Translational pharmacogenomics: a study of warfarin dosing

2014 - 2015Warfarin is one of the most commonly used oral anticoagulants worldwide and is highly efficacious for the treatment and prevention of thromboembolic disorders. However, due to its narrow therapeutic index, large inter-individual variability in dose requirements, and extensive drug and food interactions, warfarin remains a challenging drug to prescribe. Genetic factors (CYP2C9 and VKORC1), together with clinical factors (age and body weight), account for up to 60% of warfarin dose variance, whereas ~40% variability remains poorly understood. Several warfarin dosing algorithms, comprising genetic and non-genetic covariates have been published over the years. However, none of the published algorithms included patients from Southern Italy. We therefore conducted a candidate-gene study to develop an algorithm for predicting warfarin maintenance dose in patients from the Campania Region (n=266) in Southern Italy. Our pharmacogenetic dosing algorithm consisted of six variables (age, body surface area, amiodarone intake, CYP2C9*2, CYP2C9*3, and VKORC1 -1639G>A). It led to the accurate prediction of warfarin maintenance dose in 44% of patients (mean absolute error 7.41 mg/week). The prediction accuracy of the pharmacogenetic algorithm was superior to three previously published pharmacogenetic algorithms derived from patients in Northern and Central Italy. Given that previous studies suggested a role for miR-133a in warfarin response, we conducted a pilot study comparing baseline serum levels of miRNA in patients who achieved warfarin stable dose (n=10) to those who did not achieve warfarin stability (n=10), using the Affymetrix miRNA array. No association was found between miRNA-133a and warfarin response. Interestingly, circulating levels of miR-548a-3p were observed to be higher in patients who did not achieve warfarin stability (P=0.0053, fold change =1.66) compared to patients who achieved stable dose. In silico analyses showed that several target genes of miR-548a-3p are involved in the coagulation pathway. Work is currently underway to validate and replicate these findings in a larger cohort of prospectively recruited patients initiated onto warfarin therapy (n=980) using TaqMan miRNA real-time quantitative PCR. Pharmacogenetic algorithms have shown that common variants in CYP2C9 and VKORC1 genes cannot fully explain the extreme dose requirements in individuals sensitive and resistant to warfarin. To investigate the role of other genetic variants in these patients with extreme phenotypes, we performed a genome-wide association study (GWAS) comprising of warfarin sensitive patients (≤1.5 mg/day, n=55), warfarin resistant patients (≥10 mg/day, n=51), and healthy controls from the National Blood Service (NBS, n=2,501). Our results suggested that an intergenic variant on chromosome 10, rs4918797, could be involved in warfarin sensitivity. Intronic SNPs in MIR6873 on chromosome 6 (rs114213056) and PIGN on chromosome 18 (rs10163900, rs76455916, rs77118150, and rs79434376) showed suggestive association with warfarin resistance. The findings of this thesis showed that a multitude of factors affect warfarin dosing, some of which still need further investigations. Insights of the roles of other factors such as non-coding RNA and rare genetic variants will hopefully improve dose prediction and drug efficacy and ultimately patient outcomes. The work being undertaken with warfarin acts as a pathfinder project, the concepts from which could be applied to other drugs with variable dose requirement. [edited by author]XIV n.s

Exercise training in aging and diseases

Sedentary lifestyle along with high blood pressure, abnormal values for blood lipids, smoking, and obesity are recognized risk factors for cardiovascular diseases and for many other chronic diseases, such as diabetes, osteoporosis, breast and colon cancer. Several studies conducted on large cohort of individuals have documented the protective effects of physical activity for both vascular and nonvascular syndromes. Exercise training is an integral part of cardiac rehabilitation, a complex therapeutic approach, effective both in young and elderly patients. Despite the number of evidences underling the benefits associated with physical fitness, the cardiac rehabilitation is still an underused medical resource. The molecular mechanism behind physical activity protective effect is presently unresolved, and further studies are also needed to establish the best protocol in terms of specificity, volume and duration of the training

