Plasmodium falciparum Alba6 exhibits DNase activity and participates in stress response

Alba domain proteins, owing to their functional plasticity, play a significant role in organisms. Here, we report an intrinsic DNase activity of PfAlba6 from Plasmodium falciparum, an etiological agent responsible for human malignant malaria. We identified that tyrosine28 plays a critical role in the Mg2+ driven 5'-3' DNase activity of PfAlba6. PfAlba6 cleaves both dsDNA as well as ssDNA. We also characterized PfAlba6-DNA interaction and observed concentration-dependent oligomerization in the presence of DNA, which is evident from size exclusion chromatography and single molecule AFM-imaging. PfAlba6 mRNA expression level is up-regulated several folds following heat stress and treatment with artemisinin, indicating a possible role in stress response. PfAlba6 has no human orthologs and is expressed in all intra-erythrocytic stages; thus, this protein can potentially be a new anti-malarial drug target.

Honokiol, an inducer of sirtuin-3, protects against non-steroidal anti-inflammatory drug-induced gastric mucosal mitochondrial pathology, apoptosis and inflammatory tissue injury

BACKGROUND AND PURPOSE

Mitochondrial oxidative stress, inflammation and apoptosis primarily underlie gastric mucosal injury caused by the widely used non-steroidal anti-inflammatory drugs (NSAIDs). Alternative gastroprotective strategies are therefore needed. Sirtuin-3 pivotally maintains mitochondrial structural integrity and metabolism while preventing oxidative stress; however, its relevance to gastric injury was never explored. Here, we have investigated whether and how sirtuin-3 stimulation by the phytochemical, honokiol, could rescue NSAID-induced gastric injury.

EXPERIMENTAL APPROACH

Gastric injury in rats induced by indomethacin was used to assess the effects of honokiol. Next-generation sequencing-based transcriptomics followed by functional validation identified the gastroprotective function of sirtuin-3. Flow cytometry, immunoblotting, qRT-PCR and immunohistochemistry were used measure effects on oxidative stress, mitochondrial dynamics, electron transport chain function, and markers of inflammation and apoptosis. Sirtuin-3 deacetylase activity was also estimated and gastric luminal pH was measured.

KEY RESULTS

Indomethacin down-regulated sirtuin-3 to induce oxidative stress, mitochondrial hyperacetylation, 8-oxoguanine DNA glycosylase 1 depletion, mitochondrial DNA damage, respiratory chain defect and mitochondrial fragmentation leading to severe mucosal injury. Indomethacin dose-dependently inhibited sirtuin-3 deacetylase activity. Honokiol prevented mitochondrial oxidative damage and inflammatory tissue injury by attenuating indomethacin-induced depletion of both sirtuin-3 and its transcriptional regulators PGC1α and ERRα. Honokiol also accelerated gastric wound healing but did not alter gastric acid secretion, unlike lansoprazole.

CONCLUSIONS AND IMPLICATIONS

Sirtuin-3 stimulation by honokiol prevented and reversed NSAID-induced gastric injury through maintaining mitochondrial integrity. Honokiol did not affect gastric acid secretion. Sirtuin-3 stimulation by honokiol may be utilized as a mitochondria-based, acid-independent novel gastroprotective strategy against NSAIDs.

Nuclease activity of Plasmodium falciparum Alba family protein PfAlba3

Plasmodium falciparum Alba domain-containing protein Alba3 (PfAlba3) is ubiquitously expressed in intra-erythrocytic stages of Plasmodium falciparum, but the function of this protein is not yet established. Here, we report an apurinic/apyrimidinic site-driven intrinsic nuclease activity of PfAlba3 assisted by divalent metal ions. Surface plasmon resonance and atomic force microscopy confirm sequence non-specific DNA binding by PfAlba3. Upon binding, PfAlba3 cleaves double-stranded DNA (dsDNA) hydrolytically. Mutational studies coupled with mass spectrometric analysis indicate that K23 is the essential residue in modulating the binding to DNA through acetylation-deacetylation. We further demonstrate that PfSir2a interacts and deacetylates K23-acetylated PfAlba3 in favoring DNA binding. Hence, K23 serves as a putative molecular switch regulating the nuclease activity of PfAlba3. Thus, the nuclease activity of PfAlba3, along with its apurinic/apyrimidinic (AP) endonuclease feature identified in this study, indicates a role of PfAlba3 in DNA-damage response that may have a far-reaching consequence in Plasmodium pathogenicity.

Emerging role of mitochondrial DAMPs, aberrant mitochondrial dynamics and anomalous mitophagy in gut mucosal pathogenesis

Gastroduodenal inflammation and ulcerative injuries are increasing due to expanding socio-economic stress, unhealthy food habits-lifestyle, smoking, alcoholism and usage of medicines like non-steroidal anti-inflammatory drugs. In fact, gastrointestinal (GI) complications, associated with the prevailing COVID-19 pandemic, further, poses a challenge to global healthcare towards safeguarding the GI tract. Emerging evidences have discretely identified mitochondrial dysfunctions as common etiological denominators in diseases. However, it is worth realizing that mitochondrial dysfunctions are not just consequences of diseases. Rather, damaged mitochondria severely aggravate the pathogenesis thereby qualifying as perpetrable factors worth of prophylactic and therapeutic targeting. Oxidative and nitrosative stress due to endogenous and exogenous stimuli triggers mitochondrial injury causing production of mitochondrial damage associated molecular patterns (mtDAMPs), which, in a feed-forward loop, inflicts inflammatory tissue damage. Mitochondrial structural dynamics and mitophagy are crucial quality control parameters determining the extent of mitopathology and disease outcomes. Interestingly, apart from endogenous factors, mitochondria also crosstalk and in turn get detrimentally affected by gut pathobionts colonized during luminal dysbiosis. Although mitopathology is documented in various pre-clinical/clinical studies, a comprehensive account appreciating the mitochondrial basis of GI mucosal pathologies is largely lacking. Here we critically discuss the molecular events impinging on mitochondria along with the interplay of mitochondria-derived factors in fueling mucosal pathogenesis. We specifically emphasize on the potential role of aberrant mitochondrial dynamics, anomalous mitophagy, mitochondrial lipoxidation and ferroptosis as emerging regulators of GI mucosal pathogenesis. We finally discuss about the prospect of mitochondrial targeting for next-generation drug discovery against GI disorders.

Mediators of mitophagy that regulate mitochondrial quality control play crucial role in diverse pathophysiology

Mitochondria are double membrane-bound cellular work-horses constantly functioning to regulate vital aspects of cellular metabolism, bioenergetics, proliferation and death. Biogenesis, homeostasis and regulated turnover of mitochondria are stringently regulated to meet the bioenergetic requirements. Diverse external and internal stimuli including oxidative stress, diseases, xenobiotics and even age profoundly affect mitochondrial integrity. Damaged mitochondria need immediate segregation and selective culling to maintain physiological homeostasis. Mitophagy is a specialised form of macroautophagy that constantly checks mitochondrial quality followed by elimination of rogue mitochondria by lysosomal targeting through multiple pathways tightly regulated and activated in context-specific manners. Mitophagy is implicated in diverse oxidative stress-associated metabolic, proliferating and degenerative disorders owing to the centrality of mitopathology in diseases as well as the common mandate to eliminate damaged mitochondria for restoring physiological homeostasis. With improved health care and growing demand for precision medicine, specifically targeting the keystone factors in pathogenesis, more exploratory studies are focused on mitochondrial quality control as underlying guardian of cellular pathophysiology. In this context, mitophagy emerged as a promising area to focus biomedical research for identifying novel therapeutic targets against diseases linked with physiological redox perturbation. The present review provides a comprehensive account of the recent developments on mitophagy along with precise discussion on its impact on major diseases and possibilities of therapeutic modulation.

