DHHC21‐mediated α1 Adrenergic Receptor Palmitoylation Contributes to Renal Blood Flow Regulation During Sepsis

Palmitoylation is a reaction of 16-carbon palmitic acid attachment to a cysteine residue of a protein via thioester linkage, catalyzed by a family of palmitoyl acyltransferases containing the DHHC motif. This post-translational modification plays a critical role in regulating protein function, subcellular localization and interactions with other cellular molecules. A recent study shows that vascular α1 adrenergic receptor (α1AR) requires DHHC21-mediated palmitoylation for its signaling activity to induce vasoconstriction. In the kidney, arterial vasoconstriction has been implicated in the development of renal hypoperfusion following sepsis. In this study, we sought to examine whether DHHC21 contributes to kidney dysfunction by affecting renal blood flow through α1AR palmitoylation. Cecal ligation puncture (CLP) was performed to induce polymicrobial sepsis in wild type and DHHC21 functional deficient (Zdhhc21dep/dep) mice. Their renal function was dynamically assessed based on tracer (IRdye 800CW) clearance measured by multispectral optoacoustic tomography (MSOT). The results showed that in wild-type mice, IRdye 800CW movement from kidney cortex to the medulla/pelvis region was significantly slower after CLP, compared to sham control. The sepsis-induced impairment in renal clearance was alleviated in Zdhhc21dep/dep mice. Consistently, histological analysis (Periodic acid-Schiff staining) revealed that CLP caused kidney structural damages, evidenced by tubular vacuolation, brush border loss, tubular cell detachment and leukocyte infiltration; these pathologies were greatly ameliorated in DHHC21 loss-of-function mice. Moreover, compared with wild-type mice, Zdhhc21dep/dep mice exhibited reduced CLP-induced increases in circulating creatinine and urea nitrogen. Mechanistically, a decreased ratio of oxygenated to deoxygenated hemoglobin was detected in kidneys of wild-type mice following CLP, suggesting renal tissue hypoxia in response to sepsis. We then asked whether this lack of oxygenation is associated with reduced renal blood flow due to arterial constriction and whether α1AR palmitoylation is involved in this process. Indeed, we found a significant increase in α1AR palmitoylation, along with activation of the α1AR downstream effector ERK, in renal arteries of wild-type mice following CLP. These molecular responses occurred concomitantly with a reduced renal blood flow, measured by a transonic flowmeter. In contrast, sepsis-induced α1AR palmitoylation/activation in renal arteries was greatly attenuated in Zdhhc21dep/dep mice, consistent with a better-preserved renal blood flow in these mice. Taken together, our findings indicate that DHHC21-mediated α1AR palmitoylation contributes to renal blood flow reduction and kidney injury during sepsis. Support or Funding Information This work was supported by the National Institutes of Health Grant HL070752 (to SYY)