Pioglitazone enhances collateral blood flow in ischemic hindlimb of diabetic mice through an Akt-dependent VEGF-mediated mechanism, regardless of PPARgamma stimulation

Exercise and Ischemia-Activated Pathways in Limb Muscle Angiogenesis and Vascular Regeneration

Exercise has a profound effect on cardiovascular disease, particularly through vascular remodeling and regeneration. Peripheral artery disease (PAD) is one such cardiovascular condition that benefits from regular exercise or rehabilitative physical therapy in terms of slowing the progression of disease and delaying amputations. Various rodent pre-clinical studies using models of PAD and exercise have shed light on molecular pathways of vascular regeneration. Here, I review key exercise-activated signaling pathways (nuclear receptors, kinases, and hypoxia inducible factors) in the skeletal muscle that drive paracrine regenerative angiogenesis. The rationale for highlighting the skeletal muscle is that it is the largest organ recruited during exercise. During exercise, skeletal muscle releases several myokines, including angiogenic factors and cytokines that drive tissue vascular regeneration via activation of endothelial cells, as well as by recruiting immune and endothelial progenitor cells. Some of these core exercise-activated pathways can be extrapolated to vascular regeneration in other organs. I also highlight future areas of exercise research (including metabolomics, single cell transcriptomics, and extracellular vesicle biology) to advance our understanding of how exercise induces vascular regeneration at the molecular level, and propose the idea of "exercise-mimicking" therapeutics for vascular recovery.

Nuclear receptors as potential therapeutic targets in peripheral arterial disease and related myopathy

Peripheral arterial disease (PAD) is a prevalent cardiovascular complication of limb vascular insufficiency, causing ischemic injury, mitochondrial metabolic damage and functional impairment in the skeletal muscle, and ultimately leading to immobility and mortality. While potential therapies have been mostly focussed on revascularization, none of the currently available pharmacological treatments are fully effective in PAD, often leading to amputations, particularly in chronic metabolic diseases. One major limitation of focussed angiogenesis and revascularization as a therapeutic strategy is a limited effect on metabolic restoration and muscle regeneration in the affected limb. Therefore, additional preclinical investigations are needed to discover novel treatment options for PAD preferably targeting multiple aspects of muscle recovery. In this review, we propose nuclear receptors expressed in the skeletal muscle as potential candidates for ischemic muscle repair in PAD. We review classic steroid and orphan receptors that have been reported to be involved in the regulation of paracrine muscle angiogenesis, oxidative metabolism, mitochondrial biogenesis and muscle regeneration, and discuss how these receptors could be critical for recovery from ischemic muscle damage. Furthermore, we identify existing gaps in our understanding of nuclear receptor signalling in the skeletal muscle and propose future areas of research that could be instrumental in exploring nuclear receptors as therapeutic candidates for treating PAD.

Peroxisome Proliferator-Activated Receptor-Gamma (PPAR-ɣ): Molecular Effects and Its Importance as a Novel Therapeutic Target for Cerebral Ischemic Injury

Cerebral ischemic injury is a leading cause of death and long-term disability throughout the world. Peroxisome proliferator-activated receptor gamma (PPAR-ɣ) is a ligand-activated nuclear transcription factor that is a member of the PPAR family. PPAR-ɣ has been shown in several in vitro and in vivo models to prevent post-ischemic inflammation and neuronal damage by negatively controlling the expression of genes modulated by cerebral ischemic injury, indicating a neuroprotective effect during cerebral ischemic injury. A extensive literature review of PubMed, Medline, Bentham, Scopus, and EMBASE (Elsevier) databases was carried out to understand the nature of the extensive work done on the mechanistic role of Peroxisome proliferator activated receptor gamma and its modulation in Cerebral ischemic injury. PPAR-ɣ can interact with specific DNA response elements to control gene transcription and expression when triggered by its ligand. It regulates lipid metabolism, improves insulin sensitivity, modulates antitumor mechanisms, reduces oxidative stress, and inhibits inflammation. This review article provides insights on the current state of research into the neuroprotective effects of PPAR-ɣ in cerebral ischemic injury, as well as the cellular and molecular mechanisms by which these effects are modulated, such as inhibition of inflammation, reduction of oxidative stress, suppression of pro-apoptotic production, modulation of transcription factors, and restoration of injured tissue through neurogenesis and angiogenesis.

Activation of PPARγ reduces N-acetyl-cysteine -induced hypercorticoidism by down-regulating MC2R expression into adrenal glands

We previously demonstrated that oral supplementation with antioxidants induced hyperactivity of hypothalamus-pituitary-adrenal (HPA) axis, attested by hypercorticoidism, through an up-regulation of adrenocorticotrophic hormone (ACTH) receptors (MC2R) in adrenal. This study analyzed the role of peroxisome proliferator-activated receptor (PPAR)-γ on HPA axis hyperactivity induced by N-acetyl-cysteine (NAC). Male Swiss-Webster mice were orally treated with NAC for 1, 3, 5, 10, 15, or 18 consecutive days. The PPAR-γ agonist rosiglitazone and/or antagonist GW9662 were daily-injected i.p. for 5 consecutive days, starting concomitantly with NAC treatment. Rosiglitazone treatment inhibited NAC-induced adrenal hypertrophy and hypercorticoidism. Rosiglitazone also significantly reversed the NAC-induced increase in the MC2R expression in adrenal, but not steroidogenic acute regulatory protein (StAR). NAC treatment reduces the expression of PPARγ in the adrenals, but rosiglitazone did not restore the expression of this cytoprotective gene. In addition, GW9662 blocked the ability of rosiglitazone to decrease plasma corticosterone levels in NAC-treated mice. In conclusion, our findings showed that antioxidant supplementation induced a state of hypercorticoidism through down-regulation of PPARγ expression in the adrenals, in a mechanism probably related to a down-regulation of ACTH receptor expression.

