Sequence Variation in the DDAH1 Gene Predisposes for Delayed Cerebral Ischemia in Subarachnoidal Hemorrhage

A Review of Genetic Polymorphisms and Susceptibilities to Complications after Aneurysmal Subarachnoid Hemorrhage

Delayed cerebral ischemia (DCI) and vasospasm are two complications of subarachnoid hemorrhages (SAHs) which entail high risks of morbidity and mortality. However, it is unknown why only some patients who suffer SAHs will experience DCI and vasospasm. The purpose of this review is to describe the main genetic single nucleotide polymorphisms (SNPs) that have demonstrated a relationship with these complications. The SNP of the nitric oxide endothelial synthase (eNOS) has been related to the size and rupture of an aneurysm, as well as to DCI, vasospasm, and poor neurological outcome. The SNPs responsible for the asymmetric dimetilarginine and the high-mobility group box 1 have also been associated with DCI. An association between vasospasm and the SNPs of the eNOS, the haptoglobin, and the endothelin-1 receptor has been found. The SNPs of the angiotensin-converting enzyme have been related to DCI and poor neurological outcome. Studies on the SNPs of the Ryanodine Receptor yielded varying results regarding their association with vasospasm.

LC-MS/MS combined with blood-brain dual channel microdialysis for simultaneous determination of active components of astragali radix-safflower combination and neurotransmitters in rats with cerebral ischemia reperfusion injury: Application in pharmacokinetic and pharmacodynamic study

BACKGROUND

Astragali Radix-Safflower combination (ARSC) is widely utilized in clinic to treat cerebral ischemia/reperfusion injury (CI/RI). Whereas, there is no in-depth research of the pharmacokinetics (PK) and pharmacodynamics (PD) analysis of ARSC after intragastric administration in rats with CI/RI.

PURPOSE

The purpose of this research is to investigate the PK characteristics of eight active ingredients (astragaloside IV, calycosin, calycosin-7-O-β-glucoside, formononetin, ononin, hydroxysafflor yellow A, syringin and vernine) of ARSC, and the regulation of neurotransmitters disorders, revealing the pharmacodynamic substance basis and the mechanism of ARSC in treating CI/RI from the molecular level.

METHODS

We established a new method which based on blood-brain dual channel microdialysis (MD) coupled with liquid chromatography-tandem mass spectrometry (LC-MS/MS) to continuously gather, and determine the components of ARSC and neurotransmitters related to CI/RI in vivo. The collected data were analyzed by sigmoid-E_max function. The neurotransmitters primarily regulated in CI/RI rat were discussed by principal component analysis and the compound most associated with total pharmacodynamics was chosen by partial least squares regression.

RESULTS

The validated LC-MS/MS method had specificity and selectivity to simultaneously analyze the concentration of eight active components of ARSC extract and five neurotransmitters of CI/RI rats. The recovery rates of brain MD probe and blood MD probe were stable within six hours. The MD probes recovery rates decreased with the increase of flow rates, but the solution concentration had little effect on the probes recovery rates. It was feasible to correct the recovery rates of probes in vivo by using reverse dialysis method. All eight active ingredients of ARSC could pass across the blood brain barrier after CI/RI. ARSC regulated the release of glutamate (Glu), γ-aminobutyric acid (GABA), dopamine (DA), 5-hydroxytryptamine (5-HT) and aspartic acid (Asp). Notably, astragaloside IV and hydroxysafflor yellow A might have better regulatory effect on neurotransmitters in comparison with other six measured components of ARSC, and Glu was the neurotransmitter mainly regulated in CI/RI rats.

CONCLUSION

The ARSC was able to treat CI/RI through ameliorating neurotransmitters disorders. There was a hysteresis between the peaked drug concentration and maximum therapeutic effect of ARSC. The drug effective concentrations range of ASIV, calycosin, calycosin-7-O-β-glucoside, syringin and vernine in blood microdialysate and calycosin, syringin, vernine in brain microdialysate were narrow, which need be paid attention in clinical use.

