Regulation of arginine transport and metabolism by protein kinase Calpha in endothelial cells: stimulation of CAT2 transporters and arginase activity

TRPA1 Polymorphisms Modify the Hypotensive Responses to Propofol with No Change in Nitrite or Nitrate Levels

Anesthesia with propofol is frequently associated with hypotension. The TRPA1 gene contributes to the vasodilator effect of propofol. Hypotension is crucial for anesthesiologists because it is deleterious in the perioperative period. We tested whether the TRPA1 gene polymorphisms or haplotypes interfere with the hypotensive responses to propofol. PCR-determined genotypes and haplotype frequencies were estimated. Nitrite, nitrates, and NOx levels were measured. Propofol induced a more expressive lowering of the blood pressure (BP) without changing nitrite or nitrate levels in patients carrying CG+GG genotypes for the rs16937976 TRPA1 polymorphism and AG+AA genotypes for the rs13218757 TRPA1 polymorphism. The CGA haplotype presented the most remarkable drop in BP. Heart rate values were not impacted. The present exploratory analysis suggests that TRPA1 genotypes and haplotypes influence the hypotensive responses to propofol. The mechanisms involved are probably other than those related to NO bioavailability. With better genetic knowledge, planning anesthesia with fewer side effects may be possible.

There is no direct competition between arginase and nitric oxide synthase for the common substrate l-arginine

AIMS

Extrahepatic arginases are postulated to be involved in cardiovascular-related pathologies by competing with nitric oxide synthase (NOS) for the common substrate l-arginine, subsequently decreasing nitric oxide production. However, previous models used to study arginase and NOS competition did not account for steady state level of l-arginine pool, which is dependent on conditions of l-arginine supply and utilization pathways. This work aimed at revisiting the concept of NOS and arginase competition while considering different conditions of l-arginine supply and l-arginine utilization pathways.

METHODS AND RESULTS

Mouse macrophage-like RAW cells and human vascular endothelial cells co-expressing NOS and arginase were used to reevaluate the concept of substrate competition between arginase and NOS under conditions of l-arginine supply that mimicked either a continuous (similar to in vivo conditions) or a limited supply (similar to previous in vitro models). Enzyme kinetics simulation models were used to gain mechanistic insight and to evaluate the tenability of a substrate competition between the two enzymes. In addition to arginase and NOS, other l-arginine pathways such as transporters and utilization towards protein synthesis were considered to understand the intricacies of l-arginine metabolism. Our results indicate that when there is a continuous supply of l-arginine, as is the case for most cells in vivo, arginase does not affect NOS activity by a substrate competition. Furthermore, we demonstrate that l-arginine pathways such as transporters and protein synthesis are more likely to affect NOS activity than arginase.

CONCLUSIONS

Arginase does not outcompete NOS for the common substrate l-arginine. Findings from this study should be considered to better understand the role of arginase in certain pathologies and for the interpretation of in vivo studies with arginase inhibitors.

The Role of PKC-MAPK Signalling Pathways in the Development of Hyperglycemia-Induced Cardiovascular Complications

Cardiovascular disease is the most common cause of death among diabetic patients worldwide. Hence, cardiovascular wellbeing in diabetic patients requires utmost importance in disease management. Recent studies have demonstrated that protein kinase C activation plays a vital role in the development of cardiovascular complications via its activation of mitogen-activated protein kinase (MAPK) cascades, also known as PKC-MAPK pathways. In fact, persistent hyperglycaemia in diabetic conditions contribute to preserved PKC activation mediated by excessive production of diacylglycerol (DAG) and oxidative stress. PKC-MAPK pathways are involved in several cellular responses, including enhancing oxidative stress and activating signalling pathways that lead to uncontrolled cardiac and vascular remodelling and their subsequent dysfunction. In this review, we discuss the recent discovery on the role of PKC-MAPK pathways, the mechanisms involved in the development and progression of diabetic cardiovascular complications, and their potential as therapeutic targets for cardiovascular management in diabetic patients.