Non-steroidal anti-inflammatory drugs (NSAIDs) and organ damage: A current perspective

Owing to the efficacy in reducing pain and inflammation, non-steroidal anti-inflammatory drugs (NSAIDs) are amongst the most popularly used medicines confirming their position in the WHO's Model List of Essential Medicines. With escalating musculoskeletal complications, as evident from 2016 Global Burden of Disease data, NSAID usage is evidently unavoidable. Apart from analgesic, anti-inflammatory and antipyretic efficacies, NSAIDs are further documented to offer protection against diverse critical disorders including cancer and heart attacks. However, data from multiple placebo-controlled trials and meta-analyses studies alarmingly signify the adverse effects of NSAIDs in gastrointestinal, cardiovascular, hepatic, renal, cerebral and pulmonary complications. Although extensive research has elucidated the mechanisms underlying the clinical hazards of NSAIDs, no review has extensively collated the outcomes on various multiorgan toxicities of these drugs together. In this regard, the present review provides a comprehensive insight of the existing knowledge and recent developments on NSAID-induced organ damage. It precisely encompasses the current understanding of structure, classification and mode of action of NSAIDs while reiterating on the emerging instances of NSAID drug repurposing along with pharmacophore modification aimed at safer usage of NSAIDs where toxic effects are tamed without compromising the clinical benefits. The review does not intend to vilify these 'wonder drugs'; rather provides a careful understanding of their side-effects which would be beneficial in evaluating the risk-benefit threshold while rationally using NSAIDs at safer dose and duration.

Sirtuins as endogenous regulators of lung fibrosis: A current perspective

Fibrotic lung diseases qualify among the most dreaded irreversible interstitial pulmonary complications with progressive yet largely unpredictable clinical course. Idiopathic pulmonary fibrosis (IPF) is the most challenging prototype characterized by unknown and complex molecular etiology, severe dearth of non-invasive therapeutic options and average lifespan of 2-5 years in patients post diagnosis. Lung fibrosis (LF) is a leading cause of death in the industrialized world with the propensity to contract, significantly increasing with age. Approximately 45% deaths in US are attributed to fibrotic diseases while around 7% respiratory disease-associated deaths, annually in UK, are actually attributed to IPF. Recent developments in the field of LF have unambiguously pointed towards the pivotal role of Sirtuins (SIRTs) in regulating disease progression, thereby qualifying as potential anti-fibrotic drug targets. These NAD⁺-dependent lysine deacetylases, deacylases and ADP-ribosyltransferases are evolutionarily conserved proteins, regulated by diverse metabolic/environmental factors and implicated in age-related degenerative and inflammatory disorders. While SIRT1, SIRT6 and SIRT7 are predominantly nuclear, SIRT3, SIRT4, SIRT5 are mainly mitochondrial and SIRT2 is majorly cytosolic with occasional nuclear translocation. SIRT1, SIRT3, SIRT6 and SIRT7 are documented as cytoprotective sirtuins implicated in cardiovascular, pulmonary and metabolic diseases including fibrosis; however functional roles of remaining sirtuins in pulmonary pathologies are yet elusive. Here, we provide a comprehensive recent update on the regulatory role of sirtuins on LF along with discussion on potential therapeutic modulation of endogenous Sirtuin expression through synthetic/plant-derived compounds which can help synthetic chemists and ethnopharmacologists to design new-generation cheap, non-toxic Sirtuin-based drugs against LF.

Rab7 of Plasmodium falciparum is involved in its retromer complex assembly near the digestive vacuole

BACKGROUND

Intracellular protein trafficking is crucial for survival of cell and proper functioning of the organelles; however, these pathways are not well studied in the malaria parasite. Its unique cellular architecture and organellar composition raise an interesting question to investigate.

METHODS

The interaction of Plasmodium falciparum Rab7 (PfRab7) with vacuolar protein sorting-associated protein 26 (PfVPS26) of retromer complex was shown by coimmunoprecipitation (co-IP). Confocal microscopy was used to show the localization of the complex in the parasite with respect to different organelles. Further chemical tools were employed to explore the role of digestive vacuole (DV) in retromer trafficking in parasite and GTPase activity of PfRab7 was examined.

RESULTS

PfRab7 was found to be interacting with retromer complex that assembled mostly near DV and the Golgi in trophozoites. Chemical disruption of DV by chloroquine (CQ) led to its disassembly that was further validated by using compound 5f, a heme polymerization inhibitor in the DV. PfRab7 exhibited Mg²⁺ dependent weak GTPase activity that was inhibited by a specific Rab7 GTPase inhibitor, CID 1067700, which prevented the assembly of retromer complex in P. falciparum and inhibited its growth suggesting the role of GTPase activity of PfRab7 in retromer assembly.

CONCLUSION

Retromer complex was found to be interacting with PfRab7 and the functional integrity of the DV was found to be important for retromer assembly in P. falciparum.

GENERAL SIGNIFICANCE

This study explores the retromer trafficking in P. falciparum and describes amechanism to validate DV targeting antiplasmodial molecules.

Indomethacin impairs mitochondrial dynamics by activating the PKCζ-p38-DRP1 pathway and inducing apoptosis in gastric cancer and normal mucosal cells

The subcellular mechanism by which nonsteroidal anti-inflammatory drugs (NSAIDs) induce apoptosis in gastric cancer and normal mucosal cells is elusive because of the diverse cyclooxygenase-independent effects of these drugs. Using human gastric carcinoma cells (AGSs) and a rat gastric injury model, here we report that the NSAID indomethacin activates the protein kinase Cζ (PKCζ)-p38 MAPK (p38)-dynamin-related protein 1 (DRP1) pathway and thereby disrupts the physiological balance of mitochondrial dynamics by promoting mitochondrial hyper-fission and dysfunction leading to apoptosis. Notably, DRP1 knockdown or SB203580-induced p38 inhibition reduced indomethacin-induced damage to AGSs. Indomethacin impaired mitochondrial dynamics by promoting fissogenic activation and mitochondrial recruitment of DRP1 and down-regulating fusogenic optic atrophy 1 (OPA1) and mitofusins in rat gastric mucosa. Consistent with OPA1 maintaining cristae architecture, its down-regulation resulted in EM-detectable cristae deformity. Deregulated mitochondrial dynamics resulting in defective mitochondria were evident from enhanced Parkin expression and mitochondrial proteome ubiquitination. Indomethacin ultimately induced mitochondrial metabolic and bioenergetic crises in the rat stomach, indicated by compromised fatty acid oxidation, reduced complex I- associated electron transport chain activity, and ATP depletion. Interestingly, Mdivi-1, a fission-preventing mito-protective drug, reversed indomethacin-induced DRP1 phosphorylation on Ser-616, mitochondrial proteome ubiquitination, and mitochondrial metabolic crisis. Mdivi-1 also prevented indomethacin-induced mitochondrial macromolecular damage, caspase activation, mucosal inflammation, and gastric mucosal injury. Our results identify mitochondrial hyper-fission as a critical and common subcellular event triggered by indomethacin that promotes apoptosis in both gastric cancer and normal mucosal cells, thereby contributing to mucosal injury.

Hydrazonophenol, a Food Vacuole-Targeted and Ferriprotoporphyrin IX-Interacting Chemotype Prevents Drug-Resistant Malaria

The rapid emergence of resistance against frontline antimalarial drugs essentially warrants the identification of new-generation antimalarials. Here, we describe the synthesis of ( E)-2-isopropyl-5-methyl-4-((2-(pyridin-4-yl)hydrazono)methyl)phenol (18), which binds ferriprotoporphyrin-IX (Fe^III-PPIX) ( K_d = 33 nM) and offers antimalarial activity against chloroquine-resistant and sensitive strains of Plasmodium falciparum in vitro. Structure-function analysis reveals that compound 18 binds Fe^III-PPIX through the -C═N-NH- moiety and 2-pyridyl substitution at the hydrazine counterpart plays a critical role in antimalarial efficacy. Live cell confocal imaging using a fluorophore-tagged compound confirms its accumulation inside the acidic food vacuole (FV) of P. falciparum. Furthermore, this compound concentration-dependently elevates the pH in FV, implicating a plausible interference with Fe^III-PPIX crystallization (hemozoin formation) by a dual function: increasing the pH and binding free Fe^III-PPIX. Different off-target bioassays reduce the possibility of the promiscuous nature of compound 18. Compound 18 also exhibits potent in vivo antimalarial activity against chloroquine-resistant P. yoelii and P. berghei ANKA (causing cerebral malaria) in mice with negligible toxicity.

