Concerted EP2 and EP4 Receptor Signaling Stimulates Autocrine Prostaglandin E2 Activation in Human Podocytes

Abstract

Glomerular hyperfiltration is an important mechanism in the development of albuminuria. During hyperfiltration, podocytes are exposed to increased fluid flow shear stress (FFSS) in Bowman’s space. Elevated Prostaglandin E2 (PGE2) synthesis and upregulated cyclooxygenase 2 (Cox2) are associated with podocyte injury by FFSS. We aimed to elucidate a PGE2 autocrine/paracrine pathway in human podocytes (hPC). We developed a modified liquid chromatography tandem mass spectrometry (LC/ESI-MS/MS) protocol to quantify cellular PGE2, 15-keto-PGE2, and 13,14-dihydro-15-keto-PGE2 levels. hPC were treated with PGE2 with or without separate or combined blockade of prostaglandin E receptors (EP), EP2, and EP4. Furthermore, the effect of FFSS on COX2, PTGER2, and PTGER4 expression in hPC was quantified. In hPC, stimulation with PGE2 led to an EP2- and EP4-dependent increase in cyclic adenosine monophosphate (cAMP) and COX2, and induced cellular PGE2. PTGER4 was downregulated after PGE2 stimulation in hPC. In the corresponding LC/ESI-MS/MS in vivo analysis at the tissue level, increased PGE2 and 15-keto-PGE2 levels were observed in isolated glomeruli obtained from a well-established rat model with glomerular hyperfiltration, the Munich Wistar Frömter rat. COX2 and PTGER2 were upregulated by FFSS. Our data thus support an autocrine/paracrine COX2/PGE2 pathway in hPC linked to concerted EP2 and EP4 signaling.

Glomerular Biomechanical Stress and Lipid Mediators during Cellular Changes Leading to Chronic Kidney Disease

“…Our results also showed FFSS-induced upregulation of EP 2 expression but not EP 4 [ 73 ]; EP 4 was previously shown upregulated by tensile stress [ 120 ]. A recent report also described the upregulation of COX2 in podocytes treated with PGE 2 [ 174 ]. We recently described that PGE 2 -induced activation of EP 2 led to upregulation of AKT-GSK3β-β catenin signaling.…”

“…Prostaglandin E 2 (PGE 2 ), the most abundant product of arachidonic acid metabolism, binds to four receptors (EP 1–4 ). EP 2 antagonist PF-04418948 [ 292 , 293 ] and EP 4 antagonist ONO-AE3–208 [ 294 , 295 ] were recently used to demonstrate that both EP 2 and EP 4 mediate the PGE 2 -induced increase in cAMP [ 174 ]. Preliminary work in our laboratory indicates that a combination of receptor agonists and antagonists may provide better attenuation of the effects of hyperfiltration (Unpublished results).…”

Local cyclic adenosine monophosphate signalling cascades—Roles and targets in chronic kidney disease

“…111 This upregulation and an autocrine/paracrine pathway between COX2 and PGE 2 that engages the PGE 2 receptors EP 2 and EP 4 exists in human podocytes, and PGE 2 levels are elevated in glomeruli of Munich Wistar Frömter rats, a model with glomerular hyperfiltration. 112 The stimulation of EP 2 and EP 4 receptors induces cAMP synthesis. 112 However, the involved cAMP signalling compartments are unknown.…”

“…112 The stimulation of EP 2 and EP 4 receptors induces cAMP synthesis. 112 However, the involved cAMP signalling compartments are unknown. Elucidation of the podocyte cAMP pathways may provide novel targets for renoprotection against mal-adaptations of podocytes to hyperfiltration.…”

“…Excessive fluid flow shear stress causes podocyte injury, which is associated with elevated prostaglandin E 2 (PGE 2 ) synthesis and upregulation of cyclooxygenase 2 (COX2) 111 . This upregulation and an autocrine/paracrine pathway between COX2 and PGE 2 that engages the PGE 2 receptors EP 2 and EP 4 exists in human podocytes, and PGE 2 levels are elevated in glomeruli of Munich Wistar Frömter rats, a model with glomerular hyperfiltration 112 . The stimulation of EP 2 and EP 4 receptors induces cAMP synthesis 112 .…”