Both adrenomedullin (ADM) and adrenotensin (ADT) are derived from the same propeptide precursor, and both act as circulating hormones and local paracrine mediators with multiple biological activities. Compared with ADM, little is known about how ADT achieves its functions. In the present study, we investigated the effect of ADT on cell proliferation and transforming growth factor-beta (TGF-beta) secretion in cultured renal mesangial cells (MCs) and determined whether angiotensin II (Ang II) was involved in mediating this process.
Cell proliferation was measured by bromodeoxyuridine (BrdU) incorporation assay, Ang II levels were assayed using an enzyme immunoassay, and real time PCR was used to measure Ang II type 1 (AT1) receptor, Ang II type 2 (AT2) receptor, angiotensinogen (AGT), renin, angiotensin converting enzyme (ACE) and TGF-beta1 mRNA levels. TGF-beta1 and collagen type IV protein levels in cell media were measured using enzyme-linked immunoassays.
ADT treatment induced cell proliferation in a concentration-dependent manner; it also increased the levels of TGF-beta1 mRNA and protein as well as collagen type IV excretion by cultured MCs. ADT treatment increased renin and AGT mRNAs as well as Ang II protein, but did not affect the ACE mRNA level. ADT up-regulated angiotensin AT1 receptor mRNA, but not that of the AT2 receptor. The angiotensin AT1 receptor antagonist losartan blocked the effects of ADT-induced cell proliferation, TGF-beta1 and collagen type IV synthesis and secretion.
ADT has a stimulating role in cell proliferation in cultured MCs. Increases in the levels of Ang II and the AT1 receptor after ADT treatment mediate the stimulating effects of ADT on cell proliferation and extracellular matrix synthesis and secretion.