Role of Intracellular Iron in Switching Apoptosis to Ferroptosis to Target Therapy-Resistant Cancer Stem Cells.

Iron is a crucial element required for the proper functioning of the body. For instance, hemoglobin is the vital component in the blood that delivers oxygen to various parts of the body. The heme protein present in hemoglobin comprises iron in the form of a ferrous state which regulates oxygen delivery. Excess iron in the body is stored as ferritin and would be utilized under iron-deficient conditions. Surprisingly, cancer cells as well as cancer stem cells have elevated ferritin levels suggesting that iron plays a vital role in protecting these cells. However, apart from the cytoprotective role iron also has the potential to induce cell death via ferroptosis which is a non-apoptotic cell death dependent on iron reserves. Apoptosis a caspase-dependent cell death mechanism is effective on cancer cells however little is known about its impact on cancer stem cell death. This paper focuses on the molecular characteristics of apoptosis and ferroptosis and the importance of switching to ferroptosis to target cancer stem cells death thereby preventing cancer relapse. To the best of our knowledge, this is the first review to demonstrate the importance of intracellular iron in regulating the switching of tumor cells and therapy resistant CSCs from apoptosis to ferroptosis.

COVID-19, Neuropathology, and Aging: SARS-CoV-2 Neurological Infection, Mechanism, and Associated Complications.

The spectrum of health complications instigated by coronavirus disease 2019 (COVID-19, caused by the novel severe acute respiratory syndrome coronavirus 2 or SARS-CoV-2) pandemic has been diverse and complex. Besides the evident pulmonary and cardiovascular threats, accumulating clinical data points to several neurological complications, which are more common in elderly COVID-19 patients. Recent pieces of evidence have marked events of neuro infection and neuroinvasion, producing several neurological complications in COVID-19 patients; however, a systematic understanding of neuro-pathophysiology and manifested neurological complications, more specifically in elderly COVID-19 patients is largely elusive. Since the elderly population gradually develops neurological disorders with aging, COVID-19 inevitably poses a higher risk of neurological manifestations to the aged patients. In this report, we reviewed SARS-CoV-2 infection and its role in neurological manifestations with an emphasis on the elderly population. We reviewed neuropathological events including neuroinfection, neuroinvasion, and their underlying mechanisms affecting neuromuscular, central- and peripheral- nervous systems. We further assessed the imminent neurological challenges in the COVID-19 exposed population, post-SARS-CoV-2-infection. Given the present state of clinical preparedness, the emerging role of AI and machine learning was also discussed concerning COVID-19 diagnostics and its management. Taken together, the present review summarizes neurological outcomes of SARS-CoV-2 infection and associated complications, specifically in elderly patients, and underlines the need for their clinical management in advance.

SARS-CoV-2, ACE2, and Hydroxychloroquine: Cardiovascular Complications, Therapeutics, and Clinical Readouts in the Current Settings.

The rapidly evolving coronavirus disease 2019 (COVID-19, caused by severe acute respiratory syndrome coronavirus 2- SARS-CoV-2), has greatly burdened the global healthcare system and led it into crisis in several countries. Lack of targeted therapeutics led to the idea of repurposing broad-spectrum drugs for viral intervention. In vitro analyses of hydroxychloroquine (HCQ)'s anecdotal benefits prompted its widespread clinical repurposing globally. Reports of emerging cardiovascular complications due to its clinical prescription are revealing the crucial role of angiotensin-converting enzyme 2 (ACE2), which serves as a target receptor for SARS-CoV-2. In the present settings, a clear understanding of these targets, their functional aspects and physiological impact on cardiovascular function are critical. In an up-to-date format, we shed light on HCQ's anecdotal function in stalling SARS-CoV-2 replication and immunomodulatory activities. While starting with the crucial role of ACE2, we here discuss the impact of HCQ on systemic cardiovascular function, its associated risks, and the scope of HCQ-based regimes in current clinical settings. Citing the extent of HCQ efficacy, the key considerations and recommendations for the use of HCQ in clinics are further discussed. Taken together, this review provides crucial insights into the role of ACE2 in SARS-CoV-2-led cardiovascular activity, and concurrently assesses the efficacy of HCQ in contemporary clinical settings.

In vitro evaluation of antioxidant and cytotoxic activities of lignin fractions extracted from Acacia nilotica.

