Protective Effect of TRPV1 against Renal Fibrosis via Inhibition of TGF-β/Smad Signaling in DOCA-Salt Hypertension
To investigate the effects of the transient receptor potential vanilloid type 1 (TRPV1) channel on renal extracellular matrix (ECM) protein expression including collagen deposition and the transforming growth factor β (TGF-β)/Smad signaling pathway during salt-dependent hypertension, wild-type (WT) and TRPV1-null (TRPV1−/−) mutant mice were uninephrectomized and given deoxycorticosterone acetate (DOCA)-salt for 4 wks. TRPV1 gene ablation exaggerated DOCA-salt-induced impairment of renal function as evidenced by increased albumin excretion (µg/24 h) compared with WT mice (83.7 ± 7.1 versus 28.3 ± 4.8, P < 0.05), but had no apparent effect on mean arterial pressure (mmHg) as determined by radiotelemetry (141 ± 4 versus 138 ± 3, P > 0.05). Morphological analysis showed that DOCA-salt-induced glomerulosclerosis, tubular injury and macrophage infiltration (cells/mm2) were increased in TRPV1−/− compared with WT mice (0.74 ± 0.08 versus 0.34 ± 0.04; 3.14 ± 0.26 versus 2.00 ± 0.31; 68 ± 5 versus 40 ± 4, P < 0.05). Immunostaining studies showed that DOCA-salt treatment decreased nephrin but increased collagen type I and IV as well as phosphorylated Smad2/3 staining in kidneys of TRPV1−/− compared with WT mice. Hydroxyproline assay and Western blot showed that DOCA-salt treatment increased collagen content (µg/mg dry tissue) and fibronectin protein expression (%β-actin arbitrary units) in the kidney of TRPV1−/− compared with WT mice (26.7 ± 2.7 versus 17.4 ± 1.8; 0.93 ± 0.07 versus 0.65 ± 0.08, P < 0.05). Acceleration of renal ECM protein deposition in DOCA-salt-treated TRPV1−/− mice was accompanied by increased TGF-β1, as well as phosphorylation of Smad2/3 protein expression (%β-actin arbitrary units) compared with DOCA-salt-treated WT mice (0.61 ± 0.07 versus 0.32 ± 0.05; 0.57 ± 0.07 versus 0.25 ± 0.05; 0.71 ± 0.08 versus 0.40 ± 0.06, P < 0.05). These results show that exaggerated renal functional and structural injuries are accompanied by increased production of ECM protein and activation of the TGF-β/Smad2/3 signaling pathway. These data suggest that activation of TRPV1 attenuates the progression of renal fibrosis possibly via suppression of the TGF-β and its downstream regulatory signaling pathway.
This work was supported in part by National Institutes of Health grants HL-57853, HL-73287 and DK67620 and a grant from the Michigan Economic Development Corporation. The authors thank Beihua Zhong for her excellent technical assistance.
- 8.Spriewald BM, Ensminger SM, Billing JS, Morris PJ, Wood KJ. (2003) Increased expression of transforming growth factor-beta and eosinophil infiltration is associated with the development of transplant arteriosclerosis in long-term surviving cardiac allografts. Transplantation. 76:1105–11.CrossRefGoogle Scholar
- 10.Mata-Greenwood E, Meyrick B, Steinhorn RH, Fineman JR, Black SM. (2003) Alterations in TGF-beta1 expression in lambs with increased pulmonary blood flow and pulmonary hypertension. Am. J. Physiol. 285:L209–21.Google Scholar
- 23.Ying WZ, Sanders PW. (2003) The interrelationship between TGF-beta1 and nitric oxide is altered in salt-sensitive hypertension. Am. J. Physiol. 285:F902–8.Google Scholar
- 26.Ziyadeh FN, et al. (2000) Long-term prevention of renal insufficiency, excess matrix gene expression, and glomerular mesangial matrix expansion by treatment with monoclonal antitransforming growth factor-beta antibody in db/db diabetic mice. Proc. Natl. Acad. Sci. U.S.A. 97:8015–20.CrossRefGoogle Scholar
- 37.Rodriguez-Iturbe B, Vaziri ND, Herrera-Acosta J, Johnson RJ. (2004) Oxidative stress, renal infiltration of immune cells, and salt-sensitive hypertension: all for one and one for all. Am. J. Physiol. 286:F606–16.Google Scholar
- 40.Wang Y, Wang DH. (2009) Aggravated renal inflammatory responses in TRPV1 gene knockout mice subjected to DOCA-salt hypertension. Am. J. Physiol. 297:F1550–9.Google Scholar
- 41.Wang Y, Chen AF, Wang DH. (2006) Enhanced oxidative stress in kidneys of salt-sensitive hypertension: role of sensory nerves. Am. J. Physiol. 291:H3136–43.Google Scholar