Krishnendu Sinha

Oxidative stress: the mitochondria-dependent and mitochondria-independent pathways of apoptosis

Oxidative stress basically defines a condition in which prooxidant–antioxidant balance in the cell is disturbed; cellular biomolecules undergo severe oxidative damage, ultimately compromising cells viability. In recent years, a number of studies have shown that oxidative stress could cause cellular apoptosis via both the mitochondria-dependent and mitochondria-independent pathways. Since these pathways are directly related to the survival or death of various cell types in normal as well as pathophysiological situations, a clear picture of these pathways for various active molecules in their biological functions would help designing novel therapeutic strategy. This review highlights the basic mechanisms of ROS production and their sites of formation; detail mechanism of both mitochondria-dependent and mitochondria-independent pathways of apoptosis as well as their regulation by ROS. Emphasis has been given on the redox-sensitive ASK1 signalosome and its downstream JNK pathway. This review also describes the involvement of oxidative stress under various environmental toxin- and drug-induced organ pathophysiology and diabetes-mediated apoptosis. We believe that this review would provide useful information about the most recent progress in understanding the mechanism of oxidative stress–mediated regulation of apoptotic pathways. It will also help to figure out the complex cross-talks between these pathways and their modulations by oxidative stress. The literature will also shed a light on the blind alleys of this field to be explored. Finally, readers would know about the ROS-regulated and apoptosis-mediated organ pathophysiology which might help to find their probable remedies in future.

Mangiferin Attenuates Diabetic Nephropathy by Inhibiting Oxidative Stress Mediated Signaling Cascade, TNFα Related and Mitochondrial Dependent Apoptotic Pathways in Streptozotocin-Induced Diabetic Rats

Oxidative stress plays a crucial role in the progression of diabetic nephropathy in hyperglycemic conditions. It has already been reported that mangiferin, a natural C-glucosyl xanthone and polyhydroxy polyphenol compound protects kidneys from diabetic nephropathy. However, little is known about the mechanism of its beneficial action in this pathophysiology. The present study, therefore, examines the detailed mechanism of the beneficial action of mangiferin on STZ-induced diabetic nephropathy in Wister rats as the working model. A significant increase in plasma glucose level, kidney to body weight ratio, glomerular hypertrophy and hydropic changes as well as enhanced nephrotoxicity related markers (BUN, plasma creatinine, uric acid and urinary albumin) were observed in the experimental animals. Furthermore, increased oxidative stress related parameters, increased ROS production and decreased the intracellular antioxidant defenses were detected in the kidney. Studies on the oxidative stress mediated signaling cascades in diabetic nephropathy demonstrated that PKC isoforms (PKCα, PKCβ and PKCε), MAPKs (p38, JNK and ERK1/2), transcription factor (NF-κB) and TGF-β1 pathways were involved in this pathophysiology. Besides, TNFα was released in this hyperglycemic condition, which in turn activated caspase 8, cleaved Bid to tBid and finally the mitochorndia-dependent apoptotic pathway. In addition, oxidative stress also disturbed the proapoptotic-antiapoptotic (Bax and Bcl-2) balance and activated mitochorndia-dependent apoptosis via caspase 9, caspase 3 and PARP cleavage. Mangiferin treatment, post to hyperglycemia, successfully inhibited all of these changes and protected the cells from apoptotic death.

An update on oxidative stress-mediated organ pathophysiology.

Exposure to environmental pollutants and drugs can result in pathophysiological situations in the body. Research in this area is essential as the knowledge on cellular survival and death would help in designing effective therapeutic strategies that are needed for the maintenance of the normal physiological functions of the body. In this regard, naturally occurring bio-molecules can be considered as potential therapeutic targets as they are normally available in commonly consumed foodstuffs and are thought to have minimum side effects. This review article describes the detailed mechanisms of oxidative stress-mediated organ pathophysiology and the ultimate fate of the cells either to survive or to undergo necrotic or apoptotic death. The mechanisms underlying the beneficial role of a number of naturally occurring bioactive molecules in oxidative stress-mediated organ pathophysiology have also been included in the review. The review provides useful information about the recent progress in understanding the mechanism(s) of various types of organ pathophysiology, the complex cross-talk between these pathways, as well as their modulation in stressed conditions. Additionally, it suggests possible therapeutic applications of a number of naturally occurring bioactive molecules in conditions involving oxidative stress.