A hybrid model of tumor growth and angiogenesis: In silico experiments

Tumor associated angiogenesis is the development of new blood vessels in response to proteins secreted by tumor cells. These new blood vessels allow tumors to continue to grow beyond what the pre-existing vasculature could support. Here, we construct a mathematical model to simulate tumor angiogenesis by considering each endothelial cell as an agent, and allowing the vascular endothelial growth factor (VEGF) and nutrient fields to impact the dynamics and phenotypic transitions of each tumor and endothelial cell. The phenotypes of the endothelial cells (i.e., tip, stalk, and phalanx cells) are selected by the local VEGF field, and govern the migration and growth of vessel sprouts at the cellular level. Over time, these vessels grow and migrate to the tumor, forming anastomotic loops to supply nutrients, while interacting with the tumor through mechanical forces and the consumption of VEGF. The model is able to capture collapsing and breaking of vessels caused by tumor-endothelial cell interactions. This is accomplished through modeling the physical interaction between the vasculature and the tumor, resulting in vessel occlusion and tumor heterogeneity over time due to the stages of response in angiogenesis. Key parameters are identified through a sensitivity analysis based on the Sobol method, establishing which parameters should be the focus of subsequent experimental efforts. During the avascular phase (i.e., before angiogenesis is triggered), the nutrient consumption rate, followed by the rate of nutrient diffusion, yield the greatest influence on the number and distribution of tumor cells. Similarly, the consumption and diffusion of VEGF yield the greatest influence on the endothelial and tumor cell numbers during angiogenesis. In summary, we present a hybrid mathematical approach that characterizes vascular changes via an agent-based model, while treating nutrient and VEGF changes through a continuum model. The model describes the physical interaction between a tumor and the surrounding blood vessels, explicitly allowing the forces of the growing tumor to influence the nutrient delivery of the vasculature.

Activation of Angiogenesis and Wound Healing in Diabetic Mice Using NO-Delivery Dinitrosyl Iron Complexes

In diabetes, abnormal angiogenesis due to hyperglycemia and endothelial dysfunction impairs wound healing and results in high risks of diabetic foot ulcers and mortality. Alternative therapeutic methods were attempted to prevent diabetic complications through the activation of endothelial nitric oxide synthase. In this study, direct application of nitric oxide using dinitrosyl iron complexes (DNICs) to promote angiogenesis and wound healing under physiological conditions and in diabetic mice is investigated. Based on in vitro and in vivo studies, DNIC [Fe₂(μ-SCH₂CH₂OH)₂(NO)₄] (DNIC-1) with a sustainable NO-release reactivity (t_1/2 = 27.4 ± 0.5 h at 25 °C and 16.8 ± 1.8 h at 37 °C) activates the NO-sGC-cGMP pathway and displays the best pro-angiogenesis activity overwhelming other NO donors and the vascular endothelial growth factor. Moreover, this pro-angiogenesis effect of DNIC-1 restores the impaired angiogenesis in the ischemic hind limb and accelerates the recovery rate of wound closure in diabetic mice. This study translates synthetic DNIC-1 into a novel therapeutic agent for the treatment of diabetes and highlights its sustainable ^•NO-release reactivity on the activation of angiogenesis and wound healing.

Skeletal muscle energetics are compromised only during high-intensity contractions in the Goto-Kakizaki rat model of type 2 diabetes

Type 2 diabetes (T2D) presents with hyperglycemia and insulin resistance, affecting over 30 million people in the United States alone. Previous work has hypothesized that mitochondria are dysfunctional in T2D and results in both reduced ATP production and glucose disposal. However, a direct link between mitochondrial function and T2D has not been determined. In the current study, the Goto-Kakizaki (GK) rat model of T2D was used to quantify mitochondrial function in vitro and in vivo over a broad range of contraction-induced metabolic workloads. During high-frequency sciatic nerve stimulation, hindlimb muscle contractions at 2- and 4-Hz intensities, the GK rat failed to maintain similar bioenergetic steady states to Wistar control (WC) rats measured by phosphorus magnetic resonance spectroscopy, despite similar force production. Differences were not due to changes in mitochondrial content in red (RG) or white gastrocnemius (WG) muscles (cytochrome c oxidase, RG: 22.2 ± 1.6 vs. 23.3 ± 1.7 U/g wet wt; WG: 10.8 ± 1.1 vs. 12.1 ± 0.9 U/g wet wt; GK vs. WC, respectively). Mitochondria isolated from muscles of GK and WC rats also showed no difference in mitochondrial ATP production capacity in vitro, measured by high-resolution respirometry. At lower intensities (0.25-1 Hz) there were no detectable differences between GK and WC rats in sustained energy balance. There were similar phosphocreatine concentrations during steady-state contraction and postcontractile recovery (τ = 72 ± 6 s GK versus 71 ± 2 s WC). Taken together, these results suggest that deficiencies in skeletal muscle energetics seen at higher intensities are not due to mitochondrial dysfunction in the GK rat.

