Submitted by Livia Mello (liviacmello@yahoo.com.br) on 2016-09-13T20:02:43Z No. of bitstreams: 1 TeseCSS.pdf: 4525514 bytes, checksum: 85160aac636e59d1fffa7a6f9f399c54 (MD5) / Approved for entry into archive by Marina Freitas (marinapf@ufscar.br) on 2016-09-21T18:28:28Z (GMT) No. of bitstreams: 1 TeseCSS.pdf: 4525514 bytes, checksum: 85160aac636e59d1fffa7a6f9f399c54 (MD5) / Approved for entry into archive by Marina Freitas (marinapf@ufscar.br) on 2016-09-21T18:28:35Z (GMT) No. of bitstreams: 1 TeseCSS.pdf: 4525514 bytes, checksum: 85160aac636e59d1fffa7a6f9f399c54 (MD5) / Made available in DSpace on 2016-09-21T18:28:41Z (GMT). No. of bitstreams: 1 TeseCSS.pdf: 4525514 bytes, checksum: 85160aac636e59d1fffa7a6f9f399c54 (MD5) Previous issue date: 2016-02-12 / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / In this study, we aimed at investigating the involvement of the warmth-sensitive channel – TRPV4 (in vitro sensitive to temperatures in the range of approx. 24–34°C) – on the thermoregulatory mechanisms in rats. We treated rats with a chemical selective antagonist (HC-067047) of the TRPV4 channel and measured core body temperature, metabolism, heat loss index and preferred ambient temperature. The behavioral mechanism was also assessed after treatment with topical agonist (RN-1747). Our data revealed that intravenous blockade of this channel with HC-067047 caused an increase in core body temperature at ambient temperature of 26 and 30°C, but not at 22 and 32°C. At 26°C, HC-067047-induced hyperthermia was accompanied by increase in oxygen consumption (an index of thermogenesis). Furthermore, rats chemically stimulated with TRPV4 agonist choose colder ambient temperatures and the cold-seeking behaviour after thermal stimulation (28–31°C) was inhibited by TRPV4 antagonist. Our results suggest, for the first time, that TRPV4 channel is involved in the recruitment of behavioural and autonomic warmth-defence responses to regulate core body temperature. / Neste estudo, foi investigado o envolvimento dos canais sensíveis ao calor – TRPV4 (in vitro, sensíveis a uma faixa de temperatura aproximadamente entre 24 e 34°C) – nos mecanismos termorreguladores de ratos. Para tal, os animais foram tratados com antagonista químico seletivo (HC-067047) do canal TRPV4 e a temperatura corporal, o metabolismo, o índice de perda de calor e a temperatura ambiente de preferência foram medidos. O mecanismo comportamental também foi estudado após a aplicação do agonista tópico RN1747. Nossos dados revelam que o bloqueio intravenoso deste canal com HC-067047 causou um aumento na temperatura corporal nas temperaturas ambientes de 26 e 30°C, mas não a 22 nem a 32°C. A 26°C, a hipertermia induzida pelo tratamento com HC-067047 foi acompanhada por um aumento no consumo de oxigênio (um índice da termogênese). Além disso, ratos quimicamente estimulados com o agonista RN1747 escolheram temperaturas ambientes mais frias e o comportamento de busca pelo frio após estimulação térmica (28-31°C) foi inibido pelo antagonista do canal. Os resultados sugerem, pela primeira vez, que o canal TRPV4 está envolvido no recrutamento de respostas autonômicas e comportamentais de defesa ao calor. / FAPESP: 2011/19131-2

Résumé Responsable de près de 7 millions de décès prématurés par an à travers le monde, la pollution atmosphérique représente un problème sanitaire mondial majeur. L’exposition humaine à la pollution particulaire dont les émissions de diesel représentent la principale source, est responsable d’une élévation de la mortalité et de l’incidence d’événements cardiovasculaires. Les mécanismes physiopathologiques sous-tendant cette toxicité aigue restent à ce jour largement méconnus. A l’aide d’une méthodologie d’exposition standardisée aux émissions de diesel, nous avons exploré les effets vasculaires périphériques et pulmonaires ainsi que les effets hémostatiques et plaquettaires secondaires à l’inhalation particulaire chez des sujets sains. L’étude dynamique de la microcirculation périphérique par Laser Doppler Imager nous a permis de démontrer une altération de la vasomotricité endothélium-dépendante induite par l’exposition aux émissions de diesel. La dysfonction observée est associée à une diminution de la biodisponibilité locale du NO ainsi qu’à une production radicalaire accrue au sein de la cellule endothéliale. Au cours d’une épreuve dynamique d’élévation du débit cardiaque par infusion de dobutamine, l’exposition aiguë aux émissions de diesel entraîne une élévation de la résistance vasculaire pulmonaire et une diminution de la distensibilité vasculaire pulmonaire mesurées par échocardiographie. Enfin, l’expression de surface des marqueurs d’activation plaquettaire CD62p (P-selectine) et CD63 est augmentée après exposition aux émissions de diesel, en corrélation avec la quantité de particules inhalées et constitue ainsi un état d’activation plaquettaire accru sans toutefois de modification de l’agrégation plaquettaire. A travers ces effets vasculaires systémiques et pulmonaires ainsi que ces effets hémostatiques, l’exposition aux émissions de diesel entraîne une toxicité cardiovasculaire aiguë, agissant en synergie, capable de déclencher la survenue d’événements cardiovasculaires.Abstract Responsible for up to 7 million deaths/year, air pollution is a major worldwide health burden. Particulate human exposure mainly originates from diesel exhaust and is associated with an increased cardiovascular mortality and an increased onset of cardiovascular events. Physiopathologic mechanisms underlying this acute toxicity remain largely unknown. We used a standardized diesel exhaust exposure protocol to explore not only the peripheral and pulmonary vascular effects, but also the hemostatic and platelet modifications in healthy subjects after particulate inhalation. Diesel exhaust exposure impairs the endothelium-dependant vasodilation during a dynamic evaluation of the peripheral microcirculation assessed by Laser Doppler Imager, whilst the endothelial independent vasodilatation remains unaffected. Vascular dysfunction is associated to a decreased local NO bioavailability and an increased endothelial reactive oxygen species production. During a dynamic cardiac stress test using continuous dobutamine infusion, acute diesel exhaust exposure induces an increased pulmonary vascular resistance associated to a decreased pulmonary vascular distensibility, both evaluated by echocardiography. Finally, platelet activation is modified after diesel exhaust exposure with an increased CD62p (P-selectin) and CD63 platelet surface expression, correlated with the total amount of inhaled particles. We observed a state of platelet activation without change in platelet aggregation. Through these multiples effects, combining systemic and pulmonary vascular impairment with platelet prothrombotic modifications, diesel exhaust exposure induces an acute cardiovascular toxicity, which can synergistically trigger acute events. / Doctorat en Sciences médicales (Médecine) / info:eu-repo/semantics/nonPublished