Lignin is one of the most important phytomacromolecule with diverse therapeutic properties such as anticancer, antimicrobial, anti-inflammatory and immune-stimulatory. The present study was carried out to evaluate the in vitro antioxidant, free radical scavenging and anti-proliferative/cytotoxic activities of eleven different lignin fractions, extracted from the wood of Acacia nilotica by pressurized solvent extraction (PSE) and successive solvent extraction (SSE) methods. Results indicate that the PSE fractions have high polyphenolic content and reducing power. However, the antioxidant efficiency examined by DPPH and ABTS radical scavenging assay was higher in SSE fractions. All lignin fractions revealed a significant ability to scavenge nitric oxide, hydroxyl and superoxide radicals. The extracted lignin fractions display high ferric ion reducing capacity and also possess excellent antioxidant potential in the hydrophobic (linoleic acid) system. Fractions extracted by polar solvent has the highest iron (Fe(2+)) chelating activity as compared to other factions, indicating their effect on the redox cycling of iron. Four lignin fractions depicted higher cytotoxic potential (IC50: 2-15 µg/mL) towards breast cancer cell line (MCF-7) but were ineffective (IC50: ≥ 100 µg/mL) against normal primary human hepatic stellate cells (HHSteCs). These findings suggest that the lignin extracts of A. nilotica wood has a remarkable potential to prevent disease caused by the overproduction of radicals and also seem to be a promising candidate as natural antioxidant and anti-cancer agents.

Hydrogen peroxide sensing and cytotoxicity activity of Acacia lignin stabilized silver nanoparticles.

The study is aimed at detection of hydrogen peroxide (H2O2) using Acacia lignin mediated silver nanoparticles (AGNPs). The synthesis of AGNPs was achieved at conditions optimized as, 3 ml of 0.02% lignin and 1mM silver nitrate incubated for 30 min at 80°C and pH 9. Initial screening of AGNPs was performed by measuring the surface plasmon resonance peak at 410-430 nm using UV-vis spectrophotometer. Transmission electron microscopy, atomic force microscopy, X-ray diffraction and particle size analysis confirmed the spherical shaped face centered cubic structure and 10-50 nm size of AGNPs. The infrared spectroscopy study further revealed that the active functional groups present in lignin were responsible for the reduction of silver ions (Ag(+)) to metallic silver (Ag(0)). Lignin stabilized silver nanoparticles showed good sensitivity and a linear response over wide concentrations of H2O2 (10(-1) to 10(-6)M). Further, the in vitrocytotoxicity activity of the lignin mediated AGNPs (5-500 µg/ml) demonstrated toxicity effects in MCF-7 and A375 cell lines. Thus, lignin stabilized silver nanoparticles based optical sensor for H2O2 could be potentially applied in the determination of reactive oxygen species and toxic chemicals which further expands the importance of lignin stabilized silver nanoparticles.

Targeting metabolic flexibility by simultaneously inhibiting respiratory complex I and lactate generation retards melanoma progression.

Melanoma is a largely incurable skin malignancy owing to the underlying molecular and metabolic heterogeneity confounded by the development of resistance. Cancer cells have metabolic flexibility in choosing either oxidative phosphorylation (OXPHOS) or glycolysis for ATP generation depending upon the nutrient availability in tumor microenvironment. In this study, we investigated the involvement of respiratory complex I and lactate dehydrogenase (LDH) in melanoma progression. We show that inhibition of complex I by metformin promotes melanoma growth in mice via elevating lactate and VEGF levels. In contrast, it leads to the growth arrest in vitro because of enhanced extracellular acidification as a result of increased glycolysis. Inhibition of LDH or lactate generation causes decrease in glycolysis with concomitant growth arrest both in vitro and in vivo. Blocking lactate generation in metformin-treated melanoma cells results in diminished cell proliferation and tumor progression in mice. Interestingly, inhibition of either LDH or complex I alone does not induce apoptosis, whereas inhibiting both together causes depletion in cellular ATP pool resulting in metabolic catastrophe induced apoptosis. Overall, our study suggests that LDH and complex I play distinct roles in regulating glycolysis and cell proliferation. Inhibition of these two augments synthetic lethality in melanoma.

Cholesterol depletion by methyl-ß-cyclodextrin augments tamoxifen induced cell death by enhancing its uptake in melanoma.