Macrophage migration inhibitory factor regulates mitochondrial dynamics and cell growth of human cancer cell lines through CD74-NF-κB signaling

The indispensable role of macrophage migration inhibitory factor (MIF) in cancer cell proliferation is unambiguous, although which specific roles the cytokine plays to block apoptosis by preserving cell growth is still obscure. Using different cancer cell lines (AGS, HepG2, HCT116, and HeLa), here we report that the silencing of MIF severely deregulated mitochondrial structural dynamics by shifting the balance toward excess fission, besides inducing apoptosis with increasing sub-G₀ cells. Furthermore, enhanced mitochondrial Bax translocation along with cytochrome c release, down-regulation of Bcl-xL, and Bcl-2 as well as up-regulation of Bad, Bax, and p53 indicated the activation of a mitochondrial pathway of apoptosis upon MIF silencing. The data also indicate a concerted down-regulation of Opa1 and Mfn1 along with a significant elevation of Drp1, cumulatively causing mitochondrial fragmentation upon MIF silencing. Up-regulation of Drp1 was found to be further coupled with fissogenic serine 616 phosphorylation and serine 637 dephosphorylation, thus ensuring enhanced mitochondrial translocation. Interestingly, MIF silencing was found to be associated with decreased NF-κB activation. In fact, NF-κB knockdown in turn increased mitochondrial fission and cell death. In addition, the silencing of CD74, the cognate receptor of MIF, remarkably increased mitochondrial fragmentation in addition to preventing cell proliferation, inducing mitochondrial depolarization, and increasing apoptotic cell death. This indicates the active operation of a MIF-regulated CD74-NF-κB signaling axis for maintaining mitochondrial stability and cell growth. Thus, we propose that MIF, through CD74, constitutively activates NF-κB to control mitochondrial dynamics and stability for promoting carcinogenesis via averting apoptosis.

Detection of retromer assembly in Plasmodium falciparum by immunosensing coupled to Surface Plasmon Resonance

Retromer complex plays a crucial role in intracellular protein trafficking and is conserved throughout the eukaryotes including malaria parasite, Plasmodium falciparum, where it is partially conserved. The assembly of retromer complex in RBC stages of malarial parasite is extremely difficult to explore because of its complicated physiology, small size, and intra-erythrocytic location. Nonetheless, understanding of retromer assembly may pave new ways for the development of novel antimalarials targeting parasite-specific protein trafficking pathways. Here, we investigated the assembly of retromer complex in P. falciparum, by an immunosensing method through highly sensitive Surface Plasmon Resonance (SPR) technique. After taking leads from the bioinformatics search and literature, different interacting proteins were identified and specific antibodies were raised against them. The sensor chip was prepared by covalently linking antibody specific to one component and the whole cell lysate was passed through it in order to trap the interacting complex. Antibodies raised against other interacting components were used to detect them in the trapped complex on the SPR chip. We were able to detect three different components in the retromer complex trapped by the immobilized antibody specific against a different component on a sensor chip. The assay was reproduced and validated in a different two-component CD74-MIF system in mammalian cells. We, thus, illustrate the assembly of retromer complex in P. falciparum through a bio-sensing approach that combines SPR with immunosensing requiring a very small amount of sample from the native source.

Acute mental stress induces mitochondrial bioenergetic crisis and hyper-fission along with aberrant mitophagy in the gut mucosa in rodent model of stress-related mucosal disease

Psychological stress, depression and anxiety lead to multiple organ dysfunctions wherein stress-related mucosal disease (SRMD) is common to people experiencing stress and also occur as a side effect in patients admitted to intensive care units; however the underlying molecular aetiology is still obscure. We report that in rat-SRMD model, cold restraint-stress severely damaged gut mitochondrial functions to generate superoxide anion (O₂^•-), depleted ATP and shifted mitochondrial fission-fusion dynamics towards enhanced fission to induce mucosal injury. Activation of mitophagy to clear damaged and fragmented mitochondria was evident from mitochondrial translocation of Parkin and PINK1 along with enhanced mitochondrial proteome ubiquitination, depletion of mitochondrial DNA copy number and TOM 20. However, excess and sustained accumulation of O₂^•--generating defective mitochondria overpowered the mitophagic machinery, ultimately triggering Bax-dependent apoptosis and NF-κB-intervened pro-inflammatory mucosal injury. We further observed that stress-induced enhanced serum corticosterone stimulated mitochondrial recruitment of glucocorticoid receptor (GR), which contributed to gut mitochondrial dysfunctions as documented from reduced ETC complex 1 activity, mitochondrial O₂^•- accumulation, depolarization and hyper-fission. GR-antagonism by RU486 or specific scavenging of mitochondrial O₂^•- by a mitochondrially targeted antioxidant mitoTEMPO ameliorated stress-induced mucosal damage. Gut mitopathology and mucosal injury were also averted when the perception of mental stress was blocked by pre-treatment with a sedative or antipsychotic. Altogether, we suggest the role of mitochondrial GR-O₂^•--fission cohort in brain-mitochondria cross-talk during acute mental stress and advocate the utilization of this pathway as a potential target to prevent mitochondrial unrest and gastropathy bypassing central nervous system.

Management of Inflammation by Natural Polyphenols: A Comprehensive Mechanistic Update

Inflammation generates a systemic response against injury or infection from bacteria, viruses, and other pathogens. The welfare of host is the primary target of this process. However, uncontrolled or inadequate regulation of the inflammatory response produces detrimental effects leading to the generation of various chronic disorders including atherosclerosis, type-2 diabetes, neurodegenerative disease, cancer and Alzheimer's disease with severe tissue damage. The exact identity of the inflammatory stimuli is still elusive as they function in multiple pathways; therefore targeting a particular pathway does not resolve the problem. Existing therapeutics targeting the inflammatory responses include steroidal antiinflammatory drugs (SAIDs) and nonsteroidal antiinflammatory drugs (NSAIDs). In spite of their numerous beneficial effects, both SAIDs as well as NSAIDs have their independent, unavoidable side effects, which discourage their prolonged therapeutic applications. Since the management of uncontrolled inflammation is critical for the general wellbeing, therefore an alternative source of multi-targeted non-toxic therapeutic intervention is mandatory. Plant-derived phenols constitute such a group of molecules that can be utilised to manage inflammation. They synergistically modulate several important components involved in multiple signalling pathways that regulate uncontrolled inflammation to exhibit their beneficial health effects. This review discusses the recent advances in structure-function activity of some antiinflammatory polyphenols, their bioavailability enhancement, clinical/ preclinical findings with a view to provide knowledge for developing novel antiinflammatory drugs by following system biology of proinflammatory responses with minimal side effects.

Selective scavenging of intra-mitochondrial superoxide corrects diclofenac-induced mitochondrial dysfunction and gastric injury: A novel gastroprotective mechanism independent of gastric acid suppression

Non-steroidal anti-inflammatory drugs (NSAIDs) are widely used to treat multiple inflammatory diseases and pain but severe gastric mucosal damage is the worst outcome of NSAID-therapy. Here we report that mitoTEMPO, a mitochondrially targeted superoxide (O₂^-) scavenger protected as well as healed gastric injury induced by diclofenac (DCF), the most commonly used NSAID. Common existing therapy against gastric injury involves suppression of gastric acid secretion by proton pump inhibitors and histamine H₂ receptor antagonists; however, dyspepsia, vitamin B12 deficiency and gastric microfloral dysbalance are the major drawbacks of acid suppression. Interestingly, mitoTEMPO did not inhibit gastric acid secretion but offered gastroprotection by preventing DCF-induced generation of O₂^- due to mitochondrial respiratory chain failure and by preventing mitochondrial oxidative stress (MOS)-mediated mitopathology. MitoTEMPO even restored DCF-stimulated reduced fatty acid oxidation, mitochondrial depolarization and bioenergetic crisis in gastric mucosa. MitoTEMPO also prevented the activation of mitochondrial pathway of apoptosis and MOS-mediated proinflammatory signaling through NF-κB by DCF. Furthermore, mitoTEMPO when administered in rats with preformed gastric lesions expedited the healing of gastric injury and the healed stomach exhibited its normal physiology as evident from gastric acid and pepsin secretions under basal or stimulated conditions. Thus, in contrast to the existing antiulcer drugs, mitochondrially targeted O₂^- scavengers like mitoTEMPO may represent a novel class of gastroprotective molecules that does not affect gastric acid secretion and may be used in combination with DCF, keeping its anti-inflammatory action intact, while reducing its gastrodamaging effects.

