Pharmacogenetics of Statins Therapy

Silibinin A decreases statin‑induced PCSK9 expression in human hepatoblastoma HepG2 cells

Hypercholesterolemia is one of the major risk factors for the occurrence and development of atherosclerosis. The most common drugs used to treat hypercholesterolemia are 3‑hydroxy‑3‑methyl‑glutaryl‑CoA reductase inhibitors, known as statins. Statins induce a beneficial increase in the levels of the low density lipoprotein receptor (LDLR) and additionally upregulate proprotein convertase subtilisin/kexin type 9 (PCSK9), which leads to LDLR degradation. This process causes a negative feedback response that attenuates the lipid lowering effects of statins. Therefore, the development of PCSK9 inhibitors may increase the lipid‑lowering functions of statins. In the present study, a drug‑screening assay was developed using the human PCSK9 promoter, based on data from a dual‑luciferase reporter assay, and the efficacies of various compounds from Traditional Chinese Medicine were examined. Among the compounds examined, SIL was demonstrated to function by targeting PCSK9. It was identified that SIL treatment decreased the expression levels of PCSK9 in HepG2 cells by decreasing the activity of the PCSK9 promoter in a dose‑and time‑dependent manner. Notably, SIL antagonized the statin‑induced phosphorylation of the p38 MAPK signaling pathway. The present study suggested that SIL may be developed as a novel PCSK9 inhibitor that may increase the efficiency of statin treatment.

POR*28 SNP is associated with lipid response to atorvastatin in children and adolescents with familial hypercholesterolemia

BACKGROUND

In children and adolescents with familial hypercholesterolemia (FH) pharmacotherapy with statins is the cornerstone in the current regimen to reduce low-density lipoprotein cholesterol (LDLc) and premature coronary heart disease risk. There is, however, a great interindividual variation in response to therapy, partially attributed to genetic factors. The polymorphic enzyme POR transfers electrons from NADPH to CYP450 enzymes including CYP3A, which metabolize atorvastatin. POR*28 polymorphism is associated with increased CYP3A enzyme activity. We analyzed the association of POR*28 allele with response to atorvastatin.

MATERIALS & METHODS

One hundred and five FH children and adolescents treated with atorvastatin at doses 10-40 mg were included in the study. Total cholesterol (TChol) and LDLc were measured at baseline and after 6 months of treatment. POR*28 allele was analyzed with TaqMan assay. CYP3A4*22, CYP3A5*3 and SLCO1B1 521T>C and 388A>G genotypes were also determined with TaqMan or PCR-RFLP methods.

RESULTS

POR*28 carriers had significantly lower percent mean reduction of TChol (33.1% in *1/*1, 29.8% in *1/*28 and 25.9% in *28/*28 individuals, p = 0.045) and of LDLc (43.9% in *1/*1, 40.9% in *1/*28 and 30.8% in *28/*28 individuals, p = 0.013). In multivariable linear regression adjusted for confounding factors, POR*28 genotypes, additionally to baseline cholesterol level, accounted for an estimated 8.3% and 7.3% of overall variability in % TChol and LDLc reduction (β: 4.05; 95% CI: 1.73-6.37; p = 0.001 and β: 5.08; 95% CI: 1.62-8.54; p = 0.004, respectively). CYP3A4*22, CYP3A5*3 and SLCO1B1 521T>C and 388A>G polymorphisms were not associated with lipid reductions and did not modify the effect of POR*28 on atorvastatin response.

CONCLUSION

In children with FH, carriage of POR*28 allele is associated with reduced effect of atorvastatin on TChol and LDLc and therefore identifies FH children that may require higher atorvastatin doses to achieve full therapeutic benefits. Additional studies in different populations are needed to replicate this association.

Effects of rosuvastatin on the production and activation of matrix metalloproteinase-2 and migration of cultured rat vascular smooth muscle cells induced by homocysteine

OBJECTIVE

To test the influence of homocysteine on the production and activation of matrix metalloproteinase-2 (MMP-2) and tissue inhibitors of matrix metalloproteinase-2 (TIMP-2) and on cell migration of cultured rat vascular smooth muscle cells (VSMCs). Also, to explore whether rosuvastatin can alter the abnormal secretion and activation of MMP-2 and TIMP-2 and migration of VSMCs induced by homocysteine.

METHODS

Rat VSMCs were incubated with different concentrations of homocysteine (50-5000 μmol/L). Western blotting and gelatin zymography were used to investigate the expressions and activities of MMP-2 and TIMP-2 in VSMCs in culture medium when induced with homocysteine for 24, 48, and 72 h. Transwell chambers were employed to test the migratory ability of VSMCs when incubated with homocysteine for 48 h. Different concentrations of rosuvastatin (10(-9)-10(-5) mol/L) were added when VSMCs were induced with 1000 μmol/L homocysteine. The expressions and activities of MMP-2 and TIMP-2 were examined after incubating for 24, 48, and 72 h, and the migration of VSMCs was also examined after incubating for 48 h.