Topical Reappraisal of Molecular Pharmacological Approaches to Endothelial Dysfunction in Diabetes Mellitus Angiopathy

Diabetes mellitus (DM) is a frequent medical problem, affecting more than 4% of the population in most countries. In the context of diabetes, the vascular endothelium can play a crucial pathophysiological role. If a healthy endothelium—which is a dynamic endocrine organ with autocrine and paracrine activity—regulates vascular tone and permeability and assures a proper balance between coagulation and fibrinolysis, and vasodilation and vasoconstriction, then, in contrast, a dysfunctional endothelium has received increasing attention as a potential contributor to the pathogenesis of vascular disease in diabetes. Hyperglycemia is indicated to be the major causative factor in the development of endothelial dysfunction. Furthermore, many shreds of evidence suggest that the progression of insulin resistance in type 2 diabetes is parallel to the advancement of endothelial dysfunction in atherosclerosis. To present the state-of-the-art data regarding endothelial dysfunction in diabetic micro- and macroangiopathy, we constructed this literature review based on the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA). We interrogated five medical databases: Elsevier, PubMed, PMC, PEDro, and ISI Web of Science.

Potential Role of Protein Kinase C in the Pathophysiology of Diabetes-Associated Atherosclerosis

Diabetes mellitus is a metabolic syndrome that affects millions of people worldwide. Recent studies have demonstrated that protein kinase C (PKC) activation plays an important role in hyperglycemia-induced atherosclerosis. PKC activation is involved in several cellular responses such as the expression of various growth factors, activation of signaling pathways, and enhancement of oxidative stress in hyperglycemia. However, the role of PKC activation in pro-atherogenic and anti-atherogenic mechanisms remains controversial, especially under hyperglycemic condition. In this review, we discuss the role of different PKC isoforms in lipid regulation, oxidative stress, inflammatory response, and apoptosis. These intracellular events are linked to the pathogenesis of atherosclerosis in diabetes. PKC deletion or treatment with PKC inhibitors has been studied in the regulation of atherosclerotic plaque formation and evolution. Furthermore, some preclinical and clinical studies have indicated that PKCβ and PKCδ are potential targets for the treatment of diabetic vascular complications. The current review summarizes these multiple signaling pathways and cellular responses regulated by PKC activation and the potential therapeutic targets of PKC in diabetic complications.

Arginase II polymorphisms modify the hypotensive responses to propofol by affecting nitric oxide bioavailability

PURPOSE

Propofol anesthesia is usually accompanied by hypotensive responses, which are at least in part mediated by nitric oxide (NO). Arginase I (ARG1) and arginase II (ARG2) compete with NO synthases for their common substrate L-arginine, therefore influencing the NO formation. We examined here whether ARG1 and ARG2 genotypes and haplotypes affect the changes in blood pressure and NO bioavailability in response to propofol.

METHODS

Venous blood samples were collected from 167 patients at baseline and after 10 min of anesthesia with propofol. Genotypes were determined by polymerase chain reaction. Nitrite concentrations were measured by using an ozone-based chemiluminescence assay, while NO_x (nitrites + nitrates) levels were determined by using the Griess reaction.

RESULTS

We found that patients carrying the AG + GG genotypes for the rs3742879 polymorphism in ARG2 gene and the ARG2 GC haplotype show lower increases in nitrite levels and lower decreases in blood pressure after propofol anesthesia. On the other hand, subjects carrying the variant genotypes for the rs10483801 polymorphism in ARG2 gene show more intense decreases in blood pressure (CA genotype) and/or higher increases in nitrite levels (CA and AA genotypes) in response to propofol.

CONCLUSION

Our results suggest that ARG2 variants affect the hypotensive responses to propofol, possibly by modifying NO bioavailability.

TRIAL REGISTRATION

NCT02442232.