BACKGROUND: Despite modern advances in treatment, skin cancer is still one of the most common causes of death in the western countries. Chemotherapy plays an important role in melanoma management. Tamoxifen has been used either alone or in- combination with other chemotherapeutic agents to treat melanoma. However, response rate of tamoxifen as a single agent has been comparatively low. In the present study, we investigated whether treatment with methyl-ß-cyclodextrin (MCD), a cholesterol depleting agent, increases the efficacy of tamoxifen in melanoma cells. METHODS: This was a two-part study that incorporated in vitro effects of tamoxifen and MCD combination by analyzing cell survival, apoptosis and cell cycle analysis and in vivo antitumor efficacy on tumor isografts in C57BL/6J mice. RESULTS: MCD potentiated tamoxifen induced anticancer effects by causing cell cycle arrest and induction of apoptosis. Sensitization to tamoxifen was associated with down regulation of antiapoptotic protein Bcl-2, up-regulation of proapoptotic protein Bax, reduced caveolin-1 (Cav-1) and decreased pAkt/pERK levels. Co-administration of tamoxifen and MCD caused significant reduction in tumor volume and tumor weight in mice due to enhancement of drug uptake in the tumor. Supplementation with cholesterol abrogated combined effect of tamoxifen and MCD. CONCLUSION: Our results emphasize a potential synergistic effect of tamoxifen with MCD, and therefore, may provide a unique therapeutic window for improvement in melanoma treatment.

Inherent and acquired resistance to paclitaxel in hepatocellular carcinoma: molecular events involved.

Hepatocellular carcinoma (HCC) is a primary malignancy of the liver and is a major cause of cancer related deaths worldwide. Only 10 to 20% of HCC can be surgically excised. Therefore, chemotherapeutic intervention and treatment is essential for achieving favorable prognosis. However, therapeutic outcome of chemotherapy is generally poor owing to inherent resistance of cancer cells to the treatment or due to development of acquired resistance. To differentiate and delineate the molecular events, we developed drug resistant Hep3B cells (DRC) by treating cells with the increasing concentration of paclitaxel. We also developed a unique single cell clone of Hep3B cells (SCC) by selecting single cell colonies and screening them for resistant phenotype. Interestingly, both DRC and SCC were resistant to paclitaxel in comparison to parental Hep3B cells. We analyzed the contributory factors that may be involved in the development of resistance. As expected, level of P-glycoprotein (P-gp) was elevated in DRC. In addition, Caveolin-1 (Cav-1), Fatty acid synthase (FASN) and Cytochrome P450 (CYP450) protein levels were elevated in DRC whereas in SCC, FASN and CYP450 levels were elevated. Downregulation of these molecules by respective siRNAs and/or by specific pharmacological inhibitors resensitized cells to paclitaxel. Interestingly, these drug resistant cells were also less sensitive to vinblastine, doxorubicin and methotrexate with the exception of cisplatin. Our results suggested that differential levels of P-gp, Cav-1 and FASN play a major role in acquired resistant phenotype whereas FASN level was associated with the presentation of inherent resistant phenotype in HCC.

Hyperthermia-associated carboplatin resistance: differential role of p53, HSF1 and Hsp70 in hepatoma cells.

Due to substantial technical improvements, clinical application of heat as a co-adjuvant in cancer treatment is acquiring new interest. The effect of hyperthermia on hepatoma cell lines Hep3B (p53 defective) and HepG2 (p53 wild type) when investigated led to an interesting observation that Hep3B cells are more susceptible to heat stress than HepG2 cells. In addition, heat-induced carboplatin resistance was observed in HepG2 cells only. To investigate the reasons, heat shock response was explored and it was observed that heat stress augmented heat shock protein 70 (Hsp70) expression levels in HepG2 and not in Hep3B cells. Furthermore, in HepG2 cells, induced Hsp70 is regulated by both p53 and heat shock transcription factor 1 (HSF1) wherein HSF1 levels are modulated by p53. The data implies that Hep3B are more susceptible to death upon heat stress than HepG2 cells because of non-induction of Hsp70. In addition, it was observed that inhibition of heat-induced p53/HSF1 diminishes Hsp70 levels, thereby restoring the sensitivity of heat-stressed HepG2 cells to carboplatin-triggered cell death. Collectively, the present study establishes interplay of p53, HSF1, and Hsp70 upon heat stress in HepG2 cells and also defines novel strategies to overcome constraints of utility of hyperthermia in cancer therapy through p53/HSF1-targeted therapeutic intervention.