Endoplasmic reticulum (ER)-stress and unfolding protein response (UPR) has not been implied in Aeromonas hydrophila-pathogenicity. We report increased expression of the ER-stress markers: CHOP, BiP and phospho-eIF2α in A. hydrophila-infected headkidney macrophages (HKM) in Clarias
batrachus. Pre-treatment with ER-stress inhibitor, 4-PBA alleviated ER-stress and HKM apoptosis suggesting ER-UPR critical for the process. The ER-Ca2+ released via inositol-triphosphate and ryanodine receptors induced calpain-2 mediated superoxide ion generation and consequent NF-κB activation. Inhibiting NF-κB activation attenuated NO production suggesting the pro-apoptotic role of NF-κB on HKM pathology. Calpain-2 activated caspase-12 to intensify the apoptotic cascade through mitochondrial-membrane potential (ψm) dissipation and caspase-9 activation. Altered mitochondrial ultra-structure consequent to ER-Ca2+ uptake via uniporters reduced ψm and released cytochrome C. Nitric oxide induced the cGMP/PKG-dependent activation of caspase-8 and truncated-Bid formation. Both the caspases converge onto caspase-3 to execute HKM apoptosis. These findings offer a possible molecular explanation for A. hydrophila pathogenicity.
Mycobacterium fortuitum causes ‘mycobacteriosis’ in wide range of hosts although the mechanisms remain largely unknown. Here we demonstrate the role of calcium (Ca+2)-signalling cascade on M. fortuitum-induced apoptosis in headkidney macrophages (HKM) of Clarias sp. M. fortuitum could trigger intracellular-Ca+2 influx leading to the activation of calmodulin (CaM), protein kinase C alpha (PKCα) and Calmodulin kinase II gamma (CaMKIIg). Gene silencing and inhibitor studies established the role of CaM in M. fortuitum pathogenesis. We noted that CaMKIIg activation is regulated by CaM as well as PKCα-dependent superoxide anions. This is altogether first report of oxidised CaMKIIg in mycobacterial infections. Our studies with targeted-siRNA and pharmacological inhibitors implicate CaMKIIg to be pro-apoptotic and critical for the activation of extra-cellular signal regulated kinase 1/2 (ERK1/2). Inhibiting the ERK1/2 pathway attenuated nitric oxide synthase 2 (NOS2)-induced nitric oxide (NO) production. Conversely, inhibiting the NOS2-NO axis by specific-siRNA and inhibitors down-regulated ERK1/2 activation suggesting the crosstalk between ERK1/2 and NO is essential for pathogenesis induced by the bacterium. Silencing the NOS2-NO axis enhanced intracellular bacterial survival and attenuated caspase-8 mediated activation of caspase-3 in the infected HKM. Our findings unveil hitherto unknown mechanism of M. fortuitum pathogenesis. We propose that M. fortuitum triggers intracellular Ca+2 elevations resulting in CaM activation and PKCα-mediated superoxide generation. The cascade converges in common pathway mediated by CaMKIIg resulting in the activation of ERK1/2-NOS2 axis. The crosstalk between ERK1/2 and NO shifts the balance in favour of caspase dependent apoptosis of M. fortuitum-infected HKM.
Abstract::
Cancer is the deadliest disease worldwide and the development of safer chemical entities to treat cancer is one of the major challenges of medicinal chemistry. Emergence of new cases every year and development of multiple drug resistance against available molecular entities has turned the focus of researchers towards natural products. Chalcones are pharmacologically active compounds, present in plants, which have been derivatized and screened by many researchers for the treatment of cancer. Chalcones, consist of 1,3-diaryl-2-propen-1-one, is one such class exhibiting broad anticancer activities against various cancerous cell lines.
The objective of this review article is to analyze the antitumor activity of the reported chalcones via distinct mechanisms adopted by these molecules underlying their inhibitory activity. The primary focus of this review is to bring the attention of researchers towards latest and important chalcones and their derivatives having potent anticancer activity adding their possible action of mechanisms against cancerous cell lines The recent literature was surveyed and it was found that chalcone analogs with electron donating groups, indolyl, quinolone, pyrazol-ol, hydroxyaminobenzamide, hydroxamic acid and pyridyl- indole groups have shown promise as potential anticancer agents following various mechanisms. Most chalcones were found to induce significant cell cycle arrest at G2/M phase hence leading to apoptosis. A number of synthetic chalcones exhibited higher efficacy due to their ability of potent tubulin polymerization as well as dynamic enzyme inhibitory activity. This review is an immense compilation of research regarding the mechanism of action of chalcones and their identification as a promising anticancer agent for future drug developments. Thus, this review article would pave way and provide ample opportunities to design future generation of novel, highly efficacious anticancer molecules with minimal toxicity.
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