Effect of chronic elevated asymmetric dimethylarginine (ADMA) levels on granulopoiesis

Forskolin attenuates doxorubicin-induced accumulation of asymmetric dimethylarginine and s-adenosylhomocysteine via methyltransferase activity in leukemic monocytes

Doxorubicin (DOX) is an antitumor drug, associated with cardiomyopathy. Strategies to address DOX-cardiomyopathy are scarce. Here, we identify the effect of forskolin (FSK) on DOX-induced-asymmetric-dimethylarginine (ADMA) accumulation in monocytoid cells. DOX-challenge led to i) augmented cytotoxicity, reactive-oxygen-species (ROS) production and methyltransferase-enzyme-activity identified as ADMA and s-adenosylhomocysteine (SAH) accumulation (SAH-A). However, except cytotoxicity, other DOX effects were decreased by metformin and FSK. FSK, did not alter the DOX-induced cytotoxic effect, but, decreased SAH-A by >50% and a combination of three drugs restored physiological methyltransferase-enzyme-activity. Together, protective effect of FSK against DOX-induced SAH-A is associated with mitigated methyltransferase-activity, a one-of-a-kind report.

Immune function? A missing link in the gender disparity in preterm neonatal outcomes

INTRODUCTION

In neonatology, males exhibit a more severe disease course and poorer prognosis in many pathological states when compared to females. Perinatal brain injury, respiratory morbidity, and sepsis, among other complications, preferentially affect males. Preterm neonates (born <37 weeks gestation) display a particularly marked sexual disparity in pathology, especially at the borders of viability. The sex biases in preterm neonatal outcomes and underlying multifactorial mechanisms have been incompletely explored. Sex-specific clinical phenomena may be partially explained by intrinsic differences in immune function. The distinct immune system of preterm neonates renders this patient population vulnerable, and it is increasingly important to consider biological sex in disease processes and to strive for improved outcomes for both sexes. Areas covered: We discuss the cellular responses and molecular intermediates in immune function which are strongly dependent on sex-specific factors such as the genetic and hormonal milieu of premature birth and consider novel findings in a clinical context. Expert commentary: The role of immune function in the manifestation of sex-specific disease manifestations and outcomes in preterm neonates is a critical prognostic variable. Further mechanistic elucidation will yield valuable translational and clinical information of disease processes in preterm neonates which may be harnessed for modulation.

Increased plasma asymmetric dimethylarginine is associated with cognitive deficits in patients with schizophrenia

Cognitive deficits are a core feature of schizophrenia. Previous studies have shown that plasma asymmetric dimethylarginine (ADMA), an endogenous inhibitor of the nitric oxide synthase, was increased in patients with schizophrenia. This study aimed to investigate the association of ADMA with cognitive deficits in schizophrenia. Forty-seven patients with schizophrenia and 45 healthy control subjects were recruited in present study. Cognitive function was assessed with a neuropsychological battery including 7 neurocognitive tests. Schizophrenic symptoms were assessed using the Positive and Negative Syndrome Scale and plasma ADMA concentration was measured by HPLC. We found that patients with schizophrenia exhibited poorer performances in nearly all of the cognitive tests except for the visual memory index compared with healthy controls. Plasma ADMA levels were significantly increased in patients with schizophrenia when compared to normal controls, and the mean ADMA concentration in patients with multiple episode schizophrenia was much higher than that of patients with first episode schizophrenia. For the patients, ADMA was negatively associated with attention, working memory and executive function in schizophrenia. These results suggest that ADMA may be involved in the pathophysiology of schizophrenia-associated cognitive impairments, and plasma ADMA could be a peripheral biomarker for evaluation of cognitive function in schizophrenia.

Pharmacological inhibition of DDAH1 improves survival, haemodynamics and organ function in experimental septic shock

The aim of the present study was to investigate the therapeutic effects of pharmacological inhibition of DDAH1 (dimethylarginine dimethylaminohydrolase 1), an enzyme that metabolizes endogenously produced nitric oxide synthase inhibitors, principally ADMA (asymmetric dimethylarginine). The present study employs a series of rodent models to evaluate the effectiveness a DDAH1-selective inhibitor (L-257). Short-term models involved the development of endotoxaemia using lipopolysaccharide and long-term models involved the intraperitoneal administration of faecal slurry. In order to generate the most relevant model possible, following induction of severe sepsis, animals received appropriate fluid resuscitation and in some models vasopressor therapy. The effects of L-257 on survival, haemodynamics and organ function were subsequently assessed. Survival was significantly longer in all L-257 treatment groups (P<0.01) and no adverse effects on haemodynamics and organ function were observed following L-257 administration to either animals with sepsis or naïve animals. Haemodynamic performance was preserved and the noradrenaline dose required to maintain target blood pressure was reduced in the treated animals (P<0.01). Animals receiving L-257 had significantly increased plasma ADMA concentrations. Plasma nitrite/nitrate was reduced as was severity of sepsis-associated renal dysfunction. The degree of tachycardia was improved as were indices of tissue and microvascular perfusion. The results of the present study show that the selective DDAH-1 inhibitor L-257 improved haemodynamics, provided catecholamine sparing and prolonged survival in experimental sepsis. Further studies will determine its potential utility in human septic shock.

Roles of the Oxidative Stress and ADMA in the Development of Deep Venous Thrombosis

Venous thromboembolism has multifactorial origin and occurs in the context of complex interactions between environmental and genetic predisposing factors. Oxidative stress plays an important role in the physiopathology of venous thrombosis. Current study examined the role of oxidative stress and asymmetric dimethylarginine in the development of DVT with the parameters such as serum malondialdehyde (MDA), glutathione peroxidase (GSH-Px), catalase, ADMA, homocysteine, folic acid, vitamin B₆, and vitamin B₁₂ levels. Serum MDA levels were found significantly (P < 0.005) high in patients with DVT compared with control group. Additionally, serum B₆ levels were found significantly (P < 0.009) low in patients with DVT compared with healthy volunteers. There were no significant differences between the groups in terms of the other parameters (P > 0.05). This study showed that patients with DVT have increased oxidative stress compared with the healthy volunteers whereas there was no significant difference between the groups in terms of serum ADMA levels. Thus serum ADMA levels seemed to be not related with development of DVT.

Biological functional relevance of asymmetric dimethylarginine (ADMA) in cardiovascular disease

There is growing evidence that increased levels of the endogenous NO synthase inhibitor asymmetric dimethylarginine (ADMA) may contribute to endothelial dysfunction. Studies in animal models as well as in humans have suggested that the increase in ADMA occurs at a time when vascular disease has not yet become clinically evident. ADMA competitively inhibits NO elaboration by displacing L-arginine from NO synthase. In a concentration-dependent manner, it thereby interferes not only with endothelium-dependent, NO-mediated vasodilation, but also with other biological functions exerted by NO. The upshot may be a pro-atherogenic state. Recently, several studies have investigated the effect of various therapeutical interventions on ADMA plasma concentrations.