Adrenoreceptors and nitric oxide in the cardiovascular system

Nitric Oxide (NO) is a small molecule that continues to attract much attention from the scientific community. Since its discovery, it has been evident that NO has a crucial role in the modulation of vascular tone. Moreover, NO is involved in multiple signal transduction pathways thus contributing to the regulation of many cellular functions. NO effects can be either dependent or independent on cGMP, and rely also upon several mechanisms such as the amount of NO, the compartmentalization of the enzymes responsible for its biosynthesis (NOS), and the local redox conditions. Several evidences highlighted the correlation among adrenoreceptors activity, vascular redox status and NO bioavailability. It was suggested a possible crosstalk between NO and oxidative stress hallmarks in the endothelium function and adaptation, and in sympathetic vasoconstriction control. Adrenergic vasoconstriction is a balance between a direct vasoconstrictive effect on smooth muscle and an indirect vasorelaxant action caused by α(2)- and β-adrenergic endothelial receptor-triggered NO release. An increased oxidative stress and a reduction of NO bioavailability shifts this equilibrium causing the enhanced vascular adrenergic responsiveness observed in hypertension. The activity of NOS contributes to manage the adrenergic pathway, thus supporting the idea that the endothelium might control or facilitate β-adrenergic effects on the vessels and the polymorphic variants in β(2)-receptors and NOS isoforms could influence aging, some pathological conditions and individual responses to drugs. This seems to be dependent, almost in part, on differences in the control of vascular tone exerted by NO. Given its involvement in such important mechanisms, the NO pathway is implicated in aging process and in both cardiovascular and non-cardiovascular conditions. Thus, it is essential to pinpoint NO involvement in the regulation of vascular tone for the effective clinical/therapeutic management of cardiovascular diseases (CVD)

[Sulphureous mud-bath therapy and changes in blood pressure: observational investigation]

The chronic arthropathies currently appear to be a major cause of disability with a negative impact on quality of life and health care spending. The mud-bath therapy is a spa treatment that induces benefic effects in chronic rheumatic diseases. It has long been debated on the assumption that the mud-bath spa therapy could have adverse cardiovascular effects which often induce caution and even a contraindication to the use of this treatment in chronic arthropathies associated with cardiovascular alterations such as hypertension. The aim of this observational study was to investigate, in arthrorheumatic subjects, the effects of sulphureous mud-bath cycle on blood pressure and the possible appearance of adverse drug reaction

Aging-related changes in oxidative stress response of human endothelial cells

BACKGROUND: Oxidative stress is strongly associated with aging and age-related diseases and plays a crucial role in endothelial dysfunction development. AIM: To better understand the molecular mechanisms of aging and stress response in humans, we examined changes to young and older human endothelial cells over time (72, 96 and 120 h), before and after H2O2-induced stress. METHODS: We measured the expression of the deacetylase Sirtuin 1 (Sirt1) and its transcriptional target Forkhead box O3a (Foxo3a); TBARS, a well-known marker of overall oxidative stress, and catalase activity as index of antioxidation. Moreover, we quantified levels of cellular senescence by senescence-associated β galactosidase (SA-βgal) assay. RESULTS: Under oxidative stress induction older cells showed a progressive decrease of Sirt1 and Foxo3a expression, persistently high TBARS levels with high, but ineffective Cat activity to counteract such levels. In addition cellular senescence drastically increased in older cells compared with Young cells both in presence and in the absence of oxidative stress. DISCUSSION: By following the cell behavior during the time course, we can hypothesize that while in young cells an oxidative stress induction stimulated an adequate response through activation of molecular factor crucial to counteract oxidative stress, the older cells are not able to adequately adapt themselves to external stress stimuli. CONCLUSIONS: During their life, endothelial cells impair the ability to defend themselves from oxidative stress stimuli. This dysfunction involves the pathway of Sirt1 a critical regulator of oxidative stress response and cellular lifespan, underlining its crucial role in endothelial homeostasis control during aging and age-associated diseases

Adrenergic signaling and oxidative stress: a role for sirtuins?

The adrenergic system plays a central role in stress signaling and stress is often associated with increased production of ROS. However, ROS overproduction generates oxidative stress, that occurs in response to several stressors. β-adrenergic signaling is markedly attenuated in conditions such as heart failure, with downregulation and desensitization of the receptors and their uncoupling from adenylyl cyclase. Transgenic activation of β2-adrenoceptor leads to elevation of NADPH oxidase activity, with greater ROS production and p38MAPK phosphorylation. Inhibition of NADPH oxidase or ROS significantly reduced the p38MAPK signaling cascade. Chronic β2-adrenoceptor activation is associated with greater cardiac dilatation and dysfunction, augmented pro-inflammatory and profibrotic signaling, while antioxidant treatment protected hearts against these abnormalities, indicating ROS production to be central to the detrimental signaling of β2-adrenoceptors. It has been demonstrated that sirtuins are involved in modulating the cellular stress response directly by deacetylation of some factors. Sirt1 increases cellular stress resistance, by an increased insulin sensitivity, a decreased circulating free fatty acids and insulin-like growth factor (IGF-1), an increased activity of AMPK, increased activity of PGC-1a, and increased mitochondrial number. Sirt1 acts by involving signaling molecules such P-I-3-kinase-Akt, MAPK and p38-MAPK-β. βAR stimulation antagonizes the protective effect of the AKT pathway through inhibiting induction of Hif-1α and Sirt1 genes, key elements in cell survival. More studies are needed to better clarify the involvement of sirtuins in the β-adrenergic response and, overall, to better define the mechanisms by which tools such as exercise training are able to counteract the oxidative stress, by both activation of sirtuins and inhibition of GRK2 in many cardiovascular conditions and can be used to prevent or treat diseases such as heart failure

Is Physical Activity Able to Modify Oxidative Damage in Cardiovascular Aging?