RESULTS

Homocysteine (50-1000 μmol/L) increased the production and activation of MMP-2 and expression of TIMP-2 in a dose-dependent manner. However, when incubated with 5000 μmol/L homocysteine, the expression of MMP-2 was up-regulated, but its activity was down-regulated. Increased homocysteine-induced production and activation of MMP-2 were reduced by rosuvastatin in a dose-dependent manner whereas secretion of TIMP-2 was not significantly altered by rosuvastatin. Homocysteine (50-5000 μmol/L) stimulated the migration of VSMCs in a dose-dependent manner, but this effect was eliminated by rosuvastatin.

CONCLUSIONS

Homocysteine (50-1000 μmol/L) significantly increased the production and activation of MMP-2, the expression of TIMP-2, and the migration of VSMCs in a dose-dependent manner. Additional extracellular rosuvastatin can decrease the excessive expression and activation of MMP-2 and abnormal migration of VSMCs induced by homocysteine.

Targeting Trypanosoma cruzi sterol 14α-demethylase (CYP51)

There are at least two obvious features that must be considered upon targeting specific metabolic pathways/enzymes for drug development: the pathway must be essential and the enzyme must allow the design of pharmacologically useful inhibitors. Here, we describe Trypanosoma cruzi sterol 14α-demethylase as a promising target for anti-Chagasic chemotherapy. The use of anti-fungal azoles, which block sterol biosynthesis and therefore membrane formation in fungi, against the protozoan parasite has turned out to be highly successful: a broad spectrum anti-fungal drug, the triazole compound posaconazole, is now entering phase II clinical trials for treatment of Chagas disease. This review summarizes comparative information on anti-fungal azoles and novel inhibitory scaffolds selective for Trypanosomatidae sterol 14α-demethylase through the lens of recent structure/functional characterization of the target enzyme. We believe our studies open wide opportunities for rational design of novel, pathogen-specific and therefore more potent and efficient anti-trypanosomal drugs.

Common variants of HMGCR, CETP, APOAI, ABCB1, CYP3A4, and CYP7A1 genes as predictors of lipid-lowering response to atorvastatin therapy

There is interindividual variation in lipid-lowering response to statins. The objective of this study was to investigate whether common variation in genes involved in lipid and statin metabolism modify the effect of statins on serum total cholesterol (TC), low-density lipoprotein-cholesterol (LDL-C), and high-density lipoprotein-cholesterol concentration in coronary artery disease (CAD) patients. We studied the association between 18 single-nucleotide polymorphisms (SNPs) in six genes (HMGCR, CETP, APOAI, ABCB1, CYP3A4, CYP7A1) in response to atorvastatin therapy (20 mg/day) in 265 newly diagnosed CAD patients using multivariable adjusted general linear regression. Variant alleles of ABCB1 (-41A/G), HMGCR SNP29 G/T, rs5908A/G, rs12916C/T, and CYP7A1-204A/C polymorphisms were significantly associated with attenuated LDL-C reduction and variant alleles of CETP TaqI, -629C/A, and APOAI PstI polymorphisms were associated with higher increase in high-density lipoprotein-cholesterol. A three-loci interaction model consisting of CYP7A1rs892871AA/APOAIPstIP1P1/HMGCR rs12916CT was a better predictor for LDL-C lowering, when compared with single polymorphisms analysis on statin response. Variant genotypes of APOAI -2500C/T, CETP 405I/V, and ABCB1 3435C/T showed higher risk of myocardial infarction events (p < 0.05) in a 1-year follow-up of CAD patients. These results suggest that SNPs in lipid and statin pathway genes are associated with reduced LDL-C lowering by statins and identify individuals who may be resistant to maximal LDL-C lowering by statins.

Tissue factor +5466A>G polymorphism determines thrombin formation following vascular injury and thrombin-lowering effects of simvastatin in patients with ischemic heart disease

OBJECTIVE

We examined the hypothesis that the +5466A>G variant (rs3917643) of the tissue factor (TF) gene is associated with thrombin formation following simvastatin in patients with ischemic heart disease (IHD).

METHODS AND RESULTS

Prothrombin 1.2 fragments (F1.2) and thrombin-antithrombin complexes (TAT) were assessed in 95 men with stable IHD, aged 54.4+/-6.8 years, in blood collected every 60s from the bleeding-time wounds before and after a 3-month simvastatin administration (40 mg/day). We identified 16 patients with the TF +5466AG genotype and 79 subjects with the +5466AA genotype. Baseline maximum rates of F1.2 and TAT formation and their maximum levels at the site of vascular injury, but not in venous blood, were higher in +5466G allele carriers than in those with +5466AA genotype (P<0.0001). The magnitude of reduction in maximum rates of F1.2 and TAT formation following simvastatin was larger (P<0.001) in +5466G allele carriers than in +5466AA subjects. The degree of decrease in maximum local levels of F1.2 and TAT after simvastatin was similar in both genotype groups. The presence of the +5466G allele was independently associated with the maximum velocity of F1.2 and TAT generation and maximum levels of both markers before and after simvastatin in multiple regression models (P<0.01 for all analyses). Local thrombin generation, in +5466AG and +5466AA subjects, showed no significant correlations with lipid variables.

CONCLUSIONS

Thrombin formation following vascular injury and thrombin-lowering effect of statins in patients with IHD are at least in part genetically determined by the TF +5466A>G polymorphism.