RhoB loss prevents streptozotocin-induced diabetes and ameliorates diabetic complications in mice

Assessing Animal Models to Study Impaired and Chronic Wounds

Impaired healing wounds do not proceed through the normal healing processes in a timely and orderly manner, and while they do eventually heal, their healing is not optimal. Chronic wounds, on the other hand, remain unhealed for weeks or months. In the US alone, chronic wounds impact ~8.5 million people and cost ~USD 28-90 billion per year, not accounting for the psychological and physical pain and emotional suffering that patients endure. These numbers are only expected to rise in the future as the elderly populations and the incidence of comorbidities such as diabetes, hypertension, and obesity increase. Over the last few decades, scientists have used a variety of approaches to treat chronic wounds, but unfortunately, to date, there is no effective treatment. Indeed, while there are thousands of drugs to combat cancer, there is only one single drug approved for the treatment of chronic wounds. This is in part because wound healing is a very complex process involving many phases that must occur sequentially and in a timely manner. Furthermore, models that fully mimic human chronic wounds have not been developed. In this review, we assess various models currently being used to study the biology of impaired healing and chronic non-healing wounds. Among them, this paper also highlights one model which shows significant promise; this model uses aged and obese db/db-/- mice and the chronic wounds that develop show characteristics of human chronic wounds that include increased oxidative stress, chronic inflammation, damaged microvasculature, abnormal collagen matrix deposition, a lack of re-epithelialization, and the spontaneous development of multi-bacterial biofilm. We also discuss how important it is that we continue to develop chronic wound models that more closely mimic those of humans and that can be used to test potential treatments to heal chronic wounds.

Emerging Roles of Small GTPases in Islet β-Cell Function

Several small guanosine triphosphatases (GTPases) from the Ras protein superfamily regulate glucose-stimulated insulin secretion in the pancreatic islet β-cell. The Rho family GTPases Cdc42 and Rac1 are primarily involved in relaying key signals in several cellular functions, including vesicle trafficking, plasma membrane homeostasis, and cytoskeletal dynamics. They orchestrate specific changes at each spatiotemporal region within the β-cell by coordinating with signal transducers, guanine nucleotide exchange factors (GEFs), GTPase-activating factors (GAPs), and their effectors. The Arf family of small GTPases is involved in vesicular trafficking (exocytosis and endocytosis) and actin cytoskeletal dynamics. Rab-GTPases regulate pre-exocytotic and late endocytic membrane trafficking events in β-cells. Several additional functions for small GTPases include regulating transcription factor activity and mitochondrial dynamics. Importantly, defects in several of these GTPases have been found associated with type 2 diabetes (T2D) etiology. The purpose of this review is to systematically denote the identities and molecular mechanistic steps in the glucose-stimulated insulin secretion pathway that leads to the normal release of insulin. We will also note newly identified defects in these GTPases and their corresponding regulatory factors (e.g., GDP dissociation inhibitors (GDIs), GEFs, and GAPs) in the pancreatic β-cells, which contribute to the dysregulation of metabolism and the development of T2D.

NPY1R-targeted peptide-mediated delivery of a dual PPARα/γ agonist to adipocytes enhances adipogenesis and prevents diabetes progression

Objective

PPARα/γ dual agonists have been in clinical development for the treatment of metabolic diseases including type 2 diabetes and dyslipidemia. However, severe adverse side effects led to complications in clinical trials. As most of the beneficial effects rely on the compound activity in adipocytes, the selective targeting of this cell type is a cutting-edge strategy to develop safe anti-diabetic drugs. The goal of this study was to strengthen the adipocyte-specific uptake of the PPARα/γ agonist tesaglitazar via NPY₁R-mediated internalization.

Methods

NPY₁R-preferring peptide tesaglitazar-[F⁷, P³⁴]-NPY (tesa-NPY) was synthesized by a combination of automated SPPS and manual couplings. Following molecular and functional analyses for proof of concept, cell culture experiments were conducted to monitor the effects on adipogenesis. Mice treated with peptide drug conjugates or vehicle either by gavage or intraperitoneal injection were characterized phenotypically and metabolically. Histological analysis and transcriptional profiling of the adipose tissue were performed.