Runx3 inhibits endothelial progenitor cell differentiation and function via suppression of HIF-1α activity

Endothelial progenitor cells (EPCs) are bone marrow (BM)‑derived progenitor cells that can differentiate into mature endothelial cells, contributing to vasculogenesis in the blood vessel formation process. Runt‑related transcription factor 3 (RUNX3) belongs to the Runt domain family and is required for the differentiation of specific immune cells and neurons. The tumor suppressive role of RUNX3, via the induction of apoptosis and cell cycle arrest in a variety of cancers, and its deletion or frequent silencing by epigenetic mechanisms have been studied extensively; however, its role in the differentiation of EPCs is yet to be investigated. Therefore, in the present study, adult BM‑derived hematopoietic stem cells (HSCs) were isolated from Runx3 heterozygous (Rx3+/‑) or wild‑type (WT) mice. The differentiation of EPCs from the BM‑derived HSCs of Rx3+/‑ mice was found to be significantly increased compared with those of the WT mice, as determined by the number of small or large colony‑forming units. The migration and tube formation abilities of Rx3+/‑ EPCs were also observed to be significantly increased compared with those of WT EPCs. Furthermore, the number of circulating EPCs, defined as CD34+/vascular endothelial growth factor receptor 2 (VEGFR2)+ cells, was also significantly increased in Rx3+/‑ mice. Hypoxia‑inducible factor (HIF)‑1α was upregulated in Rx3+/‑ EPCs compared with WT EPCs, even under normoxic conditions. Furthermore, in a hindlimb ischemic mouse models, the recovery of blood flow was observed to be highly stimulated in Rx3+/‑ mice compared with WT mice. Also, in a Lewis lung carcinoma cell allograft model, the tumor size in Rx3+/‑ mice was significantly larger than that in WT mice, and the EPC cell population (CD34+/VEGFR2+ cells) recruited to the tumor was greater in the Rx3+/‑ mice compared with the WT mice. In conclusion, the present study revealed that Runx3 inhibits vasculogenesis via the inhibition of EPC differentiation and functions via the suppression of HIF‑1α activity.

Pioglitazone inhibits advanced glycation induced protein modifications and down-regulates expression of RAGE and NF-κB in renal cells

The present work aims to determine the effect of pioglitazone on in-vitro albumin glycation and AGE-RAGE induced oxidative stress and inflammation. Bovine serum albumin was glycated by methylglyoxal in absence or presence of pioglitazone. Glycation markers (fructosamine, carbonyl groups, β-amyloid aggregation, thiol groups, bilirubin binding capacity and AOPP); protein conformational changes (native-PAGE and HPLC analysis) were determined. Cellular study was done by estimating antioxidants, ROS levels, expression profile of membrane RAGE, NF-κB and levels of inflammatory cytokines (IL-6, TNF-α) using HEK-293 cell line. We observed that levels of glycation markers were reduced at higher concentration of pioglitazone as compared to glycated albumin. Structural analysis of glycated albumin showed inhibition of protein migration and structural changes when treated with pioglitazone. Pioglitazone has potentially restored cellular antioxidants and reduced levels of IL-6 and TNF-α by declining expression of membrane RAGE and NF-κB. In conclusion, pioglitazone preferentially binds to protein and alleviates protein structural changes by maintaining its integrity. Additionally, it suppresses RAGE and NF-κB levels hence alleviate cellular oxidative stress and inflammation.

Reduced coronary collateralization in type 2 diabetic patients with chronic total occlusion

BACKGROUND

The extent of coronary collateral formation is a primary determinant of the severity of myocardial damage and mortality after coronary artery occlusion. Type 2 diabetes mellitus (T2DM) represents an important risk factor for impaired collateral vessel growth. However, the mechanism of reduced coronary collateralization in type 2 diabetic patients remains unclear.

METHODS

With the reference to the recent researches, this review article describes the pathogenic effects of T2DM on collateral development and outlines possible clinical and biochemical markers associated with reduced coronary collateralization in type 2 diabetic patients with chronic total occlusion (CTO).

RESULTS

Diffuse coronary atherosclerosis in T2DM reduces pressure gradient between collateral donor artery and collateral recipient one, limiting collateral vessel growth and function. An interaction between advanced glycation end-products and their receptor activates several intracellular signaling pathways, enhances oxidative stress and aggravates inflammatory process. Diabetic condition decreases pro-angiogenic factors especially vascular endothelial growth factor and other collateral vessel growth related parameters. Numerous clinical and biochemical factors that could possibly attenuate the development of coronary collaterals have been reported. Increased serum levels of glycated albumin, cystatin C, and adipokine C1q tumor necrosis factor related protein 1 were associated with poor coronary collateralization in type 2 diabetic patients with stable coronary artery disease and CTO. Diastolic blood pressure and stenosis severity of the predominant collateral donor artery also play a role in coronary collateral formation.

CONCLUSIONS

T2DM impairs collateral vessel growth through multiple mechanisms involving arteriogenesis and angiogenesis, and coronary collateral formation in patients with T2DM and CTO is influenced by various clinical, biochemical and angiographic factors. This information provides insights into the understanding of coronary pathophysiology and searching for potential new therapeutic targets in T2DM.

Low molecular weight fucoidan ameliorates hindlimb ischemic injury in type 2 diabetic rats

ETHNOPHARMACOLOGICAL RELEVANCE

Low molecular weight fucoidan (LMWF), extracted from Laminaria japonica Areschoug, is a traditional Chinese medicine, commonly used to alleviate edema, particularly for feet with numbness and pain.

AIM OF THE STUDY

Diabetic mellitus (DM) patients are at high risk of developing peripheral arterial disease (PAD). Individuals with DM and PAD co-morbidity have a much higher risk of critical limb ischemia. LMWF showed several beneficial effects, such as anti-inflammation, anti-thrombosis, and enhancing revascularization. Therefore, we hypothesized that LMWF might be beneficial to diabetes-induced PAD, and investigated the therapeutic potential of LMWF on diabetic PAD rats.