Morin protects gastric mucosa from nonsteroidal anti-inflammatory drug, indomethacin induced inflammatory damage and apoptosis by modulating NF-κB pathway.

BACKGROUND Deregulation in prostaglandin (PG) biosynthesis, severe oxidative stress, inflammation and apoptosis contribute to the pathogenesis of nonsteroidal anti-inflammatory drug (NSAID)-induced gastropathy. Unfortunately, most of the prescribed anti-ulcer drugs generate various side effects. In this scenario, we could consider morin as a safe herbal potential agent against IND-gastropathy and rationalize its action systematically. METHODS Rats were pretreated with morin for 30 min followed by IND (48 mgkg(-1)) administration for 4 h. The anti-ulcerogenic nature of morin was assessed by morphological and histological analysis. Its effects on the inflammatory (MPO, cytokines, adhesion molecules), ulcer-healing (COXs, PGE(2)), and signaling parameters (NF-κB and apoptotic signaling) were assessed by biochemical, RP-HPLC, immunoblots, IHC, RT-PCR, and ELISA at the time points of their maximal changes due to IND administration. RESULTS IND induced NF-κB and apoptotic signaling in rats gastric mucosa. These increased proinflammatory responses, but reduced the antioxidant enzymes and other protective factors. Morin reversed all the adverse effects to prevent IND-induced gastric ulceration in a PGE2 independent manner. Also, it did not affect the absorption and/or primary pharmacological activity of IND. CONCLUSIONS The gastroprotective action of morin is primarily attributed to its potent antioxidant nature that also helps in controlling several IND-induced inflammatory responses. GENERAL SIGNIFICANCE For the first time, the study reveals a mechanistic basis of morin mediated protective action against IND-induced gastropathy. As morin is a naturally abundant safe antioxidant, future detailed pharmacokinetic and pharmacodynamic studies are expected to establish it as a gastroprotective agent.

Mangiferin, a natural xanthone, protects murine liver in Pb(II) induced hepatic damage and cell death via MAP kinase, NF-κB and mitochondria dependent pathways.

One of the most well-known naturally occurring environmental heavy metals, lead (Pb) has been reported to cause liver injury and cellular apoptosis by disturbing the prooxidant-antioxidant balance via oxidative stress. Several studies, on the other hand, reported that mangiferin, a naturally occurring xanthone, has been used for a broad range of therapeutic purposes. In the present study, we, therefore, investigated the molecular mechanisms of the protective action of mangiferin against lead-induced hepatic pathophysiology. Lead [Pb(II)] in the form of Pb(NO3)2 (at a dose of 5 mg/kg body weight, 6 days, orally) induced oxidative stress, hepatic dysfunction and cell death in murine liver. Post treatment of mangiferin at a dose of 100 mg/kg body weight (6 days, orally), on the other hand, diminished the formation of reactive oxygen species (ROS) and reduced the levels of serum marker enzymes [alanine aminotranferase (ALT) and alkaline phosphatase (ALP)]. Mangiferin also reduced Pb(II) induced alterations in antioxidant machineries, restored the mitochondrial membrane potential as well as mutual regulation of Bcl-2/Bax. Furthermore, mangiferin inhibited Pb(II)-induced activation of mitogen-activated protein kinases (MAPKs) (phospho-ERK 1/2, phosphor-JNK phospho- p38), nuclear translocation of NF-κB and apoptotic cell death as was evidenced by DNA fragmentation, FACS analysis and histological assessment. In vitro studies using hepatocytes as the working model also showed the protective effect of mangiferin in Pb(II) induced cytotoxicity. All these beneficial effects of mangiferin contributes to the considerable reduction of apoptotic hepatic cell death induced by Pb(II). Overall results demonstrate that mangiferin exhibit both antioxidative and antiapoptotic properties and protects the organ in Pb(II) induced hepatic dysfunction.

