Caveolin-1 in the Pathogenesis of Diabetic Nephropathy: Potential Therapeutic Target?

The critical roles of caveolin-1 in lung diseases

Caveolin-1 (Cav-1), a structural and functional component in the caveolae, plays a critical role in transcytosis, endocytosis, and signal transduction. Cav-1 has been implicated in the mediation of cellular processes by interacting with a variety of signaling molecules. Cav-1 is widely expressed in the endothelial cells, smooth muscle cells, and fibroblasts in the various organs, including the lungs. The Cav-1-mediated internalization and regulation of signaling molecules participate in the physiological and pathological processes. Particularly, the MAPK, NF-κB, TGFβ/Smad, and eNOS/NO signaling pathways have been involved in the regulatory effects of Cav-1 in lung diseases. The important effects of Cav-1 on the lungs indicate that Cav-1 can be a potential target for the treatment of lung diseases. A Cav-1 scaffolding domain peptide CSP7 targeting Cav-1 has been developed. In this article, we mainly discuss the structure of Cav-1 and its critical roles in lung diseases, such as pneumonia, acute lung injury (ALI), asthma, chronic obstructive pulmonary disease (COPD), pulmonary hypertension, pulmonary fibrosis, and lung cancer.

Positive association between circulating Caveolin-1 and microalbuminuria in overt diabetes mellitus in pregnancy

AIMS

Mounting evidence has shown that caveolin-1 plays a pathological role in the progression of albuminuria. Our study aimed to provide clinical evidence showing whether circulating caveolin-1 levels were associated with microalbuminuria (MAU) in women with overt diabetes mellitus in pregnancy (ODMIP).

METHODS

A total of 150 pregnant women were enrolled in different groups, including 40 women with ODMIP and MAU (ODMIP + MAU), 40 women with ODMIP, and 70 women without ODMIP (Non-ODMIP). Plasma caveolin-1 levels were determined by ELISA. The presence of caveolin-1 in the human umbilical vein vascular wall was evaluated by immunohistochemical and western blot analysis, respectively. Albumin transcytosis across endothelial cells was measured using an established nonradioactive in vitro approach.

RESULTS

Significantly increased levels of plasma caveolin-1 were detected in ODMIP + MAU women. The Pearson's correlation analysis revealed a positive correlation between plasma caveolin-1 levels and Hemoglobin A1c (HbA1c %) as well as with MAU in the ODMIP + MAU group. Simultaneously, experimental knockdown or overexpression of caveolin-1 significantly decreased or increased the level of albumin transcytosis across both human and mouse glomerular endothelial cells (GECs), respectively.

CONCLUSIONS

Our data showed a positive association between plasma caveolin-1 levels and microalbuminuria in ODMIP + MAU.

Increased Levels of Circulating IGFBP4 and ANGPTL8 with a Prospective Role in Diabetic Nephropathy

Diabetic nephropathy (DN) is a complicated condition related to type 2 diabetes mellitus (T2D). ANGPTL8 is a hepatic protein highlighted as a risk factor for DN in patients with T2D; additionally, recent evidence from DN studies supports the involvement of growth hormone/IGF/IGF-binding protein axis constituents. The potential link between ANGPTL8 and IGFBPs in DN has not been explored before. Here, we assessed changes in the circulating ANGPTL8 levels in patients with DN and its association with IGFBP-1, -3, and -4. Our data revealed a significant rise in circulating ANGPTL8 in people with DN, 4443.35 ± 396 ng/mL compared to 2059.73 ± 216 ng/mL in people with T2D (p < 0.001). Similarly, levels of IGFBP-3 and -4 were significantly higher in people with DN compared to the T2D group. Interestingly, the rise in ANGPTL8 levels correlated positively with IGFBP-4 levels in T2DM patients with DN (p < 0.001) and this significant correlation disappeared in T2DM patients without DN. It also correlated positively with serum creatinine and negatively with the estimated glomerular filtration rate (eGFR, All < 0.05). The area under the curve (AUC) on receiver operating characteristic (ROC) analysis of the combination of ANGPTL8 and IGFBP4 was 0.76 (0.69-0.84), p < 0.001, and the specificity was 85.9%. In conclusion, our results showed a significant increase in ANGPTL8 in patients with DN that correlated exclusively with IGFBP-4, implicating a potential role of both proteins in the pathophysiology of DN. Our findings highlight the significance of these biomarkers, suggesting them as promising diagnostic molecules for the detection of diabetic nephropathy.