MATERIALS AND METHODS

Type 2 diabetic Goto-Kakizaki (GK) rats were made PAD by injection of sodium laurate into femoral artery. LMWF (20, 40 or 80mg/kg/day) or cilostazol (100mg/kg/day) were given to diabetic PAD rats for 4 weeks, respectively. The effects of LMWF on foot ulceration and claudication, plantar blood flow, collateral vessel formation, endothelium morphology, gastrocnemius injury, platelet aggregation, vessel vasodilation, and the expressions of inflammation factors, VEGF, eNOS, and nitric oxide were measured.

RESULTS

We found that LMWF markedly ameliorated foot ulceration and claudication, and improved the plantar perfusion by reversing hyperreactive platelet aggregation, ameliorating endothelium-dependent vasodilation and revascularization on diabetic PAD rats. In addition, upregulation of several inflammatory factors, such as ICAM-1 and IL-1β in the gastrocnemius muscles of ischemic hindlimb were suppressed by LMWF administration. And eNOS phosphorylation at Ser1177 and NO production were significantly enhanced in LMWF-treated diabetic PAD rats.

CONCLUSIONS

Taken together, our findings demonstrated that LMWF exhibits therapeutic effect on hindlimb ischemia in type 2 diabetic rats likely through ameliorating endothelium eNOS dysfunction and enhancing revascularization, thus, providing a potential supplementary non-invasive treatment for diabetes-induced PAD.

Treatment with the PPARγ Agonist Pioglitazone in the Early Post-ischemia Phase Inhibits Pro-inflammatory Responses and Promotes Neurogenesis Via the Activation of Innate- and Bone Marrow-Derived Stem Cells in Rats

Neurogenesis is essential for a good post-stroke outcome. Exogenous stem cells are currently being tested to promote neurogenesis after stroke. Elsewhere, we demonstrated that treatment with the PPARγ agonist pioglitazone (PGZ) before cerebral ischemia induction reduced brain damage and activated survival-related genes in ovariectomized (OVX) rats. Here, we tested our hypothesis that post-ischemia treatment with PGZ inhibits brain damage and contributes to neurogenesis via activated stem cells. Bone marrow (BM) cells of 7-week-old Wistar female rats were replaced with BM cells from green fluorescent protein-transgenic (GFP^+BM) rats. Three weeks later, they were ovariectomized (OVX/GFP^+BM rats). We subjected 7-week-old Wistar male and 13-week-old OVX/GFP^+BM rats to 90-min cerebral ischemia. Male and OVX/GFP^+BM rats were divided into two groups, one was treated with PGZ (2.5 mg/kg/day) and the other served as the vehicle control (VC). In both male and OVX/GFP^+BM rats, post-ischemia treatment with PGZ reduced neurological deficits and the infarct volume. In male rats, PGZ decreased the mRNA level of IL-6 and M1-like macrophages after 24 h. In OVX/GFP^+BM rats, PGZ augmented the proliferation of resident stem cells in the subventricular zone (SVZ) and the recruitment of GFP^+BM stem cells on days 7–14. Both types of proliferated stem cells migrated from the SVZ into the peri-infarct area. There, they differentiated into mature neurons, glia, and blood vessels in association with activated Akt, MAP2, and VEGF. Post-ischemia treatment with PGZ may offer a new avenue for stroke treatment through contribution to neuroprotection and neurogenesis.

The angiogenic properties of human adipose-derived stem cells (HASCs) are modulated by the High mobility group box protein 1 (HMGB1)

Peripheral arterial disease (PAD), is a major health problem. Many studies have been focused on the possibilities of treatment offered by vascular regeneration. Human adipose-derived stem cells (HASCs), multipotent CD34+ stem cells found in the stromal-vascular fraction of adipose tissues, which are capable to differentiate into multiple mesenchymal cell types. The High mobility group box 1 protein (HMGB1) is a nuclear protein involved in angiogenesis. The aim of the study was to define the role of HMGB1 in cell therapy with HASCs, in an animal model of PAD. We induced unilateral ischemia in mice and we treated them with HASCs, with the specific HMGB1-inihibitor BoxA, with HMGB1 protein, and with the specific VEGF inhibitor sFlt1, alternately or concurrently. We measured the blood flow recovery in all mice. Immunohistochemical and ELISA analyses was performed to evaluate the number of vessels and the VEGF tissue content. None auto-amputation occurred and there have been no rejection reactions to the administration of HASCs. Animals co-treated with HASCs and HMGB1 protein had an improved blood flow recovery, compared to HASCs-treated mice. The post-ischemic angiogenesis was reduced when the HMGB1 pathway was blocked or when the VEGF activity was inhibited, in mice co-treated with HASCs and HMGB1. In conclusion, the HASCs treatment can be used in a mouse model of PAD to induce post-ischemic angiogenesis, modulating angiogenesis by HMGB1. This effect is mediated by VEGF activity. Although further data are needed, these findings shed light on possible new cell treatments for patients with PAD.