Divergent Dimethylarginine Dimethylaminohydrolase Isoenzyme Expression in the Central Nervous System

The endogenous methylated derivative of ʟ-arginine, Nω,Nω'-dimethyl-ʟ-arginine (asymmetric dimethylarginine, ADMA), an independent risk factor in many diseases, inhibits the activity of nitric oxide synthases and, consequently, modulates the availability of nitric oxide. While most studies on the biological role of ADMA have focused on endothelial and inducible nitric oxide synthases modulation and its contribution to cardiovascular, metabolic, and renal diseases, a role in regulating neuronal nitric oxide synthases and pathologies of the central nervous system is less understood. The two isoforms of dimethylarginine dimethylaminohydrolase (DDAH), DDAH1 and DDAH2, are thought to be the main enzymes responsible for ADMA catabolism. A current impediment is limited knowledge on specific tissue and cellular distribution of DDAH enzymes within the brain. In this study, we provide a detailed characterization of the regional and cellular distribution of DDAH1 and DDAH2 proteins in the adult murine and human brain. Immunohistochemical analysis showed a wide distribution of DDAH1, mapping to multiple cell types, while DDAH2 was detected in a limited number of brain regions and exclusively in neurons. Our results provide key information for the investigation of the pathophysiological roles of the ADMA/DDAH system in neuropsychiatric diseases and pave the way for the development of novel selective therapeutic approaches.

The role of L-arginine metabolism in neurocritical care patients

Nitric oxide is an important mediator of vascular autoregulation and is involved in pathophysiological changes after acute neurological disorders. Nitric oxide is generated by nitric oxide synthases from the amino acid L-arginine. L-arginine can also serve as a substrate for arginases or lead to the generation of dimethylarginines, asymmetric dimethylarginine, and symmetric dimethylarginine, by methylation. Asymmetric dimethylarginine is an endogenous inhibitor of nitric oxide synthase and can lead to endothelial dysfunction. This review discusses the role of L-arginine metabolism in patients suffering from acute and critical neurological disorders often requiring neuro-intensive care treatment. Conditions addressed in this review include intracerebral hemorrhage, aneurysmal subarachnoid hemorrhage, and traumatic brain injury. Recent therapeutic advances in the field are described including current randomized controlled trials for traumatic brain injuries and hemorrhagic stroke.

Love is in the hair: arginine methylation of human hair proteins as novel cardiovascular biomarkers

Cardiovascular disease is the major cause of death worldwide. Extensive cardiovascular biomarkers are available using blood tests but very few, if any, investigations have described non-invasive tests for cardiovascular biomarkers based on readily available hair samples. Here we show, first, that human hair proteins are post-translationally modified by arginine methylation (ArgMe). Using western blot, proteomic data mining and mass spectrometry, we identify several ArgMe events in hair proteins and we show that keratin-83 is extensively modified by ArgMe in the human hair. Second, using a preliminary cohort (n = 18) of heterogenous healthy donors, we show that the levels of protein ArgMe in hair correlate with serum concentrations of a well-established cardiovascular biomarker, asymmetric dimethylarginine (ADMA). Compared to blood collection, hair sampling is cheaper, simpler, requires minimal training and carries less health and safety and ethical risks. For these reasons, developing the potential of hair protein ArgMe as clinically useful cardiovascular biomarkers through further research could be useful in future prevention and diagnosis of cardiovascular disease.

Association of Variability in the DDAH1, DDAH2, AGXT2 and PRMT1 Genes with Circulating ADMA Concentration in Human Whole Blood

Asymmetric dimethylarginine is an endogenous inhibitor of nitric oxide synthesis and a cardiovascular risk factor. Its regulation has been studied extensively in experimental models, but less in humans. We studied common single-nucleotide polymorphisms (SNPs) in genes encoding for enzymes involved in ADMA biosynthesis and metabolism, i.e., PRMT1, DDAH1, DDAH2, and AGXT2, and assessed their associations with blood ADMA concentration in 377 unselected humans. The minor allele of DDAH1 SNP rs233112 was significantly more frequent in individuals with ADMA in the highest tertile or in the highest quartile, as was the major allele of DDAH2 rs805304. A combined genotype comprising both SNPs showed a significant genotype–phenotype association, with increasing ADMA concentration by an increasing number of inactive alleles. SNPs in the AGXT2 and PRMT1 genes showed no significant associations with blood ADMA concentration. Our study provides comprehensive evidence that DDAH1 and DDAH2 are the major enzymes regulating blood ADMA concentration, whilst PRMT1 indirectly affects ADMA, and AGXT2 may act as a back-up enzyme in ADMA metabolism under pathophysiological conditions only.