This paper advances the thesis of methodological mechanism, the claim that to be committed to mechanism is to adopt a certain methodological postulate, i.e. to look for causal pathways for the phenomena of interest. We argue that methodological mechanism incorporates a minimal account of understanding mechanisms, according to which a mechanism just is a causal pathway described in the language of theory. In order to argue for this position we discuss a central example of a biological mechanism, the mechanism of (...) cell death, known as apoptosis. We argue that this example shows that our philosophically deflationary account is sufficient in order to have an illuminating account of mechanisms as the concept is used in biology. (shrink)

Previous studies have shown that zinc deficiency leads to apoptosis of neuronal precursor cells in vivo and in vitro. In addition to the role of p53 as a nuclear transcription factor in zinc deficient cultured human neuronal precursors (NT-2), we have now identified the translocation of phosphorylated p53 to the mitochondria and p53-dependent increases in the pro-apoptotic mitochondrial protein BAX leading to a loss of mitochondrial membrane potential as demonstrated by a 25% decrease in JC-1 red:green fluorescence ratio. Disruption (...) of mitochondrial membrane integrity was accompanied by efflux of the apoptosis inducing factor (AIF) from the mitochondria and translocation to the nucleus with a significant increase in reactive oxygen species (ROS) after 24 h of zinc deficiency. Measurement of caspase cleavage, mRNA, and treatment with caspase inhibitors revealed the involvement of caspases 2, 3, 6, and 7 in zinc deficiency-mediated apoptosis. Down-stream targets of caspase activation, including the nuclear structure protein lamin and polyADP ribose polymerase (PARP), which participates in DNA repair, were also cleaved. Transfection with a dominant-negative p53 construct and use of the p53 inhibitor, pifithrin- ␮, established that these alterations were largely dependent on p53. Together these data identify a cascade of events involving mitochondrial p53 as well as p53-dependent caspase-mediated mechanisms leading to apoptosis during zinc deficiency. (shrink)

Objective: Lung cancer is the most common cause of morbidity and mortality. Platinum-based chemotherapy, which is the primary line of treatment, offers limited benefit due to drug resistance and side effects. Berberine (BBR), which is characterised by its potent and safe anticancer activity, represents a promising combination option in chemotherapy. To overcome the limitations in lung cancer chemotherapy, we investigated whether BBR and cisplatin (CIS) exert synergistic effects on non-small cell lung cancer cell line (A549) based on cytotoxicity and apoptotic (...) response markers. -/- Methods: The potential cytotoxic effects of the combination treatment were evaluated using the MTT and Chou-Talalay methods. Elisa assays were also performed to measure the levels of the pro-apoptotic protein Bax and the effector protein caspase (Cas)-3. -/- Results: The results showed that BBR alone reduced A549 cell viability in a dose-dependent manner and synergized with CIS (CI =0.34±0.05 at IC50 concentrations). Elisa results showed that the combined treatment (both at IC50 concentrations) modulated apoptotic signalling pathways in A549 cells. Bax and Cas3 protein levels were dramatically enhanced in A549 cells treated with CIS +BBR compared to control (0.5% DMSO) (p < 0.001). -/- Conclusion: Our results suggest that BBR can synergistically enhance the therapeutic effect of CIS in A549 cells. The potential therapeutic efficacy of BBR as part of a combination in current chemotherapy should be supported by in-depth research and clinical studies on the molecular mechanisms associated with cancer. (shrink)

Saturated free fatty acids-induced hepatocyte lipoapoptosis plays a pivotal role in non-alcoholic steatohepatitis. Theactivation of endoplasmic reticulum (ER) stress isinvolved in hepatocyte lipoapoptosis induced by thesaturated free fatty acidpalmitate (PA). However, the underlying mechanismsof the role of ER stress in hepatocyte lipoapoptosis remain largely unclear.In this study, we showed that PA and tunicamycin (Tun), a classic ER stress inducer, resulted in differential activation of ERstress pathways. Our data revealed that PA inducedchronic and persistent ER stress response, but Tuninduced acute and (...) transientER stress response. Compared with Tun treatment, PAinduced much lower glucose-regulated protein 78 (GRP78), a centralregulator of ER homeostasis, accumulation. It is noteworthy that GRP78 over-expression not only inhibited PA-induced ERstress but also decreased PA-induced apoptosis. Taken together, our data suggest that the differentialactivation of ER stresssignal plays an important role in PA-induced hepatocyte lipoapoptosis. More detailed studies on the mechanisms of PA inrepressing the accumulation of GRP78 will contribute to the understanding of molecular mechanisms of lipoapoptosis. (shrink)