Paradoxical Inhibition of Glycolysis by Pioglitazone Opposes the Mitochondriopathy Caused by AIF Deficiency

Mice with the hypomorphic AIF-Harlequin mutation exhibit a highly heterogeneous mitochondriopathy that mostly affects respiratory chain complex I, causing a cerebral pathology that resembles that found in patients with AIF loss-of-function mutations. Here we describe that the antidiabetic drug pioglitazone (PIO) can improve the phenotype of a mouse Harlequin (Hq) subgroup, presumably due to an inhibition of glycolysis that causes an increase in blood glucose levels. This glycolysis-inhibitory PIO effect was observed in cultured astrocytes from Hq mice, as well as in human skin fibroblasts from patients with AIF mutation. Glycolysis inhibition by PIO resulted from direct competitive inhibition of glyceraldehyde-3-phosphate dehydrogenase (GAPDH). Moreover, GAPDH protein levels were reduced in the cerebellum and in the muscle from Hq mice that exhibited an improved phenotype upon PIO treatment. Altogether, our results suggest that excessive glycolysis participates to the pathogenesis of mitochondriopathies and that pharmacological inhibition of glycolysis may have beneficial effects in this condition.

Mechanisms of Comorbidities Associated With the Metabolic Syndrome: Insights from the JCR:LA-cp Corpulent Rat Strain

Obesity and its metabolic complications have emerged as the epidemic of the new millennia. The use of obese rodent models continues to be a productive component of efforts to understand the concomitant metabolic complications of this disease. In 1978, the JCR:LA-cp rat model was developed with an autosomal recessive corpulent (cp) trait resulting from a premature stop codon in the extracellular domain of the leptin receptor. Rats that are heterozygous for the cp trait are lean-prone, while those that are homozygous (cp/cp) spontaneously display the pathophysiology of obesity as well as a metabolic syndrome (MetS)-like phenotype. Over the years, there have been formidable scientific contributions that have originated from this rat model, much of which has been reviewed extensively up to 2008. The premise of these earlier studies focused on characterizing the pathophysiology of MetS-like phenotype that was spontaneously apparent in this model. The purpose of this review is to highlight areas of recent advancement made possible by this model including; emerging appreciation of the "thrifty gene" hypothesis in the context of obesity, the concept of how chronic inflammation may drive obesogenesis, the impact of acute forms of inflammation to the brain and periphery during chronic obesity, the role of dysfunctional insulin metabolism on lipid metabolism and vascular damage, and the mechanistic basis for altered vascular function as well as novel parallels between the human condition and the female JCR:LA-cp rat as a model for polycystic ovary disease (PCOS).

The role of high-mobility group box protein 1 in collagen antibody-induced arthritis is dependent on vascular endothelial growth factor

High-mobility group box 1 (HMGB1) has been implicated in angiogenesis and rheumatoid arthritis (RA). The aim of this study was to define more clearly the role of HMGB1 in the synovial angiogenesis and pathogenesis of an immune model of arthritis. BALB/c mice were injected with monoclonal anti-collagen antibody cocktail followed by lipopolysaccharide to induce arthritis. HMGB1 and vascular endothelial growth factor (VEGF) were over-expressed in the areas of the synovium where more inflammation and neoangiogenesis were present. The selective blockade of HMGB1 or VEGF resulted alternatively in a lower severity of arthritis evaluated by the arthritis index. Furthermore, exogenous HMGB1 administration caused a worsening of arthritis, associated with VEGF up-regulation and increased synovial angiogenesis. The selective inhibition of VEGF also resulted in no induction of arthritis in mice receiving exogenous HMGB1. Cytokine enzyme-linked immunosorbent assay (ELISA) analyses performed on peripheral blood and synovial fluid demonstrated a significant reduction of interleukin (IL)-1β, IL-6 and tumour necrosis factor (TNF)-α in mice where HMGB1 and VEGF pathways were blocked. Interestingly, the selective blockade of HMGB1 and VEGF resulted in an increase of the peripheral IL-17A concentration. The development of arthritis mediated by HMGB1 and the synovial angiogenesis can be blocked by inhibiting the VEGF activity. The proinflammatory and proangiogenic cytokine IL-17A was increased when HMGB1 is inhibited, but the synovial angiogenesis was nevertheless reduced in this model of arthritis. Taken together, these findings shed new light on the role of this nuclear protein in the pathogenesis of arthritis in an RA-like model.

PPAR Gamma and Angiogenesis: Endothelial Cells Perspective

We summarize the current knowledge concerning PPARγ function in angiogenesis. We discuss the mechanisms of action for PPARγ and its role in vasculature development and homeostasis, focusing on endothelial cells, endothelial progenitor cells, and bone marrow-derived proangiogenic cells.

The peroxisome proliferator-activated receptors in cardiovascular diseases: experimental benefits and clinical challenges

The peroxisome proliferator-activated receptors, PPARα, PPARβ/δ and PPARγ, are ligand-activated transcriptional factors belonging to the nuclear receptors superfamily and they are known to play important roles in glucose and lipid metabolism. Experimental studies in animal models of metabolic diseases have also revealed that activation of PPARs protects against the vascular complications of diabetes, hypertension, atherosclerosis, myocardial infarction and stroke, through exerting their anti-inflammatory, anti-atherogenic and antioxidant effects. In clinical trials and post-market surveillance, agonists of PPARs have been shown to effectively prevent cardiovascular events. However, adverse effects, particularly for PPARγ agonists, are also observed with the use of investigational PPAR agonists and even some approved drugs. Further exploration of underlying mechanisms is needed to develop novel ways of PPAR activation without causing serious side effects. This article reviews the cardiovascular effects of PPARs, with emphasis on the therapeutic potential of PPAR agonists in combating metabolic vascular diseases.

