Calpain Activator Dibucaine Induces Platelet Apoptosis

Calcium-dependent calpains are a family of cysteine proteases that have been demonstrated to play key roles in both platelet glycoprotein Ibα shedding and platelet activation and altered calpain activity is associated with thrombotic thrombocytopenic purpura. Calpain activators induce apoptosis in several types of nucleated cells. However, it is not clear whether calpain activators induce platelet apoptosis. Here we show that the calpain activator dibucaine induced several platelet apoptotic events including depolarization of the mitochondrial inner transmembrane potential, up-regulation of Bax and Bak, down-regulation of Bcl-2 and Bcl-XL, caspase-3 activation and phosphatidylserine exposure. Platelet apoptosis elicited by dibucaine was not affected by the broad spectrum metalloproteinase inhibitor GM6001. Furthermore, dibucaine did not induce platelet activation as detected by P-selectin expression and PAC-1 binding. However, platelet aggregation induced by ristocetin or α-thrombin, platelet adhesion and spreading on von Willebrand factor were significantly inhibited in platelets treated with dibucaine. Taken together, these data indicate that dibucaine induces platelet apoptosis and platelet dysfunction

The association between early onset of alcohol, smokeless tobacco and marijuana use with adult binge drinking in United States.

Binge drinking is a deadly pattern of excessive alcohol use that is associated with multiple diseases in the United States. To date, little is known about the associations between the early onset of substance use and other factors with the severity of adult binge drinking. The 2018 National Survey on Drug Use and Health data was used to identify binge drinking (binary and in number of days in the past month). Age at onset was categorized into four groups as 1-12, 13-14, 15-17, or beyond 18. Weighted multivariate logistic regression and Poisson regression analyses were performed to examine the associations between early onset of alcohol, smokeless tobacco, and marijuana use with binge drinking. The severity of binge drinking was statistically significantly associated with substance use (4.15 days in a month), early onset of alcohol, smokeless tobacco, and marijuana use (2.15-4.93 days, all p-values < 0.0001), after accounting for the covariates. Past year substance use disorder is strongly associated with binge drinking. The severity of adult binge drinking is significantly associated with early onset of substance use including alcohol, smokeless tobacco, and marijuana. Continued efforts are warranted to improve substance use prevention and treatment tailored for adolescents and youths to prevent development of adult binge drinking

Obesity, Migraine, and Overlapping Comorbidities in a Rural Pediatric Population

Objective This study aims to report the prevalence of obesity and overlapping comorbidities in a rural population of children and adolescents with migraine. Design and Methods A cross-sectional, descriptive, secondary data analysis using a comprehensive patient database from the West Virginia University (WVU) Medicine Epic Clarity system will be reported. A review of electronic medical records of 990 children and adolescents, ages 7 to 17 years, evaluated for headache at a rural clinic from December 1, 2009 to December 31, 2017 was completed. The Chi-square test was used to identify any differences in demographic characteristics (age, gender, and race) and distribution of comorbidities (obstructive sleep apnea syndrome [OSAS], depression, and anxiety) among obese versus nonobese adolescents with migraine. Student’s t-test was used to identify any differences in the number of comorbidities between the two groups. Results A total of 648 children and adolescents with a diagnosis of migraine were identified. Approximately 26.4% of the children and adolescents diagnosed with migraine (n = 648) met the criteria for being obese with a mean body mass index (BMI) of 30.6 kg/m2 (standard deviation [SD] = 6.5), ranging from 20.0 to 58.5 kg/m2. There were no significant differences between migraineurs who were categorized as obese versus nonobese in terms of gender (p = 0.8587), age (p = 0.1703), race (p = 0.7655), anxiety (p = 0.1841), or depression (p = 0.2793). Obese individuals have more comorbidities than nonobese individuals (p = 0.015). Additionally, the prevalence of OSAS was significantly higher among obese versus nonobese migraineurs (20 vs. 9.9%, p = 0.0007). Conclusion Given the prevalence of obesity in rural pediatric populations and the reported neurobiological links between migraine and obesity, BMI needs to be monitored and weight management interventions included in plans of care for rural children and adolescents with migraine

A critical role for 14-3-3ζ protein in regulating the VWF binding function of platelet glycoprotein Ib-IX and its therapeutic implications

The platelet receptor for von Willebrand factor (VWF), glycoprotein (GP) Ib-IX, mediates platelet adhesion and activation. The cytoplasmic domains of the GPIb α and β subunits contain binding sites for the phosphorylation-dependent signaling molecule, 14-3-3ζ. Here we show that a novel membrane-permeable inhibitor of 14-3-3ζ-GPIbα interaction, MPαC, potently inhibited VWF binding to platelets and VWF-mediated platelet adhesion under flow conditions. MPαC also inhibited VWF-dependent platelet agglutination induced by ristocetin. Furthermore, activation of the VWF binding function of GPIb-IX induced by GPIbβ dephosphorylation is diminished by mutagenic disruption of the 14-3-3ζ binding site in the C-terminal domain of GPIbα, mimicking MPαC-induced inhibition, indicating that the inhibitory effect of MPαC is likely to be caused by disruption of 14-3-3ζ binding to GPIbα. These data suggest a novel 14-3-3ζ-dependent regulatory mechanism that controls the VWF binding function of GPIb-IX, and also suggest a new type of antiplatelet agent that may be potentially useful in preventing or treating thrombosis

Arsenic trioxide induces apoptosis in human platelets via C-Jun NH2-terminal kinase activation.

