Figure 5. The antifibrotic effect of JQ1 is abolished by the sequestration of intracellular Ca²⁺ and overexpression of CAMK2A in dcSSc fibroblasts.

(A) Cells cultured in Ca²⁺-free media had lower levels of ACTA2 and COL1A1 compared with cells cultured in Ca²⁺-containing media. The effect of JQ1 on COL1A1 is blocked in cells cultured without Ca²⁺. n = 8 patients. (B) BAPTA-AM, an intracellular Ca²⁺-chelating reagent, significantly decreased ACTA2 and COL1A1 expression in dcSSc fibroblasts. It also blocked the effect of JQ1. n = 4 patients. (C) JQ1 downregulated CAMK2A expression in dcSSc fibroblasts. Overexpression of CAMK2A not only increased ACTA2 and COL1A1 expression, but it also blocked the antifibrotic effects of JQ1. n = 4 patients. (D) CAMK2A is critical for cell proliferation, as overexpression of this gene enhanced cell proliferation. The inhibitory effect of JQ1 on cell proliferation was blocked by CAMK2A overexpression. n = 4 patients. Results are expressed as mean ± SD and P < 0.05 was considered significant. Significance was determined by 1-way ANOVA. NT, no treatment.