"Programmed Cell Death: A Process of Death for Survival" - How Far Terminology Pertinent for Cell Death in Unicellular Organisms

Non-apoptotic cell death programs in cervical cancer with an emphasis on ferroptosis

BACKGROUND

Cervical cancer, a pernicious gynecological malignancy, causes the mortality of hundreds of thousands of females worldwide. Despite a considerable decline in mortality, the surging incidence rate among younger women has raised serious concerns. Immortality is the most important characteristic of tumor cells, hence the carcinogenesis of cervical cancer cells pivotally requires compromising with cell death mechanisms.

METHODS

The current study comprehensively reviewed the mechanisms of non-apoptotic cell death programs to provide possible disease management strategies.

RESULTS

Comprehensive evidence has stated that focusing on necroptosis, pyroptosis, and autophagy for disease management is associated with significant limitations such as insufficient understanding, contradictory functions, dependence on disease stage, and complexity of intracellular pathways. However, ferroptosis represents a predictable role in cervix carcinogenesis, and ferroptosis-related genes demonstrate a remarkable correlation with patient survival and clinical outcomes.

CONCLUSION

Ferroptosis may be an appropriate option for disease management strategies from predicting prognosis to treatment.

Ferroptosis-induced Cardiotoxicity and Antitumor Drugs

The induction of regulated cell death ferroptosis in tumors is emerging as an intriguing strategy for cancer treatment. Numerous antitumor drugs (e.g., doxorubicin, etoposide, tyrosine kinase inhibitors, trastuzumab, arsenic trioxide, 5-fluorouracil) induce ferroptosis. Although this mechanism of action is interesting for fighting tumors, the clinical use of drugs that induce ferroptosis is hampered by cardiotoxicity. Besides in cancer cells, ferroptosis induced by chemotherapeutics can occur in cardiomyocytes, and this feature represents an important drawback of antitumor therapy. This inconvenience has been tackled by developing less or no cardiotoxic antitumor drugs or by discovering cardioprotective agents (e.g., berberine, propofol, fisetin, salidroside, melatonin, epigallocatechin- 3gallate, resveratrol) to use in combination with conventional chemotherapeutics. This review briefly summarizes the molecular mechanisms of ferroptosis and describes the ferroptosis dependent mechanisms responsible for cardiac toxicity developed by cancer- suffering patients following the administration of some chemotherapeutics. Additionally, the pharmacological strategies very recently proposed for potentially preventing this inconvenience are considered.

Targeted Inhibition of Hsp90 in Combination with Metformin Modulates Programmed Cell Death Pathways in A549 Lung Cancer Cells

The pathophysiology of lung cancer is dependent on the dysregulation in the apoptotic and autophagic pathways. The intricate link between apoptosis and autophagy through shared signaling pathways complicates our understanding of how lung cancer pathophysiology is regulated. As drug resistance is the primary reason behind treatment failure, it is crucial to understand how cancer cells may respond to different therapies and integrate crosstalk between apoptosis and autophagy in response to them, leading to cell death or survival. Thus, in this study, we have tried to evaluate the crosstalk between autophagy and apoptosis in A549 lung cancer cell line that could be modulated by employing a combination therapy of metformin (6 mM), an anti-diabetic drug, with gedunin (12 µM), an Hsp90 inhibitor, to provide insights into the development of new cancer therapeutics. Our results demonstrated that metformin and gedunin were cytotoxic to A549 lung cancer cells. Combination of metformin and gedunin generated ROS and promoted MMP loss and DNA damage. The combination further increased the expression of AMPKα1 and promoted the nuclear localization of AMPKα1/α2. The expression of Hsp90 was downregulated, further decreasing the expression of its clients, EGFR, PIK3CA, AKT1, and AKT3. Inhibition of the EGFR/PI3K/AKT pathway upregulated TP53 and inhibited autophagy. The combination was promoting nuclear localization of p53; however, some cytoplasmic signals were also detected. Further increase in the expression of caspase 9 and caspase 3 was observed. Thus, we concluded that the combination of metformin and gedunin upregulates apoptosis by inhibiting the EGFR/PI3K/AKT pathway and autophagy in A549 lung cancer cells.

