Txnrd1 as a prognosticator for recurrence, metastasis and response to neoadjuvant chemotherapy and radiotherapy in breast cancer patients.

Thioredoxin reductase 1 (Txnrd1) is known to have prognostic significance in a subset of breast cancer patients. Despite the pivotal role of Txnrd1 in regulating several cellular and physiological processes in cancer progression and metastasis, its clinical significance is largely unrecognized. Here, we undertook a retrospective comprehensive meta-analysis of 13,322 breast cancer patients from 43 independent cohorts to assess prognostic and predictive roles of Txnrd1. We observed that Txnrd1 has a positive correlation with tumor grade and size and it is over-expressed in higher-grade and larger tumors. Further, hormone receptor-negative and HER2-positive tumors exhibit elevated Txnrd1 gene expression. Patients with elevated Txnrd1 expression exhibit significant hazards for shorter disease-specific and overall survival. While Txnrd1 has a positive correlation with tumor recurrence and metastasis, it has a negative correlation with time to recurrence and metastasis. Txnrd1High patients exhibit 2.5 years early recurrence and 1.3 years early metastasis as compared to Txnrd1Low cohort. Interestingly, patients with high Txnrd1 gene expression exhibit a pathologic complete response (pCR) to neoadjuvant chemotherapy, but they experience early recurrence after radiotherapy. Txnrd1High MDA-MB-231 cells exhibit significant ROS generation and reduced viability after doxorubicin treatment compared to Txnrd1Low MCF7 cells. Corroborating with findings from meta-analysis, Txnrd1 depletion leads to decreased survival, enhanced sensitivity to radiation induced killing, poor scratch-wound healing, and reduced invasion potential in MDA-MB-231 cells. Thus, Txnrd1 appears to be a potential predictor of recurrence, metastasis and therapy response in breast cancer patients.

Clobetasol propionate, a Nrf-2 inhibitor, sensitizes human lung cancer cells to radiation-induced killing via mitochondrial ROS-dependent ferroptosis.

Combining radiotherapy with Nrf-2 inhibitor holds promise as a potential therapeutic strategy for radioresistant lung cancer. Here, the radiosensitizing efficacy of a synthetic glucocorticoid clobetasol propionate (CP) in A549 human lung cancer cells was evaluated. CP exhibited potent radiosensitization in lung cancer cells via inhibition of Nrf-2 pathway, leading to elevation of oxidative stress. Transcriptomic studies revealed significant modulation of pathways related to ferroptosis, fatty acid and glutathione metabolism. Consistent with these findings, CP treatment followed by radiation exposure showed characteristic features of ferroptosis in terms of mitochondrial swelling, rupture and loss of cristae. Ferroptosis is a form of regulated cell death triggered by iron-dependent ROS accumulation and lipid peroxidation. In combination with radiation, CP showed enhanced iron release, mitochondrial ROS, and lipid peroxidation, indicating ferroptosis induction. Further, iron chelation, inhibition of lipid peroxidation or scavenging mitochondrial ROS prevented CP-mediated radiosensitization. Nrf-2 negatively regulates ferroptosis through upregulation of antioxidant defense and iron homeostasis. Interestingly, Nrf-2 overexpressing A549 cells were refractory to CP-mediated ferroptosis induction and radiosensitization. Thus, this study identified anti-psoriatic drug clobetasol propionate can be repurposed as a promising radiosensitizer for Keap-1 mutant lung cancers.

Mitochondrial-targeted curcumin inhibits T-cell activation via Nrf2 and inhibits graft-versus-host-disease in a mouse model.

