Increased arginase activity and endothelial dysfunction in human inflammatory bowel disease

Cardiovascular Risk in Patients with Inflammatory Bowel Diseases-The Role of Endothelial Dysfunction

Inflammatory bowel disease (IBD) is associated with an increased risk of cardiovascular disease (CVD). Cardiovascular pathology in people with IBD has not been well studied to date, and a direct link between cardiovascular events and IBD has not been established. The mechanisms underlying this association include the parallel and dynamic interaction of inflammation, modulation of the composition of the gut microbiota, endothelial dysfunction, thrombogenicity, and increased endothelial and epithelial permeability. Endothelial dysfunction is a common aspect of the pathogenesis of IBD and atherosclerotic CVD and can be considered one of the most important factors leading to the development and progression of cardiovascular pathology in patients with IBD. The purpose of this literature review is to describe the mechanisms underlying the development of endothelial dysfunction and disorders of the structure and function of the gut-vascular barrier in the pathogenesis of the cardiovascular manifestation of IBD.

Inflammatory Bowel Disease and Cardiovascular Disease: An Integrative Review With a Focus on the Gut Microbiome

Inflammatory bowel disease (IBD), which includes Crohn's disease and ulcerative colitis, is a chronic inflammatory condition of the gastrointestinal tract. Recent research indicates a significant link between IBD and cardiovascular disease (CVD), the leading cause of global morbidity and mortality. This review examines the association between IBD and CVD, emphasizing the role of the gut microbiome in this relationship. IBD patients have a higher risk of cardiovascular events, such as coronary artery disease, heart failure, and cerebrovascular incidents, primarily due to chronic systemic inflammation, genetic factors, and gut microbiota imbalance (dysbiosis). Dysbiosis in IBD increases intestinal permeability, allowing bacterial products to enter the bloodstream, which promotes inflammation and endothelial dysfunction, contributing to CVD. Understanding the gut microbiome's role in IBD and CVD suggests new therapeutic interventions. Modulating the microbiome through diet, probiotics, and fecal microbiota transplantation (FMT) are promising research avenues. These interventions aim to restore a healthy gut microbiota balance, potentially reducing inflammation and improving cardiovascular outcomes. Additionally, the review emphasizes the importance of regular cardiovascular risk assessments and personalized preventive measures in managing IBD patients. Such measures include routine monitoring of cardiovascular health, tailored lifestyle modifications, and early intervention strategies to mitigate cardiovascular risk. By integrating current knowledge, this review aims to improve understanding and management of the interconnected pathophysiology of IBD and CVD. This approach will ultimately enhance patient outcomes and provide a foundation for future research and clinical practice guidelines in this area.

Fructose: a modulator of intestinal barrier function and hepatic health?

PURPOSE

Consumption of fructose has repeatedly been discussed to be a key factor in the development of health disturbances such as hypertension, diabetes type 2, and non-alcoholic fatty liver disease. Despite intense research efforts, the question if and how high dietary fructose intake interferes with human health has not yet been fully answered.

RESULTS

Studies suggest that besides its insulin-independent metabolism dietary fructose may also impact intestinal homeostasis and barrier function. Indeed, it has been suggested by the results of human and animal as well as in vitro studies that fructose enriched diets may alter intestinal microbiota composition. Furthermore, studies have also shown that both acute and chronic intake of fructose may lead to an increased formation of nitric oxide and a loss of tight junction proteins in small intestinal tissue. These alterations have been related to an increased translocation of pathogen-associated molecular patterns (PAMPs) like bacterial endotoxin and an induction of dependent signaling cascades in the liver but also other tissues.

CONCLUSION

In the present narrative review, results of studies assessing the effects of fructose on intestinal barrier function and their impact on the development of health disturbances with a particular focus on the liver are summarized and discussed.

Therapeutic Effects of Valeriana jatamansi on Ulcerative Colitis: Insights into Mechanisms of Action through Metabolomics and Microbiome Analysis

Ulcerative colitis (UC), belonging to inflammatory bowel disease (IBD), is a chronic and relapsing inflammatory disorder of the gastrointestinal tract, which has not been completely cured in patients so far. Valeriana jatamansi is a Chinese medicine used clinically to treat "diarrhea," which is closely related to UC. This study was to elucidate the therapeutic effects of V. jatamansi extract (VJE) on dextran sodium sulfate (DSS)-induced UC in mice and its underlying mechanism. In this work, VJE effectively ameliorates the symptoms and histopathological scores and reduces the production of inflammatory factors in UC mice. The colon untargeted metabolomics analysis and 16S rDNA sequencing showed remarkable differences in colon metabolite profiles and intestinal microbiome composition between the control and DSS groups, and VJE intervention can reduce these differences. Thirty-two biomarkers were found and modulated the primary pathways including pyrimidine metabolism, arginine biosynthesis, and glutathione metabolism. Meanwhile, twelve significant taxa of gut microbiota were found. Moreover, there is a close relationship between endogenous metabolites and intestinal flora. These findings suggested that VJE ameliorates UC by inhibiting inflammatory factors, recovering intestinal maladjustment, and regulating the interaction between intestinal microbiota and host metabolites. Therefore, the intervention of V. jatamansi is a potential therapeutic treatment for UC.

Cardiovascular manifestations of inflammatory bowel diseases and the underlying pathogenic mechanisms

Inflammatory bowel disease (IBD), consisting of ulcerative colitis and Crohn's disease, mainly affects the gastrointestinal tract but is also known to have extraintestinal manifestations because of long-standing systemic inflammation. Several national cohort studies have found that IBD is an independent risk factor for the development of cardiovascular disorders. However, the molecular mechanisms by which IBD impairs the cardiovascular system are not fully understood. Although the gut-heart axis is attracting more attention in recent years, our knowledge of the organ-to-organ communication between the gut and the heart remains limited. In patients with IBD, upregulated inflammatory factors, altered microRNAs and lipid profiles, as well as dysbiotic gut microbiota, may induce adverse cardiac remodeling. In addition, patients with IBD have a three- to four times higher risk of developing thrombosis than people without IBD, and it is believed that the increased risk of thrombosis is largely due to increased procoagulant factors, platelet count/activity, and fibrinogen concentration, in addition to decreased anticoagulant factors. The predisposing factors for atherosclerosis are present in IBD and the possible mechanisms may involve oxidative stress system, overexpression of matrix metalloproteinases, and changes in vascular smooth muscle phenotype. This review focuses mainly on 1) the prevalence of cardiovascular diseases associated with IBD, 2) the potential pathogenic mechanisms of cardiovascular diseases in patients with IBD, and 3) adverse effects of IBD drugs on the cardiovascular system. Also, we introduce here a new paradigm for the gut-heart axis that includes exosomal microRNA and the gut microbiota as a cause for cardiac remodeling and fibrosis.

Gut vascular barrier in the pathogenesis and resolution of Crohn's disease: A novel link from origination to therapy

The gut vascular barrier (GVB) is the deepest layer of the gut barrier. It mainly comprised gut vascular endothelial cells, enteric glial cells, and pericytes. The GVB facilitates nutrient absorption and blocks bacterial translocation through its size-restricted permeability. Accumulating evidence suggests that dysfunction of this barrier correlates with several clinical pathologies including Crohn's disease (CD). Significant progress has been made to elucidate the mechanism of GVB dysfunction and to confirm the participation of disrupted GVB in the course of CD. However, further analyses are required to pinpoint the specific roles of GVB in CD pathogenesis. Many preclinical models and clinical trials have demonstrated that various agents are effective in protecting the GVB integrity and thus providing a potential CD treatment strategy. Through this review, we established a systemic understanding of the role of GVB in CD pathogenesis and provided novel insights for GVB-targeting strategies in CD treatment.

Altered endocannabinoidome bioactive lipid levels accompany reduced DNBS-induced colonic inflammation in germ-free mice

BACKGROUND

Gut microbiota are involved in the onset and development of chronic intestinal inflammation. The recently described endocannabinoidome (eCBome), a diverse and complex system of bioactive lipid mediators, has been reported to play a role in various physio-pathological processes such as inflammation, immune responses and energy metabolism. The eCBome and the gut microbiome (miBIome) are closely linked and form the eCBome - miBIome axis, which may be of special relevance to colitis.