Nanoparticle-Based Antioxidants in Stress Signaling and Programmed Cell Death in Breast Cancer Treatment

Breast cancer (BC) is a complex and heterogeneous disease, and oxidative stress is a hallmark of BC. Oxidative stress is characterized by an imbalance between the production of reactive oxygen species (ROS) and antioxidant defense mechanisms. ROS has been implicated in BC development and progression by inducing DNA damage, inflammation, and angiogenesis. Antioxidants have been shown to scavenge ROS and protect cells from oxidative damage, thereby regulating signaling pathways involved in cell growth, survival, and death. Plants contain antioxidants like ascorbic acid, tocopherols, carotenoids, and flavonoids, which have been found to regulate stress signaling and PCD in BC. Combining different antioxidants has shown promise in enhancing the effectiveness of BC treatment. Antioxidant nanoparticles, when loaded with antioxidants, can effectively target breast cancer cells and enhance their cellular uptake. Notably, these nanoparticles have shown promising results in inducing PCD and sensitizing breast cancer cells to chemotherapy, even in cases where resistance is observed. This review aims to explore how nanotechnology can modulate stress signaling and PCD in breast cancer. By summarizing current research, it underscores the potential of nanotechnology in enhancing antioxidant properties for the treatment of breast cancer.

Apoptosis-inducing factor-like protein-mediated stress and metronidazole-responsive programmed cell death pathway in Entamoeba histolytica

Apoptosis-inducing factor (AIF) is the major component of the caspase-independent cell death pathway that is considered to be evolutionarily ancient. Apoptosis is generally evolved with multicellularity as a prerequisite for the elimination of aged, stressed, or infected cells promoting the survival of the organism. Our study reports the presence of a putative AIF-like protein in Entamoeba histolytica, a caspase-deficient primitive protozoan, strengthening the concept of occurrence of apoptosis in unicellular organisms as well. The putative cytoplasmic EhAIF migrates to the nucleus on receiving stresses that precede its binding with DNA, following chromatin degradation and chromatin condensation as evident from both in vitro and in vivo experiments. Down-regulating the EhAIF expression attenuates the apoptotic features of insulted cells and increases the survival potency in terms of cell viability and vitality of the trophozoites, whereas over-expression of the EhAIF effectively enhances the phenomena. Interestingly, metronidazole, the most widely used drug for amoebiasis treatment, is also potent to elicit similar AIF-mediated cell death responses like other stresses indicating the AIF-mediated cell death could be the probable mechanism of trophozoite-death by metronidazole treatment. The occurrence of apoptosis in a unicellular organism is an interesting phenomenon that might signify the altruistic death that overall improves the population health.

Venetoclax Drug Increases the Apoptosis of T and B Acute Lymphoblastic Leukemia Cells by Reducing the Expression of BCL-2

Venetoclax, a specific inhibitor of the BCL2 protein, is administered for the treatment of acute lymphoblastic leukemia. However, despite being utilized in conjunction with chemotherapy, the drug exhibits instances of resistance. The exact mechanisms responsible for this resistance remain relatively obscure. Within the context of this investigation, the study aimed to explore the involvement of anti- and pro-apoptotic proteins as one of the potential mechanisms underlying this resistance phenomenon. Blast cells were extracted from patients diagnosed with B&T acute lymphoid leukemia. Subsequently, these cells were subjected to a cultivation process. Following the cultivation, treatment with the Venetoclax drug was administered to both groups of B&T cells. Additionally, one group from each cell type was designated as a control. The relative expression levels of genes BCL-2, MCL-1, and BIM were assessed in comparison to the control group. Annexin V-fluorescein isothiocyanate and propidium iodide staining was done to check cell apoptosis. The results showed a significant increase in the expression of BIM gene and a significant decrease in BCL-2 gene compared to the control group, but the change in the expression of MCL-1 gene was not significant. Also, an increase in apoptosis was observed in the treatment groups compared to the control. Although it was shown that changes in the expression of pro- and anti-apoptotic genes can lead to an increase in cell apoptosis and a decrease in the number of blast cells, more studies are needed to investigate the simultaneous effect of Venetoclax drug with other drugs and also in the form of a clinical trial.

