Arthritis & Rheumatism, Volume 63,
November 2011 Abstract Supplement

Abstracts of the American College of
Rheumatology/Association of Rheumatology Health Professionals
Annual Scientific Meeting
Chicago, Illinois November 4-9, 2011.


Functional Inhibition of the TRPV2 Non-Selective Calcium Channel Causes a Potent Stimulation of Genes Encoding Types I and III Collagens and -Smooth Muscle Actin in Normal Dermal Fibroblasts: A Potential Mechanism of Myofibroblast Induction in SSc.

Wermuth1,  Peter J., Addya2,  Sankar, Jimenez1,  Sergio A.

Jefferson Institute of Molecular Medicine, Thomas Jefferson University, Philadelphia, PA
Kimmel Cancer Center, Thomas Jefferson University, Philadelphia, PA

Background/Purpose:

Transient receptor potential cation channel, subfamily V (TRPV) members are sensitive to a range of environmental stimuli, including heat, osmosensitivity and stress. Although originally described in sensory neurons, the ubiquitous expression of these non-selective calcium channels suggests a role in both sensory and nonsensory transduction. Systemic sclerosis (SSc) is a systemic disease characterized by fibrotic changes in skin and various internal organs. A comparison of global gene expression in early passage cultured dermal SSc fibroblasts to that in fibroblasts isolated from normal individuals identified the TRPV2 gene as one of the most downregulated genes in SSc versus normal dermal human fibroblasts. The role of TRPV1 and TRPV2 in regulating the expression of extracellular matrix (ECM) components was examined in this study.

Methods:

Total RNA was isolated from early passage (<6) dermal fibroblasts of Caucasian subjects (3 normal, 3 diffuse SSc). RNA was labeled and hybridized to Affymetrix human U133 2.0 Plus microarrays. Volcano plots were used to identify differentially expressed genes employing the parametric testing assuming equal variances (based on the results of a Student's two-sample t-test for two groups). Comparisons were made between each normal and each SSc sample. Differential gene expression was confirmed by real-time PCR on the same RNA samples employed for the microarrays. The effect of agonists and antagonists of TRPV1 and TRPV2 on expression levels of extracellular matrix components and a-smooth muscle actin in normal human dermal fibroblasts was monitored by real-time PCR and accumulation of type I collagen in culture medium was assessed by Western blot.

Results:

Microarray analyses showed that the expression of TRPV2 was downregulated 21 fold in SSc fibroblasts compared to the levels measured in normal human dermal fibroblasts whereas expression of the TRPV1 gene was unchanged. Real time-PCR analysis confirmed the dramatic decrease in TRPV2 expression. Normal dermal human fibroblasts exposed to Tranilast, a TRPV2-selective antagonist demonstrated a remarkable increase in the expression of numerous fibrosis related genes, including a 3.3-fold increase in type I collagen, a 2.8-fold increase in type III collagen and an 11.8-fold increase in a-smooth muscle actin. In contrast, the TRPV1 antagonist capsazepine, the TRPV1 agonist capsaicin, and the TRPV2 agonist probenecid did not affect the expression levels of any of these genes.

Conclusion:

Expression of the TRPV2 gene was profoundly downregulated in SSc dermal fibroblasts compared to normal dermal fibroblasts by global gene expression microarray and real time-PCR analysis. Exposure of normal human dermal fibroblasts to the TRPV2 inhibitor tranilast dramatically increased the expression of several genes encoding important ECM components and induced the expression of a-smooth muscle actin. These results suggest that downregulation of the TRPV2 receptor in SSc dermal fibroblasts may be important in the conversion of fibroblasts into activated myofibroblasts and, thus, may be involved in the dysregulated production of ECM proteins in SSc.

Supported by NIH Grants T32AR07583 (PJW) and R01AR19616 (SAJ).

To cite this abstract, please use the following information:
Wermuth, Peter J., Addya, Sankar, Jimenez, Sergio A.; Functional Inhibition of the TRPV2 Non-Selective Calcium Channel Causes a Potent Stimulation of Genes Encoding Types I and III Collagens and -Smooth Muscle Actin in Normal Dermal Fibroblasts: A Potential Mechanism of Myofibroblast Induction in SSc. [abstract]. Arthritis Rheum 2011;63 Suppl 10 :2608
DOI:

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