Aspirin-resistant patients as a group have reduced response to clopidogrel. Furthermore, we have identified a unique group of dual drug-resistant patients who may be at increased risk for thrombotic complications after PCI.

To cite this article: Guthikonda S, Lev EI, Patel R, DeLao T, Bergeron AL, Dong J-F, Kleiman NS. Reticulated platelets and uninhibited COX-1 and COX-2 decrease the antiplatelet effects of aspirin. J Thromb Haemost 2007; 5: 490-6.Summary. Background: The mechanisms for the variability in antiplatelet effects of aspirin are unclear. Immature (reticulated) platelets may modulate the antiplatelet effects of aspirin through uninhibited cyclooxygenase (COX)-1 and COX-2. Objectives: To evaluate the role of reticulated platelets in the antiplatelet effects of aspirin. Methods: Sixty healthy volunteers had platelet studies performed before and 24 h after a single 325-mg dose of aspirin. Platelet studies included light transmission aggregometry; P-selectin and integrin a IIb b 3 expression, and serum thromboxane B 2 (TxB 2 ) levels. Reticulated platelets and platelet COX-2 expression were measured using flow cytometry. Results: Subjects were divided into tertiles based on the percentage of reticulated platelets in whole blood. Baseline platelet aggregation to 1 lg mL )1 collagen, and postaspirin aggregations to 5 lM and 20 lM ADP and collagen, were greater in the upper than in the lower tertile of reticulated platelets. Stimulated P-selectin and integrin a IIb b 3 expression were also higher in the upper tertile both before and after aspirin. Platelet COX-2 expression was detected in 12 ± 7% (n ¼ 10) of platelets in the upper tertile, and in 7 ± 3% (n ¼ 12) of platelets in the lower two tertiles (P ¼ 0.03). Postaspirin serum TxB 2 levels were higher in the upper (5.5 ± 4 ng mL )1 ) than in the lower tertile (3.2 ± 2.5 ng mL )1 , P ¼ 0.03), and decreased even further with ex vivo additional COX-1 and COX-2 inhibition. The incidence of aspirin resistance ( ‡ 70% platelet aggregation to 5 lM ADP) was significantly higher in the upper tertile (45%) than in the lower tertile (5%, P < 0.0001). Conclusions: Reticulated platelets are associated with diminished antiplatelet effects of aspirin and increased aspirin resistance, possibly because of increased reactivity, and uninhibited COX-1 and COX-2 activity.

Background-Hypertrophic cardiomyopathy is a genetic disease characterized by cardiac hypertrophy, myocyte disarray, interstitial fibrosis, and left ventricular (LV) dysfunction. We have proposed that hypertrophy and fibrosis, the major determinants of mortality and morbidity, are potentially reversible. We tested this hypothesis in ␤-myosin heavy chain-Q 403 transgenic rabbits. Methods and Results-We randomized 24 ␤-myosin heavy chain-Q 403 rabbits to treatment with either a placebo or simvastatin (5 mg · kg -1 · d -1 ) for 12 weeks and included 12 nontransgenic controls. We performed 2D and Doppler echocardiography and tissue Doppler imaging before and after treatment. Demographic data were similar among the groups. Baseline mean LV mass and interventricular septal thickness in nontransgenic, placebo, and simvastatin groups were 3.9Ϯ0.7, 6.2Ϯ2.0, and 7.5Ϯ2.1 g (PϽ0.001) and 2.2Ϯ0.2, 3.1Ϯ0.5, and 3.3Ϯ0.5 mm (Pϭ0.002), respectively. Simvastatin reduced LV mass by 37%, interventricular septal thickness by 21%, and posterior wall thickness by 13%. Doppler indices of LV filling pressure were improved. Collagen volume fraction was reduced by 44% (PϽ0.001). Disarray was unchanged. Levels of activated extracellular signal-regulated kinase (ERK) 1/2 were increased in the placebo group and were less than normal in the simvastatin group. Levels of activated and total p38, Jun N-terminal kinase, p70S6 kinase, Ras, Rac, and RhoA and the membrane association of Ras, RhoA, and Rac1 were unchanged. Conclusions-Simvastatin induced the regression of hypertrophy and fibrosis, improved cardiac function, and reduced ERK1/2 activity in the ␤-myosin heavy chain-Q 403 rabbits. These findings highlight the need for clinical trials to determine the effects of simvastatin on cardiac hypertrophy, fibrosis, and dysfunction in humans with hypertrophic cardiomyopathy and heart failure.