Molecular Mechanisms of Ferroptosis and Relevance to Cardiovascular Disease

Ferroptosis has recently been demonstrated to be a novel regulated non-apoptotic cell death characterized by iron-dependence and the accumulation of lipid peroxidation that results in membrane damage. Excessive iron induces ferroptosis by promoting the generation of both soluble and lipid ROS via an iron-dependent Fenton reaction and lipoxygenase (LOX) enzyme activity. Cytosolic glutathione peroxidase 4 (cGPX4) pairing with ferroptosis suppressor protein 1 (FSP1) and mitochondrial glutathione peroxidase 4 (mGPX4) pairing with dihydroorotate dehydrogenase (DHODH) serve as two separate defense systems to detoxify lipid peroxidation in the cytoplasmic as well as the mitochondrial membrane, thereby defending against ferroptosis in cells under normal conditions. However, disruption of these defense systems may cause ferroptosis. Emerging evidence has revealed that ferroptosis plays an essential role in the development of diverse cardiovascular diseases (CVDs), such as hemochromatosis-associated cardiomyopathy, doxorubicin-induced cardiotoxicity, ischemia/reperfusion (I/R) injury, heart failure (HF), atherosclerosis, and COVID-19–related arrhythmias. Iron chelators, antioxidants, ferroptosis inhibitors, and genetic manipulations may alleviate the aforementioned CVDs by blocking ferroptosis pathways. In conclusion, ferroptosis plays a critical role in the pathogenesis of various CVDs and suppression of cardiac ferroptosis is expected to become a potential therapeutic option. Here, we provide a comprehensive review on the molecular mechanisms involved in ferroptosis and its implications in cardiovascular disease.

Type II-Metacaspases are involved in cell stress but not in cell death in the unicellular green alga Dunaliella tertiolecta

Ultraviolet radiation (UVR; 280–400 nm) has a great impact on aquatic ecosystems by affecting ecophysiological and biogeochemical processes as a consequence of the global change scenario generated by anthropogenic activities. We studied the effect of PAR (P)+UVA (A)+UVB (B) i.e. PAB, on the molecular physiology of the unicellular green alga Dunaliella tertiolecta for six days. We assessed the relationship between the triggered UVR stress response and metacaspases and caspase-like (CL)activities, which are proteases denoted to participate in cell death (CD) in phytoplankton. UVR inhibited cell growth and in vivo chlorophyll a fluorescence but did not cause cell death. Western blot analyses reflected that Type-II metacaspases (MCs) are present and appear to be involved in UVR induced-cell stress but not in dark-induced CD in D. tertiolecta. Enzyme kinetics revealed that cleavage of the MCs-reporter substrates RVRR, QRR, GRR, LKR, HEK, and VLK was 10-fold higher than WEHD, DEVD, IETD, and LETD CLs-substrates. The lowest apparent Michaelis-Menten constants (K_M^ap) corresponded to RVRRase (37.5 μM) indicating a high affinity by the RVRR substrate. The inhibition of enzymatic activities by using inhibitors with different target sites for hydrolyses demonstrated that from all of the R/ Kase activities only RVRRase was a potential candidate for being a metacaspase. In parallel, zymograms and peptide-mass fingerprinting analyses revealed the identities of such Rase activities suggesting an indirect evidence of possible natural physiological substrates of MCs. We present evidence of type II-MCs not being involved in CD in D. tertiolecta, but rather in survival strategies under the stressful irradiance conditions applied in this study.

Targeting intrinsic cell death pathways to control fungal pathogens

Fungal pathogens pose an increasing threat to public health. Limited clinical drug regimens and emerging drug-resistant isolates challenge infection control. The global burden of human fungal pathogens is estimated at 1 billion infections and 1.5 million deaths annually. In addition, plant fungal pathogens increasingly threaten global food resources. Novel strategies are needed to combat emerging fungal diseases and pan-resistant fungi. An untapped mechanistically novel approach is to pharmacologically activate the intrinsic cell death pathways encoded by pathogenic fungi. This strategy is analogous to new anti-cancer therapeutics now entering the clinic. Here we summarize the best understood examples of cell death mechanisms encoded by pathogenic fungi, contrast these to mammalian cell death pathways, and highlight the gaps in knowledge towards identifying potential death effectors as druggable targets.