Endothelial-Specific Overexpression of Histone Deacetylase 2 Protects Mice against Endothelial Dysfunction and Atherosclerosis.

BACKGROUND/AIMS: We recently described a novel regulatory role for histone deacetylase 2 (HDAC2) in protecting endothelial cells from oxidized low-density lipoprotein (OxLDL)-induced injury. In this study, we examined the effects of endothelial-specific HDAC2 overexpression on endothelial-dependent vasorelaxation and atherogenesis in vivo. METHODS: Endothelial-specific HDAC2-overexpressing transgenic mice (HDAC2-Tg) were generated under control of the Tie2 promoter. An atherosclerosis model was produced by injecting HDAC2-Tg and wild-type (WT) mice with adeno-associated virus encoding a PCSK9 gain-of-function mutant under control of a liver-specific promoter and feeding them a high-fat diet for 12 weeks. Aortic stiffness in vivo was determined by measuring pulse wave velocity. Wire myography was used to measure endothelium dependent (acetylcholine) and independent (sodium nitroprusside) relaxation in isolated mice aortas. Atherosclerotic plaque burden in aortas was determined by Oil Red O staining and protein expression was determined by western blotting. RESULTS: At baseline, HDAC2-Tg mice had normal mean arterial blood pressure (MAP) and body weight, but pulse wave velocity (PWV), an inverse measure of vascular health and stiffness, was decreased, suggesting that their vessels were more compliant. Moreover, basal nitric oxide production was enhanced in the vessels of HDAC2-Tg mice as compared to that in WT controls, although no significant differences in acetylcholine (endothelial component)- or sodium nitroprusside (non-endothelial component)-mediated relaxation were observed. However, after exposure to OxLDL, aortas from HDAC2-Tg mice exhibited greater acetylcholine-induced relaxation than did those from WT mice. Thus, endothelial-specific vasodilator production was enhanced despite oxidative injury. Atherosclerosis induction in WT mice led to a significant increase in PWV, but in HDAC2-Tg mice, PWV and MAP remained unchanged. Further, aortic rings from HDAC2-Tg exhibited better endothelial-dependent vascular relaxation than did those from WT mice, but not when treated with nitric oxide synthase inhibitor L-NAME. Finally, plaque burden, determined by Oil red O staining, was significantly increased in WT, but not HDAC2-Tg mice, subjected to the atherogenic model. Deletion of endothelial HDAC2 led to impaired endothelial cell-dependent vascular relaxation and increased PWV, compared with those in littermate controls. CONCLUSION: HDAC2 protects against endothelial dysfunction and atherogenesis induced by oxidized lipids. Hence, overexpression or activation of HDAC2 represents a novel therapy for endothelial dysfunction and atherosclerosis. HDAC2-Tg mice provide an opportunity to determine the role of endothelial HDAC2 in vascular endothelial homeostasis.

Photodynamic therapy as an alternative treatment in patients with invasive cutaneous SCC where surgery is not feasible: Single center experience.

The aim of this study was to demonstrate the efficacy of 5-aminolevulinic acid photodynamic therapy (ALA-PDT) as an alternative treatment in cutaneous squamous cell carcinoma (cSCC) patients who are not fit for surgery. Thirty-three invasive cSCC patients who, for some reasons, cannot undergo surgery were enrolled in this study. All patients received plum blossom needle (PBN) pretreated ALA-PDT combined with topical application of 5% imiquimod cream. Two patients dropped the study because of severe pain and two patients discontinue treatment due to lack of response. Of 29 patients, who completed the treatment, 5 patients had complete response after 2-9 sessions of PDT and these patients had no recurrence till 18 months after treatment. Twenty-four patients achieved partial response and are satisfied with treatment outcome in terms of decreased symptoms and improved quality of life. PBN pretreated PDT in combination with topical imiquimod may be a viable treatment option for non resectable cSCC lesions.