Anti-inflammatory and immune suppressive agents are required to moderate hyper-activation of lymphocytes under disease conditions or organ transplantation. However, selective disruption of mitochondrial redox has not been evaluated as a therapeutic strategy for suppression of T-cell-mediated pathologies. Using mitochondrial targeted curcumin (MitoC), we studied the effect of mitochondrial redox modulation on T-cell responses by flow cytometry, transmission electron microscopy, transcriptomics, and proteomics, and the role of Nrf2 was studied using Nrf2- /- mice. MitoC decreased mitochondrial TrxR activity, enhanced mitochondrial ROS (mROS) production, depleted mitochondrial glutathione, and suppressed activation-induced increase in mitochondrial biomass. This led to suppression of T-cell responses and metabolic reprogramming towards Treg differentiation. MitoC induced nuclear translocation and DNA binding of Nrf2, leading to upregulation of Nrf2-dependent genes and proteins. MitoC-mediated changes in mitochondrial redox and modulation of T-cell responses are abolished in Nrf2- /- mice. Restoration of mitochondrial thiols abrogated inhibition of T-cell responses. MitoC suppressed alloantigen-induced lymphoblast formation, inflammatory cytokines, morbidity, and mortality in acute graft-versus-host disease mice. Disruption of mitochondrial thiols but not mROS increase inculcates an Nrf2-dependent immune-suppressive disposition in T cells for the propitious treatment of graft-versus-host disease.

Repurposing of FDA approved kinase inhibitor bosutinib for mitigation of radiation induced damage via inhibition of JNK pathway.

Radiotherapy is a common modality for cancer treatment. However, it is often associated with normal tissue toxicity in 20-80% of the patients. Radioprotectors can improve the outcome of radiotherapy by selectively protecting normal cells against radiation toxicity. In the present study, compound libraries containing 54 kinase inhibitors and 80 FDA-approved drugs were screened for radioprotection of lymphocytes using high throughput cell analysis. A second-generation FDA-approved kinase inhibitor, bosutinib, was identified as a potential radioprotector for normal cells. The radioprotective efficacy of bosutinib was evinced from a reduction in radiation induced DNA damage, caspase-3 activation, DNA fragmentation and apoptosis. Oral administration of bosutinib protected mice against whole body irradiation (WBI) induced morbidity and mortality. Bosutinib also reduced radiation induced bone-marrow aplasia and hematopoietic damage in mice exposed to 4 Gy and 6 Gy dose of WBI. Mechanistic studies revealed that the radioprotective action of bosutinib involved interaction with cellular thiols and modulation of JNK pathway. The addition of glutathione and N-acetyl cysteine significantly reduced the radioprotective efficacy of bosutinib. Moreover, bosutinib did not protect cancer cells against radiation induced toxicity. On the contrary, bosutinib per se exhibited anticancer activity against human cancer cell lines. The results highlight possible use of bosutinib as a repurposable radioprotective agent for mitigation of radiation toxicity in cancer patients undergoing radiotherapy.

Malabaricone C, a constituent of spice Myristica malabarica, exhibits anti-inflammatory effects via modulation of cellular redox.

The present study primarily focuses on the efficacy of Malabaricone C (Mal C) as an anti-inflammatory agent. Mal C inhibited mitogen-induced T-cell proliferation and cytokine secretion. Mal C significantly reduced cellular thiols in lymphocytes. N-acetyl cysteine (NAC) restored cellular thiol levels and abrogated Mal C-mediated inhibition of T-cell proliferation and cytokine secretion. Physical interaction between Mal C and NAC was evinced from HPLC and spectral analysis. Mal C treatment significantly inhibited concanavalin A-induced phosphorylation of ERK/JNK and DNA binding of NF-κB. Administration of Mal C to mice suppressed T-cell proliferation and effector functions ex vivo. Mal C treatment did not alter the homeostatic proliferation of T-cells in vivo but completely abrogated acute graft-versus-host disease (GvHD)-associated morbidity and mortality. Our studies indicate probable use of Mal C for prophylaxis and treatment of immunological disorders caused due to hyper-activation of T-cells.

Withaferin A, a steroidal lactone, selectively protects normal lymphocytes against ionizing radiation induced apoptosis and genotoxicity via activation of ERK/Nrf-2/HO-1 axis.

