Veena S. Rao

Procoagulant proteins from snake venoms.

Several procoagulant proteins from snake venoms have been isolated and characterized. They are either serine proteinases or metalloproteinases, which activate specific zymogens of coagulation factors and initiate the coagulation cascade. These procoagulant proteins are useful in treating various thrombotic and hemostatic conditions and contribute to our understanding of molecular details in the activation of specific coagulation factors. Recent studies have shown that the prothrombin activators with serine proteinase activity are structurally and functionally similar to mammalian coagulation factors. Their structural studies should provide us insight into prothrombinase complex formation. Here, we present an overview of snake venom procoagulant factors.

Friend Turns Foe: Transformation of Anti-Inflammatory HDL to Proinflammatory HDL during Acute-Phase Response

High-density lipoprotein (HDL) is a major carrier of cholesterol in the blood. Unlike other lipoproteins, physiological functions of HDL influence the cardiovascular system in favorable ways except when HDL is modified pathologically. The cardioprotective mechanism of HDL is mainly based on reverse cholesterol transport, but there has been an emerging interest in the anti-inflammatory and antioxidant roles of HDL. These latter activities of HDL are compromised in many pathological states associated with inflammation. Further, abnormal HDL can become proinflammatory contributing to oxidative damage. In this paper, we discuss the functional heterogeneity of HDL, how alterations in these particles in inflammatory states result in loss of both antioxidant activity and reverse cholesterol transport in relation to atherosclerosis, and the need for assays to predict its functionality.

Polymorphisms in the IL6 gene in Asian Indian families with premature coronary artery disease – The Indian Atherosclerosis Research Study

Inflammation plays a major role in coronary artery disease (CAD). We investigated the polymorphisms in the interleukin 6 (IL6) gene and their effect on the expression of acute-phase proteins in premature CAD in Asian Indian families. One hundred and ninety affected sibling pairs (ASPs) were genotyped for three tag single nucleotide polymorphisms (SNPs) in the IL6 gene for linkage analysis. We observed suggestive logarithm of odds (LOD) score for one SNP (rs2066992) in a subset of 62 ASPs with the age at onset less than 45 years (LOD score=1.114, p=0.011 in linkage analysis; pi=0.55, p=0.008 in identity by descent; LOD score=1.06, p=0.014 in quantitative trait locus for plasma levels of high sensitivity C-reactive protein, hsCRP). This was followed by sequencing of the promoter region and haplotype analysis in 46 probands and 40 controls. Five out of the eight previously reported promoter SNPs were found to be polymorphic (rs1800797, rs1800796, rs7802307, rs7802308, rs1800795). Two novel sequence variants were also found. One promoter haplotype (GGAAG) was detected with an odds ratio (OR) of 3.676 (p=0.0017, 95% confidence interval [CI]: 1.68-8.045) and population attributable risk of 21.1% (95%CI: 9.2%-31.5%). The plasma levels of both hsCRP and fibrinogen exhibited significant association with these promoter SNP genotypes (p<0.001). In conclusion, IL6 gene polymorphisms appear to be important genetic factors in premature CAD, and in the regulation of key atherogenic markers in Asian Indian families.

Group D prothrombin activators from snake venom are structural homologues of mammalian blood coagulation factor Xa.

Procoagulant venoms of several Australian elapids contain proteinases that specifically activate prothrombin; among these, Group D activators are functionally similar to coagulation factor Xa (FXa). Structural information on this class of prothrombin activators will contribute significantly towards understanding the mechanism of FXa-mediated prothrombin activation. Here we present the purification of Group D prothrombin activators from three Australian snake venoms (Hoplocephalus stephensi, Notechis scutatus scutatus and Notechis ater niger) using a single-step method, and their N-terminal sequences. The N-terminal sequence of the heavy chain of hopsarin D (H. stephensi) revealed that a fully conserved Cys-7 was substituted with a Ser residue. We therefore determined the complete amino acid sequence of hopsarin D. Hopsarin D shows approximately 70% similarity with FXa and approximately 98% similarity with trocarin D, a Group D prothrombin activator from Tropidechis carinatus. It possesses the characteristic Gla domain, two epidermal growth factor-like domains and a serine proteinase domain. All residues important for catalysis are conserved, as are most regions involved in interactions with factor Va and prothrombin. However, there are some structural differences. Unlike FXa, hopsarin D is glycosylated in both its chains: in light-chain residue 52 and heavy-chain residue 45. The glycosylation on the heavy chain is a large carbohydrate moiety adjacent to the active-site pocket. Overall, hopsarin D is structurally and functionally similar to mammalian coagulation FXa.

