NPY_1–36and PYY_1–36activate cardiac fibroblasts: an effect enhanced by genetic hypertension and inhibition of dipeptidyl peptidase 4

Abstract

Cardiac sympathetic nerves release neuropeptide Y (NPY)1-36, and peptide YY (PYY)1-36 is a circulating peptide; therefore, these PP-fold peptides could affect cardiac fibroblasts (CFs). We examined the effects of NPY1-36 and PYY1-36 on the proliferation of and collagen production ([(3)H]proline incorporation) by CFs isolated from Wistar-Kyoto (WKY) normotensive rats and spontaneously hypertensive rats (SHRs). Experiments were performed with and without sitagliptin, an inhibitor of dipeptidyl peptidase 4 [DPP4; an ectoenzyme that metabolizes NPY1-36 and PYY1-36 (Y1 receptor agonists) to NPY3-36 and PYY3-36 (inactive at Y1 receptors), respectively]. NPY1-36 and PYY1-36, but not NPY3-36 or PYY3-36, stimulated proliferation of CFs, and these effects were more potent than ANG II, enhanced by sitagliptin, blocked by BIBP3226 (Y1 receptor antagonist), and greater in SHR CFs. SHR CF membranes expressed more receptor for activated C kinase (RACK)1 [which scaffolds the Gi/phospholipase C (PLC)/PKC pathway] compared with WKY CF membranes. RACK1 knockdown (short hairpin RNA) and inhibition of Gi (pertussis toxin), PLC (U73122), and PKC (GF109203X) blocked the proliferative effects of NPY1-36. NPY1-36 and PYY1-36 stimulated collagen production more potently than did ANG II, and this was enhanced by sitagliptin and greater in SHR CFs. In conclusion, 1) NPY1-36 and PYY1-36, via the Y1 receptor/Gi/PLC/PKC pathway, activate CFs, and this pathway is enhanced in SHR CFs due to increased localization of RACK1 in membranes; and 2) DPP4 inhibition enhances the effects of NPY1-36 and PYY1-36 on CFs, likely by inhibiting the metabolism of NPY1-36 and PYY1-36. The implications are that endogenous NPY1-36 and PYY1-36 could adversely affect cardiac structure/function by activating CFs, and this may be exacerbated in genetic hypertension and by DPP4 inhibitors.

Inhibition of Dipeptidyl Peptidase-4 Impairs Ventricular Function and Promotes Cardiac Fibrosis in High Fat–Fed Diabetic Mice

“…Moreover, high glucose levels and increased levels of free fatty acids exert complementary effects to promote cardiomyocyte Ctgf expression, which in turn may independently promote cardiac fibrosis. The plausibility of DPP4 activity controlling the extent of cardiac fibrosis is further supported by data demonstrating that DPP4 inhibition potentiated the neuropeptide Y-dependent and protein YY-dependent regulation of cell proliferation and collagen synthesis in cardiac fibroblast cultures (41). Hence, we hypothesize that, under conditions characterized by sustained hyperglycemia, dyslipidemia, and pressure overload in older animals, reduction of DPP4 activity may further accelerate the development of cardiac fibrosis.…”

“…Intriguingly, multiple DPP4 substrates increase cell proliferation and promote fibrosis, including neuropeptide Y, protein YY (40,41), and stromal-derived factor-1 (42). Furthermore, exposure to high glucose upregulates a transcriptional program enabling cardiac fibroblast proliferation, collagen synthesis, and cardiac fibrosis (43-45); upregulation of local angiotensin-II expression has also been linked to cardiac fibrosis (46).…”

SDF‐1α (Stromal Cell‐Derived Factor 1α) Induces Cardiac Fibroblasts, Renal Microvascular Smooth Muscle Cells, and Glomerular Mesangial Cells to Proliferate, Cause Hypertrophy, and Produce Collagen

“…Attenuation of the metabolism of NPY 1–36 and PYY 1–36 by DPP4 inhibitors may have adverse consequences. Our recently published results show that NPY 1–36 and PYY 1–36 , but not NPY 3–36 or PYY 3–36 , stimulate proliferation of and extracellular matrix production by cardiac fibroblasts (CFs), preglomerular vascular smooth muscle cells (PGVSMCs), and glomerular mesangial cells (GMCs) . Moreover, our results show that the effects of NPY 1–36 and PYY 1–36 are mediated by Y 1 Rs, are greater in cells from animals with genetic hypertension (spontaneously hypertensive rats [SHRs]), and are enhanced by inhibition of DPP4 .…”

“…Our recently published results show that NPY 1–36 and PYY 1–36 , but not NPY 3–36 or PYY 3–36 , stimulate proliferation of and extracellular matrix production by cardiac fibroblasts (CFs), preglomerular vascular smooth muscle cells (PGVSMCs), and glomerular mesangial cells (GMCs) . Moreover, our results show that the effects of NPY 1–36 and PYY 1–36 are mediated by Y 1 Rs, are greater in cells from animals with genetic hypertension (spontaneously hypertensive rats [SHRs]), and are enhanced by inhibition of DPP4 . Because activation of CFs can lead to cardiac fibrosis and heart failure and activation of PGVSMCs and GMCs can lead to renovascular hypertrophy, glomerulosclerosis, renal fibrosis, and renal failure, these results indicate that we must more thoroughly investigate the effects of DPP4 inhibitors on growth responses to DPP4 peptide substrates.…”

“…RACK1 was knocked down in CFs using a lentivirus encoding a RACK1 29‐bp short hairpin RNA (shRNA). See Zhu et al for details regarding our method for generating the RACK1 shRNA‐encoding lentivirus and transducing CFs with this construct.…”