Overexpression of STAMP2 suppresses atherosclerosis and stabilizes plaques in diabetic mice

Genetic influence on scar vascularity after burn injury in individuals of European ancestry: A prospective cohort study

After burn injury there is considerable variation in scar outcome, partially due to genetic factors. Scar vascularity is one characteristic that varies between individuals, and this study aimed to identify genetic variants contributing to different scar vascularity outcomes. An exome-wide array association study and gene pathway analysis was performed on a prospective cohort of 665 patients of European ancestry treated for burn injury, using their scar vascularity (SV) sub-score, part of the modified Vancouver Scar Scale (mVSS), as an outcome measure. DNA was genotyped using the Infinium HumanCoreExome-24 BeadChip, imputed to the Haplotype Reference Consortium panel. Associations between genetic variants (single nucleotide polymorphisms) and SV were estimated using an additive genetic model adjusting for sex, age, % total body surface area and number of surgical procedures, utilising linear and multinomial logistic regression. No individual genetic variants achieved the cut-off threshold for significance. Gene sets were also analysed using the Functional Mapping and Annotation (FUMA) platform, in which biological processes indirectly related to angiogenesis were significantly represented. This study suggests that SNPs in genes associated with angiogenesis may influence SV, but further studies with larger datasets are essential to validate these findings.

STEAP4 modulates cell proliferation and oxidative stress in benign prostatic hyperplasia

Benign prostatic hyperplasia (BPH) is a quite common chronic disease plagued elderly men and its etiology remains unclear. It was reported that the six-transmembrane epithelial antigen of prostate 4 (STEAP4) could modulate cell proliferation/apoptosis ratio and oxidative stress in cancers. Our current study aimed to explore the expression, biological function, and underlying mechanism of STEAP4 in BPH progress. Human prostate tissues and cell lines were utilized. qRT-PCR and immunofluorescence staining were employed. STEAP4 knockdown (STEAP4-KD) or STEAP4 overexpression (STEAP4-OE) cell models were established. Cell proliferation, cell cycle, apoptosis, and reactive oxygen species (ROS) were determined by cell counting kit-8 (CCK-8) assay and flow cytometry. Apoptosis-related proteins and antioxidant enzymes were identified by Western Blot. In addition, the epithelial-mesenchymal transition (EMT) process and fibrosis biomarker (collagen I and α-SMA) were analyzed. It was indicated that STEAP4 was mainly located in the prostate epithelium and upregulated in BPH tissues. STEAP4 deficiency induced apoptosis and inhibited cell survival, but had no effect on the cell cycle, fibrosis, and EMT process. In addition, ROS changes were observed in the STEAP4-KD model. Consistently, overproduction of STEAP4 suppressed apoptosis and promoted cell proliferation, as well as facilitated ROS production. We further examined AKT / mTOR, p38MAPK / p-p38MAPK, and WNT/ β-Catenin signaling pathway and demonstrated that STEAP4 regulated the proliferation and apoptosis of prostate cells through AKT / mTOR signaling, rather than p38MAPK / p-p38MAPK and WNT/ β-Catenin pathways. Furthermore, activating AKT / mTOR signaling with SC79 significantly reversed apoptosis triggered by STEAP4 deficiency, whereas suppressing AKT / mTOR signaling with MK2206 reduced the increase of cell viability triggered by STEAP4 overproduction. Our original data demonstrated that STEAP4 is crucial in the onset and progression of prostate hyperplasia and may become a new target for the treatment of BPH.

The Role of STAMP2 in Pathogenesis of Chronic Diseases Focusing on Nonalcoholic Fatty Liver Disease: A Review

Nonalcoholic fatty liver disease (NAFLD) is a major health issue. NAFLD can progress from simple hepatic steatosis to nonalcoholic steatohepatitis (NASH). NASH can progress to cirrhosis or hepatocellular carcinoma. Unfortunately, there is no currently approved pharmacologic therapy for NAFLD patients. The six transmembrane protein of prostate 2 (STAMP2), a metalloreductase involved in iron and copper homeostasis, is well known for its critical role in the coordination of glucose/lipid metabolism and inflammation in metabolic tissues. We previously demonstrated that hepatic STAMP2 could be a suitable therapeutic target for NAFLD. In this review, we discuss the emerging role of STAMP2 in the dysregulation of iron metabolism events leading to NAFLD and suggest therapeutic strategies targeting STAMP2.