The Alba protein family: Structure and function

Alba family proteins are small, basic, dimeric nucleic acid-binding proteins, which are widely distributed in archaea and a number of eukaryotes. This family of proteins bears the distinct features of regulation through acetylation/deacetylation, hence named as acetylation lowers binding affinity (Alba). Alba family proteins bind DNA cooperatively with no apparent sequence specificity. Besides DNA, Alba proteins also interact with diverse RNA species and associate with ribonucleo-protein complexes. Initially, Alba proteins were recognized as chromosomal proteins and supposed to be involved in the maintenance of chromatin architecture and transcription repression. However, recent studies have shown increasing evidence of functional plasticity among Alba family of proteins that widely range from genome packaging and organization, transcriptional and translational regulation, RNA metabolism, and development and differentiation processes. In recent years, Alba family proteins have attracted growing interest due to their widespread occurrence in large number of organisms. Presence in multiple copies, functional crosstalk, differential binding affinity, and posttranslational modifications are some of the key factors that might regulate the biological functions of Alba family proteins. In this review article, we present an overview of the Alba family proteins, their salient features and emphasize their functional role in different organisms reported so far.

Ellagic Acid, a Dietary Polyphenol, Inhibits Tautomerase Activity of Human Macrophage Migration Inhibitory Factor and Its Pro-inflammatory Responses in Human Peripheral Blood Mononuclear Cells

Ellagic acid (EA), a phenolic lactone, inhibited tautomerase activity of human macrophage migration inhibitory factor (MIF) noncompetitively (Ki = 1.97 ± 0.7 μM). The binding of EA to MIF was determined by following the quenching of tryptophan fluorescence. We synthesized several EA derivatives, and their structure-activity relationship studies indicated that the planar conjugated lactone moiety of EA was essential for MIF inhibition. MIF induces nuclear translocation of NF-κB and chemotaxis of peripheral blood mononuclear cells (PBMCs) to promote inflammation. We were interested in evaluating the effect of EA on nuclear translocation of NF-κB and chemotactic activity in human PBMCs in the presence of MIF. The results showed that EA inhibited MIF-induced NF-κB nuclear translocation in PBMCs, as evident from confocal immunofluorescence microscopic data. EA also inhibited MIF-mediated chemotaxis of PBMCs. Thus, we report MIF-inhibitory activity of EA and inhibition of MIF-mediated proinflammatory responses in PBMCs by EA.

TALEN mediated targeted editing of GM2/GD2-synthase gene modulates anchorage independent growth by reducing anoikis resistance in mouse tumor cells

Complex ganglioside expression is highly deregulated in several tumors which is further dependent on specific ganglioside synthase genes. Here, we designed and constructed a pair of highly specific transcription-activator like effector endonuclease (TALENs) to disrupt a particular genomic locus of mouse GM2-synthase, a region conserved in coding sequence of all four transcript variants of mouse GM2-synthase. Our designed TALENs effectively work in different mouse cell lines and TALEN induced mutation rate is over 45%. Clonal selection strategy is undertaken to generate stable GM2-synthase knockout cell line. We have also demonstrated non-homologous end joining (NHEJ) mediated integration of neomycin cassette into the TALEN targeted GM2-synthase locus. Functionally, clonally selected GM2-synthase knockout clones show reduced anchorage-independent growth (AIG), reduction in tumor growth and higher cellular adhesion as compared to wild type Renca-v cells. Insight into the mechanism shows that, reduced AIG is due to loss in anoikis resistance, as both knockout clones show increased sensitivity to detachment induced apoptosis. Therefore, TALEN mediated precise genome editing at GM2-synthase locus not only helps us in understanding the function of GM2-synthase gene and complex gangliosides in tumorigenicity but also holds tremendous potential to use TALENs in translational cancer research and therapeutics.

Nonsteroidal anti-inflammatory drug induces proinflammatory damage in gastric mucosa through NF-κB activation and neutrophil infiltration: anti-inflammatory role of heme oxygenase-1 against nonsteroidal anti-inflammatory drug

Nonsteroidal anti-inflammatory drug (NSAID)-induced mitochondrial oxidative stress (MOS) is an important prostaglandin (PG)-independent pathway of the induction of gastric mucosal injury. However, the molecular mechanism behind MOS-mediated gastric pathology is still obscure. In various pathological conditions of tissue injury oxidative stress is often linked with inflammation. Here we report that MOS induced by indomethacin (an NSAID) induces gastric mucosal inflammation leading to proinflammatory damage. Indomethacin, time dependently stimulated the expression of proinflammatory molecules such as intercellular adhesion molecule 1(ICAM-1), vascular cell adhesion molecule 1(VCAM-1), interleukin1β (IL-1β), and monocyte chemotactic protein-1 (MCP-1) in gastric mucosa in parallel with the increase of neutrophil infiltration and injury of gastric mucosa in rat. Western immunoblotting and confocal microscopic studies revealed that indomethacin induced nuclear translocation of nuclear factor kappa-B (NF-κB) in gastric mucosal cells, which resulted in proinflammatory signaling. The prevention of MOS by antioxidant tryptamine-gallic acid hybrid (SEGA) inhibited indomethacin-induced expression of ICAM-1, VCAM-1, IL-1β, and MCP-1. SEGA also prevented indomethacin-induced NF-κB activation and neutrophil infiltration as documented by chromatin immunoprecipitation studies and neutrophil migration assay, respectively. Heme oxygenase-1 (HO-1), a cytoprotective enzyme associated with tissue repair mechanisms is stimulated in response to oxidative stress. We have investigated the role of HO-1 against MOS and MOS-mediated inflammation in recovering from gastropathy. Indomethacin stimulated the expression of HO-1 and indomethacin-stimulated HO-1 expression was reduced by SEGA, an antioxidant, which could prevent MOS. Thus, the data suggested that the induction of HO-1 was a protective response against MOS developed by indomethacin. Moreover, the induction of HO-1 by cobalt protoporphyrin inhibited inflammation and chemical silencing of HO-1 by zinc protoporphyrin aggravated the inflammation by indomethacin. Thus, NSAID by promoting MOS-induced proinflammatory response damaged gastric mucosa and HO-1 protected NSAID-induced gastric mucosal damage by preventing NF-κB activation and proinflammatory activity.

Relation of iron stores to oxidative stress in type 2 diabetes

BACKGROUND

Recent studies revealed elevated serum ferritin levels predict new-onset type 2 diabetes. Further studies proved ferritin to be an important and independent predictor of the development of diabetes. The link between hyperglycemia, enhanced free radical activity (oxidative stress) and serum iron and its stores (serum ferritin levels) levels is not clear.

OBJECTIVES

The present study is an attempt to understand the relationship between serum ferritin levels and oxidative stress (measured by malondialdehyde).

MATERIALS AND METHODS

The study comprised of 30 apparently healthy controls and 30 type 2 diabetic patients who attended the outpatient and inpatient departments of Medical College, Kolkata. Levels of fasting blood glucose, postprandial blood glucose, serum iron, serum ferritin, glycosylated hemoglobin (HbA1c) and malondialdehyde (MDA), serum urea and creatinine were estimated. The statistical software SPSS 11.0 and Systat 8.0 were used for the analysis of the data and Microsoft Word and Excel have been used to generate tables and graphs.