Genetic studies on the APOA1-C3-A5 gene cluster in Asian Indians with premature coronary artery disease

BackgroundThe APOA1-C3-A5 gene cluster plays an important role in the regulation of lipids. Asian Indians have an increased tendency for abnormal lipid levels and high risk of Coronary Artery Disease (CAD). Therefore, the present study aimed to elucidate the relationship of four single nucleotide polymorphisms (SNPs) in the Apo11q cluster, namely the -75G>A, +83C>T SNPs in the APOA1 gene, the Sac1 SNP in the APOC3 gene and the S19W variant in the APOA5 gene to plasma lipids and CAD in 190 affected sibling pairs (ASPs) belonging to Asian Indian families with a strong CAD history.Methods & resultsGenotyping and lipid assays were carried out using standard protocols. Plasma lipids showed a strong heritability (h2 48% – 70%; P < 0.0001). A subset of 77 ASPs with positive sign of Logarithm of Odds (LOD) score showed significant linkage to CAD trait by multi-point analysis (LOD score 7.42, P < 0.001) and to Sac1 (LOD score 4.49) and -75G>A (LOD score 2.77) SNPs by single-point analysis (P < 0.001). There was significant proportion of mean allele sharing (pi) for the Sac1 (pi 0.59), -75G>A (pi 0.56) and +83C>T (pi 0.52) (P < 0.001) SNPs, respectively. QTL analysis showed suggestive evidence of linkage of the Sac1 SNP to Total Cholesterol (TC), High Density Lipoprotein-cholesterol (HDL-C) and Apolipoprotein B (ApoB) with LOD scores of 1.42, 1.72 and 1.19, respectively (P < 0.01). The Sac1 and -75G>A SNPs along with hypertension showed maximized correlations with TC, TG and Apo B by association analysis.ConclusionThe APOC3-Sac1 SNP is an important genetic variant that is associated with CAD through its interaction with plasma lipids and other standard risk factors among Asian Indians.

The catalytic subunit of pseutarin C, a group C prothrombin activator from the venom of Pseudonaja textilis, is structurally similar to mammalian blood coagulation factor Xa.

Pseutarin C, a group C prothrombin activator from Pseudonaja textilis venom, is a large protein complex consisting of catalytic and nonenzymatic subunits, which are functionally similar to the mammalian FXa-FVa complex. Here, we present the complete cDNA sequence of the catalytic subunit of pseutarin C. The cDNA of the catalytic subunit encodes a protein of 449 amino acids, which includes a 22-residue signal peptide, 18-residue propeptide and a mature protein of 409 amino acids. The deduced amino acid sequence shows 74-83% identity to group D prothrombin activators from snake venom and approximately 42% identity to mammalian FX and has identical domain structure. The precursor of the catalytic subunit of pseutarin C has several unique features. The activation peptide of the catalytic subunit of pseutarin C is significantly smaller (27 as compared to 52 residues in mammalian FX) and does not contain any glycosylation sites. Unlike coagulation FXa, Ser52 and Asn45 of the light and heavy chains are O- and N-glycosylated in pseutarin C catalytic sub-unit. There is a 12-residue insertion in pseutarin C catalytic sub-unit close to the region that is implicated in binding to FVa. This is the first sequence of the catalytic subunit of a group C prothrombin activator.

A common variant in chromosome 9p21 associated with coronary artery disease in Asian Indians.