Cardioprotective and anti-inflammatory effects of Caveolin 1 in experimental diabetic cardiomyopathy

Previous studies of the Caveolin 1 (Cav1) protein and caveolae, which are lipid raft structures found on the plasma membranes of certain cells, are associated with fat metabolism disorders, inflammation, diabetes, and cardiovascular disease. However, there have been no reports linking Cav1 to diabetic cardiomyopathy (DCM). In the present study, we established a relationship between Cav1 and the development of DCM. We found that compared with Cav1+/+ mice, Cav1-/- diabetic mice exhibited more severe cardiac injury, increased activation of NF-κB signaling, and up-regulation of downstream genes, including hypertrophic factors and inflammatory fibrosis factors in heart tissues. Additionally, in vitro results showed that knocking down Cav1 further activated HG-induced NF-κB signaling, increased the expression of downstream target genes, and decreased the expression of inhibitor α of NF-κB (iκBα), all of which have been linked to DCM pathogenesis. In contrast, Cav1 overexpression resulted in the opposite effects. Our study suggests that Cav1 knockdown promotes cardiac injury in DCM by activating the NF-κB signaling pathway, and targeting Cav1 may lead to the development of novel treatments for DCM.

G-Protein-Coupled Receptors Mediate Modulations of Cell Viability and Drug Sensitivity by Aberrantly Expressed Recoverin 3 within A549 Cells

To elucidate the currently unknown molecular mechanisms responsible for the aberrant expression of recoverin (Rec) within cancerous cells, we examined two-dimensional (2D) and three-dimensional (3D) cultures of Rec-negative lung adenocarcinoma A549 cells which had been transfected with a plasmid containing human recoverin cDNA (A549 Rec) or an empty plasmid as a mock control (A549 MOCK). Using these cells, we measured cytotoxicity by several anti-tumor agents (2D), cellular metabolism including mitochondrial and glycolytic functions by a Seahorse bio-analyzer (2D), the physical properties, size and stiffness of the 3D spheroids, trypsin sensitivities (2D and 3D), and RNA sequencing analysis (2D). Compared with the A549 MOCK, the A549 Rec cells showed (1) more sensitivity toward anti-tumor agents (2D) and a 0.25% solution of trypsin (3D); (2) a metabolic shift from glycolysis to oxidative phosphorylation; and (3) the formation of larger and stiffer 3D spheroids. RNA sequencing analysis and bioinformatic analyses of the differentially expressed genes (DEGs) using Gene Ontology (GO) enrichment analysis suggested that aberrantly expressed Rec is most likely associated with several canonical pathways including G-protein-coupled receptor (GPCR)-mediated signaling and signaling by the cAMP response element binding protein (CREB). The findings reported here indicate that the aberrantly expressed Rec-induced modulation of the cell viability and drug sensitivity may be GPCR mediated.

Overexpression of Plasmalemmal Vesicle-Associated Protein-1 Reflects Glomerular Endothelial Injury in Cases of Proliferative Glomerulonephritis with Monoclonal IgG Deposits

Introduction

Proliferative glomerulonephritis with monoclonal IgG deposits (PGNMID) occasionally presents refractory nephrotic syndrome resulting in poor renal prognosis, but its etiology is not fully elucidated. Given that glomerular endothelial cell (GEC) stress or damage may lead to podocytopathy and subsequent proteinuria, as in thrombotic microangiopathy (TMA), diabetic kidney disease, and focal segmental glomerulosclerosis, we investigated the evidence of glomerular endothelial injury by evaluating the expression of plasmalemmal vesicle-associated protein-1 (PV-1), a component of caveolae in the cases of PGNMID.

Methods

We measured the immunofluorescent PV-1 intensities of 23 PGNMID cases and compared with those of primary membranoproliferative glomerulonephritis (MPGN) (n = 5) and IgA nephropathy (IgAN) (n = 54) cases. PV-1 localization was evaluated with Caveolin-1, and CD31 staining, and the ultrastructural analysis was performed using a low-vacuum scanning electron microscope (LVSEM). To check the association of podocyte injury, we also conducted 8-oxoguanine and Wilms tumor 1 (WT1) double stain. We then evaluated PV-1 expression in other glomerulitis and glomerulopathy such as lupus nephritis and minimal change disease.

Results

The intensity of glomerular PV-1 expression in PGNMID is significantly higher than that in the other glomerular diseases, although the intensity is not associated with clinical outcomes such as urinary protein levels or renal prognosis. Immunostaining and LVSEM analysis revealed that glomerular PV-1 expression is localized in GECs in PGNMID. 8-oxoguanine accumulation was detected in WT1-positive podocytes but not in PV-1-expressing GECs, suggesting GEC-derived podocyte injury in PGNMID.

Conclusion

PV-1 overexpression reflects glomerular endothelial injury, which could be associated with podocyte oxidative stress in PGNMID cases.