RESULTS

Serum iron (82.16 ± 13.24 μg/dl), serum ferritin (224.53 ± 96.06 μg/L), HbA1c (8.62 ± 1.79%), MDA (2.66 ± 0.76 nmol/ml) levels were significantly higher in type 2 diabetics compared with apparently healthy controls. Elevations in serum iron, ferritin and HbA1c are accompanied by a parallel increase in blood glucose. Based on groups of glycemic control, i.e. HbA1c levels >8%, serum ferritin levels were highest, 258.63 ± 22.67 μg/dl. There is an inverse correlation of serum ferritin levels to MDA levels in the diabetic cases of longer duration of more than 10 years.

CONCLUSION

Serum ferritin level in the present study is found to be higher in the newly diagnosed cases and lower in those patients suffering from diabetes for more than 10 years. This study probably suggests that serum ferritin can represent either as a pro-oxidant or as an antioxidant in a time-dependent manner.

Novel antimalarial drug targets: hope for new antimalarial drugs

Malaria is a major global threat, that results in more than 2 million deaths each year. The treatment of malaria is becoming extremely difficult due to the emergence of drug-resistant parasites, the absence of an effective vaccine, and the spread of insecticide-resistant vectors. Thus, malarial therapy needs new chemotherapeutic approaches leading to the search for new drug targets. Here, we discuss different approaches to identifying novel antimalarial drug targets. We have also given due attention to the existing validated targets with a view to develop novel, rationally designed lead molecules. Some of the important parasite proteins are claimed to be the targets; however, further in vitro or in vivo structure-function studies of such proteins are crucial to validate these proteins as suitable targets. The interactome analysis among apicoplast, mitochondrion and genomic DNA will also be useful in identifying vital pathways or proteins regulating critical pathways for parasite growth and survival, and could be attractive targets. Molecules responsible for parasite invasion to host erythrocytes and ion channels of infected erythrocytes, essential for intra-erythrocyte survival and stage progression of parasites are also becoming attractive targets. This review will discuss and highlight the current understanding regarding the potential antimalarial drug targets, which could be utilized to develop novel antimalarials.

Redox-active antiparasitic drugs

SIGNIFICANCE

Parasitic diseases affect hundreds of millions of people worldwide and represent major health problems. Treatment is becoming extremely difficult due to the emergence of drug resistance, the absence of effective vaccines, and the spread of insecticide-resistant vectors. Thus, identification of affordable and readily available drugs against resistant parasites is of global demand.

RECENT ADVANCES

Susceptibility of many parasites to oxidative stress is a well-known phenomenon. Therefore, generation of reactive oxygen species (ROS) or inhibition of endogenous antioxidant enzymes would be a novel therapeutic approach to develop antiparasitic drugs. This article highlights the unique metabolic pathways along with redox enzymes of unicellular (Plasmodium falciparum, Trypanosoma cruzi, Trypanosoma brucei, Leishmania donovani, Entamoeba histolytica, and Trichomonas vaginalis) and multicellular parasites (Schistosoma mansoni), which could be utilized to promote ROS-mediated toxicity.

CRITICAL ISSUES

Enzymes involved in various vital redox reactions could be potential targets for drug development.

FUTURE DIRECTIONS

The identification of redox-active antiparasitic drugs along with their mode of action will help researchers around the world in designing novel drugs in the future.

Redox regulation in malaria: current concepts and pharmacotherapeutic implications

Malaria imposes a serious threat to human and becomes more prevalent due to the emergence of drug resistant parasite. Understanding of the underlying mechanism of drug resistance and identification of novel drug targets are key effective processes for the management of malaria. Malaria parasite is highly susceptible to oxidative stress but lives in a pro-oxidant rich environment containing oxygen and iron, which produce a large amount of reactive oxygen species. Management of oxidative stress in malaria parasite is tightly regulated through active redox and antioxidant defense systems. The elevation of oxidative stress as a result of inhibition of any component of this defense system leads to redox imbalance and ultimately parasite death. Therefore, redox system plays an indispensable role for the survival of parasite within the host. Identification of key molecules, which disrupt parasite redox balance by altering key redox reactions and promote oxidative stress in parasites, would be an effective approach to develop novel antimalarial drugs. During the last few decades, contributions by researchers around the globe provide even better understanding of redox biology of malaria parasite. Here, in this review, we are highlighting the knowledge gathered so far regarding the essential redox-active processes and their components in malaria parasite to overcome elevated oxidative insults. We have also given maximum efforts to enlist currently used redox-active antimalarials, their mode of action and pharmacotherapeutic implications.

Aryl aryl methyl thio arenes prevent multidrug-resistant malaria in mouse by promoting oxidative stress in parasites

We have synthesized a new series of aryl aryl methyl thio arenes (AAMTAs) and evaluated antimalarial activity in vitro and in vivo against drug-resistant malaria. These compounds interact with free heme, inhibit hemozoin formation, and prevent Plasmodium falciparum growth in vitro in a concentration-dependent manner. These compounds concentration dependently promote oxidative stress in Plasmodium falciparum as evident from the generation of intraparasitic oxidants, protein carbonyls, and lipid peroxidation products. Furthermore, AAMTAs deplete intraparasite GSH levels, which is essential for antioxidant defense and survival during intraerythrocytic stages. These compounds displayed potent antimalarial activity not only in vitro but also in vivo against multidrug-resistant Plasmodium yoelii dose dependently in a mouse model. The mixtures of enantiomers of AAMTAs containing 3-pyridyl rings were found to be more efficient in providing antimalarial activity. Efforts have been made to synthesize achiral AAMTAs 17-23 and among them, compound 18 showed significant antimalarial activity in vivo.

Impact of intravascular hemolysis in malaria on liver dysfunction: involvement of hepatic free heme overload, NF-κB activation, and neutrophil infiltration

We have investigated the impact of persistent intravascular hemolysis on liver dysfunction using the mouse malaria model. Intravascular hemolysis showed a positive correlation with liver damage along with the increased accumulation of free heme and reactive oxidants in liver. Hepatocytes overinduced heme oxygenase-1 (HO-1) to catabolize free heme in building up defense against this pro-oxidant milieu. However, in a condition of persistent free heme overload in malaria, the overactivity of HO-1 resulted in continuous transient generation of free iron to favor production of reactive oxidants as evident from 2',7'-dichlorofluorescein fluorescence studies. Electrophoretic mobility shift assay documented the activation of NF-κB, which in turn up-regulated intercellular adhesion molecule 1 as evident from chromatin immunoprecipitation studies. NF-κB activation also induced vascular cell adhesion molecule 1, keratinocyte chemoattractant, and macrophage inflammatory protein 2, which favored neutrophil extravasation and adhesion in liver. The infiltration of neutrophils correlated positively with the severity of hemolysis, and neutrophil depletion significantly prevented liver damage. The data further documented the elevation of serum TNFα in infected mice, and the treatment of anti-TNFα antibodies also significantly prevented neutrophil infiltration and liver injury. Deferoxamine, which chelates iron, interacts with free heme and bears antioxidant properties that prevented oxidative stress, NF-κB activation, neutrophil infiltration, hepatocyte apoptosis, and liver damage. Furthermore, the administration of N-acetylcysteine also prevented NF-κB activation, neutrophil infiltration, hepatocyte apoptosis, and liver damage. Thus, hepatic free heme accumulation, TNFα release, oxidative stress, and NF-κB activation established a link to favor neutrophil infiltration in inducing liver damage during hemolytic conditions in malaria.