Activin receptor-like kinase 7 promotes apoptosis of vascular smooth muscle cells via activating Smad2/3 signaling in diabetic atherosclerosis

Vascular smooth muscle cells (VSMCs) is a vital accelerator in the late phase of diabetic atherosclerosis, but the underlying mechanism remains unclear. The aim of our study was to investigate whether activin receptor-like kinase 7 (ALK7)-Smad2/3 pathway plays an important role in VSMC apoptosis of diabetic atherosclerosis. It was shown that ALK7 expression was obviously elevated in the aorta of ApoE−/− mice with type 2 diabetes mellitus. Inhibition of ALK7 expression significantly improved the stability of atherosclerotic plaques and reduced cell apoptosis. Further experiments showed that ALK7 knockdown stabilized atherosclerotic plaques by reducing VSMC apoptosis via activating Smad2/3. Our study uncovered the important role of ALK7-Smad2/3 signaling in VSMCs apoptosis, which might be a potential therapeutic target in diabetic atherosclerosis.

STAMP2 Attenuates Cardiac Dysfunction and Insulin Resistance in Diabetic Cardiomyopathy via NMRAL1-Mediated NF-κB Inhibition in Type 2 Diabetic Rats

BACKGROUND

Previous studies have reported that six transmembrane protein of prostate 2 (STAMP2) attenuates metabolic inflammation and insulin resistance in diabetes mellitus. However, the role of STAMP2 in the diabetic heart is still unclear.

METHODS

A diabetic rat cardiomyopathy model was established via intraperitoneal STZ injection. STAMP2 was overexpressed in the treatment group using adeno-associated virus. Rat heart diastolic function was measured using echocardiography and a left ventricular catheter, and cardiac interstitial fibrosis was detected by immunohistochemistry and histological staining. Insulin sensitivity and NF-κB expression were shown by Western blotting. NMRAL1 distribution was illustrated by immunofluorescence.

RESULTS

STAMP2 expression in the diabetic rat heart was reduced, and exogenous overexpression of STAMP2 improved glucose tolerance and insulin sensitivity and alleviated diastolic dysfunction and myocardial fibrosis. Furthermore, we found that NF-κB signaling is activated in the diabetic heart and that exogenous overexpression of STAMP2 promotes NMRAL1 translocation from the cytoplasm to the nucleus and inhibits p65 phosphorylation.

CONCLUSION

STAMP2 attenuates cardiac dysfunction and insulin resistance in diabetic cardiomyopathy, likely by promoting NMRAL1 retranslocation and NF-κB signaling inhibition.

Overexpressing STAMP2 attenuates diabetic renal injuries via upregulating autophagy in diabetic rats

Diabetic nephropathy (DN) is one of the most serious and major renal complications of diabetes. Previously, Six-transmembrane Protein of Prostate 2 (STAMP2) was reported to contribute to nutritional stress. The purpose of this study is to investigate whether overexpression of STAMP2 attenuates diabetic renal injuries in DN rats. We induced the DN rat model by high-fat diet and low-dose streptozotocin and evaluated the metabolite and urine albumin/creatinine. Recombinant adeno-associated virus vectors were injected for overexpression of STAMP2. Pathophysiologic and ultrastructure features of DN by histochemical stain and transmission electron microscope, autophagy-related proteins and signaling pathway by western blotting were assessed. We found the expression of STAMP2 was decreased and autophagy was blunted in DN rat kidneys. Overexpressing STAMP2 significantly ameliorated metabolic disturbance, insulin resistance, and specifically restoring diabetic renal injury. Furthermore, overexpressing STAMP2 improved the autophagy deficiency in DN rats, as revealed by changes in the expressions of Beclin1, p62, and LC3. Furthermore, STAMP2 overexpressing promoted autophagy by inhibiting the mTOR and activating the AMPK/SIRT1 signaling pathway. Our results suggested that STAMP2 overexpression attenuated renal injuries via upregulating autophagy in DN rats. STAMP2 overexpressing promoted autophagy may been involved with inhibition of the mTOR/ULK1 and activation of the AMPK/SIRT1 signaling pathway.