Increasing use of ionizing radiation (IR) in medicine, industry, agriculture and research ensues potential health hazards if not used properly or contained effectively. However, radioprotectors which are effective in clinical and/or accidental radiation exposures are still elusive. In this direction, we have explored the radioprotective potential of Withaferin A, a plant withanolide, which was recently shown to be safe and well tolerated in cancer patients in a clinical trial and is also known to be a radio-sensitizer in cancer cells. Our results show that, Withaferin A (WA) protected only normal lymphocytes, but not cancer cells, against IR-induced apoptosis and offered radioprotection even when added post-radiation exposure. WA treatment led to significant inhibition of IR-induced caspase-3 activation and decreased IR-induced DNA damage to lymphocytes and bone-marrow cells. WA reduced intracellular ROS and GSH levels and only thiol based anti-oxidants could abrogate the radio-protective effects of WA, indicating a crucial role of cellular/protein thiols in its biological activity. The inability of WA-glutathione adduct to offer radioprotection further underscored the role of cellular thiols. WA induced pro-survival transcription factor, Nrf-2, and expression of cytoprotective genes HO-1, catalase, SOD, peroxiredoxin-2 via ERK. Further, WA administration could rescue mice against radiation induced mortality, DNA damage, increase in micro-nucleated polychromatic erythrocytes (mn-PCEs) and increased ratio of polychromatic erythrocytes (PCEs) to Normochromatic Erythrocytes (NCEs) in bone-marrow, demonstrating its potent in vivo the radio-protective efficacy. In conclusion, WA selectively protects normal cells against IR-induced apoptosis via activation of cytoprotective Nrf-2 pathway.

Mitochondriotropic Derivative of Ethyl Ferulate, a Dietary Phenylpropanoid, Exhibits Enhanced Cytotoxicity in Cancer Cells via Mitochondrial Superoxide-Mediated Activation of JNK and AKT Signalling.

Specific targeting of anti-cancer drugs to mitochondria is an emerging strategy to enhance cancer cell killing whilst simultaneously overcoming the problem of drug resistance, low bioavailability and limited clinical success of natural products. We have synthesized a mitochondria targeted derivative of Ethyl Ferulate (EF, a naturally occurring ester of ferulic acid), by conjugating it with triphenylphosphonium ion and compared its cytotoxicity with the parent molecule. Mito-Ethyl Ferulate (M-EF) was found to be more potent than EF (~ 400-fold) in inhibiting the growth of A549 and MCF-7 cells and suppressing the clonogenic potential of A549 cells. Notably, M-EF did not induce any cytotoxicity in normal cells (mouse normal fibroblast cells) up to a concentration of 25 µM. Furthermore, M-EF treatment induced significantly higher cell death in MCF-7 and A549 cells, as compared to EF via induction of apoptosis. M-EF treatment increased mitochondrial superoxide production and induced mitochondrial DNA damage and phosphorylation of JNK and AKT in A549 cells. Furthermore, M-EF induced increase in mitochondrial superoxide production and cytotoxicity was attenuated on pre-treatment with mitochondria-targeted antioxidant (mitoTEMPO) indicating the involvement of mitochondrial ROS in the cytotoxic effects of M-EF. Finally, in silico prediction revealed putative mitochondrial targets of M-EF which are known to regulate mitochondrial ROS and cell viability. In conclusion, the improved cytotoxic efficacy of M-EF exemplifies the use of mitochondria-specific drug delivery in future development of natural product based mitochondrial pharmacology.

Molecular dynamic simulations reveal anti-SARS-CoV-2 activity of mitocurcumin by potentially blocking innate immune evasion proteins NSP3 and NSP16.

The coronavirus disease 19 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), is affecting human life in an unprecedented manner and has become a global public health emergency. Identification of novel inhibitors of viral infection/replication is the utmost priority to curtail COVID-19 progression. A pre-requisite for such inhibitors is good bioavailability, non-toxicity and serum stability. Computational studies have shown that curcumin can be a candidate inhibitor of certain SARS-CoV-2 proteins; however, poor bio-availability of curcumin limits its possible therapeutic application. To circumvent this limitation, we have used mitocurcumin (MC), a triphenyl phosphonium conjugated curcumin derivative, to study the ability to inhibit SARS-CoV-2 infection using molecular docking and molecular dynamics (MD) simulation. MC is serum stable and several fold more potent as compared to curcumin. Molecular docking studies revealed that MC can bind at active site of SARS-CoV-2 ADP Ribose Phosphatase (NSP3) and SARS-CoV-2 methyltransferase (NSP10-NSP16 complex) with a high binding energy of - 10.3 kcal/mol and - 10.4 kcal/mol, respectively. MD simulation (100 ns) studies revealed that binding of MC to NSP3 and NSP16 resulted in a stable complex. MC interacted with critical residues of NSP3 macro-domain and NSP10-NSP16 complex and occupied their active sites. NSP3 is known to suppress host immune responses whereas NSP10-NSP16 complex is known to prevent immune recognition of viral mRNA. Our study suggests that MC can potentially inhibit the activity of NSP3 and NSP10-NSP16 complex, resulting in compromised viral immune evasion mechanism, and thereby accentuate the innate immune mediated clearance of viral load.