Results

In vitro studies revealed that the tesaglitazar-[F⁷, P³⁴]-NPY conjugate selectively activates PPARγ in NPY₁R-expressing cells and enhances adipocyte differentiation and adiponectin expression in adipocyte precursor cells. In vivo studies using db/db mice demonstrated that the anti-diabetic activity of the peptide conjugate is as efficient as that of systemically administered tesaglitazar. Additionally, tesa-NPY induces adipocyte differentiation in vivo.

Conclusions

The use of the tesaglitazar-[F7, P34]-NPY conjugate is a promising strategy to apply the beneficial PPARα/γ effects in adipocytes while potentially omitting adverse effects in other tissues.

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Tesaglitazar-NPY targets adipocytes via NPY₁R receptor-mediated internalization.

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Peptide-drug conjugate is specifically delivered to NPY₁R-expressing cells.

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Release of tesaglitazar in adipocytes activates PPARγ.

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Drug delivery enhances adipocyte differentiation and adiponectin expression.

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Peptide conjugate exhibits antidiabetic activity in vivo.

Identification of potential therapeutic target genes in mouse mesangial cells associated with diabetic nephropathy using bioinformatics analysis

The aim of the present study was to identify genes under the effect of transforming growth factor-β (TGF-β1), high glucose (HG) and glucosamine (GlcN) in MES-13 mesangial cells and elucidate the molecular mechanisms of diabetic nephropathy (DN). The gene expression datasets GSE2557 and GSE2558 were downloaded from the Gene Expression Omnibus database. Differentially expressed genes (DEGs) were independently screened using the GEO2R online tool. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses were performed using the Database for Annotation, Visualization, and Integrated Discovery. The protein-protein interaction (PPI) network was constructed using the Search Tool for the Retrieval of Interacting Genes and Cytoscape software. The hub genes were identified by the NetworkAnalyzer plugin. Overlapping genes were subjected to molecular docking analysis using SystemsDock. A total of 202 upregulated and 158 downregulated DEGs from the HG-treated groups, 138 upregulated and 103 downregulated DEGs from the GlcN-treated groups, and 81 upregulated and 44 downregulated DEGs from the TGF-β1-treated groups were identified. The majority of the DEGs were independently enriched in 'nucleosome assembly', 'chromatin silencing' and 'xenobiotic glucuronidation'. In addition, KEGG pathways were significantly enriched in 'systemic lupus erythematosus', 'protein processing in endoplasmic reticulum' and 'aldarate metabolism pathway', and 'TNF signaling pathway' intersected in the TGF-β1-treated and HG-treated groups. In total, eight hub genes, Jun, prostaglandin-endoperoxide synthase 2 (Ptgs2), fibronectin 1 (Fn1), cyclin-dependent kinase (Cdk)2, Fos, heat shock protein family A (Hsp70) member 5 (Hspa5), Hsp90b1 and homo sapiens hypoxia upregulated 1 (Hyou1), and three overlapping genes, Ras homolog gene family, member B (RHOB), complement factor H (CFH) and Krüppel-like factor 15 (KLF15), were selected. Valsartan with RHOB, and fosinopril with CFH and KLF15 had preferential binding activity. In conclusion, Jun, Ptgs2, Fn1, Cdk2, Fos, Hspa5, Hsp90b1, Hyou1, RHOB, CFH and KLF15 may be potential therapeutic targets for mesangial cells associated with DN, which may provide insight into DN treatment strategies.

RhoB antibody alters retinal vascularization in models of murine retinopathy

Neovascularization in cancer or retinopathy is driven by pathological changes that foster abnormal sprouting of endothelial cells. Mouse genetic studies indicate that the stress-induced small GTPase RhoB is dispensable for normal physiology but required for pathogenic angiogenesis. In diabetic retinopathy, retinopathy of prematurity (ROP) or age-related wet macular degeneration (AMD), progressive pathologic anatomic changes and ischemia foster neovascularization are characterized by abnormal sprouting of endothelial cells. This process is driven by the angiogenic growth factor VEGF, which induces and supports the formation of new blood vessels. While injectable biologics targeting VEGF have been used to treat these pathological conditions, many patients respond poorly, prompting interest in other types of mechanism-based therapy. Here we report the preclinical efficacy of a monoclonal antibody that specifically targets RhoB, a signaling molecule that is genetically dispensable for normal physiology but required for pathogenic retinal angiogenesis. In murine models of proliferative retinal angiogenesis or oxygen-induced retinopathy, administering a monoclonal RhoB antibody (7F7) was sufficient to block neoangiogenesis or avascular pathology, respectively. Our findings offer preclinical proof of concept for antibody targeting of RhoB to limit diabetic retinopathy, ROP or wet AMD and perhaps other diseases of neovasculogenesis such as hemangioma or hemangiosarcoma nonresponsive to existing therapies.

