in primary cell cultures derived from transgenic adenocarcinoma of mouse prostate (TRAMP) mice chronically treated with calcitriol (20 μg/kg) or vehicle 3×/week from 4 weeks-of-age until palpable tumors developed. This is a report on the response of two representative control (Vitamin D naïve, naïve) and calcitriol-treated (Vitamin D insensitive, VDI) cells to calcitriol. VDI cells were less sensitive to calcitriol based on less cell growth inhibition and less inhibition of DNA synthesis as measured by MTT and BrdU incorporation assays. Similarly, VDI cells were less sensitive to growth inhibition by the vitamin analog, 19-nor-1,25-dihydroxyvitamin D₂ (paricalcitol). There was no change in apoptosis following treatment of naïve and VDI cells with calcitriol. Vitamin D receptor (VDR) expression was up-regulated by calcitriol in both naïve and VDI cells. In addition, calcitriol induced the Vitamin D metabolizing enzyme, 24-hydroxylase (cyp24) mRNA and enzyme activity similarly in naïve and VDI cells as measured by RT-PCR and HPLC, respectively. In summary, VDI cells are less responsive to the antiproliferative effects of calcitriol. Understanding Vitamin D insensitivity will further clinical development of Vitamin D compounds for prevention and treatment of CaP.     

Increased nuclear expression and transactivation of vitamin D receptor by the cardiotonic steroid bufalin in human myeloid leukemia cells

The active form of vitamin D₃, 1α,25-dihydroxyvitamin D₃ [1,25(OH)₂D₃], is a potent ligand for the nuclear receptor vitamin D receptor (VDR) and induces myeloid leukemia cell differentiation. The cardiotonic steroid bufalin enhances vitamin D-induced differentiation of leukemia cells and VDR transactivation activity. In this study, we examined the combined effects of 1,25(OH)₂D₃ and bufalin on differentiation and VDR target gene expression in human leukemia cells. Bufalin in combination with 1,25(OH)₂D₃ enhanced the expression of VDR target genes, such as CYP24A1 and cathelicidin antimicrobial peptide, and effectively induced differentiation phenotypes. An inhibitor of the Erk mitogen-activated protein (MAP) kinase pathway partially inhibited bufalin induction of VDR target gene expression. 1,25(OH)₂D₃ treatment induced transient nuclear expression of VDR in HL60 cells. Interestingly, bufalin enhanced 1,25(OH)₂D₃-induced nuclear VDR expression. The MAP kinase pathway inhibitor increased nuclear VDR expression induced by 1,25(OH)₂D₃ and did not change that by 1,25(OH)₂D₃ plus bufalin. A proteasome inhibitor also enhanced 1,25(OH)₂D₃-induced CYP24A1 expression and nuclear VDR expression. Bufalin-induced nuclear VDR expression was associated with histone acetylation and VDR recruitment to the CYP24A1 promoter in HL60 cells. Thus, the Na⁺,K⁺-ATPase inhibitor bufalin modulates VDR function through several mechanisms, including Erk MAP kinase activation and increased nuclear VDR expression.     

IQGAP1 mediates podocyte injury in diabetic kidney disease by regulating nephrin endocytosis

Diabetic kidney disease (DKD) is a complication associated with diabetes and is a major public health problem in modern society. Podocyte injury is the central target of the development of DKD, and the loss or dysregulation of nephrin, a key structural and signalling molecule located in the podocyte slit diaphragm (SD), initiates potentially catastrophic downstream events within podocytes. IQGAP1, a scaffold protein containing multiple protein-binding domains that regulates endocytosis, can interact with nephrin in podocytes. It is hypothesized that IQGAP1 contributes to nephrin endocytosis and may participate in the pathogenesis of DKD. The dramatically increased histo-nephrin granularity score in DKD glomeruli showed a significant positive correlation with increased IQGAP1-nephrin interaction without changes in the total protein content of nephrin and IQGAP1. In cultured human podocytes, hyperglycaemia induced the intracellular translocation of IQGAP1 from the cytosol to the vicinity of the cytomembrane, reinforced the IQGAP1-nephrin interaction, and augmented nephrin endocytosis. Moreover, impaired podocyte function, such as migration, extensibility and permeability, were further aggravated by wild-type IQGAP1 plasmid transfection, and these effects were partially restored by siRNA-mediated IQGAP1 downregulation. Collectively, these findings show that IQGAP1, an intracellular partner of nephrin, is involved in nephrin endocytosis and the functional regulation of podocytes in DKD.     