Integrated Analysis of Multiple Microarray Studies to Identify Core Gene-Expression Signatures Involved in Tubulointerstitial Injury in Diabetic Nephropathy

Diabetic nephropathy is a leading cause of end-stage renal disease in both developed and developing countries. It is lack of specific diagnosis, and the pathogenesis remains unclarified in diabetic nephropathy, following the unsatisfactory effects of existing treatments. Therefore, it is very meaningful to find biomarkers with high specificity and potential targets. Two datasets, GSE30529 and GSE47184 from GEO based on diabetic nephropathy tubular samples, were downloaded and merged after batch effect removal. A total of 545 different expression genes screened with $\log 2\text{FC}>0.5$ were weighted gene coexpression correlation network analysis, and green module and blue module were identified. The results of KEGG analyses both in green module and GSEA analysis showed the same two enriched pathway, focal adhesion and viral myocarditis. Based on the intersection among WGCNA focal adhesion/Viral myocarditis, GSEA focal adhesion/viral myocarditis, and PPI network, 17 core genes, ACTN1, CAV1, PRKCB, PDGFRA, COL1A2, COL6A3, RHOA, VWF, FN1, HLA-F, HLA-DPB1, ITGB2, HLA-DRA, HLA-DMA, HLA-DPA1, HLA-B, and HLA-DMB, were identified as potential biomarkers in diabetic tubulointerstitial injury and were further validated externally for expression at GSE99325 and GSE104954 and clinical feature at nephroseq V5 online platform. CMap analysis suggested that two compounds, LY-294002 and bufexamac, may be new insights for therapeutics of diabetic tubulointerstitial injury. Conclusively, it was raised that a series of core genes may be as potential biomarkers for diagnosis and two prospective compounds.

Empagliflozin protects glomerular endothelial cell architecture in experimental diabetes through the VEGF-A/caveolin-1/PV-1 signaling pathway

In addition to having blood glucose-lowering effects, inhibitors of sodium glucose cotransporter 2 (SGLT2) afford renoprotection in diabetes. We sought to investigate which components of the glomerular filtration barrier could be involved in the antiproteinuric and renoprotective effects of SGLT2 inhibition in diabetes. BTBR ob/ob mice that develop a type 2 diabetic nephropathy received a standard diet with or without empagliflozin for 10 weeks, starting at 8 weeks of age, when animals had developed albuminuria. Empagliflozin caused marked decreases in blood glucose levels and albuminuria but did not correct glomerular hyperfiltration. The protective effect of empagliflozin against albuminuria was not due to a reduction in podocyte damage since empagliflozin did not affect the larger podocyte filtration slit pore size nor the defective expression of nephrin and nestin. Empagliflozin did not reduce the thickening of the GBM. In BTBR ob/ob mice, the most profound abnormality seen using electron microscopy was in the endothelial aspect of the glomerular capillary, with significant loss of endothelial fenestrations. Remarkably, empagliflozin ameliorated the subverted microvascular endothelial ultrastructure. Caveolae and bridging diaphragms between adjacent endothelial fenestrae were seen in diabetic mice and associated with increased expression of caveolin-1 and the appearance of PV-1. These endothelial abnormalities were limited by the SGLT2 inhibitor. While no expression of SGLT2 was found in glomerular endothelial cells, SGLT2 was expressed in the podocytes of diabetic mice. VEGF-A which is a known stimulus for endothelial caveolin-1 and PV-1 was increased in podocytes of BTBR ob/ob mice and normalized by SGLT2 inhibitor treatment. Thus, empagliflozin's protective effect on the glomerular endothelium of diabetic mice could be due to a limitation of the paracrine signaling of podocyte-derived VEGF-A that resulted in a reduction of the abnormal endothelial caveolin-1 and PV-1, with the consequent preservation of glomerular endothelial function and permeability. This article is protected by copyright. All rights reserved.

Caveolin-1 Regulates Cellular Metabolism: A Potential Therapeutic Target in Kidney Disease

The kidney is an energy-consuming organ, and cellular metabolism plays an indispensable role in kidney-related diseases. Caveolin-1 (Cav-1), a multifunctional membrane protein, is the main component of caveolae on the plasma membrane. Caveolae are represented by tiny invaginations that are abundant on the plasma membrane and that serve as a platform to regulate cellular endocytosis, stress responses, and signal transduction. However, caveolae have received increasing attention as a metabolic platform that mediates the endocytosis of albumin, cholesterol, and glucose, participates in cellular metabolic reprogramming and is involved in the progression of kidney disease. It is worth noting that caveolae mainly depend on Cav-1 to perform the abovementioned cellular functions. Furthermore, the mechanism by which Cav-1 regulates cellular metabolism and participates in the pathophysiology of kidney diseases has not been completely elucidated. In this review, we introduce the structure and function of Cav-1 and its functions in regulating cellular metabolism, autophagy, and oxidative stress, focusing on the relationship between Cav-1 in cellular metabolism and kidney disease; in addition, Cav-1 that serves as a potential therapeutic target for treatment of kidney disease is also described.