Arsenic trioxide (ATO), one of the oldest drugs in both Western and traditional Chinese medicine, has become an effective anticancer drug, especially in the treatment of acute promyelocytic leukemia (APL). However, thrombocytopenia occurred in most of ATO-treated patients with APL or other malignant diseases, and the pathogenesis remains unclear. Here we show that ATO dose-dependently induces depolarization of mitochondrial inner transmembrane potential (ΔΨm), up-regulation of Bax and down-regulation of Bcl-2 and Bcl-XL, caspase-3 activation, and phosphotidylserine (PS) exposure in platelets. ATO did not induce surface expression of P-selectin and PAC-1 binding, whereas, obviously reduced collagen, ADP, and thrombin induced platelet aggregation. ATO dose-dependently induced c-Jun NH2-terminal kinase (JNK) activation, and JNK specific inhibitor dicumarol obviously reduced ATO-induced ΔΨm depolarization in platelets. Clinical therapeutic dosage of ATO was intraperitoneally injected into C57 mice, and the numbers of circulating platelets were significantly reduced after five days of continuous injection. The data demonstrate that ATO induces caspase-dependent apoptosis via JNK activation in platelets. ATO does not incur platelet activation, whereas, it not only impairs platelet function but also reduces circulating platelets in vivo, suggesting the possible pathogenesis of thrombocytopenia in patients treated with ATO

Crystallization and preliminary X-ray crystallographic studies of O-methyltransferase from Anabaena PCC 7120

The O-methyltransferase (OMT) from the Anabaena PCC 7120 has been overexpressed in a soluble form in E. coli, purified and crystallized. The crystals belonged to space group C2221 and diffracted to 2.4 Å resolution

TSST-1 protein exerts indirect effect on platelet activation and apoptosis

Thrombocytopenia or platelet dysfunction is a risk factor for severe infection. Staphylococcus aureus (S. aureus) releases a variety of virulence factors especially toxic shock syndrome toxin 1 (TSST-1), which may cause toxic shock syndrome. S. aureus, when carrying the tst gene, is more prone to cause toxic shock syndrome and is responsible for an especially high rate of mortality. However, the effect of TSST-1 protein on platelets is unknown. Patients with the tst gene positive S. aureus bacteremia showed more serious infection, higher mortality and lower platelet count. The tst gene positive S. aureus strains induce more platelet apoptosis and activation and corresponding up-regulation of Bak and down-regulation of Bcl-XL in addition to the activation of Caspase-3. C57BL/6 mice infected with the tst gene positive strains resulted in both a decrease in platelet count and an increase in platelet apoptosis and/or activation events and mortality. Moreover, TSST-1 protein, encoded by tst gene, caused the decrease of platelet count, the increase of platelet apoptosis and activation events and the level of inflammatory cytokines in vivo. However, TSST-1 protein was unable to induce traditional activation and apoptosis on human platelets in vitro. These results suggested that TSST-1 protein may exert indirect effects on platelet activation and apoptosis in vivo

Alantolactone induces platelet apoptosis by activating the Akt pathway

Alantolactone (ALT), a sesquiterpene lactone compound isolated from Inula helenium L., has recently attracted much attention for its anti-tumor properties. ALT reportedly functions by regulating the Akt pathway, which has been shown to be involved in programmed platelet death (apoptosis) and platelet activation. However, the precise effect of ALT on platelets remains unclear. In this study, washed platelets were treated with ALT in vitro, and apoptotic events and platelet activation were detected. In vivo, platelet transfusion experiments were employed to detect the effect of ALT on platelet clearance. Platelet counts were examined after intravenous injection of ALT. We found that ALT treatment induced Akt activation and Akt-mediated apoptosis in platelets. ALT-activated Akt elicited platelet apoptosis by activating phosphodiesterase (PDE3A) and PDE3A-mediated protein kinase A (PKA) inhibition. Pharmacological inhibition of the PI3K/Akt/PDE3A signaling pathway or PKA activation was found to protect platelets from apoptosis induced by ALT. Moreover, ALT-induced apoptotic platelets were removed faster in vivo, and ALT injection resulted in the platelet count decline. Either PI3K/Akt/PDE3A inhibitors or a PKA activator could protect platelets from clearance, ultimately ameliorating the ALT-induced decline in platelet count in the animal model. These results reveal the effects of ALT on platelets and their related mechanisms, suggesting potential therapeutic targets for the prevention and alleviation of possible side effects resulting from ALT treatments