Thioredoxin reductase: An emerging pharmacologic target for radiosensitization of cancer.

Novel agents are required to increase the radiosensitivity of cancer and improve the outcome of radiotherapy. Thioredoxin (Trx) and thioredoxin reductase (TrxR) reduce the oxidized cysteine thiols in several proteins, which regulate cellular redox, survival, proliferation, DNA synthesis, transcription factor activity and apoptosis. TrxR is essential for maintaining a conducive redox state for tumor growth, survival and resistance to therapy. Therefore, it is an appealing pharmacological target for the radiosensitization of tumors. Ionizing radiation (IR) is known to cause cytotoxicity through ROS, oxidative stress and DNA damage. Inhibition of thioredoxin system augments IR induced oxidative stress and potentiates cytotoxic effects. However, TrxR also regulates several critical cellular processes in normal cells. Here, we highlight the pre-clinical research and pharmacological studies to surmise possible utility of different TrxR inhibitors for radiosensitization. This review provides a succinct perspective on the role of TrxR inhibitors during the radiotherapy of cancer.

Chemical and biological basis for development of novel radioprotective drugs for cancer therapy.

Ionizing radiation (IR) causes chemical changes in biological systems through direct interaction with the macromolecules or by causing radiolysis of water. This property of IR is harnessed in the clinic for radiotherapy in almost 50% of cancers patients. Despite the advent of stereotactic radiotherapy instruments and other advancements in shielding techniques, the inadvertent deposition of radiation dose in the surrounding normal tissue can cause late effects of radiation injury in normal tissues. Radioprotectors, which are chemical or biological agents, can reduce or mitigate these toxic side-effects of radiotherapy in cancer patients and also during radiation accidents. The desired characteristics of an ideal radioprotector include low chemical toxicity, high risk to benefit ratio and specific protection of normal cells against the harmful effects of radiation without compromising the cytotoxic effects of IR on cancer cells. Since reactive oxygen species (ROS) are the major contributors of IR mediated toxicity, plethora of studies have highlighted the potential role of antioxidants to protect against IR induced damage. However, owing to the lack of any clinically approved radioprotector against whole body radiation, researchers have shifted the focus toward finding alternate targets that could be exploited for the development of novel agents. The present review provides a comprehensive insight in to the different strategies, encompassing prime molecular targets, which have been employed to develop radiation protectors/countermeasures. It is anticipated that understanding such factors will lead to the development of novel strategies for increasing the outcome of radiotherapy by minimizing normal tissue toxicity.

Preclinical Studies and Clinical Prospects of Wharton's Jelly-Derived MSC for Treatment of Acute Radiation Syndrome.

PURPOSE OF REVIEW: Wharton's jelly-derived mesenchymal stem cells (WJ-MSCs) have received widespread attention from researchers owing to the remarkable benefits offered by these cells over other stem cells. The primitive nature of WJ-MSCs, ease of isolation, differentiation ability, and immuno-modulatory nature make these cells superior to bone marrow MSCs and ideal to treat various human ailments. This review explores ability of WJ-MSCs to mitigate acute radiation syndrome caused by planned or unplanned radiation exposure. RECENT FINDINGS: Recent reports suggest that WJ-MSCs home to damaged tissues in irradiated host and mitigate radiation induced damage to radiosensitive tissues such as hematopoietic and gastrointestinal systems. WJ-MSCs and conditioned media were found to protect mice from radiation induced mortality and also prevent radiation dermatitis. Local irradiation-induced lung toxicity in mice was significantly reduced by CXCR4 over-expressing WJ-MSCs. SUMMARY: Emerging evidences support safety and effectiveness of WJ-MSCs for treatment of acute radiation syndrome and lung injury after planned or accidental exposure. Additionally, conditioned media collected after culturing WJ-MSCs can also be used for mitigation of radiation dermatitis. Clinical translation of these findings would be possible after careful evaluation of resilience, effectiveness, and molecular mechanism of action of xenogeneic WJ-MSCs in non-human primates.