METHODS

Colitis was induced in conventionally raised (CR), antibiotic-treated (ABX) and germ-free (GF) mice with dinitrobenzene sulfonic acid (DNBS). Inflammation was assessed by Disease Activity Index (DAI) score, body weight change, colon weight-length ratio, myeloperoxidase (MPO) activity and cytokine gene expression. Colonic eCBome lipid mediator concentrations were measured by HPLC-MS /MS.

RESULTS

GF mice showed increased levels of anti-inflammatory eCBome lipids (LEA, OEA, DHEA and 13- HODE-EA) in the healthy state and higher MPO activity. DNBS elicited reduced inflammation in GF mice, having lower colon weight/length ratios and lower expression levels of Il1b, Il6, Tnfa and neutrophil markers compared to one or both of the other DNBS-treated groups. Il10 expression was also lower and the levels of several N-acyl ethanolamines and 13-HODE-EA levels were higher in DNBS-treated GF mice than in CR and ABX mice. The levels of these eCBome lipids negatively correlated with measures of colitis and inflammation.

CONCLUSIONS

These results suggest that the depletion of the gut microbiota and subsequent differential development of the gut immune system in GF mice is followed by a compensatory effect on eCBome lipid mediators, which may explain, in part, the observed lower susceptibility of GF mice to develop DNBS-induced colitis.

Contribution of Blood Vessel Activation, Remodeling and Barrier Function to Inflammatory Bowel Diseases

Inflammatory bowel diseases (IBDs) consist of a group of chronic inflammatory disorders with a complex etiology, which represent a clinical challenge due to their often therapy-refractory nature. In IBD, inflammation of the intestinal mucosa is characterized by strong and sustained leukocyte infiltration, resulting in the loss of epithelial barrier function and subsequent tissue destruction. This is accompanied by the activation and the massive remodeling of mucosal micro-vessels. The role of the gut vasculature in the induction and perpetuation of mucosal inflammation is receiving increasing recognition. While the vascular barrier is considered to offer protection against bacterial translocation and sepsis after the breakdown of the epithelial barrier, endothelium activation and angiogenesis are thought to promote inflammation. The present review examines the respective pathological contributions of the different phenotypical changes observed in the microvascular endothelium during IBD, and provides an overview of potential vessel-specific targeted therapy options for the treatment of IBD.

Pivotal Role of Intestinal Microbiota and Intraluminal Metabolites for the Maintenance of Gut-Bone Physiology

Intestinal microbiota, and their mutual interactions with host tissues, are pivotal for the maintenance of organ physiology. Indeed, intraluminal signals influence adjacent and even distal tissues. Consequently, disruptions in the composition or functions of microbiota and subsequent altered host-microbiota interactions disturb the homeostasis of multiple organ systems, including the bone. Thus, gut microbiota can influence bone mass and physiology, as well as postnatal skeletal evolution. Alterations in nutrient or electrolyte absorption, metabolism, or immune functions, due to the translocation of microbial antigens or metabolites across intestinal barriers, affect bone tissues, as well. Intestinal microbiota can directly and indirectly alter bone density and bone remodeling. Intestinal dysbiosis and a subsequently disturbed gut-bone axis are characteristic for patients with inflammatory bowel disease (IBD) who suffer from various intestinal symptoms and multiple bone-related complications, such as arthritis or osteoporosis. Immune cells affecting the joints are presumably even primed in the gut. Furthermore, intestinal dysbiosis impairs hormone metabolism and electrolyte balance. On the other hand, less is known about the impact of bone metabolism on gut physiology. In this review, we summarized current knowledge of gut microbiota, metabolites and microbiota-primed immune cells in IBD and bone-related complications.

Role of Rho GTPases in inflammatory bowel disease

Rat sarcoma virus homolog (Rho) guanosine triphosphatases (GTPases) function as "molecular switch" in cellular signaling regulation processes and are associated with the pathogenesis of inflammatory bowel disease (IBD). This chronic intestinal tract inflammation primarily encompasses two diseases: Crohn's disease and ulcerative colitis. The pathogenesis of IBD is complex and considered to include four main factors and their interactions: genetics, intestinal microbiota, immune system, and environment. Recently, several novel pathogenic components have been identified. In addition, potential therapies for IBD targeting Rho GTPases have emerged and proven to be clinically effective. This review mainly focuses on Rho GTPases and their possible mechanisms in IBD pathogenesis. The therapeutic possibility of Rho GTPases is also discussed.

Evaluation of adalimumab effects on left ventricle performance by echocardiography indexes among patients with immunosuppressant refractory ulcerative colitis

Background and aims

Inflammatory bases lead to a simultaneous flourishing of cardiovascular complications with inflammatory bowel disease (IBD). As a released cytokine, tumor necrosis factor-α (TNF-α) can either disrupt or preserve cardiovascular performance. Due to this controversy, this study aimed to appraise the short-term anti-TNF (adalimumab [ADA]) relics on cardiac function by gauging the echocardiography indexes in patients with immunosuppressant refractory ulcerative colitis (UC).

Methods

All cases with a definite diagnosis of UC were included based on providing written informed consent and owning the severe form of active disease (Mayo score ≥7), which did not dampen with immunosuppressant. Patients were excluded in the case of previous cardiac ailments/risk factors and prior related surgical or pharmaceutical intervention. Transthoracic echocardiography (TTE) was carried out before and 3 months after biological regimen allocation and changes in indexes [ejection fraction (EF), left ventricular end-diastolic volume (LVEDV)/left ventricular end-systolic volume (LVESV), and global longitudinal strain (GLS) in standard parasternal short axis from mid-ventricular level, two-, three-, and four-chamber apical long axes] were compared via statistical analyses.

Results

The study consisted of 13 (65%) men and 7 (35%) women, with a mean age of 36.54 ± 11.3 years. Participants mainly possessed Montreal class I (45%) and an average of 3.25 years of disease duration. The intervention significantly controlled inflammation [endoscopic Mayo score (P = 0.001), partial Mayo score (P = 0.001), and C-reactive protein (P = 0.001)]. Endoscopic and clinical remission was obtained in 7 (35%) and 9 (45%) patients, respectively; however, no significant discrepancy related to the LVEDV (P = 0.86), LVESV (P-value = 0.25), EF (P-value = 0.06), and GLS in standard parasternal short axis (P = 0.73), long axis [apical 2-chamber (P-value = 0.61), apical 3-chamber (P-value = 0.15), and apical 4-chamber (P-value = 0.19) views] was observed before and after the intervention. Furthermore, no statistically significant correlation between disease activity and cardiac function was found, neither before nor after ADA administration.

Conclusion

The present perusal found no deterioration in left ventricular function indexes with ADA intervention among patients with IBD without cardiac ailment. Thus, prescribing the anti-TNF to alleviate the inflammation can be carried out with less concern about cardiac consequences and considering other adverse traces in the target group.

Is Salt at Fault? Dietary Salt Consumption and Inflammatory Bowel Disease

Epidemiological trends have led to a growing consensus that diet plays a central role in the etiopathogenesis of inflammatory bowel diseases (IBD). A Western diet high in ultra-processed foods has been associated with an increased prevalence of IBD worldwide. Much attention has focused on components of the Western diet, including the high fat content, lack of fiber, added sugars, and use of additives, such as carrageenan and other emulsifiers. Less attention has been paid to the impact of high salt intake, an integral component of ultra-processed foods, which has increased dramatically in the US diet over the past 50 years. We review a growing body of literature linking the rise in dietary salt intake with the epidemiology of IBD, increased consumption of salt as a component of ultra-processed foods, high salt intake and imbalances in immune homeostasis, the effects of a high-salt diet on other inflammatory disorders, salt's impact on animal colitis models, salt as an underrecognized component in diet modification-induced remission of IBD, and directions for future investigation.