Background-Human hypertrophic cardiomyopathy (HCM), the most common cause of sudden cardiac death in the young, is characterized by cardiac hypertrophy, myocyte disarray, and interstitial fibrosis. The genetic basis of HCM is largely known; however, the molecular mediators of cardiac phenotypes are unknown. Methods and Results-We show myocardial aldosterone and aldosterone synthase mRNA levels were elevated by 4-to 6-fold in humans with HCM, whereas cAMP levels were normal. Aldosterone provoked expression of hypertrophic markers (NPPA, NPPB, and ACTA1) in rat cardiac myocytes by phosphorylation of protein kinase D (PKD) and expression of collagens (COL1A1, COL1A2, and COL3A1) and transforming growth factor-␤1 in rat cardiac fibroblasts by upregulation of phosphoinositide 3-kinase (PI3K)-p100␦. Inhibition of PKD and PI3K-p110␦ abrogated the hypertrophic and profibrotic effects, respectively, as did the mineralocorticoid receptor (MR) antagonist spironolactone. Spironolactone reversed interstitial fibrosis, attenuated myocyte disarray by 50%, and improved diastolic function in the cardiac troponin T (cTnT)-Q92 transgenic mouse model of human HCM. Myocyte disarray was associated with increased levels of phosphorylated ␤-catenin (serine 38) and reduced ␤-catenin-N-cadherin complexing in the heart of cTnT-Q92 mice. Concordantly, distribution of N-cadherin, predominantly localized to cell membrane in normal myocardium, was diffuse in disarrayed myocardium. Spironolactone restored ␤-catenin-N-cadherin complexing and cellular distribution of N-cadherin and reduced myocyte disarray in 2 independent randomized studies. Conclusions-The results implicate aldosterone as a major link between sarcomeric mutations and cardiac phenotype in HCM and, if confirmed in additional models, signal the need for clinical studies to determine the potential beneficial effects of MR blockade in human HCM.

Giardia lamblia (syn G. intestinalis, G. duodenalis) is the most common pathogenic intestinal parasite of humans worldwide and is a frequent cause of endemic and epidemic diarrhea. G. lamblia is divided into eight genotypes (A–H) which infect a wide range of mammals and humans, but human infections are caused by Genotypes A and B. To unambiguously determine the relationship among genotypes, we sequenced GS and DH (Genotypes B and A2) to high depth coverage and compared the assemblies with the nearly completed WB genome and draft sequencing surveys of Genotypes E (P15; pig isolate) and B (GS; human isolate). Our results identified DH as the smallest Giardia genome sequenced to date, while GS is the largest. Our open reading frame analyses and phylogenetic analyses showed that GS was more distant from the other three genomes than any of the other three were from each other. Whole-genome comparisons of DH_A2 and GS_B with the optically mapped WB_A1 demonstrated substantial synteny across all five chromosomes but also included a number of rearrangements, inversions, and chromosomal translocations that were more common toward the chromosome ends. However, the WB_A1/GS_B alignment demonstrated only about 70% sequence identity across the syntenic regions. Our findings add to information presented in previous reports suggesting that GS is a different species of Giardia as supported by the degree of genomic diversity, coding capacity, heterozygosity, phylogenetic distance, and known biological differences from WB_A1 and other G. lamblia genotypes.