Role of protein S-Glutathionylation in cancer progression and development of resistance to anti-cancer drugs.

The survival, functioning and proliferation of mammalian cells are highly dependent on the cellular response and adaptation to changes in their redox environment. Cancer cells often live in an altered redox environment due to aberrant neo-vasculature, metabolic reprogramming and dysregulated proliferation. Thus, redox adaptations are critical for their survival. Glutathione plays an essential role in maintaining redox homeostasis inside the cells by binding to redox-sensitive cysteine residues in proteins by a process called S-glutathionylation. S-Glutathionylation not only protects the labile cysteine residues from oxidation, but also serves as a sensor of redox status, and acts as a signal for stimulation of downstream processes and adaptive responses to ensure redox equilibrium. The present review aims to provide an updated overview of the role of the unique redox adaptations during carcinogenesis and cancer progression, focusing on their dependence on S-glutathionylation of specific redox-sensitive proteins involved in a wide range of processes including signalling, transcription, structural maintenance, mitochondrial functions, apoptosis and protein recycling. We also provide insights into the role of S-glutathionylation in the development of resistance to chemotherapy. Finally, we provide a strong rationale for the development of redox targeting drugs for treatment of refractory/resistant cancers.

Pre-clinical evaluation of an innovative oral nano-formulation of baicalein for modulation of radiation responses.

There is an unmet medical need for non-toxic and effective radiation countermeasures for prevention of radiation toxicity during planned exposures. We have earlier shown that intraperitoneal administration of baicalein (BCL) offers significant survival benefit in animal model. Safety, tolerability, pharmacokinetics (PK) and pharmacodynamics of baicalein has been reported in pre-clinical model systems and also in healthy human volunteers. However, clinical translation of baicalein is hindered owing to poor bioavailability due to lipophilicity. In view of this, we fabricated and characterized in-situ solid lipid nanoparticles of baicalein (SLNB) with effective drug entrapment and release kinetics. SLNB offered significant protection to murine splenic lymphocytes against 4 Gy ionizing radiation (IR) induced apoptosis. Oral administration of SLNB exhibited ~70% protection to mice against whole body irradiation (WBI 7.5 Gy) induced mortality. Oral relative bioavailability of BCL was enhanced by over ~300% after entrapment in the SLNB as compared to BCL. Oral dosing of SLNB resulted in transient increase in neutrophil abundance in peripheral blood. Interestingly, we observed that treatment of human lung cancer cells (A549) with radioprotective dose of SLNB exhibited radio-sensitization as evinced by decrease in survival and clonogenic potential. Contrary to antioxidant nature of baicalein in normal cells, SLNB treatment induced significant increase in cellular ROS levels in A549 cells probably due to higher uptake and inhibition of TrxR. Thus, a pharmaceutically acceptable SLNB exhibited improved bioavailability, better radioprotection to normal cells and sensitized cancer cells to radiation induced killing as compared to BCL suggesting its possible utility as an adjuvant during cancer radiotherapy.

Oxidative stress associated metabolic adaptations regulate radioresistance in human lung cancer cells.

Differential inherent and acquired radioresistance of human lung cancer cells contribute to poor therapeutic outcome and tumor recurrence after radiotherapy. Inherent radioresistance of lung cancer cells is known to be associated with ROSLow cancer stem cells (CSCs). However, mechanism of acquired radioresistance in lung cancer cells is poorly understood. Here, we exposed human lung cancer cells (A549) to a cumulative dose of 40Gy and allowed the radioresistant (RR) survivors to divide and form macroscopic colonies after each fraction of 5Gy dose. The RR subline exhibited enrichment of cytosolic ROSHigh cells without specific increase in mitochondrial ROS levels. We found a concomitant increase in the expression of redox regulatory transcription factor Nrf2 and its dependent antioxidant genes in RR cells and cell cycle delay as compared to parental cells. The treatment of RR cells with Nrf2 inhibitor resulted in decreased clonogenic survival indicating their addiction to Nrf2 for metabolic adaptations under high levels of cytosolic ROS. A causal role of inherent ROS levels in conferring radioresistance was established by sorting ROSHigh and ROSLow populations from parental and RR cells. It was observed that ROSHigh population from both parental and RR cells exhibited radioresistance as observed by clonogenic assay. Interestingly, ROSHigh population of cells exhibited higher levels of cellular thiols in both parental and RR cells. Thus, our observations highlight presence of a novel subpopulation in lung cancer cells, which exhibits radioresistance by maintaining 'oxidative stress' and Nrf2 dependent metabolic adaptations. We also posit Nrf2 pathway as a druggable target for radiosensitization of RR A549 cells.