Arginine metabolism regulates the pathogenesis of inflammatory bowel disease

The pathogenesis of inflammatory bowel disease (IBD) is related to genetic susceptibility, enteric dysbiosis, and uncontrolled, chronic inflammatory responses that lead to colonic tissue damage and impaired intestinal absorption. As a consequence, patients with IBD are prone to nutrition deficits after each episode of disease resurgence. Nutritional supplementation, especially for protein components, is often implemented during the remission phase of IBD. Notably, ingested nutrients could affect the progression of IBD and the prognostic outcome of patients; therefore, they should be cautiously evaluated prior to being used for IBD intervention. Arginine (Arg) is a semi-essential amino acid required for protein synthesis and intimately associated with gut pathophysiology. To help optimize arginine-based nutritional intervention strategies, the present work summarizes that during the process of IBD, patients manifest colonic Arg deficiency and the turbulence of Arg metabolic pathways. The roles of Arg–nitric oxide (catalyzed by inducible nitric oxide synthase) and Arg–urea (catalyzed by arginases) pathways in IBD are debatable; the Arg–polyamine and Arg–creatine pathways are mainly protective. Overall, supplementation with Arg is a promising therapeutic strategy for IBD; however, the dosage of Arg may need to be carefully tailored for different individuals at different disease stages. Additionally, the combination of Arg supplementation with inhibitors of Arg metabolic pathways as well as other treatment options is worthy of further exploration.

Metabolomics and Biomarkers in Retinal and Choroidal Vascular Diseases

The retina is one of the most important structures in the eye, and the vascular health of the retina and choroid is critical to visual function. Metabolomics provides an analytical approach to endogenous small molecule metabolites in organisms, summarizes the results of “gene-environment interactions”, and is an ideal analytical tool to obtain “biomarkers” related to disease information. This study discusses the metabolic changes in neovascular diseases involving the retina and discusses the progress of the study from the perspective of metabolomics design and analysis. This study advocates a comparative strategy based on existing studies, which encompasses optimization of the performance of newly identified biomarkers and the consideration of the basis of existing studies, which facilitates quality control of newly discovered biomarkers and is recommended as an additional reference strategy for new biomarker discovery. Finally, by describing the metabolic mechanisms of retinal and choroidal neovascularization, based on the results of existing studies, this study provides potential opportunities to find new therapeutic approaches.

Alterations of nitric oxide homeostasis as trigger of intestinal barrier dysfunction in non-alcoholic fatty liver disease

Changes in intestinal nitric oxide metabolism are discussed to contribute for the development of intestinal barrier dysfunction in non‐alcoholic fatty liver disease (NAFLD). To induce steatosis, female C57BL/6J mice were pair‐fed with a liquid control diet (C) or a fat‐, fructose‐ and cholesterol‐rich diet (FFC) for 8 weeks. Mice received the diets ± 2.49 g L‐arginine/kg bw/day for additional 5 weeks. Furthermore, mice fed C or FFC ± L‐arginine/kg bw/day for 8 weeks were concomitantly treated with the arginase inhibitor N^ω‐hydroxy‐nor‐L‐arginine (nor‐NOHA, 0.01 g/kg bw). Liver damage, intestinal barrier function, nitric oxide levels and arginase activity in small intestine were assessed. Also, arginase activity was measured in serum from 13 patients with steatosis (NAFL) and 14 controls. The development of steatosis with beginning inflammation was associated with impaired intestinal barrier function, increased nitric oxide levels and a loss of arginase activity in small intestine in mice. L‐arginine supplementation abolished the latter along with an improvement of intestinal barrier dysfunction; nor‐NOHA attenuated these effects. In patients with NAFL, arginase activity in serum was significantly lower than in healthy controls. Our data suggest that increased formation of nitric oxide and a loss of intestinal arginase activity is critical in NAFLD‐associated intestinal barrier dysfunction.

Diet in Intestinal Fibrosis: A Double-Edged Sword

The natural history of inflammatory bowel diseases, especially Crohn’s disease, is frequently complicated by intestinal fibrosis. Because of the lack of effective treatments for intestinal fibrosis, there is an urgent need to develop new therapies. Factors promoting intestinal fibrosis are currently unclear, but diet is a potential culprit. Diet may influence predisposition to develop intestinal fibrosis or alter its natural history by modification of both the host immune response and intestinal microbial composition. Few studies have documented the effects of dietary factors in modulating IBD-induced intestinal fibrosis. As the mechanisms behind fibrogenesis in the gut are believed to be broadly similar to those from extra-intestinal organs, it may be relevant to investigate which dietary components can inhibit or promote fibrosis factors such as myofibroblasts progenitor activation in other fibrotic diseases.

Thromboembolic and atherosclerotic cardiovascular events in inflammatory bowel disease: epidemiology, pathogenesis and clinical management

Inflammatory bowel disease (IBD) is associated with an increased risk of cardiovascular disease (CVD). The increased risk of CVD concerns an increased risk of venous thromboembolism (VTE), atherosclerotic cardiovascular disease (ASCVD) and heart failure (HF), at corresponding relative risks of 2.5, 1.2 and 2.0, respectively, as compared with the general population. Especially young patients under the age of 40 years run a relatively high risk of these complications when compared with the general population. Chronic systemic inflammation causes a hypercoagulable state leading to the prothrombotic tendency characteristic of VTE, and accelerates all stages involved during atherogenesis in ASCVD. Increased awareness of VTE risk is warranted in patients with extensive colonic disease in both ulcerative colitis and Crohn's disease, as well as during hospitalization, especially when patients are scheduled for surgery. Similarly, critical periods for ASCVD events are the 3 months prior to and 3 months after an IBD-related hospital admission. The increased ASCVD risk is not fully explained by an increased prevalence of traditional risk factors and includes pro-atherogenc lipid profiles with high levels of small dense low-density lipoprotein cholesterol particles and dysfunctional high-density lipoprotein cholesterol. Risk factors associated with HF are location and extent of inflammation, female sex, and age exceeding 40 years. A dose-dependent increase of overall CVD risk has been reported for corticosteroids. Immunomodulating maintenance therapy might reduce CVD risk in IBD, not only by a direct reduction of chronic systemic inflammation but possibly also by a direct effect of IBD medication on platelet aggregation, endothelial function and lipid and glucose metabolism. More data are needed to define these effects accurately. Despite accumulating evidence on the increased CVD risk in IBD, congruent recommendations to develop preventive strategies are lacking. This literature review provides an overview of current knowledge and identifies gaps in evidence regarding CVD risk in IBD, by discussing epidemiology, pathogenesis, and clinical management.

Preclinical Development of FA5, a Novel AMP-Activated Protein Kinase (AMPK) Activator as an Innovative Drug for the Management of Bowel Inflammation

Acadesine (ACA), a pharmacological activator of AMP-activated protein kinase (AMPK), showed a promising beneficial effect in a mouse model of colitis, indicating this drug as an alternative tool to manage IBDs. However, ACA displays some pharmacodynamic limitations precluding its therapeutical applications. Our study was aimed at evaluating the in vitro and in vivo effects of FA-5 (a novel direct AMPK activator synthesized in our laboratories) in an experimental model of colitis in rats. A set of experiments evaluated the ability of FA5 to activate AMPK and to compare the efficacy of FA5 with ACA in an experimental model of colitis. The effects of FA-5, ACA, or dexamethasone were tested in rats with 2,4-dinitrobenzenesulfonic acid (DNBS)-induced colitis to assess systemic and tissue inflammatory parameters. In in vitro experiments, FA5 induced phosphorylation, and thus the activation, of AMPK, contextually to the activation of SIRT-1. In vivo, FA5 counteracted the increase in spleen weight, improved the colon length, ameliorated macroscopic damage score, and reduced TNF and MDA tissue levels in DNBS-treated rats. Of note, FA-5 displayed an increased anti-inflammatory efficacy as compared with ACA. The novel AMPK activator FA-5 displays an improved anti-inflammatory efficacy representing a promising pharmacological tool against bowel inflammation.

Citrulline supplementation attenuates the development of non-alcoholic steatohepatitis in female mice through mechanisms involving intestinal arginase

Non-alcoholic fatty liver disease (NAFLD) is by now the most prevalent liver disease worldwide. The non-proteogenic amino acid l-citrulline (L-Cit) has been shown to protect mice from the development of NAFLD. Here, we aimed to further assess if L-Cit also attenuates the progression of a pre-existing diet-induced NAFLD and to determine molecular mechanisms involved. Female C57BL/6J mice were either fed a liquid fat-, fructose- and cholesterol-rich diet (FFC) or control diet (C) for 8 weeks to induce early stages of NASH followed by 5 more weeks with either FFC-feeding +/- 2.5 g L-Cit/kg bw or C-feeding. In addition, female C57BL/6J mice were either pair-fed a FFC +/- 2.5 g L-Cit/kg bw +/- 0.01 g/kg bw i.p. N(ω)-hydroxy-nor-l-arginine (NOHA) or C diet for 8 weeks.

