Mechanism of Bradykinin-Induced Ca²⁺Mobilization in Murine Proximal Tubule Epithelial Cells

Abstract

Despite the recognized physiological role of bradykinin (BK) in the kidney in maintaining glomerular and tubule function and its role in pathological states such as endotoxemia, diabetes, and other diseases, relatively little is known about the mechanisms by which BK can impact kidney function. Furthermore, the signaling of BK receptors in the murine nephron has not been fully characterized. The present studies were undertaken to examine BK-stimulated Ca 2ϩ signaling using Fura-2 in the murine proximal tubule epithelial cell line TKPTS. BK produced a concentration-dependent rise in intracellular Kinins are a family of peptides that exert their effects through two receptor subtypes, B1 and B2. Bradykinin (BK) is a nine-amino acid peptide generated by the plasma kallikrein-kinin system of proteinases and is the natural agonist for B2 receptors. Carboxypeptidase M degrades BK to a second member of the kinin family, des-Arg 9 -BK, which is a selective agonist at B1 receptors (Bathon and Proud, 1991). Kallidin is a 10-amino acid peptide produced by the tissue kallikrein-kinin system and is also a natural agonist for B2 receptors and can be converted to BK by plasma aminopeptidase. The efficient catabolism of filtered kinins by the renal tubule (Casarini et al., 1999) suggests that local activation of the kallikrein-kinin system is responsible for the generation of B1 and B2 agonists in the kidney.The renal kallikrein-kinin system is a paracrine/autocrine system that participates in the regulation of renal hemodynamics and tubular function (Siragy et al., 1996;Wang et al., 2000). The effects of the kinins are thought to be primarily mediated by B2 receptors constitutively expressed throughout the nephron under physiological conditions (Figueroa et al., 1995). The B1 receptor is not considered to be constitutively expressed but can be induced by inflammatory stimuli or by chronic inhibition of angiotensin-converting enzyme (Marin-Castano et al., 2002).The physiological role of renal B2 receptors has been studied extensively in rats, and the distribution of B2 receptors along the nephron has been well documented in this species Article, publication date, and citation information can be found at

The bradykinin B2 receptor induces multiple cellular responses leading to the proliferation of human renal carcinoma cell lines

“…We demonstrated that BK causes an elevation of intracellular Ca 2+ in A498 cells, which was blocked by the BK B 2 receptor antagonist HOE-140, but not by the BK B 1 receptor antagonist des-Arg 10 -HOE-140, indicating a role for the BK B 2 receptor (Figure 2). Similar BK-induced intracellular Ca 2+ mobilization has been described in several kidney cell lines, including rat mesangial cells,29 the mIMCD-3 murine inner medullary collecting duct cell line,25 Kirsten murine sarcoma-virus transformed rat kidney KNRK cells,30 the mouse proximal tubule epithelial cell line,31 and in the human embryonic kidney (HEK293) cell line 26…”

Identification of functional bradykinin B2 receptors endogenously expressed in HEK293 cells

“…The BK B 2 receptor usually couples to the GTP-binding protein G q , and stimulates phospholipase C activity, causing phosphoinositide hydrolysis, that leads to generation of inositol triphosphate and to subsequent mobilization of intracellular Ca 2+ from the endoplasmic reticulum [22, 23]. BK-induced intracellular Ca 2+ mobilization has been described in several kidney cell lines including rat mesangial cells [24], the mIMCD-3 murine inner medullary collecting duct cell line [20], Kirsten murine sarcoma-virus transformed rat kidney KNRK cells, [25] and the TKPTS mouse proximal tubule epithelial cell line [26]. BK produced a concentration-dependent elevation of intracellular Ca 2+ in HEK293 cells (Figure 2) with a EC 50 value of 36.5 ± 8.0 10 −9 M which is somewhat higher than EC 50 values reported for other renal cell lines that demonstrate nanomolar potency of BK for stimulating Ca 2+ mobilization [20,24,25,26].…”

“…BK-induced intracellular Ca 2+ mobilization has been described in several kidney cell lines including rat mesangial cells [24], the mIMCD-3 murine inner medullary collecting duct cell line [20], Kirsten murine sarcoma-virus transformed rat kidney KNRK cells, [25] and the TKPTS mouse proximal tubule epithelial cell line [26]. BK produced a concentration-dependent elevation of intracellular Ca 2+ in HEK293 cells (Figure 2) with a EC 50 value of 36.5 ± 8.0 10 −9 M which is somewhat higher than EC 50 values reported for other renal cell lines that demonstrate nanomolar potency of BK for stimulating Ca 2+ mobilization [20,24,25,26]. Intracellular Ca 2+ mobilization was completely blocked by the specific phospholipase C (PLC) inhibitor, U-73122 supporting the requirement for PLC activation in the BK-induced Ca 2+ signal.…”

Functional expression of bradykinin B1 and B2 receptors in neonatal rat trigeminal ganglion neurons

“…Previous studies have indicated that B 2 receptors couple with the Gq protein. Activation of the Gq protein activates phospholipase C, which induces a number of intracellular second messenger systems, including 1, 2-diacylglycerol and inositol 1, 4, 5-trisphosphate, which activates protein kinase C and mobilizes intracellular Ca 2+ , respectively (Walker et al, 1995; Tiwari et al, 2005). …”