Transcriptomics and metabonomics analyses of maternal DEHP exposure on male offspring

The objectives of this study were to evaluate the effect of maternal Di-2-ethylhexyl phthalate (DEHP) exposure on male offspring and to explore the mechanism of changes with the metabolic alterations and differential genes. Pregnant female Sprague-Dawley (SD) rats were intragastrically administered with 600 mg/kg body weight of DEHP or corn oil (CON) throughout pregnancy and lactation. The growth of male offspring was investigated until 14 weeks old, the indices of blood were detected, and mechanism was studied using metabonomics and transcriptomics. Compared with the CON group, body weight, body length, food intake, body fat weight, Lee's index, organ coefficient, blood lipids, and oral glucose tolerance test (OGTT) of male offspring were not significantly changed in maternal DEHP group. However, serum biochemical indexes such as alanine transaminase (ALT), total protein (TP), albumin (ALB), blood urea nitrogen (BUN), and creatinine (CREA) were markedly reduced in maternal DEHP group (p < 0.05). In addition, insulin level was elevated and catalase (CAT) level was decreased notably in maternal DEHP group compared with the CON group (p < 0.05). Furthermore, thyroxine (T₄) level was lower and thyroid stimulating hormone (TSH) level was higher in maternal DEHP group (p < 0.05). Metabonomics revealed seven principal metabolites were identified, including increased L-allothreonine, creatine, uric acid, retinyl ester, L-palmitoylcarnitine, and decreased glycocholic acid and LysoPC (18:3). Transcriptomics displayed 35 differential genes were involved in the mechanism of maternal DEHP exposure. Therefore, this research confirms the effect of a certain dose of maternal DEHP exposure on male offspring and understands exactly the mechanism of these changes with metabonomics and transcriptomics.

RhoB blockade selectively inhibits autoantibody production in autoimmune models of rheumatoid arthritis and lupus

During the development of autoimmune disease, a switch occurs in the antibody repertoire of B cells so that the production of pathogenic rather than non-pathogenic autoantibodies is enabled. However, there is limited knowledge concerning how this pivotal step occurs. Here, we present genetic and pharmacological evidence of a positive modifier function for the vesicular small GTPase RhoB in specifically mediating the generation of pathogenic autoantibodies and disease progression in the K/BxN preclinical mouse model of inflammatory arthritis. Genetic deletion of RhoB abolished the production of pathogenic autoantibodies and ablated joint inflammation in the model. Similarly, administration of a novel RhoB-targeted monoclonal antibody was sufficient to ablate autoantibody production and joint inflammation. In the MRL/lpr mouse model of systemic lupus erythematosus (SLE), another established preclinical model of autoimmune disease associated with autoantibody production, administration of the anti-RhoB antibody also reduced serum levels of anti-dsDNA antibodies. Notably, the therapeutic effects of RhoB blockade reflected a selective deficiency in response to self-antigens, insofar as RhoB-deficient mice and mice treated with anti-RhoB immunoglobulin (Ig) both mounted comparable productive antibody responses after immunization with a model foreign antigen. Overall, our results highlight a newly identified function for RhoB in supporting the specific production of pathogenic autoantibodies, and offer a preclinical proof of concept for use of anti-RhoB Ig as a disease-selective therapy to treat autoimmune disorders driven by pathogenic autoantibodies.