The protective effects of supplementing L-Cit on the progression of a pre-existing NAFLD were associated with an attenuation of 1) the increased translocation of bacterial endotoxin and 2) the loss of tight junction proteins as well as 3) arginase activity in small intestinal tissue, while no marked changes in intestinal microbiota composition were prevalent in small intestine. Treatment of mice with the arginase inhibitor NOHA abolished the protective effects of L-Cit on diet-induced NAFLD. Our results suggest that the protective effects of L-Cit on the development and progression of NAFLD are related to alterations of intestinal arginase activity and intestinal permeability.

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l-citrulline diminished progression of non-alcoholic fatty liver disease (NAFLD).

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l-citrulline protects from fructose-induced small intestinal barrier dysfunction.

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NASH development is associated with a loss of arginase activity in small intestine.

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l-citrulline improves intestinal arginase activity in diet-induced NAFLD.

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Arginase inhibitor attenuates effects of l-citrulline on NAFLD development.

Arginase impedes the resolution of colitis by altering the microbiome and metabolome

Arginase 1 (Arg1), which converts l-arginine into ornithine and urea, exerts pleiotropic immunoregulatory effects. However, the function of Arg1 in inflammatory bowel disease (IBD) remains poorly characterized. Here, we found that Arg1 expression correlated with the degree of inflammation in intestinal tissues from IBD patients. In mice, Arg1 was upregulated in an IL-4/IL-13- and intestinal microbiota-dependent manner. Tie2-Cre Arg1fl/fl mice lacking Arg1 in hematopoietic and endothelial cells recovered faster from colitis than Arg1-expressing (Arg1fl/fl) littermates. This correlated with decreased vessel density, compositional changes in intestinal microbiota, diminished infiltration by myeloid cells, and an accumulation of intraluminal polyamines that promote epithelial healing. The proresolving effect of Arg1 deletion was reduced by an l-arginine-free diet, but rescued by simultaneous deletion of other l-arginine-metabolizing enzymes, such as Arg2 or Nos2, demonstrating that protection from colitis requires l-arginine. Fecal microbiota transfers from Tie2-Cre Arg1fl/fl mice into WT recipients ameliorated intestinal inflammation, while transfers from WT littermates into Arg1-deficient mice prevented an advanced recovery from colitis. Thus, an increased availability of l-arginine as well as altered intestinal microbiota and metabolic products accounts for the accelerated resolution from colitis in the absence of Arg1. Consequently, l-arginine metabolism may serve as a target for clinical intervention in IBD patients.

The risk of cardiovascular complications in inflammatory bowel disease

Inflammatory bowel disease (IBD) is a chronic, relapsing disease of unknown etiology involving gastrointestinal tract. IBD comprises two main entities: ulcerative colitis and Crohn's disease. Several studies showed increased risk of cardiovascular complications in chronic inflammatory disorders, especially during IBD relapses. Endothelium plays a role in physiologic regulation of vascular tone, cell adhesion, migration and resistance to thrombosis. Also, its dysfunction is associated with increased risk of atherosclerosis development. There are several potential links between chronic IBD-related inflammatory processes and the risk of cardiovascular disease, but insight into pathogenetic pathways remains unclear. We present the current concepts and review of adult and pediatric studies on the risk of CVD in IBD.

Experimental and Clinical Evidence of Endothelial Dysfunction in Inflammatory Bowel Disease

The endothelium has a crucial role in proper hemodynamics. Inflammatory bowel disease (IBD) is mainly a chronic inflammatory condition of the gastrointestinal tract. However, considerable evidence points to high cardiovascular risk in patients with IBD. This review positions the basic mechanisms of endothelial dysfunction in the IBD setting (both clinical and experimental). Furthermore, we review the main effects of drugs used to treat IBD in endothelial (dys)function. Moreover, we leave challenging points for enlarging the therapeutic arsenal for IBD with new or repurposed drugs that target endothelial dysfunction besides inflammation.

Oxidative Stress and Redox-Modulating Therapeutics in Inflammatory Bowel Disease

Inflammatory bowel disease (IBD) is associated with the production of reactive species that target cysteine redox switches in proteins, thereby affecting gene regulation, DNA damage, ion transport, intermediary metabolism, and mitochondrial function. Precursors of reactive species are derived from organic and inorganic compounds and their cofactors, including amino acids, vitamins, oxygen, nitrite, and sulfate. Nutrition and the gut microbiome fuel this process to a significant extent. The production of reactive species in IBD is reflected by a reduction in systemic free thiols, the major components of the antioxidant machinery. Systemic free thiols are amenable to nutritional or therapeutic intervention. This opens up future avenues for therapeutic modulation of redox status in IBD.

The role of arginase in the microcirculation in cardiovascular disease

In the microcirculation, the exchange of nutrients, water, gas, hormones, and waste takes place, and it is divided into the three main sections arterioles, capillaries, and venules. Disturbances in the microcirculation can be measured using surrogate parameters or be visualized either indirectly or directly.Arginase is a manganese metalloenzyme hydrolyzing L-arginine to urea and L-ornithine. It is located in different cell types, including vascular cells, but also in circulating cells such as red blood cells. A variety of pro-inflammatory factors, as well as interleukins, stimulate increased arginase expression. An increase in arginase activity consequently leads to a consumption of L-arginine needed for nitric oxide (NO) production by endothelial NO synthase. A vast body of evidence convincingly showed that increased arginase activity is associated with endothelial dysfunction in larger vessels of the vascular tree. Of note, arginase also influences the microcirculation. Arginase inhibition leads to an increase in the bioavailability of NO and reduces superoxide levels, resulting in improved endothelial function. Arginase inhibition might, therefore, be a potent treatment strategy in cardiovascular medicine. Recently, red blood cells emerged as an influential player in the development from increased arginase activity to endothelial dysfunction. As red blood cells directly interact with the microcirculation in gas exchange, this could constitute a potential link between arginase activity, endothelial dysfunction and microcirculatory disturbances.The aim of this review is to summarize recent findings revealing the role of arginase in regulating vascular function with particular emphasis on the microcirculation.

Protective effects of oxymatrine against DSS-induced acute intestinal inflammation in mice via blocking the RhoA/ROCK signaling pathway

Oxymatrine (OMT) is an important quinoxaline alkaloid that has a wide range of pharmacological effects and has been shown to alleviate ulcerative colitis due to its profound anti-inflammatory effects. The RhoA/ROCK (Rho kinase) signaling pathway has been shown to be related to the pathogenesis of several autoimmune diseases; however, the specific mechanisms of RhoA/ROCK signaling in inflammatory bowel disease (IBD) remain elusive. Therefore, we sought to determine whether OMT could ameliorate acute intestinal inflammation by targeting the RhoA/ROCK signaling pathway. The potential therapeutic effect of OMT on acute intestinal inflammation and its impact on the RhoA/ROCK signaling pathway were assessed in six groups of mice treated with low, medium and high doses of OMT (25, 50 and 100 mg/kg, respectively), and an inhibitor of ROCK, Y-27632, as a positive control, after initiating dextran sodium sulfate (DSS)-induced acute intestinal inflammation. The model group and normal group were injected intraperitoneally with equal doses of PBS. Our results showed that OMT treatment could protect the integrity of the epithelial barrier, relieve oxidative stress, inhibit the expression of inflammatory mediators and pro-inflammatory cytokines, restrain the differentiation of Th17 cells and promote the differentiation of Treg cells via inhibition of the RhoA/ROCK pathway, thus providing therapeutic benefits for ulcerative colitis (UC). Therefore, inhibiting the RhoA/ROCK pathway might be a new approach that can be used in UC therapy, which deserves to be investigated further.

Measurement of Microvascular Function in Pediatric Inflammatory Bowel Disease

BACKGROUND AND AIMS

Altered vascular flow is known to both play a role in the pathogenesis and influence the severity of inflammatory bowel disease (IBD). This phenomenon has been described in other systemic conditions and contributes to disease progression by facilitating inflammation and thrombosis. Microvascular dysfunction may represent an early sign of generalized vascular disease (VD). It manifests by failure to achieve a normal response of vasodilation and increased blood flow following a period of vaso-occlusion. Although thromboembolic complications are well described in IBD, their pathogenesis is not fully understood. This study sought to assess microvascular responsiveness in pediatric subjects with IBD, by recording postocclusion peripheral arterial pulsatile volume changes.