Cadmium (Cd2+) exposure differentially elicits both cell proliferation and cell death related responses in SK-RC-45

Cadmium (Cd(2+)) is a major nephrotoxic environmental pollutant, affecting mostly proximal convoluted tubule (PCT) cells of the mammalian kidney, while conditionally Cd(2+) could also elicit protective responses with great variety and variability in different systems. The present study was designed to evaluate the molecular mechanism of Cd(2+) toxicity on human PCT derived Renal Cell Carcinoma (RCC), SK-RC-45 and compare its responses with normal human PCT derived cell line, NKE. Exposure of SK-RC-45 cells with different concentrations of CdCl2 (e.g. 0, 10 and 20μM) in serum free medium for 24h generate considerable amount of ROS, accompanied with decreased cell viability and alternations in the cellular and nuclear morphologies, heat shock responses and GCLC mediated protective responses. Also phosphatidylserine externalization, augmentation in the level of caspase-3, PARP, BAD, Apaf1 and cleaved caspase-9 along with decreased expression of Bcl2 and release of cytochrome c confirmed that, Cd(2+) dose dependently induces solely intrinsic pathway of apoptosis in SK-RC-45, independent of JNK. Furthermore, the non-toxic concentration (10μM) of Cd(2+) induced nuclear translocation of Nrf2 and increased expression in the level of HO-1 enzyme suggesting that at the milder concentration, Cd(2+) induces protective signaling pathways. On the other hand, exposure of NKE to different concentrations of CdCl2 (e.g. 0, 10, 20, 30 and 50μM) under the same conditions elevate stronger heat shock and SOD2 mediated protective responses. In contrary to the RCC PCT, the normal PCT derived cell follows JNK dependent and extrinsic pathways of apoptosis. Cumulatively, these results suggest that Cd(2+) exposure dose dependently elicit both cell proliferative and cell death related responses in SK-RC-45 cells and is differentially regulated with respect to normal kidney epithelia derived NKE cells.

Mangiferin attenuates oxidative stress induced renal cell damage through activation of PI3K induced Akt and Nrf-2 mediated signaling pathways

Background Mangiferin is a polyphenolic xanthonoid with remarkable antioxidant activity. Oxidative stress plays the key role in tert-butyl hydroperoxide (tBHP) induced renal cell damage. In this scenario, we consider mangiferin, as a safe agent in tBHP induced renal cell death and rationalize its action systematically, in normal human kidney epithelial cells (NKE). Methods NKE cells were exposed to 20 µM mangiferin for 2 h followed by 50 µM tBHP for 18 h. The effect on endogenous ROS production, antioxidant status (antioxidant enzymes and thiols), mitochondrial membrane potential, apoptotic signaling molecules, PI3K mediated signaling cascades and cell cycle progression were examined using various biochemical assays, FACS and immunoblot analyses. Results tBHP exposure damaged the NKE cells and decreased its viability. It also elevated the intracellular ROS and other oxidative stress-related biomarkers within the cells. However, mangiferin dose dependently, exhibited significant protection against this oxidative cellular damage. Mangiferin inhibited tBHP induced activation of different pro-apoptotic signals and thus protected the renal cells against mitochondrial permeabilization. Further, mangiferin enhanced the expression of cell proliferative signaling cascade molecules, Cyclin d1, NFκB and antioxidant molecules HO-1, SOD2, by PI3K/Akt dependent pathway. However, the inhibitor of PI3K abolished mangiferins protective activity. Conclusions Results show Mangiferin maintains the intracellular anti-oxidant status, induces the expression of PI3K and its downstream molecules and shields NKE cells against the tBHP induced cytotoxicity. General significance Mangiferin can be indicated as a therapeutic agent in oxidative stress-mediated renal toxicity. This protective action of mangiferin primarily attributes to its potent antioxidant and antiapoptotic nature.