CCL8 enhances sensitivity of cutaneous squamous cell carcinoma to photodynamic therapy by recruiting M1 macrophages.

BACKGROUND: Antitumor immunity induced by photodynamic therapy (PDT) is believed to depend on the degree of local and systemic inflammation. The recruitment of leukocytes, in particular by the chemokine CCL8, to the sites of tissue damage has been strongly associated with the initiation of inflammatory reactions. OBJECTIVE: To evaluate whether and how CCL8 enhances the immune response against tumors in 5-aminolevulinic acid (ALA)-mediated PDT. METHODS: In this study, we investigated the effect of ALA-PDT-induced CCL8 expression on the recruitment and polarization of macrophages using immunohistochemistry, western blot and Transwell cell migration assay. We evaluated CCL8 expression following ALA-PDT in vitro and in vivo by using RT-PCR, western blot, and ELISA in clinical cutaneous squamous cell carcinoma (cSCC) samples, a mouse model of cSCC, tumor cells, and macrophages. The effect of the combination of ALA-PDT with CCL8 treatment on anti-tumor immunity was tested in the mouse model. RESULTS: We found that ALA-PDT enhanced CCL8 expression, increased the number of macrophages in tumor, and stimulated their M1 pro-inflammatory phenotype characterized by high expression levels of CD16 and CD80, low expression level of CD163, and absence of CD206 expression. Furthermore, CCL8 enhanced the effect of ALA-PDT on cSCC in mice, such a combination of CCL8 and ALA-PDT had a stronger positive effect in the treatment of mouse cSCC than PDT alone and suppressed tumor volume regrowth. CONCLUSION: ALA-PDT induces CCL8 expression and recruits M1 macrophages, thus suppressing tumor growth.

Present and future perspectives of photodynamic therapy for cutaneous squamous cell carcinoma.

Cutaneous squamous cell carcinoma (SCC) is the second most common skin cancer. Surgery remains the main stay of treatment, but some patients are not eligible for surgery and, more importantly, lesions at critical sites need nonsurgical approaches for tissue preservation. In this context, photodynamic therapy (PDT) has been extensively studied as noninvasive or minimally invasive treatment, and studies have shown promising results in terms of safety, efficacy, and cosmetic outcome. Also, studies have proposed different mechanism for its efficacy. However, human studies demonstrating its efficacy are limited in terms of sample size and tumor depth of invasion. Good results are mainly seen in case reports of microinvasive SCC, which is defined as SCC limited to papillary dermis. This inadequacy is due to inadequate penetration of topically applied photosensitizers through keratinized tumor surfaces. To overcome these hurdles, pretreatment with lasers or microneedles and encapsulation of photosensitizers into nanoparticles have been tried. Hence, the present article will discuss studies that have demonstrated the efficacy and safety of PDT for cutaneous SCC, studies that have postulated the mechanism of action of PDT, agents that have been used as PDT enhancers, and finally, the recent use of adjuvant therapy in combination with PDT.

Therapeutic effect of Imiquimod enhanced ALA-PDT on cutaneous squamous cell carcinoma.

