Date of Award

2020-01-01

Degree Name

Doctor of Philosophy

Department

Interdisciplinary Health Sciences

Advisor(s)

Fadi T. Khasawneh

Second Advisor

Fatima Z. Alshbool

Abstract

Abstract (Hookah)

Cardiovascular diseases (CVD’s) is a major public health problem. Among CVD’s risk factors, tobacco smoking is considered the single most preventable cause of death, with thrombosis being the main mechanism of CVD’s mortality in smokers. While tobacco smoking has been on the decline, the use of waterpipe/hookah has been rising, mainly due to the perception that they are “less harmful” than regular cigarettes. Strikingly, there are few studies on the negative effects of waterpipes on the cardiovascular system, and none regarding their direct contribution to thrombus formation. We employed a waterpipe whole-body exposure protocol that mimics real‐life human exposure scenarios, and investigated its effects, relative to clean air, on platelet function, hemostasis and thrombogenesis. We found that both adults as well as in utero waterpipe smoke (WPS) exposed mice exhibited shortened thrombus occlusion and bleeding times. Further, our results show that platelets from adults and in utero WPS exposed mice are hyperactive, with enhanced agonist-induced aggregation, dense and α-granule secretion, αIIbβ3 (GPIIb/IIIa) integrin activation, phosphatidylserine expression and platelet spreading, when compared with clean air-exposed platelets. Finally, at the molecular level, it was found that Akt and ERK phosphorylation are enhanced in the adult WPS exposed-, and in nicotine-treated platelets. Our findings demonstrate, for the first time, that adult and in utero WPS exposure directly modulate hemostasis and increases the risk of thrombosis, and that this is mediated, in part, via a state of platelet hyperactivity. The negative health impact of WPS/hookah, therefore, should not be underestimated. Moreover, this study should also help in raising public awareness of the toxic effects of waterpipe/hookah.

Abstract (Gβγ subunits)

Platelet activation involves tightly regulated processes to ensure a proper hemostasis response, but when unbalanced, it can lead to pathological consequences such as thrombus formation. G-protein coupled receptors (GPCRs) regulate platelet function by mediating the response to various physiological agonists. To this end, an essential mediator of GPCR signaling is the G protein Gαβγ heterotrimers, and the βγ subunits are central players in downstream signaling pathways. While much is known regarding the role of the Gα subunit in platelet function, that of the βγ remains poorly understood. Therefore, we investigated the role of Gβγ subunits in platelet function using a Gβγ (small molecule) inhibitor, namely gallein. We observed that gallein inhibits platelet aggregation and secretion in response to agonist stimulation, in both mouse and human platelets. Furthermore, gallein also exerted inhibitory effects on integrin αIIbβ3 activation and clot retraction. Finally, gallein’s inhibitory effects manifested in vivo, as documented by its ability to impair physiological hemostasis and delay thrombus formation. Taken together, our findings demonstrate, for the first time, that Gβγ directly regulates GPCR-dependent platelet function, in vitro and in vivo. Moreover, these data highlight Gβγ as a novel therapeutic target for managing thrombotic disorders.

Language

en

Provenance

Received from ProQuest

File Size

115 pages

File Format

application/pdf

Rights Holder

Ahmed Alarabi

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