PATIENTS AND METHODS

A total of 32 pediatric subjects were studied, including 16 with IBD and 16 age-matched controls. All patients with IBD were in clinical remission, and none had known VD. Vascular reactivity was evaluated using the Itamar Medical EndoPAT2000, a noninvasive device utilizing plethysmography to measure microvascular flow. Results were reported as the reactive hyperemia index (RHI), indicating post- to preocclusion pulsatile volume changes.

RESULTS

Baseline characteristics, including body mass index, plasma lipid levels, hemoglobin, and serum albumin, were similar in both study groups. All patients with IBD were in clinical remission, assessed by standard disease activity scoring methods. Measurements of microvascular function indicated patients with IBD exhibited a mean RHI both within the range associated with VD risk in adults (≤1.67) and significantly lower than that in controls (IBD vs control = 1.66 vs 2.02, P = 0.036).

CONCLUSIONS

Microvascular plethysmography is a safe and noninvasive method for assessing microvascular function in children with IBD. Patients with IBD in clinical remission demonstrate an attenuated, postocclusion microvascular hyperemic response, compared with the normal response in controls. These findings suggest pediatric IBD subjects with a mean RHI within the VD "at risk" range should be monitored for thromboembolic phenomena. Further studies in a larger patient population and over longer periods should be conducted to validate our findings and to determine the importance of these measurements in guiding IBD management.

Hyperpolarized [6-13C,15N3]-Arginine as a Probe for in Vivo Arginase Activity

Alterations in arginase enzyme expression are linked with various diseases and have been shown to support disease progression, thus motivating the development of an imaging probe for this enzymatic target. ¹³C-enriched arginine can be used as a hyperpolarized (HP) magnetic resonance (MR) probe for arginase flux since the arginine carbon-6 resonance (157 ppm) is converted to urea (163 ppm) following arginase-catalyzed hydrolysis. However, scalar relaxation from adjacent ¹⁴N-nuclei shortens cabon-6 T ₁ and T ₂ times, yielding poor spectral properties. To address these limitations, we report the synthesis of [6-¹³C,¹⁵N₃]-arginine and demonstrate that ¹⁵N-enrichment increases carbon-6 relaxation times, thereby improving signal-to-noise ratio and spectral resolution. By overcoming these limitations with this novel isotope-labeling scheme, we were able to perform in vitro and in vivo arginase activity measurements with HP MR. We present HP [6-¹³C,¹⁵N₃]-arginine as a noninvasive arginase imaging agent for preclinical studies, with the potential for future clinical diagnostic use.

Bacteroides thetaiotaomicron Ameliorates Colon Inflammation in Preclinical Models of Crohn's Disease

Background

Alterations in the gut microbiota are strongly associated with the development of inflammatory bowel disease (IBD), particularly with Crohn's disease, which is characterized by reduced abundance of commensal anaerobic bacteria including members of the Bacteroides genus. Our aim was to investigate the protective effects of Bacteroides thetaiotaomicron, an abundant member of this genus, in different rodent models of IBD.

Methods

We assessed the effect of B. thetaiotaomicron administration on primary readouts of colitis (weight loss, histopathology, and immune parameters) in dextran sodium sulphate (DSS) and interleukin-10 knockout (IL10KO) models of IBD. Efficacy of a freeze-dried bacterial formulation and a purified recombinant protein of B. thetaiotaomicron was also investigated.

Results

B. thetaiotaomicron showed protective effects in both DSS and IL10KO rodent models, as demonstrated by significant amelioration of weight loss, colon shortening, histopathological damage and immune activation. This efficacy was not exclusive to actively growing bacterial preparations but was retained by freeze-dried cells of B. thetaiotaomicron. A pirin-like protein (PLP) of B. thetaiotaomicron, identified by microarray analysis during coculture of the bacterial strain with Caco-2 cells, reduced pro-inflammatory NF-κB signalling in these intestinal epithelial cells. Recombinant PLP partially recapitulated the effect of the whole strain in a rat DSS model.

Conclusions

B. thetaiotaomicron displays strong efficacy in preclinical models of IBD and protects against weight loss, histopathological changes in the colon and inflammatory markers. These data indicate that the live strain or its products may be a novel alternative to current treatment options for Crohn's disease.

Hyperglycemia-impaired aortic vasorelaxation mediated through arginase elevation: Role of stress kinase pathways

Diabetes-induced vascular endothelial dysfunction has been reported to involve hyperglycemia-induced increases in arginase activity. However, upstream mediators of this effect are not clear. Here, we have tested involvement of Rho kinase, ERK1/2 and p38 MAPK pathways in this process. Studies were performed with aortas isolated from wild type or hemizygous arginase 1 knockout (Arg1^+/-) mice and bovine aortic endothelial cells exposed to high glucose (HG, 25 mmol/l) or normal glucose (NG, 5.5 mmol/l) conditions for different times. Effects of inhibitors of arginase, p38 MAPK, ERK1/2 or ROCK and ex vivo adenoviral delivery of active Arg1 and inactive (D128-Arg1) cDNA were also determined. Exposure in wild type aorta or endothelial cells to HG significantly increased arginase activity and Arg1 expression and impaired aortic relaxation. Transduction of wild type aorta with active Arg1 cDNA impaired vascular relaxation, whereas inactive Arg1 had no effect. The HG-induced vascular endothelial dysfunction was associated with increased phosphorylation (activation) of ERK1/2 and p38 MAPK. Pretreatment with inhibitors of ERK1/2, p38 MAPK, ROCK or arginase blocked HG-induced elevation of arginase activity and Arg1 expression and prevented the vascular dysfunction. Inhibition of ROCK blunted the HG-induced activation of ERK1/2 and p38 MAPK. In summary, activated ROCK and subsequent activation of ERK1/2 or p38 MAPK elevates arginase activity and Arg1 expression in hyperglycemic states. Targeting this pathway may provide an effective means for preventing diabetes/hyperglycemia-induced vascular endothelial dysfunction.

Increased arterial stiffness - similar findings in patients with inflammatory bowel disease without prior hypertension or diabetes and in patients with well-controlled hypertension

PURPOSE

Chronic inflammatory diseases are related with earlier onset of atherosclerosis. We hypothesized that inflammatory bowel disease patients with chronic, systemic inflammation have an increased arterial stiffness associated with the disease duration. Also, we wanted to compare arterial stiffness markers between inflammatory bowel disease and well-controlled hypertension patients.

MATERIALS AND METHODS

A total of 89 inflammatory bowel disease patients (60 patients with Crohn's disease and 29 patients with ulcerative colitis, age range 20-64 years) without history of arterial hypertension or diabetes were enrolled and age matched with a control group of patients (73 patients, age range 25-69 years, 41 (56.1%) males) with known history of well-controlled arterial hypertension. We have used a noninvasive device that simultaneously measures brachial blood pressure and estimates PWV and AIx in inflammatory bowel disease and hypertension groups of patients.

RESULTS

Patients with pathological PWV values were significantly older, had significantly longer duration of inflammatory bowel disease, higher values of serum cholesterol and HDL-cholesterol, and higher AIx (17.4% vs. 9.8%) (all p < .05). Higher PWV was associated with age and duration of inflammatory bowel disease in the linear regression model. PWV values were higher in hypertensive patients in the first two age quartiles while interestingly, in the last two quartiles, PWV was lower than in inflammatory bowel disease group of patients.

CONCLUSIONS

Chronic subclinical inflammation is responsible for dyslipidemia and accelerated atherosclerosis which consequently alterates arterial elasticity. Inflammatory bowel disease and its duration should also be considered a risk factor for subclinical organ damage, as well as hypertension.