BACKGROUND: Topical photodynamic therapy (PDT) is approved treatment for actinic keratosis, basal cell carcinoma and Bowen's disease. But currently it is not recommended for invasive squamous cell carcinoma (SCC) of the skin because inadequate penetration of topically applied photosensitizers lead to poor treatment response. Imiquimod (IMQ) as an immune response modifier and Toll-like receptor 7 (TLR7) agonist, is known to exhibit antitumor activity. As an adjunct therapy, it is recently seen to enhance the effect of PDT. METHOD: This is an in vivo experiment performed on 52 SCC implanted mice model. The mice were equally divided into four groups: IMQ group, IMQ + PDT group, PDT group and control group. The mice in IMQ + PDT group were treated with 3 sessions of 5% IMQ cream and ALA-PDT. Mice in IMQ group received only 5% IMQ cream. Similarly, mice in PDT group received only ALA-PDT and control mice received no treatment. The treatment efficacy was compared among these groups via tumor volume and digital photographs. In addition, immunohistochemical (IHC) markers, q PCR and detection of apoptosis were studied on 12 UV induced mice model. After successful result of this animal experiment, we performed human study on two patients with invasive cSCC on lips and foot. The patients were treated with daily application of 5% imiquimod cream and ALA-PDT at 2 weeks interval. Treatment response was assessed via clinical examination, digital photographs and dermoscopy findings. RESULTS: The study demonstrated that combination approach of IMQ + PDT has better effect than IMQ alone or PDT alone. It also showed increased expression of IL-6, IL-8, IFN-α, CXCL9, CXCL10 and TNF-α in IMQ + PDT group but at different time points following treatment (P < 0.05). IHC staining showed that the number of CD4+ cells was similar in IMQ + PDT and PDT groups but CD8+ cells was almost double in IMQ + PDT group when compared to PDT group. In addition, the number of apoptotic cell was maximum in IMQ + PDT group. Human study also delivered excellent results in both the patients with complete clearance of lesion after 3-6 sessions of treatment. CONCLUSION: PDT combined with imiquimod may have enhanced effect for the treatment of invasive cSCC. Maximum number of apoptotic cells in IMQ + PDT group can be attributed to increased number of CD8 + T cells in this group. Additional mechanism of enhanced efficacy in IMQ + PDT group may be due to increased expression of markers tested in this study.

Dermatologic manifestations of inflammatory bowel disease: a review.

Inflammatory bowel disease (IBD) is a chronic relapsing disease of the gastrointestinal tract with unknown etiology and pathogenesis. It includes Crohn's disease (CD) and ulcerative colitis (UC). Approximately one-third of the patients with IBD are seen to develop extraintestinal manifestations, among which cutaneous manifestations are the most common and should be managed in close collaboration with a dermatologist. Depending upon the nature of the association, skin conditions associated with IBD can be listed under 4 categories: specific, reactive, secondary to malnutrition or malabsorption, and secondary to drug therapy. Skin conditions that do not fit into these categories are listed under the fifth category named as miscellaneous by some authors. The aim of the present review is to discuss some of the noteworthy skin disorders associated with IBD and highlight their importance in context to IBD.

Zinc pthalocyanine-loaded chitosan/mPEG-PLA nanoparticles-mediated photodynamic therapy for the treatment of cutaneous squamous cell carcinoma.

Zinc pthalocyanine (ZnPc) is a second-generation photodynamic therapy (PDT) sensitizer with sufficient PDT activity for squamous cell carcinoma (SCC). ZnPc is hydrophobic and insoluble in water, which creates hurdles in systemic administration and hence restricts its use in clinic. Here we have loaded ZnPc on chitosan/methoxy polyethylene glycol-polylactic acid (CPP) nanoparticles to form Z-CPP to enhance PDT efficacy. In vitro and in vivo studies were performed to see dark toxicity of the compounds ZnPc, CPP and Z-CPP. Then PDT was done and its growth inhibitory effect on SCC cells was evaluated. In addition, reactive oxygen species (ROS) formation and apoptosis of cancer cells following PDT were studied. The results showed that the tested compounds exhibit no dark toxicity and the effect of PDT was significantly better with Z-CPP when compared to free ZnPc (P < .05). Photoactivation of Z-CPP led to a dose-dependent growth inhibition of cancer cells of >50% at 1 µM to >80% at 10 µM concentration. Also Z-CPP-treated cells had highest number of apoptotic cells and produced more ROS compared to free ZnPc-treated cells (P < .05). Hence, this study suggests that Z-CPP is a suitable pharmaceutical compound to increase PDT efficacy.

Hypoxia Triggers SENP1 (Sentrin-Specific Protease 1) Modulation of KLF15 (Kruppel-Like Factor 15) and Transcriptional Regulation of Arg2 (Arginase 2) in Pulmonary Endothelium.