Therapeutic potential of resveratrol in diabetic nephropathy according to molecular signaling

BACKGROUND

Diabetic nephropathy (DN) as a severe complication of diabetes mellitus (DM), is a crucial menace for human health and survival and remarkably elevates the healthcare systems' costs. Therefore, it is worth noting to identify novel preventive and therapeutic strategies to alleviate the disease conditions. Resveratrol, as a well-defined anti-diabetic/ antioxidant agent has capabilities to counteract diabetic complications. It has been predicted that resveratrol will be a fantastic natural polyphenol for diabetes therapy in the next few years.

OBJECTIVE

Accordingly, the current review aims to depict the role of resveratrol in the regulation of different signaling pathways that are involved in the reactive oxygen species (ROS) production, inflammatory processes, autophagy, and mitochondrial dysfunction, as critical contributors to DN pathophysiology.

RESULTS

The pathogenesis of DN can be multifactorial; hyperglycemia is one of the prominent risk factors of DN development that is closely related to oxidative stress. Resveratrol, as a well-defined polyphenol, has various biological and medicinal properties, including anti-diabetic, anti-inflammatory, and anti-oxidative effects.

CONCLUSION

Resveratrol prevents kidney damages that are caused by oxidative stress, enhances antioxidant capacity, and attenuates the inflammatory and fibrotic responses. For this reason, resveratrol is considered an interesting target in DN research due to its therapeutic possibilities during diabetic disorders and renal protection.

Caveolin-1: A promising therapeutic target for diverse diseases

The plasma membrane of eukaryotic cells contains small flask-shaped invaginations known as caveolae that are involved in the regulation of cellular signaling. Caveolin-1 is a 21-24kDa protein localized in the caveolar membrane. Caveolin-1 (Cav-1) has been considered as a master regulator among the various signaling molecules. It has been emerging as a chief protein regulating cellular events associated with homeostasis, caveolae formation, and caveolae trafficking. In addition to the physiological role of cav-1, it has a complex role in the progression of various diseases. Caveolin-1 has been identified as a prognosticator in patients with cancer and has a dual role in tumorigenesis. The expression of Cav-1 in hippocampal neurons and synapses is related to neurodegeneration, cognitive decline, and aging. Despite the ubiquitous association of caveolin-1 in various pathological processes, the mechanisms associated with these events are still unclear. Caveolin-1 has a significant role in various events of the viral cycle, such as viral entry. This review will summarize the role of cav-1 in the development of cancer, neurodegeneration, glaucoma, cardiovascular diseases, and infectious diseases. The therapeutic perspectives involving clinical applications of Caveolin-1 have also been discussed. The understanding of the involvement of caveolin-1 in various diseased states provides insights into how it can be explored as a novel therapeutic target.

Efficacy and safety of acupuncture combined with Chinese Herbal Medicine for diabetic nephropathy: A protocol for systematic review and meta-analysis

BACKGROUND

Diabetic nephropathy (DN) is one of the most serious complications in the development of diabetes mellitus, which has become the main cause of end-stage renal disease and one of the main causes of death in diabetic patients. With the prevalence of diabetes, the number of patients at risk for developing DN is increasing, with 20-40 percent of all patients with diabetes at risk for developing DN. Acupuncture and Chinese herbal medicine treatments are often combined to treat DN; however, there has been no meta-analysis on their synergistic effects. Therefore, we aimed to perform a systematic review and meta-analysis to estimate the effectiveness of acupuncture combined with Chinese herbal medicine for DN treatment.

METHODS

Nine electronic databases were retrieved for this study. The English databases mainly retrieved PubMed, Web of Science, Embase, AMED, and the Cochrane Library, while the CNKI, VIP, CBM, and Wanfang databases were used to retrieve the Chinese literature. There is no definite time limit for the retrieval literature, and the languages are limited to Chinese and English. We will consider articles published between database initiation and August 2021. We used Review Manager 5.4, provided by the Cochrane Collaborative Network for statistical analysis. Clinical randomized controlled trials related to acupuncture combined with Chinese herbal medicine for DN were included in this study. Research selection, data extraction, and research quality assessments were independently completed by two researchers. We then assessed the quality and risk of the included studies and observed the outcome measures.

RESULTS

This study provides a high-quality synthesis to assess the effectiveness and safety of acupuncture combined with Chinese herbal medicine for treating DN.

CONCLUSION

This systematic review will provide evidence to determine whether acupuncture combined with Chinese herbal medicine is an effective and safe intervention for patients with DN.