Redox regulation of regulatory T-cell differentiation and functions.

The choice between immunity or tolerance is a consequence of T-cell fate determined by T-cell receptor affinity to cognate MHC-peptide complex, costimulatory molecules and cytokines from antigen presenting cells. While activated, effector and memory T-cells provide immunity against antigens, regulatory T-cells play a pivotal non-redundant role in immune tolerance and tissue repair. T-cell differentiation and functions are also well known to be governed by the redox status. Physiological redox status is determined by oxygen concentration, reactive oxygen species levels and antioxidant concentration (vitamin C, glutathione, vitamin E). Cellular redox state influences the levels of oxygen-dependent ten-eleven translocase (TET) demethylase, hypoxia inducible factor-1α (HIF-1α), and metabolic reprogramming which in turn control the epigenetic modification, transcription, translation and post-translational stability of FoxP3, the master regulator of regulatory T-cell induction and maintenance. Redox changes during foetal development, pregnancy, ageing, infections and cancer bolster Treg differentiation for immune tolerance to non-dangerous non-self-antigens. Incidentally, the changes in blood oxygen levels in pregnant women and developing foetus are accompanied by increase in tolerance due to increased frequency of CD4 + CD25 + FoxP3+ regulatory T-cells. Ageing associated oxidative stress and solid tumour associated hypoxia are also associated with an increase in the number and function of regulatory T-cells. This review covers the aspects of redox regulation of Treg differentiation and functions during development, ageing, immunity and stem cell homeostasis. We also propose redox modulation based therapeutic interventions for prevention and treatment of T-cell associated disorders.

Xenogeneic transplantation of human WJ-MSCs rescues mice from acute radiation syndrome via Nrf-2-dependent regeneration of damaged tissues.

There is an unmet medical need for radiation countermeasures that can be deployed for treatment of exposed individuals during ionizing radiation (IR) accidents or terrorism. Wharton's jelly mesenchymal stem cells (WJ-MSCs) from human umbilical cord have been shown to avoid allorecognition and induce a tissue-regenerating microenvironment, which makes them an attractive candidate for mitigating IR injury. We found that WJ-MSCs protected mice from a lethal dose of IR even when transplanted up to 24 hours after irradiation, and a combination of WJ-MSCs and antibiotic (tetracycline) could further expand the window of protection offered by WJ-MSCs. This combinatorial approach mitigated IR-induced damage to the hematopoietic and gastrointestinal system. WJ-MSCs increased the serum concentration of the cytoprotective cytokines granulocyte colony-stimulating factor (G-CSF) and IL-6 in mice. Knockdown of G-CSF and IL-6 in WJ-MSCs before injection to lethally irradiated mice or transplantation of WJ-MSCs to lethally irradiated Nrf-2 knockout mice significantly nullified the therapeutic protective efficacy. Hence, WJ-MSCs could be a potential cell-based therapy for individuals accidentally exposed to radiation.

Pharmacological characterization of a structurally new class of antibacterial compound, triphenyl-phosphonium conjugated diarylheptanoid: Antibacterial activity and molecular mechanism.