Vascular Endothelial Dysfunction in Inflammatory Bowel Diseases: Pharmacological and Nonpharmacological Targets

Inflammatory bowel diseases, including Crohn's disease and ulcerative colitis, are chronic inflammatory conditions involving primarily the gastrointestinal tract. However, they may be also associated with systemic manifestations and comorbidities. The relationship between chronic inflammation and endothelial dysfunction has been extensively demonstrated. Mucosal immunity and gastrointestinal physiology are modified in inflammatory bowel diseases, and these modifications are mainly sustained by alterations of endothelial function. The key elements involved in this process are cytokines, inflammatory cells, growth factors, nitric oxide, endothelial adhesion molecules, and coagulation cascade factors. In this review, we discuss available data in literature concerning endothelial dysfunction in patients affected by inflammatory bowel disease and we focus our attention on both pharmacological and nonpharmacological therapeutic targets.

Effectiveness of arginase inhibitors against experimentally induced stroke

Stroke is a lethal disease, but it disables more than it kills. Stroke is the second leading cause of death and the most frequent cause of permanent disability in adults worldwide, with 90% of survivors having residual deficits. The pathophysiology of stroke is complex and involves a strong inflammatory response associated with oxidative stress and activation of several proteolytic enzymes. The current study was designed to investigate the effect of arginase inhibitors (L-citruline and L-ornithine) against ischemic stroke induced in rats by middle cerebral artery occlusion (MCAO). MCAO resulted in alteration in rat behavior, brain infarct, and edema associated with disruption of the blood-brain barrier (BBB). This was mediated through overexpression of arginase I and II, inducible NOS (iNOS), malondialdehyde (MDA), advanced glycation end products (AGEs), TNF-α, and IL-1β and downregulation of endothelial nitric oxide synthase (eNOS). Treatment with L-citruline and L-ornithine and the standard neuroprotective drug cerebrolysin ameliorated all the deleterious effects of stroke. These results indicate the possible use of arginase inhibitors in the treatment of stroke after suitable clinical trials are done.

Obesity-induced vascular dysfunction and arterial stiffening requires endothelial cell arginase 1

AIMS

Elevation of arginase activity has been linked to vascular dysfunction in diabetes and hypertension by a mechanism involving decreased nitric oxide (NO) bioavailability due to L-arginine depletion. Excessive arginase activity also can drive L-arginine metabolism towards the production of ornithine, polyamines, and proline, promoting proliferation of vascular smooth muscle cells and collagen formation, leading to perivascular fibrosis. We hypothesized that there is a specific involvement of arginase 1 expression within the vascular endothelial cells in this pathology.

METHODS AND RESULTS

To test this proposition, we used models of type 2 diabetes and metabolic syndrome. Studies were performed using wild type (WT), endothelial-specific arginase 1 knockout (EC-A1-/-) and littermate controls(A1con) mice fed high fat-high sucrose (HFHS) or normal diet (ND) for 6 months and isolated vessels exposed to palmitate-high glucose (PA/HG) media. Some WT mice or isolated vessels were treated with an arginase inhibitor, ABH [2-(S)-amino-6-boronohexanoic acid. In WT mice, the HFHS diet promoted increases in body weight, fasting blood glucose, and post-prandial insulin levels along with arterial stiffening and fibrosis, elevated blood pressure, decreased plasma levels of L-arginine, and elevated L-ornithine. The HFHS diet or PA/HG treatment also induced increases in vascular arginase activity along with oxidative stress, reduced vascular NO levels, and impaired endothelial-dependent vasorelaxation. All of these effects except obesity and hypercholesterolemia were prevented or significantly reduced by endothelial-specific deletion of arginase 1 or ABH treatment.

CONCLUSION

Vascular dysfunctions in diet-induced obesity are prevented by deletion of arginase 1 in vascular endothelial cells or arginase inhibition. These findings indicate that upregulation of arginase 1 expression/activity in vascular endothelial cells has an integral role in diet-induced cardiovascular dysfunction and metabolic syndrome.

The signaling axis of microRNA-31/interleukin-25 regulates Th1/Th17-mediated inflammation response in colitis

Interleukin-25 (IL-25) is an important regulatory cytokine that has a key role on mucosal immune tolerance during inflammation response. However, the molecular mechanism that regulates the colonic IL-25 expression in Crohn's disease (CD) remains unclear. In this study, IL-25 level was proved to decrease in 2,4,6-trinitrobenzene sulfonic acid (TNBS)-induced colitis mice and IL-10 knockout (KO) spontaneous colitis mice. An inverse correlation between IL-25 and miR-31 was discovered in the colons from model mice and CD patients. Furthermore, target validation analysis demonstrated that miR-31 directly regulated IL-25 expression by binding to its messenger RNA 3'-untranslated region. Changing colonic miR-31 level in the colitis mice could affect the mucosal IL-12/23-mediated Th1/Th17 pathway and lead to either amelioration or aggravation of colonic inflammation. In addition, the therapeutic effects of anti-miR-31 in TNBS-induced colitis were abolished by colonic treatment with IL-25 antibody or colonic down-expression of IL-25. Our findings demonstrated that IL-25 could be a crucial anti-inflammatory cytokine in TNBS-induced colitis and the signaling of miR-31 targeting IL-25 might be a possible mechanism that regulates IL-12/23-mediated Th1/Th17 inflammatory responses during colonic inflammation process. Restoring colonic IL-25 expression and blocking Th1/Th17 responses via intracolonic administration of miR-31 inhibitor may represent a promising approach for CD treatment.

Innate Immune Pathways Associated with Lung Radioprotection by Soy Isoflavones

Introduction

Radiation therapy for lung cancer causes pneumonitis and fibrosis. Soy isoflavones protect against radiation-induced lung injury, but the mediators of radioprotection remain unclear. We investigated the effect of radiation on myeloid-derived suppressor cells (MDSCs) in the lung and their modulation by soy isoflavones for a potential role in protection from radiation-induced lung injury.

Methods

BALB/c mice (5–6 weeks old) received a single 10 Gy dose of thoracic irradiation and soy isoflavones were orally administrated daily before and after radiation at 1 mg/day. Arginase-1 (Arg-1) and nuclear factor κB (NF-κB) p65 were detected in lung tissue by western blot analysis and immunohistochemistry. Lung MDSC subsets and their Arg-1 expression were analyzed by flow cytometry. Cytokine levels in the lungs were measured by ELISA.

Results

At 1 week after radiation, CD11b⁺ cells expressing Arg-1 were decreased by radiation in lung tissue yet maintained in the lungs treated with radiation and soy isoflavones. Arg-1 was predominantly expressed by CD11b⁺Ly6C^lowLy6G⁺ granulocytic MDSCs (gr-MDSCs). Arg-1 expression in gr-MDSCs was reduced by radiation and preserved by supplementation with soy isoflavones. A persistent increase in Arg-1⁺ cells was observed in lung tissue treated with combined radiation and soy isoflavones at early and late time points, compared to radiation alone. The increase in Arg-1 expression mediated by soy isoflavones could be associated with the inhibition of radiation-induced activation of NF-κB and the control of pro-inflammatory cytokine production demonstrated in this study.

Conclusion

A radioprotective mechanism of soy isoflavones may involve the promotion of Arg-1-expressing gr-MDSCs that could play a role in downregulation of inflammation and lung radioprotection.

Rocuronium Bromide Inhibits Inflammation and Pain by Suppressing Nitric Oxide Production and Enhancing Prostaglandin E2 Synthesis in Endothelial Cells

Purpose

Rocuronium bromide is a nondepolarizing neuromuscular blocking drug and has been used as an adjunct for relaxation or paralysis of the skeletal muscles, facilitation of endotracheal intubation, and improving surgical conditions during general anesthesia. However, intravenous injection of rocuronium bromide induces injection pain or withdrawal movement. The exact mechanism of rocuronium bromide-induced injection pain or withdrawal movement is not yet understood. We investigated whether rocuronium bromide treatment is involved in the induction of inflammation and pain in vascular endothelial cells.

Methods

For this study, calf pulmonary artery endothelial (CPAE) cells were used, and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay, Western blot, nitric oxide detection, and prostaglandin E₂ immunoassay were conducted.

Results

Rocuronium bromide treatment inhibited endothelial nitric oxide synthase and suppressed nitric oxide production in CPAE cells. Rocuronium bromide activated cyclooxygenase-2, inducible nitric oxide synthase and increased prostaglandin E₂ synthesis in CPAE cells.