ETHICS AND DISSEMINATION

The protocol of the systematic review does not require ethical approval because it does not involve humans. This article will be published in peer-reviewed journals and presented at relevant conferences.

REGISTRATION NUMBER

INPLASY202180018.

Apelin‑13 alleviates diabetic nephropathy by enhancing nitric oxide production and suppressing kidney tissue fibrosis

Diabetes is a serious metabolic disease, and the kidney damage induced by diabetes also seriously affects the survival of patients. Apelin is a molecule that plays a crucial role in lipid metabolism, and recent studies have revealed that apelin-13, a subtype of apelin, plays an important role in regulating blood glucose levels. However, the role of apelin-13 in diabetic nephropathy remains unclear. In the present study, a rat model of diabetic nephropathy was constructed by the injection of streptozocin (STZ). During this process, these rats were injected with apelin-13. The blood glucose, urine protein and insulin levels were determined weekly. Next, the expression of angiotensin domain type 1 receptor-associated protein (APJ), endothelial nitric oxide synthase (eNOS), E-cadherin and α-smooth muscle actin (α-SMA) in the kidney tissues was determined with western blotting. Then, the endothelial cells of glomerular vessels were cultured with high glucose medium. These cells were treated with apelin-13 for 24 h. Finally, cell viability of these cells and the expression of APJ, eNOS, E-cadherin and α-SMA in these cells were determined with western blotting. As a result, treatment of apelin-13 induced the lower levels of blood glucose and urine protein. In addition, application of apelin-13 promoted the production of insulin and alleviated the insulin resistance. Treatment with apelin-13 promoted the expression of APJ, eNOS and E-cadherin while it suppressed the expression of α-SMA in kidney tissues of rats and endothelial cells of glomerular vessels. Furthermore, application of apelin-13 also promoted the cell viability of these cells. In conclusion, apelin-13 relieved diabetic nephropathy by promoting the production of nitric oxide (NO) and alleviating the fibrosis of kidney tissues.

Review on experimental study and clinical application of low-intensity pulsed ultrasound in inflammation

Low-intensity pulsed ultrasound (LIPUS), as physical therapy, is widely used in both research and clinical settings. It induces multiple bioeffects, such as alleviating pain, promoting tissue repair, and shortening disease duration. LIPUS can also mediate inflammation. This paper reviews the application of LIPUS in inflammation and discusses the underlying mechanism. In basic experiments, LIPUS can regulate inflammatory responses at the cellular level by affecting some signaling pathways. In a clinical trial, LIPUS has been shown to alleviate inflammatory responses efficiently. As a cheap, safe, and convenient physical method, LIPUS is promising as anti-inflammatory therapy.

Resveratrol: Evidence for Its Nephroprotective Effect in Diabetic Nephropathy

Diabetic nephropathy (DN) is a severe complication of diabetes mellitus (DM). Dietary habits play a major role in determining the onset and progression of DM-related disorders and a proper diet (rich in fruits and vegetables) can delay or prevent the process of DM pathogenesis. Thus, increasing attention has been paid to polyphenols and polyphenol-rich foods since their increased intake has been associated with a reduced incidence of DM and its associated complications. Resveratrol is a polyphenolic phytoalexin that is mainly found in grapevines and berries. It is available in various pharmaceutical dosages and is widely recommended as a dietary supplement due to its beneficial effects. Remarkably, resveratrol's capability to effectively lower blood glucose levels without any side effects has been amply demonstrated in many in vitro and in vivo studies. Herein, we comprehensively review and discuss the nephroprotective effect of resveratrol during DN and its associated mechanisms. Resveratrol exerts its nephroprotective effects via various mechanisms including reducing oxidative stress and advanced glycation end-product (AGE) production, stimulating autophagy, inhibiting endoplasmic reticulum (ER) stress and inflammation, ameliorating lipotoxicity, activating the AMP kinase (AMPK) pathway, and modulating angiogenesis. Moreover, the use of resveratrol as an adjuvant to conventional antidiabetic therapies could be an effective approach to manage DN in humans. However, evidence is scarce to support whether resveratrol has beneficial effects in humans during DN. Therefore, clinical studies are warranted to elucidate resveratrol's role against DN.

miR-136 improves renal fibrosis in diabetic rats by targeting down-regulation of tyrosine kinase SYK and inhibition of TGF-β1/Smad3 signaling pathway

