Calcium-dependent phosphodiesterase 1C inhibits renin release from isolated juxtaglomerular cells

Abstract

release from the juxtaglomerular (JG) cell is stimulated by the second messenger cAMP and inhibited by calcium. We previously showed JG cells contain a calcium sensing receptor (CaSR), which, when stimulated, decreases cAMP formation and inhibits renin release. We hypothesize CaSR activation decreases cAMP and renin release, in part, by stimulating a calcium calmodulin-activated phosphodiesterase 1 (PDE1). We incubated our primary culture of JG cells with two selective PDE1 inhibitors [8-methoxymethil-IBMX (8-MM-IBMX; 20 M) and vinpocetine (40 M)] and the calmodulin inhibitor W-7 (10 M) and measured cAMP and renin release. Stimulation of the JG cell CaSR with the calcimimetic cinacalcet (1 M) resulted in decreased cAMP from a basal of 1.13 Ϯ 0.14 to 0.69 Ϯ 0.08 pM/mg protein (P Ͻ 0.001) and in renin release from 0.89 Ϯ 0.16 to 0.38 Ϯ 0.08 g ANG I/ml ⅐ h Ϫ1 ⅐ mg protein Ϫ1 (P Ͻ 0.001). However, the addition of 8-MM-IBMX with cinacalcet returned both cAMP (1.10 Ϯ 0.19 pM/mg protein) and renin (0.57 Ϯ 0.16 g ANG I/ml ⅐ h Ϫ1 ⅐ mg protein Ϫ1 ) to basal levels. Similar results were obtained with vinpocetine, and also with W-7. Combining 8-MM-IBMX and W-7 had no additive effect. To determine which PDE1 isoform is involved, we performed Western blot analysis for PDE1A, B, and C. Only Western blot analysis for PDE1C showed a characteristic band apparent at 80 kDa. Immunofluorescence showed cytoplasmic distribution of PDE1C and renin in the JG cells. In conclusion, PDE1C is expressed in isolated JG cells, and contributes to calcium's inhibitory modulation of renin release from JG cells.angiotensin; calmodulin; phosphodiesterase; cAMP; adenylyl cyclase RENIN IS THE RATE-LIMITING enzymatic step in the production of angiotensin, a hormone that integrates cardiovascular and renal function in the control of blood pressure as well as salt and volume homeostasis (33). Renin is produced by, stored in, and released from juxtaglomerular (JG) cells, which are derived from renin progenitor cells (42) and are located in the afferent arteriole near the hilus of the glomerulus (2, 43, 35). Two main intracellular second messenger systems are known to regulate renin synthesis and secretion: the cyclic nucleotide, cyclic adenosine monophosphate (cAMP) (8, 41), and intracellular calcium (Ca) (21).Renin secretion by the JG cells demonstrates a paradoxical inverse relationship with intracellular calcium concentration, such that millimolar changes in extracellular Ca or micromolar elevations in intracellular calcium retard renin release (1,9,14,20,22). The primary second messenger involved in the regulation of renin release is cAMP (8), and the concentration of cAMP in cells is determined by a balance between the rate of cAMP generation by adenylyl cyclases and cAMP hydrolysis by phosphodiesterases (PDE) (7, 16). We (30, 31), and also Grünberger et al. (18), have reported JG cells express calciuminhibitable adenylyl cyclase (27). Furthermore, we have identified the JG-specific isoform-regulating renin release to be adenylyl cyclase type V (30)...

Physiology and pathophysiology of the calcium-sensing receptor in the kidney

“…A variety of stimuli trigger renin secretion by juxtaglomerular (JG) cells of the lamina media of the afferent arteriole (9), largely through production of intracellular cAMP (11). Recent evidence suggests that the CaSR is expressed in JG cells and that activation of the receptor decreases renin secretion by suppressing the activity of the Ca 2ϩ -inhibitable type V adenylate cyclase (AC-V) (115), and through stimulation of calcium/calmodulinactivated phosphodiesterases (114). Several earlier studies had shown that decreases in Ca o 2ϩ concentration produce large increases in basal and stimulated renin release (47).…”

Juxtaglomerular cell CaSR stimulation decreases renin release via activation of the PLC/IP3pathway and the ryanodine receptor

“…We used primary cultures of mouse isolated juxtaglomerular (JG) cells, with a protocol modified in our laboratory (43)(44)(45)(46) to improve the harvest, purity, and stability of the primary culture (39). The JG cells were incubated at 37°C in a humidified atmosphere containing 5% CO 2 in air.…”

“…We have previously found that CaSRmediated increases in intracellular calcium result in suppression of the calcium-inhibitable isoform-five (45) of adenylyl cyclase (AC-V), and also enhance the calcium-activated isoform of phosphodiesterase, 1C (PDE1C) (43). Thus activation of the JG cell CaSR results in intracellular calcium-mediated suppression of cAMP formation and inhibition of renin release (43,45,46). But what couples the receptor to calcium-mediated events?…”

“…In the secretory juxtaglomerular (JG) cells, like the parathyroids, increased calcium results in the suppression of renin secretion (21,43,44). We have previously reported, both in vitro (44) and in vivo (6), that the JG cells contain CaSR, and that increased media calcium or activation of the CaSR with a calcimimetic (6,43,44) leads to suppression of renin secretion.…”

“…We have previously reported, both in vitro (44) and in vivo (6), that the JG cells contain CaSR, and that increased media calcium or activation of the CaSR with a calcimimetic (6,43,44) leads to suppression of renin secretion. JG cells synthesize, store, and release renin, the rate-limiting enzyme involved in the formation of angiotensin II (9).…”