OBJECTIVE: KLF15 (Kruppel-like factor 15) has recently been shown to suppress activation of proinflammatory processes that contribute to atherogenesis in vascular smooth muscle, however, the role of KLF15 in vascular endothelial function is unknown. Arginase mediates inflammatory vasculopathy and vascular injury in pulmonary hypertension. Here, we tested the hypothesis that KLF15 is a critical regulator of hypoxia-induced Arg2 (arginase 2) transcription in human pulmonary microvascular endothelial cells (HPMEC). APPROACH AND RESULTS: Quiescent HPMEC express ample amounts of full-length KLF15. HPMECs exposed to 24 hours of hypoxia exhibited a marked decrease in KLF15 protein levels and a reciprocal increase in Arg2 protein and mRNA. Chromatin immunoprecipitation indicated direct binding of KLF15 to the Arg2 promoter, which was relieved with HPMEC exposure to hypoxia. Furthermore, overexpression of KLF15 in HPMEC reversed hypoxia-induced augmentation of Arg2 abundance and arginase activity and rescued nitric oxide (NO) production. Ectopic KLF15 also reversed hypoxia-induced endothelium-mediated vasodilatation in isolated rat pulmonary artery rings. Mechanisms by which hypoxia regulates KLF15 abundance, stability, and compartmentalization to the nucleus in HPMEC were then investigated. Hypoxia triggered deSUMOylation of KLF15 by SENP1 (sentrin-specific protease 1), and translocation of KLF15 from nucleus to cytoplasm. CONCLUSIONS: KLF15 is a critical regulator of pulmonary endothelial homeostasis via repression of endothelial Arg2 expression. KLF15 abundance and nuclear compartmentalization are regulated by SUMOylation/deSUMOylation-a hypoxia-sensitive process that is controlled by SENP1. Strategies including overexpression of KLF15 or inhibition of SENP1 may represent novel therapeutic targets for pulmonary hypertension.

Opsin 3 and 4 mediate light-induced pulmonary vasorelaxation that is potentiated by G protein-coupled receptor kinase 2 inhibition.

We recently demonstrated that blue light induces vasorelaxation in the systemic mouse circulation, a phenomenon mediated by the nonvisual G protein-coupled receptor melanopsin (Opsin 4; Opn4). Here we tested the hypothesis that nonvisual opsins mediate photorelaxation in the pulmonary circulation. We discovered Opsin 3 (Opn3), Opn4, and G protein-coupled receptor kinase 2 (GRK2) in rat pulmonary arteries (PAs) and in pulmonary arterial smooth muscle cells (PASMCs), where the opsins interact directly with GRK2, as demonstrated with a proximity ligation assay. Light elicited an intensity-dependent relaxation of PAs preconstricted with phenylephrine (PE), with a maximum response between 400 and 460 nm (blue light). Wavelength-specific photorelaxation was attenuated in PAs from Opn4-/- mice and further reduced following shRNA-mediated knockdown of Opn3. Inhibition of GRK2 amplified the response and prevented physiological desensitization to repeated light exposure. Blue light also prevented PE-induced constriction in isolated PAs, decreased basal tone, ablated PE-induced single-cell contraction of PASMCs, and reversed PE-induced depolarization in PASMCs when GRK2 was inhibited. The photorelaxation response was modulated by soluble guanylyl cyclase but not by protein kinase G or nitric oxide. Most importantly, blue light induced significant vasorelaxation of PAs from rats with chronic pulmonary hypertension and effectively lowered pulmonary arterial pressure in isolated intact perfused rat lungs subjected to acute hypoxia. These findings show that functional Opn3 and Opn4 in PAs represent an endogenous "optogenetic system" that mediates photorelaxation in the pulmonary vasculature. Phototherapy in conjunction with GRK2 inhibition could therefore provide an alternative treatment strategy for pulmonary vasoconstrictive disorders.