Objective: To investigate the way that miR-136 regulated spleen tyrosine kinase (SYK) and transforming growth factor-β1 (TGF-β1)/Smad3 signaling pathways on renal fibrosis.Methods: 100 male SD (Sprague-Dawley) rats were randomly divided into diabetic nephropathy (DN) group, normal control (NC) group, miR-136 mimics group, and control group. The renal fibrosis model of diabetic rats was established by streptozotocin (STZ) method. NRK-52E cells were transfected into six groups: HG group, HG + miR-136 group, HG + miR-NC group, miR-136 + SYK group, miR-136 + NC group, and control group. Histopathological examination, the expressions of miR-136 and SYK mRNA, the expression of mTOR, blood glucose, urine protein, body weight, creatinine level, blood urea nitrogen (BUN), and KW/BW were detected in each group. Transfection efficiency, the targeted binding, and regulation between miR-136 and SYK, as well as the expression level of related inflammatory factors, the expression levels of SYK, E-Cad (E-cadherin), Vimentin, Collagen I, α-smooth muscle actin (α-SMA), and vascular endothelial growth factor A (VEGFA) were detected.Results: It was shown that the expression level of miR-136 in DN group significantly decreased. The blood glucose and urine protein concentrations in the DN group and miR-136 mimics group significantly increased and the body weight was decreased, but the blood glucose concentration in the miR-136 mimics group increased with time. The prolongation of the decline significantly decreased, and the growth rate of urinary protein reduced. Creatinine, BUN, and the kidney weight to body weight ratio (KW/BW) in DN group increased significantly. Cell culture results showed that SYK was a target gene of miR-136 and miR-136/SYK-mediated renal fibrosis by activating TGF-β1/Smad3 signal.Conclusion: SYK activates TGF-β1/Smad3 signaling, while miR-136 inhibits TGF-β1/Smad3 signaling mediating tubular epithelial cell fibrosis by down-regulating SYK.

Kidney-targeted baicalin-lysozyme conjugate ameliorates renal fibrosis in rats with diabetic nephropathy induced by streptozotocin

BACKGROUND

Diabetic nephropathy (DN) is one of the most common and serious complications of diabetes, and is the most important cause of death for diabetic patients. Baicalin (BAI) has anti-oxidative, anti-inflammatory and anti-apoptotic activities, which play a role in attenuating insulin resistance and protecting the kidney. Moreover, cell-specific targeting of renal tubular cells is an approach to enhance drug accumulation in the kidney.

METHODS

Forty-five Sprague-Dawley rats were divided into four groups. A diabetes model was created using streptozotocin (STZ) intraperitoneally injection. The four groups included: Control group (n = 10), DN (n = 15), BAI treatment (BAI; n = 10) and BAI-LZM treatment (BAI-LZM; n = 10) groups. In the current study, the renoprotection and anti-fibrotic effects of BAI-lysozyme (LZM) conjugate were further investigated in rats with DN induced by STZ compared with BAI treatment alone.

RESULTS

The results suggest that BAI-LZM better ameliorates renal impairment, metabolic disorder and renal fibrosis than BAI alone in rats with DN, and the potential regulatory mechanism likely involves inhibiting inflammation via the nuclear factor-κB signaling pathway, inhibiting extracellular matrix accumulation via the transforming growth factor-β/Smad3 pathway and regulating cell proliferation via the insulin-like growth factor (IGF)-1/IGF-1 receptor/p38 Mitogen-activated protein kinase (MAPK) pathway. BAI and the kidney-targeted BAI-LZM can utilize the body's cytoprotective pathways to reactivate autophagy (as indicated by the autophagy markers mechanistic target of rapamycin and sirtuin 1 to ameliorate DN outcomes.

CONCLUSIONS

Our data support the traditional use of S. baicalensis as an important anti-DN traditional chinese medicine (TCM), and BAI, above all BAI-LZM, is a promising source for the identification of molecules with anti-DN effects.

Role of Caveolin-1 in Diabetes and Its Complications

It is estimated that in 2017 there were 451 million people with diabetes worldwide. These figures are expected to increase to 693 million by 2045; thus, innovative preventative programs and treatments are a necessity to fight this escalating pandemic disorder. Caveolin-1 (CAV1), an integral membrane protein, is the principal component of caveolae in membranes and is involved in multiple cellular functions such as endocytosis, cholesterol homeostasis, signal transduction, and mechanoprotection. Previous studies demonstrated that CAV1 is critical for insulin receptor-mediated signaling, insulin secretion, and potentially the development of insulin resistance. Here, we summarize the recent progress on the role of CAV1 in diabetes and diabetic complications.

Caveolin-1 as a critical component in the pathogenesis of lung fibrosis of different etiology: Evidences and mechanisms

Caveolin is a structural protein of flask-shaped invaginations of the plasma membrane termed as caveolae and is widely expressed on the endothelial cells, smooth muscle cells and fibroblasts in the different parts of the body including the lung tissues. The expression of caveolin-1 in the lung tissues is important to prevent the fibrogenic actions of TGF-β1 in lung fibrosis of different etiology including idiopathic pulmonary fibrosis, systemic sclerosis-associated interstitial lung disease and allergen-induced airway remodeling. Caveolin-1-mediated internalization and degradation of TGF-β1 receptors may possibly account for the decreased actions of TGF-β1. Studies have shown that the deficiency of caveolin-1 is very important in inducing lung fibrosis and its upregulation is reported to prevent lung fibrosis. The biological actions of caveolin-1 involve signaling pathways including JNK signaling, IL-4, STAT-3, miR199a-5p, CXCR4⁺ and CXCL12. The present review discusses the key role of caveolin and associated signaling pathways in the pathogenesis of lung fibrosis of different etiology.