Novel anti-inflammatory activity of epoxyazadiradione against macrophage migration inhibitory factor: inhibition of tautomerase and proinflammatory activities of macrophage migration inhibitory factor

Macrophage migration inhibitory factor (MIF) is responsible for proinflammatory reactions in various infectious and non-infectious diseases. We have investigated the mechanism of anti-inflammatory activity of epoxyazadiradione, a limonoid purified from neem (Azadirachta indica) fruits, against MIF. Epoxyazadiradione inhibited the tautomerase activity of MIF of both human (huMIF) and malaria parasites (Plasmodium falciparum (PfMIF) and Plasmodium yoelii (PyMIF)) non-competitively in a reversible fashion (K(i), 2.11-5.23 μm). Epoxyazadiradione also significantly inhibited MIF (huMIF, PyMIF, and PfMIF)-mediated proinflammatory activities in RAW 264.7 cells. It prevented MIF-induced macrophage chemotactic migration, NF-κB translocation to the nucleus, up-regulation of inducible nitric-oxide synthase, and nitric oxide production in RAW 264.7 cells. Epoxyazadiradione not only exhibited anti-inflammatory activity in vitro but also in vivo. We tested the anti-inflammatory activity of epoxyazadiradione in vivo after co-administering LPS and MIF in mice to mimic the disease state of sepsis or bacterial infection. Epoxyazadiradione prevented the release of proinflammatory cytokines such as IL-1α, IL-1β, IL-6, and TNF-α when LPS and PyMIF were co-administered to BALB/c mice. The molecular basis of interaction of epoxyazadiradione with MIFs was explored with the help of computational chemistry tools and a biological knowledgebase. Docking simulation indicated that the binding was highly specific and allosteric in nature. The well known MIF inhibitor (S,R)-3-(4-hydroxyphenyl)-4,5-dihydro-5-isoxazole acetic acid methyl ester (ISO-1) inhibited huMIF but not MIF of parasitic origin. In contrast, epoxyazadiradione inhibited both huMIF and plasmodial MIF, thus bearing an immense therapeutic potential against proinflammatory reactions induced by MIF of both malaria parasites and human.

Tryptamine-gallic acid hybrid prevents non-steroidal anti-inflammatory drug-induced gastropathy: correction of mitochondrial dysfunction and inhibition of apoptosis in gastric mucosal cells

We have investigated the gastroprotective effect of SEGA (3a), a newly synthesized tryptamine-gallic acid hybrid molecule against non-steroidal anti-inflammatory drug (NSAID)-induced gastropathy with mechanistic details. SEGA (3a) prevents indomethacin (NSAID)-induced mitochondrial oxidative stress (MOS) and dysfunctions in gastric mucosal cells, which play a pathogenic role in inducing gastropathy. SEGA (3a) offers this mitoprotective effect by scavenging of mitochondrial superoxide anion (O(2)(·-)) and intramitochondrial free iron released as a result of MOS. SEGA (3a) in vivo blocks indomethacin-mediated MOS, as is evident from the inhibition of indomethacin-induced mitochondrial protein carbonyl formation, lipid peroxidation, and thiol depletion. SEGA (3a) corrects indomethacin-mediated mitochondrial dysfunction in vivo by restoring defective electron transport chain function, collapse of transmembrane potential, and loss of dehydrogenase activity. SEGA (3a) not only corrects mitochondrial dysfunction but also inhibits the activation of the mitochondrial pathway of apoptosis by indomethacin. SEGA (3a) inhibits indomethacin-induced down-regulation of bcl-2 and up-regulation of bax genes in gastric mucosa. SEGA (3a) also inhibits indometacin-induced activation of caspase-9 and caspase-3 in gastric mucosa. Besides the gastroprotective effect against NSAID, SEGA (3a) also expedites the healing of already damaged gastric mucosa. Radiolabeled ((99m)Tc-labeled SEGA (3a)) tracer studies confirm that SEGA (3a) enters into mitochondria of gastric mucosal cell in vivo, and it is quite stable in serum. Thus, SEGA (3a) bears an immense potential to be a novel gastroprotective agent against NSAID-induced gastropathy.

Translocation of heme oxygenase-1 to mitochondria is a novel cytoprotective mechanism against non-steroidal anti-inflammatory drug-induced mitochondrial oxidative stress, apoptosis, and gastric mucosal injury

The mechanism of action of heme oxygenase-1 (HO-1) in mitochondrial oxidative stress (MOS)-mediated apoptotic tissue injury was investigated. MOS-mediated gastric mucosal apoptosis and injury were introduced in rat by indomethacin, a non-steroidal anti-inflammatory drug. Here, we report that HO-1 was not only induced but also translocated to mitochondria during gastric mucosal injury to favor repair mechanisms. Furthermore, mitochondrial translocation of HO-1 resulted in the prevention of MOS and mitochondrial pathology as evident from the restoration of the complex I-driven mitochondrial respiratory control ratio and transmembrane potential. Mitochondrial translocation of HO-1 also resulted in time-dependent inhibition of apoptosis. We searched for the plausible mechanisms responsible for HO-1 induction and mitochondrial localization. Free heme, the substrate for HO-1, was increased inside mitochondria during gastric injury, and mitochondrial entry of HO-1 decreased intramitochondrial free heme content, suggesting that a purpose of mitochondrial translocation of HO-1 is to detoxify accumulated heme. Heme may activate nuclear translocation of NF-E2-related factor 2 to induce HO-1 through reactive oxygen species generation. Electrophoretic mobility shift assay and chromatin immunoprecipitation studies indicated nuclear translocation of NF-E2-related factor 2 and its binding to HO-1 promoter to induce HO-1 expression during gastric injury. Inhibition of HO-1 by zinc protoporphyrin aggravated the mucosal injury and delayed healing. Zinc protoporphyrin further reduced the respiratory control ratio and transmembrane potential and enhanced MOS and apoptosis. In contrast, induction of HO-1 by cobalt protoporphyrin reduced MOS, corrected mitochondrial dysfunctions, and prevented apoptosis and gastric injury. Thus, induction and mitochondrial localization of HO-1 are a novel cytoprotective mechanism against MOS-mediated apoptotic tissue injury.

Identification and molecular characterization of an Alba-family protein from human malaria parasite Plasmodium falciparum

We have investigated the DNA-binding nature as well as the function of a putative Alba (Acetylation lowers binding affinity) family protein (PfAlba3) from Plasmodium falciparum. PfAlba3 possesses DNA-binding property like Alba family proteins. PfAlba3 binds to DNA sequence non-specifically at the minor groove and acetylation lowers its DNA-binding affinity. The protein is ubiquitously expressed in all the erythrocytic stages of P. falciparum and it exists predominantly in the acetylated form. PfAlba3 inhibits transcription in vitro by binding to DNA. Plasmodium falciparum Sir2 (PfSir2A), a nuclear localized deacetylase interacts with PfAlba3 and deacetylates the lysine residue of N-terminal peptide of PfAlba3 specific for DNA binding. PfAlba3 is localized with PfSir2A in the periphery of the nucleus. Fluorescence in situ hybridization studies revealed the presence of PfAlba3 in the telomeric and subtelomeric regions. ChIP and ChIP ReChIP analyses further confirmed that PfAlba3 binds to the telomeric and subtelomeric regions as well as to var gene promoter.

Cysteine-3 and cysteine-4 are essential for the thioredoxin-like oxidoreductase and antioxidant activities of Plasmodium falciparum macrophage migration inhibitory factor

Plasmodium falciparum macrophage migration inhibitory factor (PfMIF) exhibits thioredoxin (Trx)-like oxidoreductase activity but the active site for this activity and its function have not been evaluated. A bioinformatics search revealed that the conserved CXXC motif, which is responsible for Trx-like oxidoreductase activity, is absent from PfMIF. In contrast, the adjacent N-terminal Cys-3 and Cys-4 are conserved in MIF across species of malarial parasites. Mutation of either vicinal Cys-3 or Cys-4 of PfMIF abolished the Trx-like activity, whereas the mutation of the remaining Cys-59 or Cys-103 did not affect it. PfMIF has an antioxidant function. It prevents reactive oxygen species-mediated lipid peroxidation and oxidative damage of DNA as evident from DNA nicking assay. Interestingly, chemical modification of the vicinal cysteines by phenylarsine oxide (PAO), a specific vicinal thiol modifier, significantly prevented this antioxidant activity. Modification of Cys-3 and Cys-4 was confirmed by MALDI-TOF mass spectroscopy of peptide fragments obtained after cyanogen bromide digestion of PAO-modified PfMIF. Furthermore, mutation of either Cys-3 or Cys-4 of PfMIF resulted in the loss of both Trx-like oxidoreductase and antioxidant activities of PfMIF. Altogether, our results suggest that the vicinal Cys-3 and Cys-4 play a critical role in the Trx-like oxidoreductase activity and antioxidant property of PfMIF.