Pioglitazone and Endothelial Dysfunction: Pleiotropic Effects and Possible Therapeutic Implications

The vascular endothelium has a central role in the modulation of vascular tone with associated antioxidant, anti-inflammatory, pro-fibrinolytic, anti-adhesive, and anticoagulant effects. This is primarily accomplished by the timely release of endothelial autacoids. On the other hand, endothelial dysfunction (ED) provoked by insulin resistance has been linked with reduced nitric oxide bioavailability, increased production of reactive oxygen species, and alterations of endothelial regeneration. Pioglitazone is classified as an insulin-sensitizing, anti-hyperglycemic agent. The mechanism of action associated with pioglitazone includes the activation of peroxisome proliferator-activated receptor-gamma with stable improvement in glycemic control in diabetic patients. Today, it is known that apart from the beneficial effects on glucose homeostasis, pioglitazone exerts several pleiotropic effects, including the improvement of ED. Thus, the aim of this article was to summarize the current knowledge related to signaling mechanisms of the pioglitazone-induced improvement or reversal of ED. The relevant clinical studies and possible therapeutic implications connected to pioglitazone-related action on the endothelium were analyzed too.

Loss of miR125a expression in a model of K-ras-dependent pulmonary premalignancy

Understanding the molecular pathogenesis of lung cancer is necessary to identify biomarkers/targets specific to individual airway molecular profiles and to identify options for targeted chemoprevention. Herein, we identify mechanisms by which loss of microRNA (miRNA)125a-3p (miR125a) contributes to the malignant potential of human bronchial epithelial cells (HBEC) harboring an activating point mutation of the K-ras proto-oncogene (HBEC K-ras). Among other miRNAs, we identified significant miR125a loss in HBEC K-ras lines and determined that miR125a is regulated by the PEA3 transcription factor. PEA3 is upregulated in HBEC K-ras cells, and genetic knockdown of PEA3 restores miR125a expression. From a panel of inflammatory/angiogenic factors, we identified increased CXCL1 and vascular endothelial growth factor (VEGF) production by HBEC K-ras cells and determined that miR125a overexpression significantly reduces K-ras-mediated production of these tumorigenic factors. miR125a overexpression also abrogates increased proliferation of HBEC K-ras cells and suppresses anchorage-independent growth (AIG) of HBEC K-ras/P53 cells, the latter of which is CXCL1-dependent. Finally, pioglitazone increases levels of miR125a in HBEC K-ras cells via PEA3 downregulation. In addition, pioglitazone and miR125a overexpression elicit similar phenotypic responses, including suppression of both proliferation and VEGF production. Our findings implicate miR125a loss in lung carcinogenesis and lay the groundwork for future studies to determine whether miR125a is a possible biomarker for lung carcinogenesis and/or a chemoprevention target. Moreover, our studies illustrate that pharmacologic augmentation of miR125a in K-ras-mutated pulmonary epithelium effectively abrogates several deleterious downstream events associated with the mutation.

Effect of angiogenesis induced by consecutive intramuscular injections of vascular endothelial growth factor in a hindlimb ischemic mouse model

PURPOSE

Angiogenesis plays a major role in various physiological and pathological situations. Thus, an angiogenic therapy with vascular endothelial growth factor (VEGF) has been commonly recommended as a representative therapeutic solution to recover the insufficient blood supply of collateral vessels in an ischemic lesion. In this study, the injection method and injection time point of VEGF proteins were focused to discover how to enhance the angiogenic effect with VEGF.

METHODS

Mouse models (n = 15) were divided into control, VEGF treatment by intra-venous injection (VEGF-IV) and VEGF treatment by intra-muscular injection (VEGF-IM). Right proximal femoral arteries of mice were firmly sutured to obstruct arterial blood-flow. In the VEGF-IV treatment group, VEGF proteins were injected into the tail vein and, in the VEGF-IM treatment group, VEGF proteins were directly injected into the ischemic site of the right thigh after postoperative day 5, 10, 15, 20 and 25 follow-ups. Blood-flow images were acquired by (99m)Tc Gamma Image Acquisition System to compare the ischemic-to-non-ischemic bloodstream ratio at postoperative days 5, 15, and 30.

RESULTS

VEGF-IM treatment significantly induced higher an angiogenic effect rather than both the control group (P = 0.008) and VEGF-IV treatment group (P = 0.039) at the 30th day.

CONCLUSION

During all experiments, angiogenesis of VEGF-IM treatment represented the most evident effect compared with control and VEGF-IV group in a mouse model of hindlimb ischemia.

Cilostazol improves the response to ischemia in diabetic mice by a mechanism dependent on PPARγ

Cilostazol is effective for the treatment of peripheral ischemia. This compound has several beneficial effects on platelet aggregation, serum lipids and endothelial cells, and we recently found that it enhances collateral blood flow in the ischemic hind limbs of mice. Peroxisome proliferator-activated receptor (PPAR)γ, a receptor for thiazolidinediones, plays a role in angiogenesis. The aim of this work was to investigate the underlying molecular mechanisms and effects of cilostazol in a model of peripheral ischemia in diabetic mice. We induced diabetes in mice by streptozotocin (STZ) administration and studied ischemia-induced angiogenesis in the ischemic hind limbs of cilostazol-treated and untreated control mice. We found that perfusion recovery was significantly improved in treated compared with control diabetic mice. Interestingly, we found that the expression of PPARγ is reduced in ischemic tissues of diabetic mice. Furthermore, we discovered that local inhibition of the activity of this nuclear receptor decreased the angiogenic response to cilostazol treatment. Finally, we noted that this phenomenon is dependent on VEGF and modulated by PPARγ. Cilostazol administration enhances collateral blood flow in the ischemic hind limbs of STZ-induced diabetic mice through a PPARγ-dependent mechanism.