Aging is a multifactorial process resulting in damage of molecules, cells, and tissues. It has been demonstrated that the expression and activity of antioxidant systems (SOD, HSPs) are modified in aging, with reduced cell ability to counteract the oxidant molecules, and consequent weak resistance to ROS accumulation. An important mechanism involved is represented by sirtuins, the activity of which is reduced by aging. Physical activity increases the expression and the activity of antioxidant enzymes, with consequent reduction of ROS. Positive effects of physical exercise in terms of antioxidant activity could be ascribable to a greater expression and activity of SOD enzymes, HSPs and SIRT1 activity. The antioxidant effects could increase, decrease, or not change in relation to the exercise protocol. Therefore, some authors by using a new approach based on the in vivo/vitro technique demonstrated that the highest survival and proliferation and the lowest senescence were obtained by performing an aerobic training. Therefore, the in vivo/vitro technique described could represent a good tool to better understand how the exercise training mediates its effects on aging-related diseases, as elderly with heart failure that represents a special population in which the exercise plays an important role in the improvement of cardiovascular function, quality of life, and survival

Sirtuins: Possible Clinical Implications in Cardio and Cerebrovascular Diseases

Mammalian sirtuins (SIRT1-7) are NAD+-dependent deacetylases, which play an important role in aging and in a wide range of cellular functions. SIRT1, the best-characterized member of the family, acts as a sensor of the redox state and triggers in the cell the appropriate defense response. A large body of evidence has showed that SIRT1 induces both cellular and systemic protective effects in the cardiovascular system by preventing stress-induced apoptosis and senescence, and mitigating endothelial dysfunction. Hence, SIRT1 is now foreseen as a potential therapeutic target for a growing number of cardiovascular diseases. Recently, it has been suggested that SIRT1 activation could also be considered as a neuroprotective strategy. Indeed, SIRT1 protects against ischemia/reperfusion injury both in vitro and in vivo and avoids severe ischemic damage by preserving cerebral blood flow. In the last years it was suggested that others sirtuins, in particular SIRT3 and SIRT6, could exert beneficial effects in vascular syndromes. The aim of this review was to describe and discuss recent experimental evidence on the effects of SIRT1 and other sirtuins on the pathophysiology of cardio- and cerebrovascular diseases, underlying a potential therapeutic effect of these enzymes in the treatment and/or prevention of such conditions

Analysis of serum microRNA-122 in a randomized controlled trial of N-acetylcysteine for treatment of antituberculosis drug-induced liver injury

AimSerum microRNA-122 (miR-122) is a novel biomarker for drug-induced liver injury, with good sensitivity in the early diagnosis of paracetamol-induced liver injury. We describe miR-122 concentrations in participants with antituberculosis drug-induced liver injury (AT-DILI). We explored the relationship between miR-122 and alanine aminotransferase (ALT) concentrations and the effect of N-acetylcysteine (NAC) on miR-122 concentrations.MethodsWe included participants from a randomized placebo-controlled trial of intravenous NAC in AT-DILI. ALT and miR-122 concentrations were quantified before and after infusion of NAC/placebo. We assessed correlations between ALT and miR-122 concentrations and described changes in ALT and miR-122 concentrations between sampling occasions.ResultsWe included 45 participants; mean age (± standard deviation) 38 (±10) years, 58% female and 91% HIV positive. The median (interquartile range) time between pre- and post-infusion biomarker specimens was 68 h (47-77 h). The median pre-infusion ALT and miR-122 concentrations were 420 U/L (238-580) and 0.58 pM (0.18-1.47), respectively. Pre-infusion ALT and miR-122 concentrations were correlated (Spearman's ρ = .54, P = .0001). Median fold-changes in ALT and miR-122 concentrations between sampling were 0.56 (0.43-0.69) and 0.75 (0.23-1.53), respectively, and were similar in the NAC and placebo groups (P = .40 and P = .68 respectively).ConclusionsmiR-122 concentrations in our participants with AT-DILI were considerably higher than previously reported in healthy volunteers and in patients on antituberculosis therapy without liver injury. We did not detect an effect of NAC on miR-122 concentrations. Further research is needed to determine the utility of miR-122 in the diagnosis and management of AT-DILI