Suberoylanilide Hydroxamic Acid Enhances Gap Junctional Intercellular Communication via Acetylation of Histone Containing Connexin 43 Gene Locus

Abstract

A histone deacetylase (HDAC) inhibitor, suberoylanilide hydroxamic acid (SAHA), induces apoptosis in neoplastic cells, but its effect on gap junctional intercellular communication in relation to apoptosis was unclear. Therefore, we carried out a comparative study of the effects of two HDAC inhibitors, SAHA and trichostatin-A, on gap junctional intercellular communication in nonmalignant human peritoneal mesothelial cells (HPMC) and tumorigenic ras oncogenetransformed rat liver epithelial cells (WB-ras) that showed a significantly lower level of gap junctional intercellular communication than did HPMC. Gap junctional intercellular communication was assessed by recovery rate of fluorescence recovery after photobleaching. Treatment of HPMC with SAHA at nanomolar concentrations caused a dose-dependent increase of recovery rate without inducing apoptosis. This effect was accompanied by enhanced connexin 43 (Cx43) mRNA and protein expression and increased presence of Cx43 protein on cell membrane. Trichostatin-A induced apoptosis in HPMC but was less potent than SAHA in enhancing the recovery rate. In contrast, treatment of WB-ras cells with SAHA or trichostatin-A induced apoptosis at low concentrations, in spite of smaller increases in recovery rate, Cx43 mRNA, and protein than in HPMC. Chromatin immunoprecipitation analysis revealed that SAHA enhanced acetylated histones H3 and H4 in the chromatin fragments associated with Cx43 gene in HPMC. These results indicate that SAHA at low concentrations selectively up-regulates Cx43 expression in normal human cells without induction of apoptosis, as a result of histone acetylation in selective chromatin fragments, in contrast to the apoptotic effect observed in tumorigenic WB-ras cells. These results support a cancer therapeutic and preventive role for specific HDAC inhibitors. (Cancer Res 2005; 65(21): 9771-8)

Negative and Positive Regulation of Gene Expression by Mouse Histone Deacetylase 1

“…HDAC1 was recruited either constitutively (Gja1) or, in the case of the Irf1 and Gbp2 IFN-responsive genes, in response to the IFN signal, strongly suggesting that these genes are direct HDAC1 targets. Gja1 is the major protein of gap junctions in the heart and seems to display differential responses to deacetylase inhibitors in normal versus transformed cells (55). The Irf1 gene was shown to be a tumor susceptibility gene which encodes a protein with tumor suppressor-like function (reviewed in reference 69).…”

Connexin-related signaling in cell death: to live or let die?

“…96 Increased Cx phosphorylation does not always go hand in hand with a loss of GJIC. Indeed, in the WB-F344 rat liver epithelial cell model, serum deprivation 91 and exposure to the histone deacetylase inhibitor suberoylanilide hydroxamic acid 97 enhanced GJIC, particularly during the early phases of apoptosis, and simultaneously increased Cx43 phosphorylation. Inversely, inhibition of GJIC in primary bovine lens epithelial cells and primary human corneal fibroblasts by staurosporine 92 and TNFa 98 was accompanied by a decrease in the Cx43 phosphorylation status.…”

Reflections on the use of 10 IARC carcinogenic characteristics for an objective approach to identifying and organizing results from certain mechanistic studies

“…While cancer chemo-preventive agents either block the inhibition of GJIC by non-genetic, but epigenetically acting tumor promoters, several anti-cancer therapeutic agents, such as SAHA, 76 an inhibitor of histone deacetylase, can induce GJIC in non-gap junction expressing cancer cells.…”