UVA1 a promising approach for scleroderma.

Scleroderma is a complex connective tissue disease characterized by fibrosis, vasculopathy, and immune system dysfunction. The heterogeneity of disease presentation and poorly understood etiology has made the management of scleroderma difficult. The available treatment options like immunosuppressive agents are associated with potentially hazardous side effects and physiotherapy, which to a certain degree helps to minimize the loss of function in digits and limbs, has only limited success. Also, studies investigating antifibrotic therapies have failed to report any significant improvement. Hence, there is currently no effective therapy for scleroderma. Recently, phototherapy has been extensively studied and found to be effective in treating scleroderma. Initially psoralen + ultraviolet A (PUVA) significantly enriched the therapeutic panel, but more recently ultraviolet A1 (UVA1) is seen to replace PUVA therapy. This might be because of UVA1 therapy being free of side effects seen with psoralens such as nausea, vomiting or photokeratitis. In addition, UVA1 is seen to lower risk of phototoxic reactions with deeper penetration of radiation. The present review will put some light on the use of UVA1 for treating cutaneous lesion in scleroderma and we aim to find the most benefitted group of patients and most effective dose of UVA1 for different types of scleroderma.

Obesity-induced vascular inflammation involves elevated arginase activity.

Obesity-induced vascular dysfunction involves pathological remodeling of the visceral adipose tissue (VAT) and increased inflammation. Our previous studies showed that arginase 1 (A1) in endothelial cells (ECs) is critically involved in obesity-induced vascular dysfunction. We tested the hypothesis that EC-A1 activity also drives obesity-related VAT remodeling and inflammation. Our studies utilized wild-type and EC-A1 knockout (KO) mice made obese by high-fat/high-sucrose (HFHS) diet. HFHS diet induced increases in body weight, fasting blood glucose, and VAT expansion. This was accompanied by increased arginase activity and A1 expression in vascular ECs and increased expression of tumor necrosis factor-α (TNF-α), monocyte chemoattractant protein-1 (MCP-1), interleukin-10 (IL-10), vascular cell adhesion molecule-1 (VCAM-1), and intercellular adhesion molecule-1 (ICAM-1) mRNA and protein in both VAT and ECs. HFHS also markedly increased circulating inflammatory monocytes and VAT infiltration by inflammatory macrophages, while reducing reparative macrophages. Additionally, adipocyte size and fibrosis increased and capillary density decreased in VAT. These effects of HFHS, except for weight gain and hyperglycemia, were prevented or reduced in mice lacking EC-A1 or treated with the arginase inhibitor 2-(S)-amino-6-boronohexanoic acid (ABH). In mouse aortic ECs, exposure to high glucose (25 mM) and Na palmitate (200 µM) reduced nitric oxide production and increased A1, TNF-α, VCAM-1, ICAM-1, and MCP-1 mRNA, and monocyte adhesion. Knockout of EC-A1 or ABH prevented these effects. HFHS diet-induced VAT inflammation is mediated by EC-A1 expression/activity. Limiting arginase activity is a possible therapeutic means of controlling obesity-induced vascular and VAT inflammation.

Erythema elevatum diutinum involving palms and soles: a case report and literature review.

Erythema elevatum diutinum (EED) is a rare chronic inflammatory dermatosis and a part of the spectrum of cutaneous leukocytoclasticvasculitis. The most common site of involvement is extensor surface of the extremities, with a predilection for the skin overlying joints, particularly hands, feet, elbows and knees, as well as buttocks and Achilles tendons. Here we report a case of EED with atypical presentation involving palms and soles. The patient showed dramatic response to the treatment with prednisolone combined with Tripterygium wilfordii glycoside (TWP). The lesions improved significantly after three months of therapy. We will also review the atypical cases of EED that were previously published in English literature.

Pemphigus vulgaris induced by 5-aminolaevulinic acid-based photodynamic therapy.