MicroRNA-301a-3p promotes diabetic retinopathy via regulation of six-transmembrane epithelial antigen of prostate 4

OBJECTIVE AND DESIGN

Diabetic retinopathy (DR) is one of the most serious microvascular complications of diabetes mellitus (DM). MicroRNAs (miRNAs) have been discovered to play a crucial role in DR, but the mechanisms underlying the effects of miR-301a-3p on DR are poorly understood. This paper was designed to explore the possible role of miR-301a-3p in DR.

METHODS

The diabetic rat model was established by a single intraperitoneal injection of streptozotocin (STZ). The effects of miR-301a-3p on the biological functions of HRECs were determined through a series of experiments in vitro/vivo.

RESULTS

The results revealed that interference with miR-301a-3p could decrease the expressions of inflammatory factors and apoptosis in the retinal tissue of DR. Furthermore, it can alleviate the oxidative stress in DR serum, reduce VEGF expression, increase endothelial cell marker expression, and inhibit (High Glucose) HG-induced apoptosis of HRECs. Six-transmembrane epithelial antigen of prostate 4 (STEAP4) was the target of miR-301a-3p. All the effects of miR-301a-3p in DR model were reversed by STEAP4 inhibitor.

CONCLUSION

miR-301a-3p promotes diabetic retinopathy via regulation of STEAP4. The findings in this study may provide a vital reference for the drug research and development in DR treatment.

The six-transmembrane protein Stamp2 ameliorates pulmonary vascular remodeling and pulmonary hypertension in mice

Six-transmembrane protein of prostate (Stamp2) protects from diabetes and atherosclerosis in mice via anti-inflammatory mechanisms. As chronic inflammation is a hallmark of pulmonary arterial hypertension (PAH), we investigated the role of Stamp2. Stamp2 expression was substantially reduced in the lung of humans with idiopathic PAH, as well as in experimental PAH. In Stamp2-deficient mice, hypoxia modestly aggravated pulmonary vascular remodeling and right ventricular pressure compared to WT. As endothelial cell (EC) and pulmonary arterial smooth muscle cell (PASMC) phenotypes drive remodeling in PAH, we explored the role of Stamp2. Knock-down of Stamp2 in human EC neither affected apoptosis, viability, nor release of IL-6. Moreover, Stamp2 deficiency in primary PASMC did not alter mitogenic or migratory properties. As Stamp2 deficiency augmented expression of inflammatory cytokines and numbers of CD68-positive cells in the lung, actions of Stamp2 in macrophages may drive vascular remodeling. Thus, PASMC responses were assessed following treatment with conditioned media of primary Stamp2^−/− or WT macrophages. Stamp2^−/− supernatants induced PASMC proliferation and migration stronger compared to WT. A cytokine array revealed CXCL12, MCP-1 and IL-6 as most relevant candidates. Experiments with neutralizing antibodies confirmed the role of these cytokines in driving Stamp2’s responses. In conclusion, Stamp2 deficiency aggravates pulmonary vascular remodeling via cross-talk between macrophages and PASMC. Despite a substantial pro-inflammatory response, the hemodynamic effect of Stamp2 deficiency is modest suggesting that additional mechanisms apart from inflammation are necessary to induce severe PAH.

STEAP4 Inhibits HIF-1α/PKM2 Signaling and Reduces High Glucose-Induced Apoptosis of Retinal Vascular Endothelial Cells

BACKGROUND

Diabetic retinopathy (DR) is a vascular lesion induced by high glucose. STEAP4 is an indispensable membrane protein, which is closely related to hyperglycemic-induced cell inflammation and injury, while STEPT4 has not been studied in hyperglycemic-induced retinal vascular endothelial cell injury.

METHODS

The expression of STEAP4 was detected by RT-qPCR and Western blot. CCK-8 was used to detect cell survival. STEAP4 was overexpressed by cell transfection. The expressions of cytokines TNF-α, IL-1, IL-6, ICAM-1, MDA, SOD and ROS were detected by ELISA. Cell apoptosis was detected by flow cytometry. The expressions of proteins associated with cell damage VEGF, KLF2, eNOS and apoptosis-related proteins Bax, cleaved caspase3 and Bcl2 were detected by Western blot. Finally, the expressions of HIFα and PKM2 were detected by immunofluorescence and Western blot.