Suppression of Receptor for Advanced Glycation End Products Improves Angiogenic Responses to Ischemia in Diabetic Mouse Hindlimb Ischemia Model

Background. The role of the receptor for advanced glycation end products (RAGE) for the impaired angiogenic response in diabetic patients is not well known. We investigated the impact of RAGE suppression by soluble RAGE (sRAGE) on the angiogenic response in a diabetic hindlimb ischemia mouse model. Materials and Methods. Hindlimb ischemia model was prepared by ligation of femoral artery in diabetic and nondiabetic mice. Ischemia-induced angiogenic response was evaluated by laser-Doppler perfusion imaging, muscle capillary density, and protein expression of vascular endothelial growth factor (VEGF) and high-mobility group box (HMGB)-1. Results. Diabetic mice showed attenuated recovery of ischemic limb perfusion on laser-Doppler perfusion imaging compared with nondiabetic mice. The treatment with sRAGE significantly improved blood flow in the ischemic limbs of diabetic mice. The expression levels of VEGF and HMGB-1 in the limb muscle tissues of diabetic mice were lower than in those of nondiabetic mice. The treatment with sRAGE significantly increased the VEGF and HMGB-1 protein expression in the ischemic limb muscle tissues in the diabetic mice. Conclusion. The suppression of RAGE by sRAGE administration improved angiogenic response to ischemia in diabetic mice and was associated with increased HMGB-1 and VEGF levels in muscle tissues.

Activation of PPARγ by restores mast cell numbers and reactivity in alloxan-diabetic rats by reducing the systemic glucocorticoid levels

Mast cell function and survival have been shown to be down-regulated under diabetic conditions. This study investigates the role of the peroxisome proliferator-activated receptor (PPAR)-γ in reducing mast cell number and reactivity in diabetic rats. The effect of rosiglitazone on mast cell apoptosis was also evaluated. Diabetes was induced by intravenous injection of alloxan into fasted rats and PPARγ agonist rosiglitazone and/or specific antagonist 2-chloro-5-nitrobenzanilide (GW9662) were administered 3 day after diabetes induction, once daily for 18 consecutive days. Mast cell apoptosis and plasma corticosterone levels were evaluated by TUNEL and radioimmunoassay, respectively. Treatment with rosiglitazone restored mast cell numbers in the pleural cavity and mesenteric tissue of diabetic rats. Rosiglitazone also significantly reversed the diabetes-induced reduction of histamine release by mast cells, as measured by fluorescence, following activation with the antigen in vitro. Increased apoptosis in mast cells from diabetic rats were inhibited by rosiglitazone. Moreover, we noted that the increase in plasma corticosterone levels in diabetic rats was inhibited by rosiglitazone. In addition, GW9662 blocked the ability of rosiglitazone to restore baseline numbers of mast cells and plasma corticosterone in diabetic rats. In conclusion, our findings showed that rosiglitazone restored the number and reactivity of mast cells in diabetic rats, accompanied with a suppression of apoptosis, in parallel with impairment of diabetes hypercorticolism, indicating that PPARγ has an important role in these phenomena.

Circulating angiopoietin-2 and soluble Tie-2 in type 2 diabetes mellitus: a cross-sectional study

BACKGROUND

Type 2 diabetes is associated with increased levels of Angiopoietin-2 (Ang-2) and soluble Tie-2 (sTie-2), but its impact on vascular disease is still unknown. This study aimed to further explore the associations of Ang-2 and sTie-2 with metabolic control and diabetic complications.

METHODS

In a cross-sectional designed study, levels of Ang-2 and sTie-2 as well as their relationships to cardiometabolic parameters were determined in 80 type 2 diabetic subjects (age 65 ± 7 years, female 47.4%).

RESULTS

After controlling for age and BMI, Ang-2 levels were associated with levels of sTie-2, diastolic blood pressure, plasma insulin, homeostasis model assessment of insulin resistance (HOMA-IR), creatinine, glomerular filtration rate (GFR), and gamma-glutamyl transferase (GGT) (all p < 0.02). Presence of diabetic macrovascular complications, polyneuropathy and insulin therapy were associated with higher Ang-2 levels (p < 0.05). Conversely, sTie-2 levels were associated with glycated hemoglobin (HbA1c), fasting plasma glucose and insulin, HOMA-IR, triglyceride, and liver function parameters (all p < 0.03). Multiple linear regression analysis showed that Ang-2 remained significantly associated only with levels of GGT (p < 0.04), whereas sTie-2 remained significantly associated with HbA(1c), insulin levels, and HOMA-IR (p < 0.03). No differences in Ang-2 and sTie-2 levels were observed with regard to gender of participants.

CONCLUSIONS

Ang-2 is independently associated with levels of GGT while sTie-2 is independently associated with levels of HbA(1c), plasma insulin and HOMA-IR in type 2 diabetic subjects. Therefore we suggest that the associations of Ang-2 and sTie-2 with type 2 diabetes are based on different patho-physiological mechanisms.

