Dexamethasone inhibits spontaneous apoptosis in primary cultures of human and rat hepatocytes via Bcl-2 and Bcl-xL induction

Abstract

We examined the effects of dexamethasone (DEX) on the apoptotic process in primary cultures of human and rat hepatocytes. DEX prolonged cell viability, inhibited the development of an apoptotic morphology, and stabilised the expression of procaspase-3 in both human and rat hepatocytes. In addition, the inhibition of apoptosis by DEX was strongly correlated with a decrease of caspase-3-like protease activity. Moreover, DEX treatment increased the expression of anti-apoptotic Bcl-2 and Bcl-xL proteins in human and rat hepatocytes, respectively, whereas the expression of pro-apoptotic proteins Bcl-xS or Bad was not detected or remained unchanged. The bcl-xL transcript is regulated at the transcriptional level and its expression paralleled that of Bcl-xL protein in DEX-treated rat hepatocytes. Taken together, these results indicate that this glucocorticoid exerts a protective role on cell survival and it delays apoptosis of human and rat hepatocytes by modulating caspase-3-like protease activity and bcl-2 and bcl-x gene expression. Cell Death and Differentiation (2001) 8, 279 ± 288.

Dexamethasone protects primary cultured hepatocytes from death receptor-mediated apoptosis by upregulation of cFLIP

“…6,12,26 The antiapoptotic effect by DEX has been shown to be due to the upregulation of the Bcl-2 family proteins such as Bcl-2 and Bcl-xL in hepatocytes. 8 These protein levels have been shown to be upregulated in hepatocytes only after long-term treatment with DEX Figure 6 Pretreatment with DEX protects hepatocytes from Jo2-induced apoptosis by inhibiting DISC formation and caspase-8 activation. Hepatocytes were incubated with 500 ng/ml Jo2 plus 100 ng/ml ActD (Jo2 þ ActD) following pretreatment with 5 mM DEX for 6 h. (a) After 12 h, cell viability was measured by crystal violet staining.…”

“…3 days), and this treatment decreased the susceptibility of hepatocytes to spontaneous apoptosis. 8 However, we here showed that pretreatment of hepatocytes with DEX for 6-18 h almost fully prevents cells from acute apoptosis (within 18 h) induced by TNF-a and Jo2 in the presence of ActD. In this experimental condition, DEX pretreatment did not alter the protein levels of the antiapoptotic genes such as Bcl-2, Bcl-xL, Mcl-1, and cIAP and the activation of the antiapoptotic serine/threoine kinase Akt, indicating that these genes are not involved in DEX-mediated hepatoprotection.…”

“…5 Furthermore, DEX has been shown to either inhibit apoptosis in some cells such as human neutrophils, 6 tumor cells, 7 and primary human and rat hepatocytes 8 or induce apoptosis in others including thymocytes and lymphocytes. 9,10 The antiapoptotic effect by DEX is regulated by several sets of genes, the best characterized of which are the Bcl-2 family such as Bcl-2 and Bcl-xL, which prevent spontaneous apoptosis of cultured primary hepatocytes.…”

Spontaneous apoptosis in primary cultures of human and rat hepatocytes: molecular mechanisms and regulation by dexamethasone

“…22 We previously demonstrated that apoptosis was spontaneously activated in primary human and rat hepatocytes cultivated ex vivo and that dexamethasone significantly prevented this process. 9 In this study, we wished to determine the mechanism by which DEX protects against spontaneous hepatocyte apoptosis. We first analyzed the effects of increasing concentrations of dexamethasone on hepatocyte viability, by using the MTT dye-reduction assay.…”

Molecular Mechanisms Conferring Resistance/Sensitivity to Glucocorticoid-Induced Apoptosis

“…The involvement of the Bcl-2 family members in the glucocorticoid-induced apoptosis has been shown in cellular and animal studies [49]. For example, the expression of the anti-apoptotic Bcl-2 family member in glucocorticoid-sensitive thymocytes is lower compared to that in glucocorticoid-resistant ones [2], and overexpression of the anti-apoptotic Bcl-2 and B-cell lymphoma-extra large (Bcl-xL) in human ALL prevents glucocorticoids induced apoptosis [50,51,52,53] whereas knock down of the pro-apoptotic member Bim confers resistance to dexamethasone mediated apoptosis [54]. Furthermore, over-expression of the proapoptotic Bax [55] and knock down of the myeloid cell leukemia sequence 1 (Mcl-1) sensitises ALL cells to glucocorticoid treatment [56].…”