Synthesis of novel heme-interacting acridone derivatives to prevent free heme-mediated protein oxidation and degradation

Heme is an important prosthetic molecule for various hemoproteins and serves important function in living aerobic organisms. But degradation of hemoprotein, for example, hemoglobin during different pathological conditions leads to the release of heme, which is very toxic as it induces oxidative stress and inflammation due to its pro-oxidant nature. Thus, synthesis of compound that will detoxify free heme by interacting with it would be fruitful for the management of heme-induced pathogenesis. Here, we report the synthesis of a novel natural product arborinine and some other acridone derivatives, which interact with free heme. These acridones in vitro block heme-mediated protein oxidation and degradation, markers for heme-induced oxidative stress.

Gallic acid prevents nonsteroidal anti-inflammatory drug-induced gastropathy in rat by blocking oxidative stress and apoptosis

Nonsteroidal anti-inflammatory drug (NSAID)-induced oxidative stress plays a critical role in gastric mucosal cell apoptosis and gastropathy. NSAIDs induce the generation of hydroxyl radical ((*)OH) through the release of free iron, which plays an important role in developing gastropathy. Thus, molecules having both iron-chelating and antiapoptotic properties will be beneficial in preventing NSAID-induced gastropathy. Gallic acid (GA), a polyphenolic natural product, has the capacity to chelate free iron. Here, we report that GA significantly prevents, as well as heals, NSAID-induced gastropathy. In vivo, GA blocks NSAID-mediated mitochondrial oxidative stress by preventing mitochondrial protein carbonyl formation, lipid peroxidation, and thiol depletion. In vitro, GA scavenges free radicals and blocks (*)OH-mediated oxidative damage. GA also attenuates gastric mucosal cell apoptosis in vivo as well as in vitro in cultured gastric mucosal cells as evident from the TUNEL assay. GA prevents NSAID-induced activation of caspase-9, a marker for the mitochondrial pathway of apoptosis, and restores NSAID-mediated collapse of the mitochondrial transmembrane potential and dehydrogenase activity. Thus, the inhibition of mitochondrial oxidative stress by GA is associated with the inhibition of NSAID-induced mitochondrial dysfunction and activation of apoptosis in gastric mucosal cells, which are responsible for gastric injury or gastropathy.

Biological activities of crude extracts and chemical constituents of Bael, Aegle marmelos (L.) Corr

Bael (Aegle marmelos (L.) Corr.) is an important medicinal plant of India. Leaves, fruits, stem and roots of A. marmelos have been used in ethno medicine to exploit its' medicinal properties including astringent, antidiarrheal antidysenteric, demulcent, antipyretic and anti-inflammatory activities. Compounds purified from bael have been proven to be biologically active against several major diseases including cancer, diabetes and cardiovascular diseases. Preclinical studies indicate the therapeutic potential of crude extracts of A. marmelos in the treatment of many microbial diseases, diabetes and gastric ulcer. This review covers the biological activities of some isolated chemical constituents of A. marmelos and preclinical studies on some crude extracts and pure compounds to explore novel bioactive compounds for therapeutic application.

The use of neem for controlling gastric hyperacidity and ulcer

H(2)-receptor blockers and proton pump inhibitors are now used extensively to control gastric and duodenal ulcer, inflammation and pain, but these drugs have limitations and are not always affordable. The development of novel nontoxic antiulcer drugs, including from medicinal plants, is therefore desirable, and Azadirachta indica A. Juss, commonly known as Neem, is known to have potent gastroprotective and antiulcer effects. This review deals with the pharmacological and biochemical studies carried out regarding the antiulcer activities of Neem extracts and their mechanism of action, including the inhibition of acid secretion. A comparison with ranitidine and omeprazole in some animal models has been included and clinical studies, where available, have also been incorporated, along with a safety evaluation. Neem bark extract has the potential for the development of novel medicines for the therapeutic control of gastric hyperacidity and ulcer.

Melatonin reduces indomethacin-induced gastric mucosal cell apoptosis by preventing mitochondrial oxidative stress and the activation of mitochondrial pathway of apoptosis

Augmentation of gastric mucosal cell apoptosis due to development of oxidative stress is one of the main pathogenic events in the development of nonsteroidal anti-inflammatory drug (NSAID)-induced gastropathy. Identification of a nontoxic, anti-apoptotic molecule is warranted for therapy against NSAID-induced gastropathy. The objective of the present study was to define the mechanism of the anti-apoptotic effect of melatonin, a nontoxic molecule which scavenges reactive oxygen species. Using an array of experimental approaches, we have shown that melatonin prevents the development of mitochondrial oxidative stress and activation of mitochondrial pathway of apoptosis induced by indomethacin (a NSAID) in the gastric mucosa. Melatonin inhibits the important steps of indomethacin-induced activation of mitochondrial pathway of apoptosis such as upregulation of the expression of Bax and Bak, and the downregulation of Bcl-2 and BclxL. Melatonin also prevents indomethacin-induced mitochondrial translocation of Bax and prevents the collapse of mitochondrial membrane potential. Moreover, melatonin reduces indomethacin-mediated activation of caspase-9 and caspase-3 by blocking the release of cytochrome c and finally rescues gastric mucosal cells from indomethacin-induced apoptosis as measured by the TUNEL assay. Histologic studies of gastric mucosa further document that melatonin almost completely protects against gastric damage induced by indomethacin. Thus, melatonin has significant anti-apoptotic effects to protect gastric mucosa from NSAID-induced apoptosis and gastropathy, which makes its use as potential therapy against gastric damage during NSAID treatment.

Malarial infection develops mitochondrial pathology and mitochondrial oxidative stress to promote hepatocyte apoptosis

Activation of the mitochondrial apoptosis pathway by oxidative stress has been implicated in hepatocyte apoptosis during malaria. Because mitochondria are the source and target of reactive oxygen species (ROS), we have investigated whether hepatocyte apoptosis is linked to mitochondrial pathology and mitochondrial ROS generation during malaria. Malarial infection induces mitochondrial pathology by inhibiting mitochondrial respiration, dehydrogenases, and transmembrane potential and damaging the ultrastructure as evident from transmission electron microscopic studies. Mitochondrial GSH depletion and formation of protein carbonyl indicate that mitochondrial pathology is associated with mitochondrial oxidative stress. Fluorescence imaging of hepatocytes documents intramitochondrial superoxide anion (O(2)(-)) generation during malaria. O(2)(-) inactivates mitochondrial aconitase to release iron from iron-sulfur clusters, which forms the hydroxyl radical ((.)OH) interacting with H(2)O(2) produced concurrently. Malarial infection inactivates mitochondrial aconitase, and carbonylation of aconitase is evident from Western immunoblotting. The release of iron has been documented by fluorescence imaging of hepatocytes using Phen Green SK, and mitochondrial (.)OH generation has been confirmed. During malaria, the depletion of cardiolipin and formation of the mitochondrial permeability transition pore favor cytochrome c release to activate caspase-9. Interestingly, mitochondrial (.)OH generation correlates with the activation of both caspase-9 and caspase-3 with the progress of malarial infection, indicating the critical role of (.)OH.