Pioglitazone limits myocardial infarct size, activates Akt, and upregulates cPLA2 and COX-2 in a PPAR-γ-independent manner

Pioglitazone (PIO), a PPAR-γ agonist, limits myocardial infarct size by activating Akt and upregulating cytosolic phospholipase A(2) (cPLA(2)) and cyclooxygenase (COX)-2. However, PIO has several PPAR-γ-independent effects. We assessed whether PIO limits myocardial infarct size in PPAR-γ-knockout mice, attenuates hypoxia-reoxygenation injury and upregulates P-Akt, cPLA(2), and COX-2 expression in PPAR-γ-knockout cardiomyocytes. Cardiac-specific inducible PPAR-γ knockout mice were generated by crossing αMHC-Cre mice to PPAR-γ(loxp/loxp) mice. PPAR-γ deletion was achieved after 7 days of intraperitoneal tamoxifen (20 mg/kg/day) administration. Mice received PIO (10 mg/kg/day), or vehicle, for 3 days and underwent coronary occlusion (30 min) followed by reperfusion (4 h). We assessed the area at risk by blue dye and infarct size by TTC. Cultured adult cardiomyocytes of PPAR-γ(loxp/loxp/cre) mice without or with pretreatment with tamoxifen were incubated with or without PIO and subjected to 2 h hypoxia/2 h reoxygenation. Cardiac-specific PPAR-γ knockout significantly increased infarct size. PIO reduced infarct size by 51% in PPAR-γ knockout mice and by 55% in mice with intact PPAR-γ. Deleting the PPAR-γ gene increased cell death in vitro. PIO reduced cell death in cells with and without intact PPAR-γ. PIO similarly increased myocardial Ser-473 P-Akt, cPLA(2), and COX-2 levels after hypoxia/reoxygenation in cells with and without intact PPAR-γ. PIO limited infarct size in mice in a PPAR-γ-independent manner. PIO activated Akt, increased the expression of cPLA(2) and COX-2, and protected adult cardiomyocytes against the effects of hypoxia/reoxygenation independent of PPAR-γ activation.

Lack of effects of pioglitazone on cardiac function in patients with type 2 diabetes and evidence of left ventricular diastolic dysfunction: a tissue doppler imaging study

Background

Thiazolidinediones, used for the treatment of patients with type 2 diabetes mellitus (DM2), are associated with an increased incidence of heart failure. We sought to investigate the effects of pioglitazone on novel echocardiographic indices of left ventricular (LV) diastolic function in DM2 patients with LV diastolic dysfunction (LVDD).

Methods

Eighty-eight asymptomatic DM2 patients on metformin and/or sulfonylureas, aged 64.5 ± 7.7 years, without known cardiovascular disease, with normal LV systolic function and evidence of LVDD were randomly assigned to pioglitazone 30 mg/day (n = 42) or an increase in dose of other oral agents (n = 39) for 6 months. All patients underwent transthoracic conventional and Tissue Doppler Imaging echocardiography at baseline and follow-up. The primary end-point was change in early diastolic velocity of the mitral annulus (E').

Results

Improvement of glycaemic control was similar in the 2 groups. A significant difference (p < 0.05) between the 2 groups was found in the treatment-induced changes in fasting insulin, the insulin resistance index HOMA, HDL cholesterol, triglycerides, diastolic blood pressure (all in favor of pioglitazone) and in body weight (increase with pioglitazone). No significant changes were observed in any echocardiographic parameter in either group and did not differ between groups (p = NS for all). E' increased non-significantly and to a similar extent in both groups (p = NS).

Conclusions

In asymptomatic DM2 patients with LVDD, the addition of pioglitazone to oral conventional treatment for 6 months does not induce any adverse or favorable changes in LV diastolic or systolic function despite improvements in glycaemic control, insulin sensitivity, lipid profile, and blood pressure.

[Macular oedema due to rosiglitazone treatment in diabetes mellitus]

CASE REPORT

A 61-year-old woman with type 2 diabetes mellitus for 7 years for which she was prescribed insulin therapy. Rosiglitazone (4 mg once daily) was introduced with adequate blood glucose control. One month later, she presented with complaints of systemic oedema and loss of vision. Fundoscopy showed bilateral macular oedema. A systemic study demonstrated peripheral oedema. Rosiglitazone was stopped and she was managed conservatively with a rapid resolution of the oedemas and at fundus examination there was no decrease in the macular oedema.

DISCUSSION

This case reminds us of the importance of identifying potential toxicities of glitazone regimens. Glitazone use appears to be a cause of macular oedema, and stopping the drug may not resolve this oedema.

High-mobility group box-1 protein promotes angiogenesis after peripheral ischemia in diabetic mice through a VEGF-dependent mechanism

OBJECTIVE

High-mobility group box-1 (HMGB1) protein is a nuclear DNA-binding protein released from necrotic cells, inducing inflammatory responses and promoting tissue repair and angiogenesis. Diabetic human and mouse tissues contain lower levels of HMGB1 than their normoglycemic counterparts. Deficient angiogenesis after ischemia contributes to worse outcomes of peripheral arterial disease in patients with diabetes. To test the hypothesis that HMGB1 enhances ischemia-induced angiogenesis in diabetes, we administered HMGB1 protein in a mouse hind limb ischemia model using diabetic mice.

RESEARCH DESIGN AND METHODS

After the induction of diabetes by streptozotocin, we studied ischemia-induced neovascularization in the ischemic hind limb of normoglycemic, diabetic, and HMGB1-treated diabetic mice.

RESULTS

We found that the perfusion recovery was significantly attenuated in diabetic mice compared with normoglycemic control mice. Interestingly, HMGB1 protein expression was lower in the ischemic tissue of diabetic mice than in normoglycemic mice. Furthermore, we observed that HMGB1 administration restored the blood flow recovery and capillary density in the ischemic muscle of diabetic mice, that this process was associated with the increased expression of vascular endothelial growth factor (VEGF), and that HMGB1-induced angiogenesis was significantly reduced by inhibiting VEGF activity.

CONCLUSIONS

The results of this study show that endogenous HMGB1 is crucial for ischemia-induced angiogenesis in diabetic mice and that HMGB1 protein administration enhances collateral blood flow in the ischemic hind limbs of diabetic mice through a VEGF-dependent mechanism.