BimEL‐dependent apoptosis induced in peripheral blood lymphocytes with n‐butyric acid is moderated by variation in expression of c‐myc and p21(WAF1)

Abstract

We have examined the effect of sodium butyrate (SB) on the viability of normal peripheral blood lymphocytes (PBLs) in vitro and the effect of this agent on the expression of 20 apoptosis-related genes. Data suggest that PBL treated with 2 mmol L(-1) SB resisted for at least 8 h the destructive activity of the agent, but eventually 30% of cells died within 72 h. As documented by flow cytometry and cytochrome c release study, cells underwent mitochondrial-derived apoptosis. While the expression of the majority of genes examined by RT-PCR and Western blots remained indifferent to 2 mmol L(-1) SB, the cellular levels of BimEL, c-myc, p53, and p21(WAF1) varied profoundly with the time of SB treatment. The Bax activator BimEL increased rapidly, driving cells toward apoptosis likely controlled by c-myc and p21(WAF1) activities. The c-myc, exercising the role of mediator of the function of BimEL and inhibitor of p21(WAF1) expression, decreased significantly for several hours after adding SB but within 48 h it returned to close to its original value. An apoptosis inhibitor and executive caspase substrate p21(WAF1) increased early at the beginning of treatment but subsequently, within a time frame of 72 h, profoundly dropped in terms of both a caspase-dependent and caspase-independent way. We suggest that variations in c-myc and p21(WAF1) expression delay apoptosis making PBL resistant to SB for several hours, and together with fast catabolism of SB in vivo protect PBL against the destructive activity of this anti-cancerous metabolite of colonic bacteria.

Variations in c‐Myc and p21WAF1 expression protect normal peripheral blood lymphocytes against BimEL‐mediated cell death

“…This is in contrast with our previous studies with another HDACi, sodium butyrate, which manifested progressive generation of ROS in the cells treated with 2 mmol/L n-butyric acid 19 . Heider and co-workers 28 revealed that combination of SAHA and bortezomib treatment of mantle cell lymphoma was accompanied by strongly enhanced ROS generation, while each agent alone only modestly induced ROS.…”

“…Our experiments revealed that SAHA induced mitochondrial dysfunction (likely without significant ROS generation) in normal PBL at concentration similar to clinically used doses. Just like another HDACi, sodium butyrate 19 , SAHA triggered an intrinsic apoptotic pathway opened by the induction of BimEL. Variations of transcriptional activity of c-Myc and p21WAF1 genes indicate their regulatory function in the apoptotic death of PBL.…”

Butyrate regulates the expression of inflammatory and chemotactic cytokines in human acute leukemic cells during apoptosis

“…Another study demonstrated normal lymphocytes undergo a 30% decline in viable cells 72 hours after treatment with butyrate. The authors suggested variations in c-myc and p21 expression delayed butyrate-induced apoptosis for several hours [50]. The delay in the induction of apoptosis, evidence showing lymphocytes and monocytes behave similarly to butyrate, our data demonstrating the absence of butyrate-induced apoptosis on normal monocytes 24 hours post-treatment (Figure 2) and the high rate of degradation of butyrate in vivo [51] suggests lymphocytes and monocytes may be protected from the anti-cancer activities of butyrate.…”

Generation of Reactive Oxygen Species during Apoptosis Induced by DNA-Damaging Agents and/or Histone Deacetylase Inhibitors

“…Physiological concentrations of butyrate induce ROS that transiently alter intracellular redox balance of intestinal cells [27], preincubation by butyrate protects colonocytes against H 2 O 2 -induced damage [28]. In normal peripheral blood lymphocytes, butyrate induces apoptosis, which is partly mediated by ROS [29]. Another histone deacetylase inhibitor, suberoylanilide hydroxamic acid (Vorinostat, SAHA), increased reactive oxygen species levels in gastrointestinal tumor cells [30] as well as in leukemia [31] or small cell lung cancer cells [32].…”