Dietary methionine level alters growth, digestibility, and gene expression of amino acid transporters in meat-type chickens

Imbalance in nutrients can affect digestibility of amino acids by altering gene expression of amino acid transporters. We investigated digestibility and molecular transporters of essential amino acids in chickens fed a methionine-deficient diet. A total of 40 chicks (23 D old) were randomly assigned to either a control (0.49% methionine) or a deficient (0.28%) diet until 41 D when they were sampled for Pectoralis (P.) major, kidney, ileum, and hypothalamus for mRNA expression analysis. The ileal content was collected for apparent ileal digestibility (AID) analysis. Birds fed the deficient diet had reduced growth and worse feed efficiency compared to control. The AID of methionine was similar between both groups. The AID of other essential amino acids was higher in the deficient group than control. mRNA expression of b0,+ AT and LAT4 were upregulated in the ileum and kidney but LAT1 was downregulated only in kidney of the deficient group compared to control. In the P. major, SNAT1, SNAT2, and CAT1 were upregulated in the deficient group compared to control. A diet deficiency in methionine affects digestibility of essential amino acids and cysteine, but not the digestibility of methionine. The change in digestibility is reflected in the mRNA expression of amino acid transporters across different tissues.

Citrulline protects mice from experimental cerebral malaria by ameliorating hypoargininemia, urea cycle changes and vascular leak

Clinical and model studies indicate that low nitric oxide (NO) bioavailability due in part to profound hypoargininemia contributes to cerebral malaria (CM) pathogenesis. Protection against CM pathogenesis may be achieved by altering the diet before infection with Plasmodium falciparum infection (nutraceutical) or by administering adjunctive therapy that decreases CM mortality (adjunctive therapy). This hypothesis was tested by administering citrulline or arginine in experimental CM (eCM). We report that citrulline injected as prophylaxis immediately post infection (PI) protected virtually all mice by ameliorating (i) hypoargininemia, (ii) urea cycle impairment, and (iii) disruption of blood brain barrier. Citrulline prophylaxis inhibited plasma arginase activity. Parasitemia was similar in citrulline- and vehicle control-groups, indicating that protection from pathogenesis was not due to decreased parasitemia. Both citrulline and arginine administered from day 1 PI in the drinking water significantly protected mice from eCM. These observations collectively indicate that increasing dietary citrulline or arginine decreases eCM mortality. Citrulline injected ip on day 4 PI with quinine-injected ip on day 6 PI partially protected mice from eCM; citrulline plus scavenging of superoxide with pegylated superoxide dismutase and pegylated catalase protected all recipients from eCM. These findings indicate that ameliorating hypoargininemia with citrulline plus superoxide scavenging decreases eCM mortality.

Matrine attenuates high-fat diet-induced in vivo and ox-LDL-induced in vitro vascular injury by regulating the PKCα/eNOS and PI3K/Akt/eNOS pathways

Lipid metabolism disorders lead to vascular endothelial injury. Matrine is an alkaloid that has been used to improve obesity and diabetes and for the treatment of hepatitis B. However, its effect on lipid metabolism disorders and vascular injury is unclear. Here, we investigated the effect of matrine on high‐fat diet fed mice and oxidized low‐density lipoprotein (ox‐LDL)‐induced human umbilical vein endothelial cells (HUVECs). Computational virtual docking analyses, phosphoinositide 3‐kinase (PI3K) and protein kinase C‐α (PKCα) inhibitors were used to localize matrine in vascular injuries. The results showed that matrine‐treated mice were more resistant to abnormal lipid metabolism and inflammation than vehicle‐treated mice and exhibited significantly alleviated ox‐LDL‐stimulated dysfunction of HUVECs, restored diminished nitric oxide release, decreased reactive oxygen species generation and increased expression phosphorylation of AKT‐Ser473 and endothelial nitric oxide synthase (eNOS)‐Ser1177. Matrine not only up‐regulates eNOS‐Ser1177 but also down‐regulates eNOS‐Thr495, a PKCα‐controlled negative regulator of eNOS. Using computational virtual docking analyses and biochemical assays, matrine was also shown to influence eNOS/NO via PKCα inhibition. Moreover, the protective effects of matrine were significantly abolished by the simultaneous application of PKCα and the PI3K inhibitor. Matrine may thus be potentially employed as a novel therapeutic strategy against high‐fat diet‐induced vascular injury.