Many pathogenic species of bacteria are showing increasing drug resistance against clinically used antibiotics. Molecules structurally distant from known antibiotics and possessing membrane targeting bactericidal activities are more likely to display activity against drug-resistant pathogens. Mitocurcumin (MitoC) is one of such compounds, synthesized by triphenyl-phosphonium conjugation with curcumin, and has been shown recently from our laboratory to have broad-spectrum bactericidal activity (Kumari et al. 2019 Free Radic. Biol. Med. 143, 140-145). Here, we further demonstrate the antibacterial properties of MitoC against resistant strains and also its mechanism of action. It displays efficient bactericidal activity against multidrug-resistant Staphylococcus aureus and Streptococcus pneumoniae (MIC values in the 1.5-12.5 µM range), and coagulase-negative Staphylococci do not show resistance development against MitoC. Liposome based studies and MIC values against TolC deletion mutant (Δ tolC; outer membrane protein) of E. coli suggest extensive membrane damage to be the primary mechanism of bactericidal activity. MitoC did not exhibit toxicity in BALB/c mice with an oral administration of 250 mg/kg body weight and was found to be totally safe without any significant effect on haematological, biochemical parameters and inflammatory responses. Its rapid bactericidal action as assessed by in vitro time-kill assay against B. subtilis, compared to ciprofloxacin, and long half-life in rodent serum, suggest that MitoC could be an excellent lead-molecule against drug-resistant pathogens. The highlights of the study are that mitocurcumin belongs to a structurally new class of bactericidal compounds. It displays activity against MDR strains of pathogenic bacteria and challenging MRSA. Liposome-based studies confirm the membrane damaging property of the molecule. Mitocurcumin does not show resistance development even after 27 bacterial generations.

Modulation of Caspase-3 activity using a redox active vitamin K3 analogue, plumbagin, as a novel strategy for radioprotection.

Radiation induced damage to normal cells is a major shortcoming of conventional radiotherapy, which necessitates the development of novel radio-protective drugs. An ideal radio-modulator would protect normal cells while having cytotoxic effects on cancer cells. Plumbagin is a potent anti-tumour agent and has been shown to sensitize tumour cells to radiation-induced damage. In the present study, we have evaluated the radio-protective potential of plumbagin and found that it protected normal lymphocytes against radiation-induced apoptosis, but did not protect cancer cells against radiation. Plumbagin offered radioprotection even when it was added to cells after irradiation. The ability of only thiol based antioxidants to abrogate the radio-protective effects of plumbagin suggested a pivotal role of thiol groups in the radio-protective activity of plumbagin. Further, protein interaction network (PIN) analysis was used to predict the molecular targets of plumbagin. Based on the inputs from plumbagin's PIN and in light of its well-documented ability to modulate thiol groups, we proposed that plumbagin may act via modulation of caspase enzyme which harbours a critical catalytic cysteine. Indeed, plumbagin suppressed radiation-induced increase in homogenous caspase and caspase-3 activity in lymphocytes. Plumbagin also inhibited the activity of recombinant caspase-3 and mass spectrometric analysis revealed that plumbagin covalently interacts with caspase-3. Further, the in vivo radioprotective efficacy of plumbagin (single dose of 2mg/kg body weight) was demonstrated by its ability to rescue mice against radiation (7.5 Gy; Whole Body Irradiation) induced mortality. These results indicate that plumbagin prevents radiation induced apoptosis specifically in normal cells by inhibition of caspase-3 activity.

Antibacterial activity of new structural class of semisynthetic molecule, triphenyl-phosphonium conjugated diarylheptanoid.

Antibiotic resistance in bacteria is a serious threat to public health due to limited therapeutic options. Bactericidal agents with polypharmacological profiles or targeting bacterial membrane have lower propensity to develop resistance. Mitocurcumin (MitoC) is a novel compound synthesized by triphenyl-phosphonium conjugation with curcumin. Here, we demonstrate the antibacterial properties of MitoC that structurally differs markedly from the known antibacterial compounds. MitoC shows efficient bactericidal activity against Gram-positive and Gram-negative bacteria, including Mycobacteria, with MIC values in 1.5-12.5 µM range, but does not affect the viability of human leukocytes and human lung normal cell lines. Even at sub-MIC values, MitoC displays bactericidal properties. MitoC bactericidal action involves rapid disruption of bacterial membrane potential. Scanning electron microscope images of MitoC treated cells show structural deformations in terms of shrinking, loss of turgidity and formation of blisters and bubbles on their surface. Although MitoC increases ROS levels in bacterial cells, it may not be the primary cause of cell death as prior treatment with anti-oxidant trolox did not affect the MIC. This is the first report on bactericidal activity of MitoC and represents an excellent alternative for development of new generation bactericidal molecules that may be slow to develop resistance.