RESULTS

The expression of STEAP4 in hyperglycemic-induced retinal vascular endothelial cells (HRCECs) decreased gradually. Overexpression of STEAP4 reduced inflammation and apoptosis of HRCECs and improved dysfunction of them. Meanwhile, overexpression of steap4 inhibited the expression of HIF-1α/PKM2 signal.

CONCLUSION

STEAP4 can be a potential therapeutic target for diabetic retinopathy by inhibiting HIF1/PKM2 signaling to reduce hyperglycemic-induced retinal cell apoptosis.

Inflammation and ER stress differentially regulate STAMP2 expression and localization in adipocytes

BACKGROUND

Chronic ER stress and dysfunction is a hallmark of obesity and a critical contributor to metaflammation, abnormal hormone action and altered substrate metabolism in metabolic tissues, such as liver and adipocytes. Lack of STAMP2 in lean mice induces inflammation and insulin resistance on a regular diet, and it is dysregulated in the adipose tissue of obese mice and humans. We hypothesized that the regulation of STAMP2 is disrupted by ER stress.

METHODS

3T3-L1 and MEF adipocytes were treated with ER stress inducers thapsigargin and tunicamycin, and inflammation inducer TNFα. The treatments effect on STAMP2 expression and enzymatic function was assessed. In addition, 3T3-L1 adipocytes and HEK cells were utilized for Stamp2 promoter activity investigation performed with luciferase and ChIP assays.

RESULTS

ER stress significantly reduced both STAMP2 mRNA and protein expression in cultured adipocytes whereas TNFα had the opposite effect. Concomitant with loss of STAMP2 expression during ER stress, intracellular localization of STAMP2 was altered and total iron reductase activity was reduced. Stamp2 promoter analysis by reporter assays and chromatin immunoprecipitation, showed that induction of ER stress disrupts C/EBPα-mediated STAMP2 expression.

CONCLUSION

These data suggest a clear link between ER stress and quantitative and functional STAMP2-deficiency.

STEAP4: its emerging role in metabolism and homeostasis of cellular iron and copper

Preserving energy homeostasis in the presence of stressors such as proinflammatory cytokines and nutrient overload is crucial to maintaining normal cellular function. Six transmembrane epithelial antigen of the prostate 4 (STEAP4), a metalloreductase involved in iron and copper homeostasis, is thought to play a potentially important role in the cellular response to inflammatory stress. Genome-wide association studies have linked various mutations in STEAP4 with the development of metabolic disorders such as obesity, metabolic syndrome and type 2 diabetes. Several studies have shown that expression of Steap4 is modulated by inflammatory cytokines, hormones and other indicators of cellular stress and that STEAP4 may protect cells from damage, helping to maintain normal metabolic function. STEAP4 appears to be particularly relevant in metabolically oriented cells, such as adipocytes, hepatocytes and pancreatic islet cells. These cells struggle to maintain their function in iron or copper overloaded states, presumably due to increased oxidative stress, suggesting STEAP4's role in metal homeostasis is critical to the maintenance of cellular homeostasis in general, and in preventing the onset of metabolic disease. In this review, we explore genetic associations of STEAP4 with metabolic disorders, and we examine STEAP4 tissue expression, subcellular localization, regulation, structure and function as it relates to metabolic diseases. We then examine how STEAP4's role as a regulator of cellular iron and copper may relate to type 2 diabetes.

Overexpressing STAMP2 attenuates adipose tissue angiogenesis and insulin resistance in diabetic ApoE-/- /LDLR-/- mouse via a PPARγ/CD36 pathway