Astragaloside II promotes intestinal epithelial repair by enhancing L-arginine uptake and activating the mTOR pathway

Astragaloside II (AS II) extracted from Astragalus membranaceus has been reported to promote tissue wound repair. However, the effect of AS II on inflammatory bowel disease is unknown. We investigated the effects and mechanism of AS II on intestinal wound healing in both in vitro and in vivo models. Human intestinal Caco-2 cells were treated with multiple concentrations of AS II to assess cell proliferation, scratch wound closure, L-arginine uptake, cationic amino acid transporter activity, and activation of the mTOR signaling pathway. These effects were also measured in a mouse model of colitis. AS II promoted wound closure and increased cell proliferation, L-arginine uptake, CAT1 and CAT2 protein levels, total protein synthesis, and phosphorylation of mTOR, S6K, and 4E-BP1 in Caco-2 cells. These effects were suppressed by lysine or rapamycin treatment, suggesting that the enhanced arginine uptake mediates AS II-induced wound healing. Similar results were also observed in vivo. Our findings indicate that AS II can contribute to epithelial barrier repair following intestinal injury, and may offer a therapeutic avenue in treating irritable bowel disease.

Polydatin Attenuates H2O2-Induced Oxidative Stress via PKC Pathway

Oxidative stress plays an important role in the pathogenesis of endothelial dysfunction, which is found to precede the development of diverse cardiovascular diseases (CVDs). The aim of this study was to observe the protective effects of PD against H₂O₂-induced oxidative stress injury (OSI) in human umbilical vein endothelial cells (HUVECs) and the possible mechanism of PD in OSI treatment. HUVECs were subjected to H₂O₂ in the absence or presence of PD. It turned out that PD improved cell viability and adhesive and migratory abilities, inhibited the release of lactate dehydrogenase (LDH) and reactive oxygen species (ROS), and elevated the content of glutathione peroxidase (GSH-Px) and superoxide dismutase (SOD). TUNEL, fluorometric assays, and Western blotting showed that OSI upregulated the apoptosis ratio, the activity of caspase-3 and the level of proapoptotic protein Bax and decreased the level of antiapoptotic protein Bcl-2. However, PD treatment partially reversed these damage effects and Protein Kinase C (PKC) activation by thymeleatoxin (THX) in turn eliminated the antiapoptotic effect of PD. Furthermore, PD attenuated the H₂O₂-induced phosphorylation of PKCs α and δ and increased the phosphorylation of PKC ε. Our results indicated that PD might exert protective effects against OSI through various interactions with PKC pathway.

Arginase induction and activation during ischemia and reperfusion and functional consequences for the heart

Induction and activation of arginase is among the fastest responses of the heart to ischemic events. Induction of arginase expression and enzyme activation under ischemic conditions shifts arginine consumption from nitric oxide formation (NO) to the formation of ornithine and urea. In the heart such a switch in substrate utilization reduces the impact of the NO/cGMP-pathway on cardiac function that requires intact electromechanical coupling but at the same time it induces ornithine-dependent pathways such as the polyamine metabolism. Both effects significantly reduce the recovery of heart function during reperfusion and thereby limits the success of reperfusion strategies. In this context, changes in arginine consumption trigger cardiac remodeling in an unfavorable way and increases the risk of arrhythmia, specifically in the initial post-ischemic period in which arginase activity is dominating. However, during the entire ischemic period arginase activation might be a meaningful adaptation that is specifically relevant for reperfusion following prolonged ischemic periods. Therefore, a precise understanding about the underlying mechanism that leads to arginase induction as well as of it's mechanistic impact on post-ischemic hearts is required for optimizing reperfusion strategies. In this review we will summarize our current understanding of these processes and give an outlook about possible treatment options for the future.