SMPDL3b modulates insulin receptor signaling in diabetic kidney disease

Sphingomyelin phosphodiesterase acid-like 3b (SMPDL3b) is a lipid raft enzyme that regulates plasma membrane (PM) fluidity. Here we report that SMPDL3b excess, as observed in podocytes in diabetic kidney disease (DKD), impairs insulin receptor isoform B-dependent pro-survival insulin signaling by interfering with insulin receptor isoforms binding to caveolin-1 in the PM. SMPDL3b excess affects the production of active sphingolipids resulting in decreased ceramide-1-phosphate (C1P) content as observed in human podocytes in vitro and in kidney cortexes of diabetic db/db mice in vivo. Podocyte-specific Smpdl3b deficiency in db/db mice is sufficient to restore kidney cortex C1P content and to protect from DKD. Exogenous administration of C1P restores IR signaling in vitro and prevents established DKD progression in vivo. Taken together, we identify SMPDL3b as a modulator of insulin signaling and demonstrate that supplementation with exogenous C1P may represent a lipid therapeutic strategy to treat diabetic complications such as DKD.

Caveolin-1 regulation of Sp1 controls production of the antifibrotic protein follistatin in kidney mesangial cells

BACKGROUND

We previously showed that caveolin-1 (cav-1), an integral membrane protein, is required for the synthesis of matrix proteins by glomerular mesangial cells (MC). In a previous study to understand how cav-1 is involved in regulating matrix production, we had identified significant upregulation of the antifibrotic protein follistatin in cav-1 knockout MC. Follistatin inhibits the profibrotic effects of several members of the transforming growth factor beta superfamily, in particular the activins. Here, we characterize the molecular mechanism through which cav-1 regulates the expression of follistatin.

METHODS

Kidneys from cav-1 wild type and knockout (KO) mice were analyzed and primary cultures of MC from cav-1 wild-type and KO mice were utilized. FST promoter deletion constructs were generated to determine the region of the promoter important for mediating FST upregulation in cav-1 KO MC. siRNA-mediated down-regulation and overexpression of Sp1 in conjunction with luciferase activity assays, immunoprecipitation, western blotting and ChiP was used to assess the role of Sp1 in transcriptionally regulating FST expression. Pharmacologic kinase inhibitors and specific siRNA were used to determine the post-translational mechanism through which cav-1 affects Sp1 activity.

RESULTS

Our results establish that follistatin upregulation occurs at the transcript level. We identified Sp1 as the critical transcription factor regulating activation of the FST promoter in cav-1 KO MC through binding to a region within 123 bp of the transcription start site. We further determined that the lack of cav-1 increases Sp1 nuclear levels and transcriptional activity. This occurred through increased phosphoinositide 3-kinase (PI3K) activity and downstream protein kinase C (PKC) zeta-mediated phosphorylation and activation of Sp1.

CONCLUSIONS

These findings shed light on the transcriptional mechanism by which cav-1 represses the expression of a major antifibrotic protein, and can inform the development of novel antifibrotic treatment strategies.

Spatially controlled assembly of affinity ligand and enzyme cargo enables targeting ferritin nanocarriers to caveolae

One of the goals of nanomedicine is targeted delivery of therapeutic enzymes to the sub-cellular compartments where their action is needed. Endothelial caveolae-derived endosomes represent an important yet challenging destination for targeting, in part due to smaller size of the entry aperture of caveolae (ca. 30-50 nm). Here, we designed modular, multi-molecular, ferritin-based nanocarriers with uniform size (20 nm diameter) for easy drug-loading and targeted delivery of enzymatic cargo to these specific vesicles. These nanocarriers targeted to caveolar Plasmalemmal Vesicle-Associated Protein (Plvap) deliver superoxide dismutase (SOD) into endosomes in endothelial cells, the specific site of influx of superoxide mediating by such pro-inflammatory signaling as some cytokines and lipopolysaccharide (LPS). Cell studies showed efficient internalization of Plvap-targeted SOD-loaded nanocarriers followed by dissociation from caveolin-containing vesicles and intracellular transport to endosomes. The nanocarriers had a profound protective anti-inflammatory effect in an animal model of LPS-induced inflammation, in agreement with the characteristics of their endothelial uptake and intracellular transport, indicating that these novel, targeted nanocarriers provide an advantageous platform for caveolae-dependent delivery of biotherapeutics.