Pemphigus vulgaris (PV) is an autoimmune disorder resulting from the interaction between autoantibodies and desmoglein. Here, we report a case of PV developed after 5-aminolaevulinic acid-based photodynamic therapy (ALA-PDT). The harmful and deleterious effects of UV radiation on the onset, during course, and perpetuation of PV have been observed for decades. Correlation between reactive oxygen species (ROS) and PV have also been reported. Oxidative proteins, which are modified by ROS, and subsequent production of antibodies by immune system seem to be responsible for PV developed following ALA-PDT. We emphasize that ALA-PDT should be added to the list of possible factors triggering PV and this condition should be considered if blistering arises following ALA-PDT.

Cystathionine γ-lyase protects vascular endothelium: a role for inhibition of histone deacetylase 6.

Endothelial cystathionine γ-lyase (CSEγ) contributes to cardiovascular homeostasis, mainly through production of H2S. However, the molecular mechanisms that control CSEγ gene expression in the endothelium during cardiovascular diseases are unclear. The aim of the current study is to determine the role of specific histone deacetylases (HDACs) in the regulation of endothelial CSEγ. Reduced CSEγ mRNA expression and protein abundance were observed in human aortic endothelial cells (HAEC) exposed to oxidized LDL (OxLDL) and in aortas from atherogenic apolipoprotein E knockout (ApoE-/-) mice fed a high-fat diet compared with controls. Intact murine aortic rings exposed to OxLDL (50 µg/ml) for 24 h exhibited impaired endothelium-dependent vasorelaxation that was blocked by CSEγ overexpression or the H2S donor NaHS. CSEγ expression was upregulated by pan-HDAC inhibitors and by class II-specific HDAC inhibitors, but not by other class-specific inhibitors. The HDAC6 selective inhibitor tubacin and HDAC6-specific siRNA increased CSEγ expression and blocked OxLDL-mediated reductions in endothelial CSEγ expression and CSEγ promoter activity, indicating that HDAC6 is a specific regulator of CSEγ expression. Consistent with this finding, HDAC6 mRNA, protein expression, and activity were upregulated in OxLDL-exposed HAEC, but not in human aortic smooth muscle cells. HDAC6 protein levels in aortas from high-fat diet-fed ApoE-/- mice were comparable to those in controls, whereas HDAC6 activity was robustly upregulated. Together, our findings indicate that HDAC6 is upregulated by atherogenic stimuli via posttranslational modifications and is a critical regulator of CSEγ expression in vascular endothelium. Inhibition of HDAC6 activity may improve endothelial function and prevent or reverse the development of atherosclerosis.NEW & NOTEWORTHY Oxidative injury to endothelial cells by oxidized LDL reduced cystathionine γ-lyase (CSEγ) expression and H2S production, leading to endothelial dysfunction, which was prevented by histone deacetylase 6 (HDAC6) inhibition. Our data suggest HDAC6 as a novel therapeutic target to prevent the development of atherosclerosis.

Antifungal effect of plant extract and essential oil.

The advancement of phytochemical and phytopharmacological sciences has enabled elucidation of the composition and biological activities of several medicinal plant products including plant extract and essential oils. These products have been widely used around the world since ancient times for the treatment of various disorders such as diabetes, hypertension, peptic ulcer disease, microbial infection, sexual disorder and many more. Its popularity in the modern system of medicine is mainly due to their availability and fewer adverse reactions compared to synthetic drugs. Various scientifific investigations have been conducted to look for the potential of the extract from the plant or isolated compounds for the continued use of these products in the treatment and prevention of various kinds of human diseases. It is evident from the available literature and scientifific investigations that many plant species possess potential for use as a benefificial therapeutic remedy with multiple pharmacological actions such as analgesic, anti-inflflammatory, antipyretic, hypoglycemic, hypotensive, antimicrobial, antiulcer and anticonvulsant activities. The present review aims to provide relevant updated information about certain plant products, its composition, preparation and its fungicidal or fungistatic effects on different species of fungus as evaluated by studies done in the past. It introduces six medicinal plants that have been studied for their antifungal property and are found to be effective. The overall objective is to provide comprehensive information about the use of plant extract and essential oil for treating fungal infections and to explore the evidence supporting its effectiveness in treating fungal diseases without causing any serious adverse reactions.