RhoB controls coordination of adult angiogenesis and lymphangiogenesis following injury by regulating VEZF1-mediated transcription

Mechanisms governing the distinct temporal dynamics that characterize post-natal angiogenesis and lymphangiogenesis elicited by cutaneous wounds and inflammation remain unclear. RhoB, a stress-induced small GTPase, modulates cellular responses to growth factors, genotoxic stress and neoplastic transformation. Here we show, using RhoB null mice, that loss of RhoB decreases pathological angiogenesis in the ischaemic retina and reduces angiogenesis in response to cutaneous wounding, but enhances lymphangiogenesis following both dermal wounding and inflammatory challenge. We link these unique and opposing roles of RhoB in blood versus lymphatic vasculatures to the RhoB-mediated differential regulation of sprouting and proliferation in primary human blood versus lymphatic endothelial cells. We demonstrate that nuclear RhoB-GTP controls expression of distinct gene sets in each endothelial lineage by regulating VEZF1-mediated transcription. Finally, we identify a small-molecule inhibitor of VEZF1-DNA interaction that recapitulates RhoB loss in ischaemic retinopathy. Our findings establish the first intra-endothelial molecular pathway governing the phased response of angiogenesis and lymphangiogenesis following injury.

RhoB differentially controls Akt function in tumor cells and stromal endothelial cells during breast tumorigenesis

Tumors are composed of cancer cells but also a larger number of diverse stromal cells in the tumor microenvironment. Stromal cells provide essential supports to tumor pathophysiology but the distinct characteristics of their signaling networks are not usually considered in developing drugs to target tumors. This oversight potentially confounds proof-of-concept studies and increases drug development risks. Here, we show in established murine and human models of breast cancer how differential regulation of Akt by the small GTPase RhoB in cancer cells or stromal endothelial cells determines their dormancy versus outgrowth when angiogenesis becomes critical. In cancer cells in vitro or in vivo, RhoB functions as a tumor suppressor that restricts EGF receptor (EGFR) cell surface occupancy as well as Akt signaling. However, after activation of the angiogenic switch, RhoB functions as a tumor promoter by sustaining endothelial Akt signaling, growth, and survival of stromal endothelial cells that mediate tumor neoangiogenesis. Altogether, the positive impact of RhoB on angiogenesis and progression supercedes its negative impact in cancer cells themselves. Our findings elucidate the dominant positive role of RhoB in cancer. More generally, they illustrate how differential gene function effects on signaling pathways in the tumor stromal component can complicate the challenge of developing therapeutics to target cancer pathophysiology.

Inflammation-Mediated Regulation of MicroRNA Expression in Transplanted Pancreatic Islets

Nonspecific inflammation in the transplant microenvironment results in β-cell dysfunction and death influencing negatively graft outcome. MicroRNA (miRNA) expression and gene target regulation in transplanted islets are not yet well characterized. We evaluated the impact of inflammation on miRNA expression in transplanted rat islets. Islets exposed in vitro to proinflammatory cytokines and explanted syngeneic islet grafts were evaluated by miRNA arrays. A subset of 26 islet miRNAs was affected by inflammation both in vivo and in vitro. Induction of miRNAs was dependent on NF-κB, a pathway linked with cytokine-mediated islet cell death. RT-PCR confirmed expression of 8 miRNAs. The association between these miRNAs and mRNA target-predicting algorithms in genome-wide RNA studies of β-cell inflammation identified 238 potential miRNA gene targets. Several genes were ontologically associated with regulation of insulin signaling and secretion, diabetes, and islet physiology. One of the most activated miRNAs was miR-21. Overexpression of miR-21 in insulin-secreting MIN6 cells downregulated endogenous expression of the tumor suppressor Pdcd4 and of Pclo, a Ca²⁺ sensor protein involved in insulin secretion. Bioinformatics identified both as potential targets. The integrated analysis of miRNA and mRNA expression profiles revealed potential targets that may identify molecular targets for therapeutic interventions.

Small G proteins and their regulators in cellular signalling

Small molecular weight GTPases (small G proteins) are essential in the transduction of signals from different plasma membrane receptors. Due to their endogenous GTP-hydrolyzing activity, these proteins function as time-dependent biological switches controlling diverse cellular functions including cell shape and migration, cell proliferation, gene transcription, vesicular transport and membrane-trafficking. This review focuses on endocrine diseases linked to small G proteins. We provide examples for the regulation of the activity of small G proteins by various mechanisms such as posttranslational modifications, guanine nucleotide exchange factors (GEFs), GTPase activating proteins (GAPs) or guanine nucleotide dissociation inhibitors (GDIs). Finally we summarize endocrine diseases where small G proteins or their regulatory proteins have been revealed as the cause.