Expression and clinical association of MFG-E8 and TAM receptors in diabetic patients with different stages of microvascular complication: An experimental study.

BACKGROUND: Diabetic nephropathy (DN) is a major microvascular complication of diabetes mellitus that leads to end-stage renal disease. Hyperglycemia triggers apoptosis and kidney damage. Milk fat globule-epidermal growth factor 8 (MFG-E8) and TAM receptor tyrosine kinases, Tyro3, Axl, and Mer, are phagocytic receptors that mediate the clearance of apoptotic cells. This study aimed to identify the role of MFG-E8 and TAM receptors in the development of DN. METHODS: A total of 146 patients with type 2 diabetes mellitus (T2DM), early stage DN, clinical DN and 48 healthy controls were employed to analyze the serum levels of MFG-E8, soluble Tyro3, Axl, Mer, and RAGE by enzyme-linked immunosorbent assay. The serum levels of CREA, hsCRP, CysC, and ß2-microglobulin were measured by spectrophotometric analysis using a biochemical analyzer (AU5800). RESULTS: Our results showed that the serum levels of MFG-E8 were elevated in patients with T2DM compared with healthy controls; however, it decreased gradually in patients with DN with the severity of kidney injury, especially in the clinical DN group. Moreover, the levels of sTyro3, sAxl, and sMer were reduced in patients with T2DM and DN compared to healthy controls, particularly in patients with DN. The levels of MFG-E8, sTyro3, sAxl, and sMer were negatively correlated with UAER at 24 hours, CREA, hsCRP, CysC, ß2-microglobulin, and RAGE, respectively. In addition, TAM receptors had significantly higher predictive and diagnostic values for early stage DN from T2DM than hsCRP, ß2-microglobulin, and CysC, which are also predictive biomarkers of early stage DN from clinical DN. CONCLUSIONS: Decreased MFG-E8 and TAM receptor expression is associated with an increased risk of microvascular complications in patients with T2DM, which plays a critical role in the diagnosis of diabetic patients with microvascular complications, especially early stage DN, and in monitoring the development of DN.

MFG-E8 accelerates wound healing in diabetes by regulating "NLRP3 inflammasome-neutrophil extracellular traps" axis.

Sustained activation of NLRP3 inflammasome and release of neutrophil extracellular traps (NETs) impair wound healing of diabetic foot ulcers (DFUs). Our previous study reported that milk fat globule epidermal growth factor VIII (MFG-E8) attenuates tissue damage in systemic lupus erythematosus. However, the functional effect of MFG-E8 on "NLRP3 inflammasome-NETs" inflammatory loop in wound healing of diabetes is not completely elucidated. In this study, neutrophils from DFU patients are susceptible to undergo NETosis, releasing more NETs. The circulating levels of NET components neutrophil elastase and proteinase 3 and inflammatory cytokines IL-1ß and IL-18 were significantly elevated in DFU patients compared with healthy controls or diabetic patients, in spite of higher levels of MFG-E8 in DFU patients. In Mfge8-/- diabetic mice, skin wound displayed exaggerated inflammatory response, including leukocyte infiltration, excessive activation of NLRP3 inflammasome (release of higher IL-1ß, IL-18, and TNF-α), largely lodged NETs, resulting in poor angiogenesis and wound closure. When stimulated with high-dose glucose or IL-18, MFG-E8-deficient neutrophils release more NETs than WT neutrophils. After administration of recombinant MFG-E8, IL-18-primed NETosis of WT or Mfge8-/- neutrophils was significantly inhibited. Furthermore, NET and mCRAMP (component of NETs, the murine equivalent of cathelicidin LL-37 in human)-mediated activation of NLRP3 inflammasome and production of IL-1ß/IL-18 were significantly elevated in Mfge8-/- macrophages compared with WT macrophages, which were also significantly dampened by the administration of rmMFG-E8. Therefore, our study demonstrated that as inhibitor of the "NLRP3 inflammasome-NETs" inflammatory loop, exogenous rMFG-E8 improves angiogenesis and accelerates wound healing, highlighting possible therapeutic potential for DFUs.

Glucocorticoid exposure induces preeclampsia via dampening 1,25-dihydroxyvitamin D3.

The pathogenesis of preeclampsia (PE) involves a number of biological processes that may be directly or indirectly affected by glucocorticoid (GC) and vitamin D. GC exposure increases the risk of PE, and 1,25-dihydroxyvitamin D3 (1,25-(OH)2D3) deficiency may result in PE. The purpose of the present study was to confirm the involvement of GC/1,25-(OH)2D3 axis in the pathogenesis of PE. In the study, cortisol levels of PE patients were found to be higher than that of non-complicated pregnancies, while 1,25-(OH)2D3 were decreased in both PE women and GC-induced PE rats. Mechanically, GC reduced 1,25-(OH)2D3 levels via disturbing its biosynthetic and catabolic enzymes, including Cyp3a1,Cyp24a1 and Cyp27b1, especially enhancing the expressions of Cyp3a1, the dominant enzyme for vitamin D degeneration. Moreover, replenishing 1,25-(OH)2D3 ameliorated the symptoms and placental oxidative stress of GC-induced rat PE. The protective actions of 1,25-(OH)2D3 might be explained by its roles in antagonizing the effects of GC on trophoblast proliferation and apoptosis. Together, these findings suggest that GC exposure could lead to PE via dampening 1,25-(OH)2D3 biosynthesis, and GC/1,25-(OH)2D3 axis might represent a common pathway through which PE occurs.

Cadmium-induced immune abnormality is a key pathogenic event in human and rat models of preeclampsia.

With increased industrial development, cadmium is an increasingly important environmental pollutant. Studies have identified various adverse effects of cadmium on human beings. However, the relationships between cadmium pollution and the pathogenesis of preeclampsia remain elusive. The objective of this study is to explore the effects of cadmium on immune system among preeclamptic patients and rats. The results showed that the cadmium levels in the peripheral blood of preeclamptic patients were significantly higher than those observed in normal pregnancy. Based on it, a novel rat model of preeclampsia was established by the intraperitoneal administration of cadmium chloride (CdCl2) (0.125 mg of Cd/kg body weight) on gestational days 9-14. Key features of preeclampsia, including hypertension, proteinuria, placental abnormalities and small foetal size, appeared in pregnant rats after the administration of low-dose of CdCl2. Cadmium increased immunoglobulin production, mainly angiotensin II type 1-receptor-agonistic autoantibodies (AT1-AA), by increasing the expression of activation-induced cytosine deaminase (AID) in B cells. AID is critical for the maturation of antibody and autoantibody responses. In addition, angiotensin II type 1-receptor-agonistic autoantibody, which emerged recently as a potential pathogenic contributor to PE, was responsible for the deposition of complement component 5 (C5) in kidneys of pregnant rats via angiotensin II type 1 receptor (AT1R) activation. C5a is a fragment of C5 that is released during C5 activation. Selectively interfering with C5a signalling by a complement C5a receptor-specific antagonist significantly attenuated hypertension and proteinuria in Cd-injected pregnant rats. Our results suggest that cadmium induces immune abnormalities that may be a key pathogenic contributor to preeclampsia and provide new insights into treatment strategies of preeclampsia.