Photodynamic therapy for onychomycosis: A systematic review.

Other than a cosmetic concern, Onychomycosis is also a prevalent nail disease, which is extremely difficult to treat, and sometimes is refractory to conventional therapy. Moreover, many patients are not eligible to take oral antifungals owing to polypharmacy and comorbidities. Systemic side effects seen with oral antifungals have lead to patient nonadherence and adverse events. Therefore, newer therapies are being investigated for onychomycosis that would be free of systemic complications posed by oral therapy. Photodynamic therapy (PDT) is one of those being currently studied, which involves the use of photosensitizer and a light source to excite the photosensitizer to generate reactive oxygen species. The present review will put some light on PDT as an upcoming treatment modality for onychomycosis. We performed a systematic review of the literature to find the articles relevant to the use of PDT for onychomycosis. From the primary search of 43 articles, 17 papers are included in this review.

Deregulation of arginase induces bone complications in high-fat/high-sucrose diet diabetic mouse model.

A balanced diet is crucial for healthy development and prevention of musculoskeletal related diseases. Diets high in fat content are known to cause obesity, diabetes and a number of other disease states. Our group and others have previously reported that activity of the urea cycle enzyme arginase is involved in diabetes-induced dysregulation of vascular function due to decreases in nitric oxide formation. We hypothesized that diabetes may also elevate arginase activity in bone and bone marrow, which could lead to bone-related complications. To test this we determined the effects of diabetes on expression and activity of arginase, in bone and bone marrow stromal cells (BMSCs). We demonstrated that arginase 1 is abundantly present in the bone and BMSCs. We also demonstrated that arginase activity and expression in bone and bone marrow is up-regulated in models of diabetes induced by HFHS diet and streptozotocin (STZ). HFHS diet down-regulated expression of healthy bone metabolism markers (BMP2, COL-1, ALP, and RUNX2) and reduced bone mineral density, bone volume and trabecular thickness. However, treatment with an arginase inhibitor (ABH) prevented these bone-related complications of diabetes. In-vitro study of BMSCs showed that high glucose treatment increased arginase activity and decreased nitric oxide production. These effects were reversed by treatment with an arginase inhibitor (ABH). Our study provides evidence that deregulation of l-arginine metabolism plays a vital role in HFHS diet-induced diabetic complications and that these complications can be prevented by treatment with arginase inhibitors. The modulation of l-arginine metabolism in disease could offer a novel therapeutic approach for osteoporosis and other musculoskeletal related diseases.

Arginase inhibition enhances angiogenesis in endothelial cells exposed to hypoxia.

Hypoxia-induced arginase elevation plays an essential role in several vascular diseases but influence of arginase on hypoxia-mediated angiogenesis is completely unknown. In this study, in vitro network formation in bovine aortic endothelial cells (BAEC) was examined after exposure to hypoxia for 24h with or without arginase inhibition. Arginase activity, protein levels of the two arginase isoforms, eNOS, and VEGF as well as production of NO and ROS were examined to determine the involvement of arginase in hypoxia-mediated angiogenesis. Hypoxia elevated arginase activity and arginase 2 expression but reduced active p-eNOS(Ser1177) and NO levels in BAEC. In addition, both VEGF protein levels and endothelial elongation and network formation were reduced with continued hypoxia, whereas ROS levels increased and NO levels decreased. Arginase inhibition limited ROS, restored NO formation and VEGF expression, and prevented the reduction of angiogenesis. These results suggest a fundamental role of arginase activity in regulating angiogenic function.