Table 3. Analysis of variance of the plasma lipid biomarkers and rs10757278 SNP. AA AG GG Plasma lipid Mean ± s.e. [mg/dl] Mean ± s.e. [mg/dl] Mean ± s.e. [mg/dl] P value Total cholesterol 5.09 ± 0.05 (164.02) 5.11 ± 0.02 (165.67) 5.13 ± 0.03 (169.02) 0.828 Triglycerides 4.75 ± 0.09 (115.58) 4.89 ± 0.04 (132.95) 4.93 ± 0.06 (138.38) 0.261 HDL cholesterol 3.7 ± 0.04 (40.45) 3.7 ± 0.02 (40.45) 3.78 ± 0.03 (43.82) 0.085 LDL cholesterol 4.55 ± 0.07 (94.63) 4.53 ± 0.03 (92.76) 4.51 ± 0.05 (90.92) 0.888

Role of vitamin D levels and vitamin D receptor polymorphisms in relation to coronary artery disease: the Indian atherosclerosis research study.

ObjectiveAssessment of association between plasma vitamin D levels, vitamin D receptor (VDR) gene polymorphisms, and coronary artery disease (CAD) in a predisposed Asian Indian cohort. Materials and methodsPatients with angiographically proven CAD having age at onset less than 60 years for men and less than 65 years for women were recruited in the Indian Atherosclerosis Research Study and treated as cases (N=287), whereas asymptomatic healthy matched individuals were enrolled from the population, who showed normal electrocardiogram and acted as controls (N=241). Plasma [vitamin D (25-hydroxy vitamin D)] levels were measured by enzyme-linked immunosorbent assay, and five haplotype-tagging single nucleotide polymorphisms were genotyped by ABI Taqman assays. ResultsMean vitamin D levels were significantly lower in patients with CAD (10.59 ng/ml) than in controls (11.82 ng/ml) (P=0.036). Vitamin D showed protective association against CAD (odds ratio: 0.54, 95% confidence interval: 0.34–0.84, P=0.007) after adjusting for conventional risk factors. Patients in the first vitamin D quartile showed 2.54 times greater risk for CAD than those in the fourth quartile. There was no significant association of VDR single nucleotide polymorphisms/haplotypes with either vitamin D or CAD. Vitamin D levels were significantly lower in vegetarians than in nonvegetarians (P=0.048) and showed inverse association with body weight (P=0.054), triglyceride (P=0.031), and body mass index (P=0.020). ConclusionLow vitamin D level was associated with an enhanced risk for incident CAD. VDR genotypes did not show any association with either vitamin D levels or CAD.

Association of Inflammatory and Oxidative Stress Markers with Metabolic Syndrome in Asian Indians in India

Metabolic syndrome (MetS) is a primary risk factor for cardiovascular disease and is associated with a proinflammatory state. Here, we assessed the contribution of inflammatory and oxidative stress markers towards prediction of MetS. A total of 2316 individuals were recruited in Phase I of the Indian Atherosclerosis Research Study (IARS). Modified ATPIII guidelines were used for classification of subjects with MetS. Among the inflammatory and oxidative stress markers studied, levels of hsCRP (P < .0001), Neopterin (P = .036), and oxLDL (P < .0001) were significantly higher among subjects with MetS. Among the markers we tested, oxLDL stood out as a robust predictor of MetS in the IARS population (OR 4.956 95% CI 2.504–9.810; P < .0001) followed by hsCRP (OR 1.324 95% CI 1.070–1.638; P = .010). In conclusion, oxLDL is a candidate predictor for MetS in the Asian Indian population.

Usefulness of C-Reactive Protein as a Marker for Prediction of Future Coronary Events in the Asian Indian Population: Indian Atherosclerosis Research Study

Inflammation plays a pivotal role in all stages of atherosclerosis. Numerous inflammatory, lipid, and cytokines markers have been associated with coronary artery disease (CAD) risk but data directly comparing their predictive value are limited. Studies were carried to elucidate the role of high-sensitivity C-reactive protein (hsCRP), other inflammatory as well as lipid markers and their associations. Among 1021 subjects, comprising 774 CAD affected members from Indian Atherosclerosis Research Study (IARS), plasma hsCRP levels showed strong correlation with inflammatory markers, namely, IL6 (r = .373; P = <.0001), sPLA2 (r = .544; P = <.0001) as also with fibrinogen (r = .579; P = <.0001). Levels of hsCRP were higher among subjects affected by CAD who suffered a repeat coronary event as compared to those who remained event free and subjects in the top quartile of hsCRP (>3.58 mg/L) were found to have a fourfold higher risk. In conclusion, hsCRP appears to be an independent predictor of recurrent CAD events in Asian Indian population.