Conclusions

Rocuronium bromide induced inflammation and pain in CPAE cells. Suppressing nitric oxide production and enhancing prostaglandin E₂ synthesis might be associated with rocuronium bromide-induced injection pain or withdrawal movement.

Risk of cardiovascular disease in inflammatory bowel disease

Cardiovascular disease (CVD) can arise because of chronic inflammation and inflammatory bowel disease (IBD) is one such disease where the risk for CVD and eventual heart failure is increased considerably. The incidence of IBD, which refers to both ulcerative colitis and Crohn's disease, has been on the increase in several countries and is a potential risk factor for CVD. Although IBD can potentially cause venous thromboembolism, its significance in arterial stiffening, atherosclerosis, ischemic heart disease and myocardial infarction is only being realized now and it is currently under debate. However, several studies with large groups of patients have demonstrated the association of IBD with heart disease. It has been suggested that systemic inflammation as observed in IBD patients leads to oxidative stress and elevated levels of inflammatory cytokines such as tumor necrosis factor-α (TNF-α), which lead to phenotypic changes in smooth muscle cells and sets into motion a series of events that culminate in atherosclerosis and CVD. Besides the endogenous factors and cytokines, it has been suggested that due to the compromised intestinal mucosal barrier, endotoxins and bacterial lipopolysaccharides produced by intestinal microflora can enter into circulation and activate inflammatory responses that lead to atherosclerosis. Therapeutic management of IBD-associated heart diseases cannot be achieved with simple anti-inflammatory drugs such as corticosteroids and anti-TNF-α antibodies. Treatment with existing medications for CVDs, aspirin, platelet aggregation inhibitors and statins is found to be acceptable and safe. Nevertheless, further research is needed to assess their efficacy in IBD patients suffering from heart disease.

Nuclear Countermeasure Activity of TP508 Linked to Restoration of Endothelial Function and Acceleration of DNA Repair

There is increasing evidence that radiation-induced damage to endothelial cells and loss of endothelial function may contribute to both acute radiation syndromes and long-term effects of whole-body nuclear irradiation. Therefore, several drugs are being developed to mitigate the effects of nuclear radiation, most of these drugs will target and protect or regenerate leukocytes and platelets. Our laboratory has demonstrated that TP508, a 23-amino acid thrombin peptide, activates endothelial cells and stem cells to revascularize and regenerate tissues. We now show that TP508 can mitigate radiation-induced damage to endothelial cells in vitro and in vivo. Our in vitro results demonstrate that human endothelial cells irradiation attenuates nitric oxide (NO) signaling, disrupts tube formation and induces DNA double-strand breaks (DSB). TP508 treatment reverses radiation effects on NO signaling, restores tube formation and accelerates the repair of radiation-induced DSB. The radiation-mitigating effects of TP508 on endothelial cells were also seen in CD-1 mice where systemic injection of TP508 stimulated endothelial cell sprouting from aortic explants after 8 Gy irradiation. Systemic doses of TP508 that mitigated radiation-induced endothelial cell damage, also significantly increased survival of CD-1 mice when injected 24 h after 8.5 Gy exposure. These data suggest that increased survival observed with TP508 treatment may be due to its effects on vascular and microvascular endothelial cells. Our study supports the usage of a regenerative drug such as TP508 to activate endothelial cells as a countermeasure for mitigating the effects of nuclear radiation.

Rho Kinases in Health and Disease: From Basic Science to Translational Research

Rho-associated kinases ROCK1 and ROCK2 are key regulators of actin cytoskeleton dynamics downstream of Rho GTPases that participate in the control of important physiologic functions, S including cell contraction, migration, proliferation, adhesion, and inflammation. Several excellent review articles dealing with ROCK function and regulation have been published over the past few years. Although a brief overview of general molecular, biochemical, and functional properties of ROCKs is included, an effort has been made to produce an original work by collecting and synthesizing recent studies aimed at translating basic discoveries from cell and experimental models into knowledge of human physiology, pathophysiological mechanisms, and medical therapeutics. This review points out the specificity and distinct roles of ROCK1 and ROCK2 isoforms highlighted in the last few years. Results obtained from genetically modified mice and genetic analysis in humans are discussed. This review also addresses the involvement of ROCKs in human diseases and the potential use of ROCK activity as a biomarker or a pharmacological target for specific inhibitors.

Differential Roles of M1 and M2 Microglia in Neurodegenerative Diseases

One of the most striking hallmarks shared by various neurodegenerative diseases, including Parkinson's disease, Alzheimer's disease (AD), and amyotrophic lateral sclerosis, is microglia-mediated neuroinflammation. Increasing evidence indicates that microglial activation in the central nervous system is heterogeneous, which can be categorized into two opposite types: M1 phenotype and M2 phenotype. Depending on the phenotypes activated, microglia can produce either cytotoxic or neuroprotective effects. In this review, we focus on the potential role of M1 and M2 microglia and the dynamic changes of M1/M2 phenotypes that are critically associated with the neurodegenerative diseases. Generally, M1 microglia predominate at the injury site at the end stage of disease, when the immunoresolution and repair process of M2 microglia are dampened. This phenotype transformation is very complicated in AD due to the phagocytosis of regionally distributed β-amyloid (Aβ) plaque and tangles that are released into the extracellular space. The endogenous stimuli including aggregated α-synuclein, mutated superoxide dismutase, Aβ, and tau oligomers exist in the milieu that may persistently activate M1 pro-inflammatory responses and finally lead to irreversible neuron loss. The changes of microglial phenotypes depend on the disease stages and severity; mastering the stage-specific switching of M1/M2 phenotypes within appropriate time windows may provide better therapeutic benefit.

Endothelial dysfunction in inflammatory bowel diseases: Pathogenesis, assessment and implications

Endothelial dysfunction is considered one of the etiological factors of inflammatory bowel disease (IBD). An inflammatory process leads to functional and structural changes in the vascular endothelium. An increase of leukocyte adhesiveness and leukocyte diapedesis, as well as an increased vascular smooth muscle tone and procoagulant activity is observed. Structural changes of the vascular endothelium comprise as well capillary and venule remodeling and proliferation of endothelial cells. Hypoxia in the inflammatory area stimulates angiogenesis by up-regulation of vascular endothelial growth factor, fibroblast growth factor and tumor necrosis factor-α. Inflammatory mediators also alter the lymphatic vessel function and impair lymph flow, exacerbating tissue edema and accumulation of dead cells and bacteria. The endothelial dysfunction might be diagnosed by the use of two main methods: physical and biochemical. Physical methods are based on the assessment of large arteries vasodilatation in response to an increased flow and receptors stimulation. Flow-mediated vasodilatation (FMD) is the method that is the most widely used; however, it is less sensitive in detecting early changes of the endothelium function. Most of the studies demonstrated a decrease of FMD in IBD patients but no changes in the carotic intima-media thickness. Biochemical methods of detecting the endothelial dysfunction are based on the assessment of the synthesis of compounds produced both by the normal and damaged endothelium. The endothelial dysfunction is considered an initial step in the pathogenesis of atherosclerosis in the general population. In IBD patients, the risk of cardiovascular diseases is controversial. Large, prospective studies are needed to establish the role of particular medications or dietary elements in the endothelial dysfunction as well to determine the real risk of cardiovascular diseases.

Expression of arginase I and inducible nitric oxide synthase in the peripheral blood and lymph nodes of HIV‑positive patients

Arginase I (Arg I) and inducible nitric oxide synthase (iNOS) are important in regulating immune functions through their metabolites. Previous studies have revealed that the expression of Arg I is increased and the expression of iNOS is reduced in the serum and peripheral blood mononuclear cells of human immunodeficiency virus (HIV)-infected patients. As one of the most important immune organs and HIV replication sites, whether similar changes are present in the lymph nodes following HIV infection remains to be elucidated. To investigate this, the present study collected lymph node and blood specimens from 52 HIV-infected patients to measure the expression levels of Arg I and iNOS by immunohistochemistry and fluoresence-based flow cytometry. Compared with control subjects without HIV infection, the patients with HIV had significantly higher expression levels of Arg I in the lymph nodes and higher frequencies of Arg I⁺ CD4⁺ T cells and CD8⁺ T cells in the blood and lymph nodes, and these results were contrary the those of iNOS in the corresponding compartments. The expression levels of Arg I in the lymph nodes and blood were negatively associated with peripheral CD4⁺ T cell count and positively associated with viral load. However, the expression levels of iNOS in the lymph nodes and blood were positively associated with peripheral CD4⁺ T cell count and negatively associated with viral load. These results showed that alterations in the expression levels of Arg I and iNOS in the peripheral T cells and peripheral nodes of HIV infected patients are associated with disease progression in these patients. These results indicate a potential to therapeutic strategy for delaying disease progression through regulating and manipulating the expression levels of Arg I and iNOS in patients infected with HIV.