Deletion 101 residue at caveolin-1 scaffolding domain peptides impairs the ability of increasing heme oxygenase-1 activity

OBJECTIVE

Resident alveolar macrophages (AMs) are activated and release proinflammatory mediators and chemokines during acute lung injury. We have previous reported that caveolin-1 (Cav-1) scaffolding domain (CSD) peptide inhibited the proinflammatory cytokines expression by up-regulating heme oxygenase-1 (HO-1) activity. In this study, we aimed to investigate the effect of residue R101 in CSD peptide on the activity of HO-1 in AMs.

METHODS

The binding mode between HO-1 and CSD peptides (WT CSD and Δ101 CSD truncation peptides) was analyzed and the free energy was calculated. The inflammatory genes and M1/M2macrophage polarization-associated genes expression were measured by real-time PCR. The activities of HO-1 were determined by the spectrophotometical method. Western blot analyzed the content of Cav-1, HO-1, IκB and MAPK signals (phosphorylated ERK, JNK and p38 MAPK).

RESULTS

Δ101CSD peptide could bind to HO-1 protein and to disrupt the interaction of HO-1 and Cav-1. However, Δ101CSD peptide had lower activity of HO-1 in LPS-treated AMs compared with WT CSD. The expression of IL-1β and MCP-1 and NO content were decreased by WT CSD peptide in LPS treated AMs. However, only MCP-1 expression and NO content were downregulated byΔ101CSD peptide. Meanwhile, compared with those in LPS + hemin + WT CSD group, the mRNA expression of TNF-α, Cd86, IL-12b and NOS2 significantly increased while expression of IL10, Arg1 and CD163 significantly decreased in LPS + hemin + Δ101CSD group. The effect of WT CSD peptide on the inhibition of MAPK signaling pathway were stronger than Δ101 CSD peptide evidenced by the level of phosphorylated ERK, JNK and p38 MAPK.

CONCLUSION

Deletion of residue R101 impairs the ability of CSD peptide to increase HO-1 activity and to dampen inflammatory response in LPS-challenged rat AMs.

Flexible Nanoparticles Reach Sterically Obscured Endothelial Targets Inaccessible to Rigid Nanoparticles

Molecular targeting of nanoparticle drug carriers promises maximized therapeutic impact to sites of disease or injury with minimized systemic effects. Precise targeting demands addressing to subcellular features. Caveolae, invaginations in cell membranes implicated in transcytosis and inflammatory signaling, are appealing subcellular targets. Caveolar geometry has been reported to impose a ≈50 nm size cutoff on nanocarrier access to plasmalemma vesicle associated protein (PLVAP), a marker found in caveolae in the lungs. The use of deformable nanocarriers to overcome that size cutoff is explored in this study. Lysozyme-dextran nanogels (NGs) are synthesized with ≈150 or ≈300 nm mean diameter. Atomic force microscopy indicates the NGs deform on complementary surfaces. Quartz crystal microbalance data indicate that NGs form softer monolayers (≈60 kPa) than polystyrene particles (≈8 MPa). NGs deform during flow through microfluidic channels, and modeling of NG extrusion through porous filters yields sieving diameters less than 25 nm for NGs with 150 and 300 nm hydrodynamic diameters. NGs of 150 and 300 nm diameter target PLVAP in mouse lungs while counterpart rigid polystyrene particles do not. The data in this study indicate a role for mechanical deformability in targeting large high-payload drug-delivery vehicles to sterically obscured targets like PLVAP.

The new frontiers of the targeted interventions in the pulmonary vasculature: precision and safety (2017 Grover Conference Series)

The pulmonary vasculature plays an important role in many lung pathologies, such as pulmonary arterial hypertension, primary graft dysfunction of lung transplant, and acute respiratory distress syndrome. Therapy for these diseases is quite limited, largely due to dose-limiting side effects of numerous drugs that have been trialed or approved. High doses of drugs targeting the pulmonary vasculature are needed due to the lack of specific affinity of therapeutic compounds to the vasculature. To overcome this problem, the field of targeted drug delivery aims to target drugs to the pulmonary endothelial cells, especially those in pathological regions. The field uses a variety of drug delivery systems (DDSs), ranging from nano-scale drug carriers, such as liposomes, to methods of conjugating drugs to affinity moieites, such as antibodies. These DDSs can deliver small molecule drugs, protein therapeutics, and imaging agents. Here we review targeted drug delivery to the pulmonary endothelium for the treatment of pulmonary diseases. Cautionary notes are made of the risk–benefit ratio and safety—parameters one should keep in mind when developing a translational therapeutic.