Suppression of PTH by the vitamin D analog eldecalcitol is modulated by its high affinity for the serum vitamin D-binding protein and resistance to metabolism

Eldecalcitol [1α,25‐dihydroxy‐2β‐(3‐hydroxypropyloxy)vitamin D₃], a vitamin D analog with enhanced efficacy for treatment of osteoporosis, has been found to be less potent than 1,25‐dihydroxyvitamin D₃ (calcitriol) in suppressing PTH in vivo. To define the mechanism for the latter observation, we compared the effects of eldecalcitol and calcitriol on PTH secretion by bovine parathyroid cells. While the two compounds showed similar potency when the cells were cultured in medium containing 15% newborn calf serum, eldecalcitol was 100 times more potent than calcitriol in the absence of serum. Eldecalcitol has a higher affinity for the serum vitamin D‐binding protein (DBP), and therefore binding to DBP, and possibly other serum components, appears to limit the uptake and activity of eldecalcitol in parathyroid cells, providing an explanation for the lower PTH suppressing activity in vivo (100% serum). However, the 100‐fold higher activity of eldecalcitol in the absence of serum was unexpected since the VDR affinity for eldecalcitol is eightfold lower than for calcitriol. The enhanced activity was not due to preferential uptake, but to a resistance to metabolism. While 1 nM [³H]calcitriol was completely degraded within 24 h, [³H]eldecalcitol was not metabolized, despite the induction of the vitamin D catabolic enzyme, 24‐hydroxylase (CYP24A). The resistance to metabolism is the likely explanation for the higher potency of eldecalcitol in suppressing PTH in cell culture lacking serum. Thus, the unique properties of eldecalcitol in vivo can be attributed, at least in part, to its high‐DBP affinity which increases the half‐life, but limits the uptake of eldecalcitol, and to its reduced metabolism, which prolongs the activity of this analog in target tissues. J. Cell. Biochem. 112: 1348–1352, 2011. © 2011 Wiley‐Liss, Inc.     

Inhibiting the urokinase‐type plasminogen activator receptor system recovers STZ‐induced diabetic nephropathy

The urokinase‐type plasminogen activator (uPA) receptor (uPAR) participates to the mechanisms causing renal damage in response to hyperglycaemia. The main function of uPAR in podocytes (as well as soluble uPAR ‐(s)uPAR‐ from circulation) is to regulate podocyte function through αvβ3 integrin/Rac‐1. We addressed the question of whether blocking the uPAR pathway with the small peptide UPARANT, which inhibits uPAR binding to the formyl peptide receptors (FPRs) can improve kidney lesions in a rat model of streptozotocin (STZ)‐induced diabetes. The concentration of systemically administered UPARANT was measured in the plasma, in kidney and liver extracts and UPARANT effects on dysregulated uPAR pathway, αvβ3 integrin/Rac‐1 activity, renal fibrosis and kidney morphology were determined. UPARANT was found to revert STZ‐induced up‐regulation of uPA levels and activity, while uPAR on podocytes and (s)uPAR were unaffected. In glomeruli, UPARANT inhibited FPR2 expression suggesting that the drug may act downstream uPAR, and recovered the increased activity of the αvβ3 integrin/Rac‐1 pathway indicating a major role of uPAR in regulating podocyte function. At the functional level, UPARANT was shown to ameliorate: (a) the standard renal parameters, (b) the vascular permeability, (c) the renal inflammation, (d) the renal fibrosis including dysregulated plasminogen‐plasmin system, extracellular matrix accumulation and glomerular fibrotic areas and (e) morphological alterations of the glomerulus including diseased filtration barrier. These results provide the first demonstration that blocking the uPAR pathway can improve diabetic kidney lesion in the STZ model, thus suggesting the uPA/uPAR system as a promising target for the development of novel uPAR‐targeting approaches.     

Effects of 1,25(OH)2D3 and vitamin D receptor on peripheral CD4+/CD8+ double‐positive T lymphocytes in a mouse model of systemic lupus erythematosus

This study aims to explore effects of 1,25(OH)₂D₃ and vitamin D receptor (VDR) on peripheral CD4⁺/CD8⁺ double‐positive (DP) T lymphocytes in systemic lupus erythematosus (SLE). MRL‐LPr/LPr mice with SLE (n = 20) and normal MRL mice (n = 20) were assigned into the control group (normal mice, without feeding with 1,25(OH)₂D₃), the 1,25(OH)₂D₃ group (SLE mice, feeding with 1,25(OH)₂D₃), the VDR‐knock‐in + 1,25(OH)₂D₃ group (SLE mice, VDR‐knock‐in, feeding with 1,25(OH)₂D₃) and the VDR‐knockout group (normal mice, VDR‐knockout, without feeding with 1,25(OH)₂D₃) (n = 10 per group). Levels of T lymphocytes were measured by flow cytometry. The mRNA and proteins expressions of inflammatory factors were measured by qRT‐PCR and ELISA. Extracellular signal‐regulated kinase‐1/2 (ERK1/2) expression was measured by Western blotting. Compared with normal mice, SLE mice showed reduced levels of CD4⁺, CD4⁺/CD8⁺ ratio, and DP lymphocytes. The levels of SLE‐related indicators all increased significantly, followed with severe skin ulcers and urinary system infection. With the increase in time, skin ulcers and urinary system infection were significantly improved, levels of CD4⁺, CD4⁺/CD8⁺ ratio, and DP lymphocytes increased, and levels of SLE‐related indicators all decreased in the 1,25(OH)₂D₃ group. There were no significant changes in bioindicators in the control and the VDR‐knock‐in + 1,25(OH)₂D₃ groups. The symptoms of SLE gradually occurred in the VDR‐knockout group. This study demonstrates that VDR and 1,25(OH)₂D₃ could elevate CD4⁺/CD8⁺ DP T lymphocytes and reduce expressions of inflammatory factors, thus inhibiting the development and progression of SLE.