Gliadin activates arginase pathway in RAW264.7 cells and in human monocytes

Celiac disease (CD) is an autoimmune enteropathy triggered in susceptible individuals by the ingestion of gliadin-containing grains. Recent studies have demonstrated that macrophages play a key role in the pathogenesis of CD through the release of inflammatory mediators such as cytokines and nitric oxide (NO). Since arginine is the obliged substrate of iNOS (inducible nitric oxide synthase), the enzyme that produces large amount of NO, the aim of this work is to investigate arginine metabolic pathways in RAW264.7 murine macrophages after treatment with PT-gliadin (PTG) in the absence and in the presence of IFNγ. Our results demonstrate that, besides strengthening the IFNγ-dependent activation of iNOS, gliadin is also an inducer of arginase, the enzyme that transforms arginine into ornithine and urea. Gliadin treatment increases, indeed, the expression and the activity of arginase, leading to the production of polyamines through the subsequent induction of ornithine decarboxylase. This effect is strengthened by IFNγ. The activation of these pathways takes advantage of the increased availability of arginine due to a decreased system y(+)l-mediated efflux, likely ascribable to a reduced expression of Slc7a6 transporter. A significant induction of arginase expression is also observed in human monocytes from healthy subject upon treatment with gliadin, thus demonstrating that gluten components trigger changes in arginine metabolism in monocyte/macrophage cells.

Contribution of SLC7A1 genetic variant to hypertension, the TAMRISK study

BACKGROUND

The rs41318021 polymorphism in the SLC7A1 gene affects endothelial NO production through changes in L-arginine transport. This variation could thus hypothetically cause dysfunction of endothelium and lead to hypertension. The association of rs41318021 with hypertension was therefore studied in a Finnish cohort.

METHODS

A total of 412 hypertensive cases and 771 non-hypertensive controls from a Finnish 50-year-old cohort were included in this study. The data was collected from the Tampere adult population cardiovascular risk study (TAMRISK). DNA was extracted from buccal swabs and amplified using PCR. A subpopulation of men and women who had available follow-up data of blood pressure measurements at the age of 35-, 40-, 45- and 50 years was also analyzed.

RESULTS

There was no difference between the variant frequencies of the hypertension group and normotensive group at the age of 50 years (p = 0.209). However, repeated measures analysis from the 15-year follow-up showed that subjects having gene variants CT or TT had slightly higher diastolic blood pressure than subjects having genotype CC (p = 0.047). By post-hoc analysis, this was most pronounced at the age of 35 years (p = 0.044).

CONCLUSION

The rs41318021 polymorphism in the SLC7A1 gene was not associated with essential hypertension in 50-year-old subjects. However, a borderline effect of this variation upon diastolic blood pressure was seen in these same subjects in a 15-year follow-up from a 35-year-old cohort to 50 years of age.

Solute carrier protein family may involve in radiation-induced radioresistance of non-small cell lung cancer

PURPOSE

To find new signaling pathways that may be involved in the cellular response to ionizing radiation.

METHODS

Two radioresistant subclones (A549/R and SPCA1/R) derived from lung adenocarcinoma cell lines A549 and SPCA1 were established after eight rounds of sublethal irradiation. The new subclones were tested for radioresistant features using clonogenic assay and apoptosis analysis. The genes expressed differentially were screened with cDNA microarray analysis consisting of 48,000 transcript probes and confirmed by quantitative real-time PCR.

RESULTS

Stable and significant radioresistance was observed in the screened subclones. The microarray analysis showed 65 genes were up-regulated and 141 genes down-regulated in SPCA1/R cells. The up-regulated and down-regulated genes were 708 and 230 in A549/R cells, respectively. Twenty-seven altered genes were consistent in both subclones. Interestingly, members the of human solute carrier (SLC) gene superfamily were among in 27 genes.

CONCLUSIONS

The differentially expressed genes in both cell lines may contribute to their radioresistant phenotype. This extensive list of genes identified in the experiment provides a large body of potentially valuable information for studying the molecular mechanism(s) of radiosensitivity and identification of candidate molecular markers of radiation sensitivity. Thus, to our knowledge, the SLC gene superfamily is the first being reported to involve in acquired radioresistance.