Morin and Its Role in Chronic Diseases

Chronic diseases can be referred to the long-term medical conditions which are mostly progressive in nature, i.e., it deteriorates over time. Diabetes, arthritis, heart disease, stroke, cancer, and chronic respiratory problems (e.g., COPD) are not a few examples of chronic diseases and chronic diseases are the leading causes of death and disability all over the world. Chronic diseases and conditions are among the most common, costly, and preventable of all health problems. Affordable cost, presence mostly in the consumables, and minimal side effects make the naturally occurring compounds interesting and attractive for pharmacological study in recent years. Plants produce diverse types of low molecular weight products mainly for the defense purpose. Among them, the group of secondary metabolites related to a polyphenolic group has been named flavonoids and are of great interest due to their incredible pharmacological properties. In these regard, due to its potent anti-inflammatory, anti-apoptotic and many important pharmacological properties (relevant to chronic diseases, e.g., urate transporter inhibitor related to gout, modulator of immunosystem related to chronic hypersensitivity, etc.), morin [morin hydrate:2-(2,4-dihydroxyphenyl)-3,5,7-trihydroxy-4H-1-benzopy ran-4-one; 3,5,7,20,40 pentahydroxyflavone], widely found among the Moraceae family, considered as one of the most important key bioflavonols. However, little is known about the molecular mechanisms of its action on such conditions. In this chapter, we have summarized most of the findings, if not all, available till date.

New pesticides: a cutting-edge view of contributions from nanotechnology for the development of sustainable agricultural pest control

Nanotechnology holds immense potential in the era of new age pesticides. In agriculture, possible use of nanotechnology includes delivery of nanocides, nanomaterials encapsulated pesticides, for controlled and targeted release, as well as the stabilization of pesticides with nanomaterials. This section will focus on how nanotechnology promises a breakthrough in refining our present understanding the expansion of new-generation nanocides and safe carriers, nanotechnology based biocides, and chemical pesticides. In addition, a vivid account on polymer nanoformulation, applications of nanoparticles like nanosilver, titanium dioxide, and so on in management of plant diseases will be presented. New ideas about nanotechnology based surveillance and control of pests, diseases, as well as insect pest management will also be discussed. Last, we would include nanobiosensors for pesticide detection and degradation. In this book chapter, all these information unties the up-to-date knowledge on the nanotechnology based new age pesticides.

Phytochemicals and Human Health

The World Health Organization (WHO) defined health as “a state of complete physical, mental, and social well-being and not merely the absence of disease or infirmity.” Any disturbance in this well-being leads to ill-health and a related condition called pathophysiology. Disease conditions, xenobiotics, and environmental and social stresses are the most common causes behind these pathophysiological conditions, and this can be generalized from recent studies that in most of the cases ROS plays the pivotal role as the main effector. However, fortunately in many cases, these health problems are preventable. Reasonable cost, presence in the daily consumables, and negligible side effects make the naturally occurring plant-derived compounds interesting and attractive for pharmacological study in recent years. Primarily for the defense purpose, plants yield assorted types of low-molecular-weight products. These are generally termed as phytochemicals. Among them, a group of secondary metabolites associated with a polyphenolic group have been named flavonoids and are of pronounced interest due to their implausible pharmacological properties. Flavonoids are widely accepted as potent antioxidant agents which can prevent injury caused by free radicals by scavenging of ROS, activation of antioxidant enzymes, and inhibiting oxidases. In addition, increase in antioxidant properties of low-molecular antioxidants, metal chelating activity, and reduction of α-tocopheryl radicals and mitigation of oxidative stress caused by NO also plays important role. In this chapter, we have summarized most of the findings, if not all, available till date related to five very noticeable phytochemicals, namely, morin, quercetin, rutin, mangiferin, and myricetin. Hope this chapter will help readers in understanding the utmost importance of the phytochemicals and will motivate them to further dig into the mechanistic study to fetch more novel information.