Indomethacin, a non-steroidal anti-inflammatory drug, develops gastropathy by inducing reactive oxygen species-mediated mitochondrial pathology and associated apoptosis in gastric mucosa: a novel role of mitochondrial aconitase oxidation

We have investigated the role of mitochondria on the development of indomethacin (a non-steroidal anti-inflammatory drug)-induced gastric mucosal apoptosis and associated gastropathy in rat. Transmission electron microscopic studies indicate that indomethacin damages mitochondrial ultrastructure and causes mitochondrial dysfunction as evident from decreased stage-3 respiration, dehydrogenase activity, and transmembrane potential (DeltaPsi(m)). Mitochondrial pathology is associated with increased generation of intra-mitochondrial-reactive oxygen species, such as O(2)(*), H(2)O(2) and *OH, leading to oxidative stress. O(2)(*) is the most effective to damage mitochondrial aconitase, leading to the release of iron from its iron-sulfur cluster. The released iron, by interacting with intra-mitochondrial H(2)O(2), forms *OH. Immunoprecipitation of mitochondrial aconitase and subsequent Western immunoblotting indicate carbonylation of aconitase along with the loss of activity in vivo after indomethacin treatment. The release of iron has been documented by fluorescence imaging of mucosal cells by using Phen Green SK, a specific probe for chelatable iron. Interestingly, intra-mitochondrial *OH generation is crucial for the development of mitochondrial pathology and activation of mitochondrial death pathway by indomethacin. Scavenging of *OH by dimethyl sulfoxide or alpha-phenyl-n-tert-butylnitrone, a spin-trap, prevents indomethacin-induced mitochondrial ultrastructural changes, oxidative stress, collapse of DeltaPsi(m), and mitochondrial dysfunction. The scavengers also restore indomethacin-induced activation of caspase-9 and caspase-3 to block mitochondrial pathway of apoptosis and gastric mucosal damage. This study, thus, reveals the critical role of O(2)(*)-mediated mitochondrial aconitase inactivation to release intra-mitochondrial iron, which by generating *OH promotes gastric mucosal cell apoptosis and gastropathy during indomethacin treatment.

Lansoprazole protects and heals gastric mucosa from non-steroidal anti-inflammatory drug (NSAID)-induced gastropathy by inhibiting mitochondrial as well as Fas-mediated death pathways with concurrent induction of mucosal cell renewal

We have investigated the mechanism of antiapoptotic and cell renewal effects of lansoprazole, a proton pump inhibitor, to protect and heal gastric mucosal injury in vivo induced by indomethacin, a non-steroidal anti-inflammatory drug (NSAID). Lansoprazole prevents indomethacin-induced gastric damage by blocking activation of mitochondrial and Fas pathways of apoptosis. Lansoprazole prevents indomethacin-induced up-regulation of proapoptotic Bax and Bak and down-regulation of antiapoptotic Bcl-2 and Bcl(xL) to maintain the normal proapoptotic/antiapoptotic ratio and thereby arrests indomethacin-induced mitochondrial translocation of Bax and collapse of mitochondrial membrane potential followed by cytochrome c release and caspase-9 activation. Lansoprazole also inhibits indomethacin-induced Fas-mediated mucosal cell death by down-regulating Fas or FasL expression and inhibiting caspase-8 activation. Lansoprazole favors mucosal cell renewal simultaneously by stimulating gene expression of prosurvival proliferating cell nuclear antigen, survivin, epidermal growth factor, and basic fibroblast growth factor. The up-regulation of Flt-1 further indicates that lansoprazole activates vascular epidermal growth factor-mediated controlled angiogenesis to repair gastric mucosa. Lansoprazole also stimulates the healing of already formed ulcers induced by indomethacin. Time course study of healing indicates that it switches off the mitochondrial death pathway completely but not the Fas pathway. However, lansoprazole heals mucosal lesions almost completely after overcoming the persisting Fas pathway, probably by favoring the prosurvival genes expression. This study thus provides the detailed mechanism of antiapoptotic and prosurvival effects of lansoprazole for offering gastroprotection against indomethacin-induced gastropathy.

Bilirubin inhibits Plasmodium falciparum growth through the generation of reactive oxygen species

Free heme is very toxic because it generates highly reactive hydroxyl radicals ((.)OH) to cause oxidative damage. Detoxification of free heme by the heme oxygenase (HO) system is a very common phenomenon by which free heme is catabolized to form bilirubin as an end product. Interestingly, the malaria parasite, Plasmodium falciparum, lacks an HO system, but it forms hemozoin, mainly to detoxify free heme. Here, we report that bilirubin significantly induces oxidative stress in the parasite as evident from the increased formation of lipid peroxide, decrease in glutathione content, and increased formation of H(2)O(2) and (.)OH. Bilirubin can effectively inhibit hemozoin formation also. Furthermore, results indicate that bilirubin inhibits parasite growth and induces caspase-like protease activity, up-regulates the expression of apoptosis-related protein (Gene ID PFI0450c), and reduces the mitochondrial membrane potential. (.)OH scavengers such as mannitol, as well as the spin trap alpha-phenyl-n-tert-butylnitrone, effectively protect the parasite from bilirubin-induced oxidative stress and growth inhibition. These findings suggest that bilirubin, through the development of oxidative stress, induces P. falciparum cell death and that the malaria parasite lacks an HO system probably to protect itself from bilirubin-induced cell death as a second line of defense.

Melatonin inhibits free radical-mediated mitochondrial-dependent hepatocyte apoptosis and liver damage induced during malarial infection

We showed earlier that malarial infection significantly induces liver apoptosis mediated by oxidative stress mechanisms. Thus, a nontoxic antioxidant-antiapoptotic molecule may be beneficial for hepatoprotection. Melatonin remarkably prevents hepatocyte apoptosis in mice induced during malaria as indicated by caspase 3 and TUNEL assays as well as transmission electron microscopy (TEM) of the liver tissue. The mitochondrial apoptotic pathway, which plays a critical role in liver cell death during malarial infection, was almost completely suppressed by melatonin as it corrects both the overexpression of Bax and down-regulation of bcl-2 as revealed by semiquantitative RT-PCR. Fluorometric studies using JC-1 documented that melatonin also restores mitochondrial transmembrane potential (DeltaPsim) in malaria-infected mice liver. The antiapoptotic effect of melatonin is associated with its antioxidant role because melatonin protects liver from oxidative stress induced during malaria by scavenging the hydroxyl radicals, preventing the depletion of reduced glutathione, inhibiting lipid peroxidation and protein carbonyl formation. The effective antioxidant dose of melatonin to protect liver from oxidative stress during malaria is 20 times lower than that of known antioxidants, vitamin C and vitamin E. Apoptosis of hepatocytes during malarial infection is well correlated with dysfunction of the liver while melatonin offers hepatoprotective effects as indicated by different liver function tests. Thus, melatonin may well be effective in combating oxidative stress-induced apoptosis and liver damage during malaria infection.

Overexpression, purification and localization of apoptosis related protein from Plasmodium falciparum

A growing body of evidence has ascertained that apoptosis is not only restricted to metazoans but also exists in unicellular parasites. In Plasmodium falciparum, the presence of a putative gene having sequence homology with apoptosis related protein (PfARP) (Gene ID PFI0450c) has raised enormous interest to unravel the function of this unique protein in cell death of malaria parasite. To characterize this protein, the PfARP gene has been amplified from the P. falciparum transcriptome by RT-PCR and the amplified gene has been successfully cloned, over-expressed and purified to homogeneity. The purified PfARP exhibits minimum subunit MW of approximately 24kDa as evident from SDS-PAGE. CD analysis reveals that the alpha and beta content of the recombinant PfARP are 61% and 15%, respectively. Semiquantitative RT-PCR analysis indicates the expression of PfARP at both metabolically less active ring and highly active trophozoite stages of malaria parasite. Immunofluorescence microscopy further supports that PfARP expresses stage specifically with the highest expression at trophozite stage and very little in the schizont stage. PfARP is a cytosolic protein as evident from immunofluorescence microscopy. The role of this protein in P. falciparum cell death and stage progression is not yet known. The identification, purification and characterization would certainly be a step to initiate work on this protein to evaluate its role in P. falciparum growth, multiplication and stage progression.