Interpretation
Martinique is an insular region of France located in the Lesser Antilles of the West Indies in the eastern Caribbean Sea. Coastlines of Martinique have witnessed successive and massive waves of sargassum seaweed invasions over the last two decades 12-14. Ecological prediction models indicate that these massive strandings are likely to repeat leading to economic, social and public health concerns34. Due to marine currents and maritime trade winds, strandings of sargassum seaweed only impacted the Atlantic coastlines of Martinique. Specific areas are particularly impacted by sargassum strandings, which motivated the installation of ground gas sensors to monitor H2S released from anaerobic degradation of sargassum strandings. Since 2016, this network has allowed to evaluate exposure of the population, to inform the local population and authorities about air quality on a daily basis, as well as to launch population evacuation warnings when required. In our study, we used the living place and/or workplace by define H2S exposure13. We observed that less than a half of pregnant women had a job, which was located in the borough of residency in more than ninety percent of cases (data no shown). Overall, qualitative classification of H2S exposure of pregnant women was reasonable well defined.
The increased risk of preeclampsia that we found in H2S exposure pregnant women seem to conflict the large body of literature showing protective action of H2S in cardiovascular pathologies such as hypertension, atherosclerosis and pulmonary hypertension 30-32. Proposed mechanisms of H2S-induced vascular beneficial effects include anti-oxidative action, preservation of mitochondrial function, reduction of apoptosis, anti-inflammatory responses, angiogenic action, regulation of ion channel, and increasing the production of NO9,10, 30-32. In line, few epidemiological studies have previously suggested a protective role of H2S in atherosclerosis onset and development 20,23,24,27. As a different paradigm, H2S have several mechanisms of toxicity, including inhibition of cytochrome c oxidase activity, protein kinases (JNK and Erk) activation and cellular damage from reactive oxygen species, which participate to vascular structure and function impairment 30-32. Although the primary action of H2S on the vasculature is relaxation, H2S can exert vasoconstriction under some conditions9. Indeed, H2S exerts biphasic effect on vascular tissue and produces vasoconstriction at low concentrations, while inducing vasorelaxation at higher concentrations. H2S-induced vasoconstriction has been attributed to NO quenching or inactivation, inhibition of endothelial cell NO synthase, and NO-independent mechanisms which include lowering cyclic adenosine monophosphate (cAMP) levels in vascular smooth muscle cells9,11,31,33. Such impact of H2S on the vasculature may explain the deleterious cardiovascular effects of H2S exposure observed in geothermal areas and industrial regions. For example, a significant increase of incidence for diseases of circulatory system and of mortality for hypertensive disease was observed in the geothermal area and industrial regions20,26,27. Overall, increased risk of preeclampsia that we found in H2S-exposed pregnant women is consistent with these previous studies.