The aim of this study was to investigate whether overexpression of STAMP2 improves insulin resistance by regulating angiogenesis in adipose tissues. The characteristics of diabetic mice were measured by serial metabolite and pathology tests. Samples were obtained from epididymal, subcutaneous and brown adipose tissues. Histological and morphological analysis demonstrated that STAMP2 gene overexpression reduced adipocyte size, angiogenesis in epididymal and brown adipose tissues. On aortic ring assay, microvessels sprouting from aortas were significantly inhibited after STAMP2 gene overexpression. The cellular effect of STAMP2 on angiogenesis was explored in human umbilical vein endothelial cells (HUVECs) model. Correlation of STAMP2 and angiogenesis was validated by Ad‐STAMP2 transfection and STAMP2 siRNA inhibition. In vitro, overexpression of STAMP2 significantly inhibited endothelial cell migration, tube formation. The effects of Ad‐STAMP2 transfection on HUVECs were abolished by treatment with PPARγ antagonist GW9662 (2.5 μM), and the roles of STAMP2 siRNA on HUVECs were also reversed by treatment with PPARγ agonist rosiglitazone (RSG) (0.1 mM). RT‐PCR indicated that STAMP2 could regulate levels of adhesion molecules, vascular endothelial growth factor A and CD36. The expression of PPARγ and CD36 was decreased when STAMP2 was inhibited by siRNA, while PPARγ and CD36 were highly expressed after overexpression of STAMP2. Our results suggested that STAMP2 gene overexpression may improve insulin resistance via attenuating angiogenesis in epididymal and brown adipose tissues through the PPARγ/CD36 signalling pathway.

STAMPing at the crossroads of normal physiology and disease states

The six transmembrane protein of prostate (STAMP) proteins, also known as six transmembrane epithelial antigen of prostate (STEAPs), comprises three members: STAMP1-3. Their expression is regulated by a variety of stimuli, including hormones and cytokines, in varied settings and tissues with important roles in secretion and cell differentiation. In addition, they are implicated in metabolic and inflammatory diseases and cancer. Here, we review the current knowledge on the role of STAMPs in both physiological and pathological states.

Physical Activity Protects the Human Brain against Metabolic Stress Induced by a Postprandial and Chronic Inflammation

In recent years, it has become clear that chronic systemic low-grade inflammation is at the root of many, if not all, typically Western diseases associated with the metabolic syndrome. While much focus has been given to sedentary lifestyle as a cause of chronic inflammation, it is less often appreciated that chronic inflammation may also promote a sedentary lifestyle, which in turn causes chronic inflammation. Given that even minor increases in chronic inflammation reduce brain volume in otherwise healthy individuals, the bidirectional relationship between inflammation and sedentary behaviour may explain why humans have lost brain volume in the last 30,000 years and also intelligence in the last 30 years. We review evidence that lack of physical activity induces chronic low-grade inflammation and, consequently, an energy conflict between the selfish immune system and the selfish brain. Although the notion that increased physical activity would improve health in the modern world is widespread, here we provide a novel perspective on this truism by providing evidence that recovery of normal human behaviour, such as spontaneous physical activity, would calm proinflammatory activity, thereby allocating more energy to the brain and other organs, and by doing so would improve human health.

Steap4 attenuates high glucose and S100B-induced effects in mesangial cells

Six-transmembrane epithelial antigen of prostate 4 (Steap4)-knockout mice develop hyperglycaemia and inflammation whereas Steap4 overexpression attenuates atherosclerosis in diabetic mice. Thus, we studied the roles of Steap4 in high glucose (HG, 27.5 mM) or S100B (1 μM, a ligand for the receptor for advanced glycation end-product or RAGE)-induced effects in mouse mesangial (MES13) cells. We found that HG-induced Steap4 protein expression was dependent on S100B. HG increased cell membrane, but not cytosolic, Steap4 protein expression. HG increased protein-protein interaction between Steap4 and S100B, which was confirmed by mass spectrometry of immunoprecipitated S100B. SP600125, LY294002 and AG490 attenuated S100B-induced Steap4 protein expression or gene transcriptional activity. A mutation in signal transducer and activator of transcription 3 (Stat3) site 2 of the Steap4 promoter constructs resulted in a marked decrease in HG or S100B-induced activation of Steap4 gene transcription. Overexpression of Steap4 attenuates HG or S100B-induced collagen IV, fibronectin and cyclooxygenase 2 protein expression. Overexpression of Steap4 attenuates HG or S100B-induced transforming growth factor-β (TGF-β). Moreover, overexpression of Steap4 attenuates S100B-induced signalling. Finally, overexpressing Steap4 attenuated renal expression of fibronectin, S100B, TGF-β, type IV collagen, p-Akt, p-extracellular signal regulated kinase 1/2 and p-Stat3 in streptozotocin-diabetic mice. Thus, overexpression of Steap4 attenuated HG or S100B-induced effects in MES13 cells and attenuated some of S100B-induced effects in diabetic mouse kidneys.