Cell‐Specific Actions of the Prostaglandin E‐Prostanoid Receptor 4 Attenuating Hypertension: A Dominant Role for Kidney Epithelial Cells Compared With Macrophages

Background A beneficial role for prostanoids in hypertension is suggested by clinical studies showing nonsteroidal anti‐inflammatory drugs, which block the production of all prostanoids, cause sodium retention and exacerbate hypertension. Among prostanoids, prostaglandin E2 and its E‐prostanoid receptor 4 receptor (EP4R) have been implicated in blood pressure control. Our previous study found that conditional deletion of EP4R from all tissues in adult mice exacerbates angiotensin II‐dependent hypertension, suggesting a powerful effect of EP4R to resist blood pressure elevation. We also found that elimination of EP4R from vascular smooth muscle cells did not affect the severity of hypertension, suggesting nonvascular targets of prostaglandin E mediate this antihypertensive effect. Methods and Results Here we generated mice with cell‐specific deletion of EP4R from macrophage‐specific EP4 receptor knockouts or kidney epithelial cells (KEKO) to assess the contributions of EP4R in these cells to hypertension pathogenesis. Macrophage‐specific EP4 receptor knockouts showed similar blood pressure responses to alterations in dietary sodium or chronic angiotensin II infusion as Controls. By contrast, angiotensin II‐dependent hypertension was significantly augmented in KEKOs (mean arterial pressure: 146±3 mm Hg) compared with Controls (137±4 mm Hg; P=0.02), which was accompanied by impaired natriuresis in KEKOs. Because EP4R expression in the kidney is enriched in the collecting duct, we compared responses to amiloride in angiotensin II‐infused KEKOs and Controls. Blockade of the epithelial sodium channel with amiloride caused exaggerated natriuresis in KEKOs compared with Controls (0.21±0.01 versus 0.15±0.02 mmol/24 hour per 20 g; P=0.015). Conclusions Our data suggest EP4R in kidney epithelia attenuates hypertension. This antihypertension effect of EP4R may be mediated by reducing the activity of the epithelial sodium channel, thereby promoting natriuresis

Adaptation to compound climate risks: A systematic global stocktake

This article provides a stocktake of the adaptation literature between 2013 and 2019 to better understand how adaptation responses affect risk under the particularly challenging conditions of compound climate events. Across 39 countries, 45 response types to compound hazards display anticipatory (9%), reactive (33%), and maladaptive (41%) characteristics, as well as hard (18%) and soft (68%) limits to adaptation. Low income, food insecurity, and access to institutional resources and finance are the most prominent of 23 vulnerabilities observed to negatively affect responses. Risk for food security, health, livelihoods, and economic outputs are commonly associated risks driving responses. Narrow geographical and sectoral foci of the literature highlight important conceptual, sectoral, and geographic areas for future research to better understand the way responses shape risk. When responses are integrated within climate risk assessment and management, there is greater potential to advance the urgency of response and safeguards for the most vulnerable

Adaptation to compound climate risks: A systematic global stocktake

Summary: This article provides a stocktake of the adaptation literature between 2013 and 2019 to better understand how adaptation responses affect risk under the particularly challenging conditions of compound climate events. Across 39 countries, 45 response types to compound hazards display anticipatory (9%), reactive (33%), and maladaptive (41%) characteristics, as well as hard (18%) and soft (68%) limits to adaptation. Low income, food insecurity, and access to institutional resources and finance are the most prominent of 23 vulnerabilities observed to negatively affect responses. Risk for food security, health, livelihoods, and economic outputs are commonly associated risks driving responses. Narrow geographical and sectoral foci of the literature highlight important conceptual, sectoral, and geographic areas for future research to better understand the way responses shape risk. When responses are integrated within climate risk assessment and management, there is greater potential to advance the urgency of response and safeguards for the most vulnerable