Dysregulated expression of arginine metabolic enzymes in human intestinal tissues of necrotizing enterocolitis and response of CaCO2 cells to bacterial components

The small intestine is the exclusive site of arginine synthesis in neonates. Low levels of circulating arginine have been associated with the occurrence of necrotizing enterocolitis (NEC) but the mechanism of arginine dysregulation has not been fully elucidated. We aimed to investigate (i) expressional changes of arginine synthesizing and catabolic enzymes in human intestinal tissues of NEC, spontaneous intestinal perforation (SIP) and noninflammatory surgical conditions (Surg-CTL) and to investigate the (ii) mechanisms of arginine dysregulation and enterocyte proliferation upon stimulation by bacterial components, arginine depletion, ARG1 overexpression and nitric oxide (NO) supplementation. Our results showed that expressions of arginine synthesizing enzymes ALDH18A1, ASL, ASS1, CPS1, GLS, OAT and PRODH were significantly decreased in NEC compared with Surg-CTL or SIP tissues. Catabolic enzyme ARG1 was increased (>100-fold) in NEC tissues and histologically demonstrated to be expressed by infiltrating neutrophils. No change in arginine metabolic enzymes was observed between SIP and Surg-CTL tissues. In CaCO2 cells, arginine metabolic enzymes were differentially dysregulated by lipopolysaccharide or lipoteichoic acid. Depletion of arginine reduced cell proliferation and this phenomenon could be partially rescued by NO. Overexpression of ARG1 also reduced enterocyte proliferation. We provided the first expressional profile of arginine metabolic enzymes at the tissue level of NEC. Our findings suggested that arginine homeostasis was severely disturbed and could be triggered by inflammatory responses of enterocytes and infiltrating neutrophils as well as bacterial components. Such reactions could reduce arginine and NO, resulting in mucosal damage. The benefit of arginine supplementation for NEC prophylaxis merits further clinical evaluation.

Arterial structure and function in inflammatory bowel disease

Inflammatory bowel disease (IBD) is the result of a combination of environmental, genetic and immunologic factors that trigger an uncontrolled immune response within the intestine, which results in inflammation among genetically predisposed individuals. Several studies have reported that the prevalence of classic cardiovascular risk factors is lower among subjects with IBD than in the general population, including obesity, dyslipidaemia, diabetes and hypertension. Therefore, given the risk profile of IBD subjects, the expected cardiovascular morbidity and mortality should be lower in these patients than in the general population. However, this is not the case because the standardized mortality ratio is not reduced and the risk of coronary heart disease is increased in patients with IBD. It is reasonable to hypothesize that other factors not considered in the classical stratification of cardiovascular risk may be involved in these subjects. Therefore, IBD may be a useful model with which to evaluate the effects of chronic low-grade inflammation in the development of cardiovascular diseases. Arterial stiffness is both a marker of subclinical target organ damage and a cardiovascular risk factor. In diseases characterized by chronic systemic inflammation, there is evidence that the inflammation affects arterial properties and induces both endothelial dysfunction and arterial stiffening. It has been reported that decreasing inflammation via anti tumor necrosis factor alpha therapy decreases arterial stiffness and restores endothelial function in patients with chronic inflammatory disorders. Consistent with these results, several recent studies have been conducted to determine whether arterial properties are altered among patients with IBD. In this review, we discuss the evidence pertaining to arterial structure and function and present the available data regarding arterial stiffness and endothelial function in patients with IBD.

Inflammation Modulates RLIP76/RALBP1 Electrophile-Glutathione Conjugate Transporter and Housekeeping Genes in Human Blood-Brain Barrier Endothelial Cells

Endothelial cells are often present at inflammation sites. This is the case of endothelial cells of the blood-brain barrier (BBB) of patients afflicted with neurodegenerative disorders such as Alzheimer's, Parkinson's, or multiple sclerosis, as well as in cases of bacterial meningitis, trauma, or tumor-associated ischemia. Inflammation is a known modulator of gene expression through the activation of transcription factors, mostly NF-κB. RLIP76 (a.k.a. RALBP1), an ATP-dependent transporter of electrophile-glutathione conjugates, modulates BBB permeability through the regulation of tight junction function, cell adhesion, and exocytosis. Genes and pathways regulated by RLIP76 are transcriptional targets of tumor necrosis factor alpha (TNF-α) pro-inflammatory molecule, suggesting that RLIP76 may also be an inflammation target. To assess the effects of TNF-α on RLIP76, we faced the problem of choosing reference genes impervious to TNF-α. Since such genes were not known in human BBB endothelial cells, we subjected these to TNF-α, and measured by quantitative RT-PCR the expression of housekeeping genes commonly used as reference genes. We find most to be modulated, and analysis of several inflammation datasets as well as a metaanalysis of more than 5000 human tissue samples encompassing more than 300 cell types and diseases show that no single housekeeping gene may be used as a reference gene. Using three different algorithms, however, we uncovered a reference geneset impervious to TNF-α, and show for the first time that RLIP76 expression is induced by TNF-α and follows the induction kinetics of inflammation markers, suggesting that inflammation can influence RLIP76 expression at the BBB. We also show that MRP1 (a.k.a. ABCC1), another electrophile-glutathione transporter, is not modulated in the same cells and conditions, indicating that RLIP76 regulation by TNF-α is not a general property of glutathione transporters. The reference geneset uncovered herein should aid in future gene expression studies in inflammatory conditions of the BBB.

Microglia in the TBI brain: The good, the bad, and the dysregulated

As the major cellular component of the innate immune system in the central nervous system (CNS) and the first line of defense whenever injury or disease occurs, microglia play a critical role in neuroinflammation following a traumatic brain injury (TBI). In the injured brain microglia can produce neuroprotective factors, clear cellular debris and orchestrate neurorestorative processes that are beneficial for neurological recovery after TBI. However, microglia can also become dysregulated and can produce high levels of pro-inflammatory and cytotoxic mediators that hinder CNS repair and contribute to neuronal dysfunction and cell death. The dual role of microglial activation in promoting beneficial and detrimental effects on neurons may be accounted for by their polarization state and functional responses after injury. In this review article we discuss emerging research on microglial activation phenotypes in the context of acute brain injury, and the potential role of microglia in phenotype-specific neurorestorative processes such as neurogenesis, angiogenesis, oligodendrogenesis and regeneration. We also describe some of the known molecular mechanisms that regulate phenotype switching, and highlight new therapeutic approaches that alter microglial activation state balance to enhance long-term functional recovery after TBI. An improved understanding of the regulatory mechanisms that control microglial phenotypic shifts may advance our knowledge of post-injury recovery and repair, and provide opportunities for the development of novel therapeutic strategies for TBI.

Inflammatory bowel disease, liver diseases and endothelial function: is there a linkage?

Atherosclerosis is a systemic inflammatory disease able to deeply worsen the outcome of patients because of its serious clinical consequences. The complex inflammatory background underlining such a disease makes atherosclerosis linked to several systemic inflammatory conditions able to impair endothelial function and morphology. Inflammatory bowel diseases are a group of gastrointestinal diseases including Crohn's disease and ulcerative colitis, that is, syndromes characterized by changes in mucosal immunity and gastrointestinal physiology, which could negatively influence the vascular endothelial function and structure. Hepatitis (i.e. inflammatory diseases of the liver mainly due to viral infections) and nonalcoholic fatty liver disease could be aligned to inflammatory bowel disease in such an induction of atherosclerosis disease.Many studies tried to point out the relationship between bowel and liver inflammatory diseases and early vascular changes, considered the first step for atherosclerosis development.The aim of such a narrative review is to explain the relationship between inflammatory bowel disease, hepatitis and nonalcoholic fatty liver disease and their role in increasing cardiovascular risk profile due to early impairment in vascular function and morphology.