Management of Colorectal Cancer Using Nanocarriers-based Drug Delivery for Herbal Bioactives: Current and Emerging Approaches.

Colorectal cancer (CRC) is a complex and multifactorial disorder in middle-aged people. Several modern medicines are available for treating and preventing it. However, their therapeutic uses are limited due to drawbacks, such as gastric perforation, diarrhea, intestinal bleeding, abdominal cramps, hair loss, nausea, vomiting, weight loss, and adverse reactions. Hence, there is a continuous quest for safe and effective medicines to manage human health problems, like CRC. In this context, herbal medicines are considered an alternative disease control system. It has become popular in countries, like American, European, and Asian, due to its safety and effectiveness, which has been practiced for 1000 years. During the last few decades, herbal medicines have been widely explored through multidisciplinary fields for getting active compounds against human diseases. Several herbal bioactives, like curcumin, glycyrrhizin, paclitaxel, chlorogenic acid, gallic acid, catechin, berberine, ursolic acid, betulinic acid, chrysin, resveratrol, quercetin, etc., have been found to be effective against CRC. However, their pharmacological applications are limited due to low bioavailability and therapeutic efficacy apart from their several health benefits. An effective delivery system is required to increase their bioavailability and efficacy. Therefore, targeted novel drug delivery approaches are promising for improving these substances' solubility, bioavailability, and therapeutic effects. Novel carrier systems, such as liposomes, nanoparticles, micelles, microspheres, dendrimers, microbeads, and hydrogels, are promising for delivering poorly soluble drugs to the target site, i.e., the colon. Thus, the present review is focused on the pathophysiology, molecular pathways, and diagnostic and treatment approaches for CRC. Moreover, an emphasis has been laid especially on herbal bioactive-based novel delivery systems and their clinical updates.

A Review on Novel Therapeutic Modalities and Evidence-based Drug Treatments against Allergic Rhinitis.

Allergic rhinitis (AR) is an IgE-mediated atopic disease that occurs due to inhaled antigens in the immediate phase. Misdiagnosis, insufficient treatment, or no treatment at all are frequent problems associated with the widespread condition known as chronic allergic rhinitis. AR symptoms include runny, itchy, stuffy, and sneezing noses. Asthma and nasal polyps, for example, sometimes occur simultaneously in patients. In order for people living with AR to be as comfortable and productive as possible, treatment should center on reducing their symptoms. The online sources and literature, such as Pubmed, ScienceDirect, and Medline, were reviewed to gather information regarding therapeutic modalities of AR and evidence-based treatments for the disease as the objectives of the present study. An increasing number of people are suffering from AR, resulting in a heavy financial and medical burden on healthcare systems around the world. Undertreating AR frequently results in a decline in quality of life. Treatment compliance is a critical challenge in the administration of AR. Innovative therapies are needed for RA to provide patients with symptom alleviation that is less expensive, more effective, and longer duration of action. Evidence-based guidelines are helpful for managing AR illness. Treating AR according to evidence-based standards can help in disease management. AR treatment includes allergen avoidance, drug therapy, immunotherapy, patient education, and follow-up. However, AR treatment with intranasal corticosteroids is more popular. Hence, in this review article, treatment options for AR are discussed in depth. We also discussed the incidence, causes, and new treatments for this clinical condition.

A Snapshot of Selenium-enclosed Nanoparticles for the Management of Cancer.

Among the primary causes of mortality in today's world is cancer. Many drugs are employed to give lengthy and severe chemotherapy and radiation therapy, like nitrosoureas (Cisplatin, Oxaliplatin), Antimetabolites (5-fluorouracil, Methotrexate), Topoisomerase inhibitors (Etoposide), Mitotic inhibitors (Doxorubicin); such treatment is associated with significant adverse effects. Antitumor antibiotics have side effects similar to chemotherapy and radiotherapy. Selenium (Se) is an essential trace element for humans and animals, and additional Se supplementation is required, particularly for individuals deficient in Se. Due to its unique features and high bioactivities, selenium nanoparticles (SeNPs), which act as a supplement to counter Se deficiency, have recently gained worldwide attention. This study presented a safer and more economical way of preparing stable SeNPs. The researcher has assessed the antiproliferative efficiency of SeNPs-based paclitaxel delivery systems against tumor cells in vitro with relevant mechanistic visualization. SeNPs stabilized by Pluronic F-127 were synthesized and studied. The significant properties and biological activities of PTX-loaded SeNPs on cancer cells from the lungs, breasts, cervical, and colons. In one study, SeNPs were formulated using chitosan (CTS) polymer and then incorporated into CTS/citrate gel, resulting in a SeNPs-loaded chitosan/citrate complex; in another study, CTS was used in the synthesis of SeNPs and then situated into CTS/citrate gel, resulting in Se loaded nanoparticles. These formulations were found to be more successful in cancer treatment.

Emerging Trends of Nanomedicines in the Management of Prostate Cancer: Perspectives and Potential Applications.

Prostate cancer is one of the most life-threatening disorders that occur in males. It has now become the third most common disease all over the world, and emerging cases and spiking mortality rates are becoming more challenging day by day. Several approaches have been used to treat prostate cancer, including surgery, radiation therapy, chemotherapy, etc. These are painful and invasive ways of treatment. Primarily, chemotherapy has been associated with numerous drawbacks restricting its further application. The majority of prostate cancers have the potential to become castration-resistant. Prostate cancer cells exhibit resistance to chemotherapy, resistance to radiation, ADT (androgen-deprivation therapy) resistance, and immune stiffness as a result of activating tumor-promoting signaling pathways and developing resistance to various treatment modalities. Nanomedicines such as liposomes, nanoparticles, branched dendrimers, carbon nanotubes, and quantum dots are promising disease management techniques in this context. Nanomedicines can target the drugs to the target site and enhance the drug's action for a prolonged period. They may also increase the solubility and bioavailability of poorly soluble drugs. This review summarizes the current data on nanomedicines for the prevention and treatment of prostate cancer. Thus, nanomedicine is pioneering in disease management.

Recent Updates on the Therapeutics Benefits, Clinical Trials, and Novel Delivery Systems of Chlorogenic Acid for the Management of Diseases with a Special Emphasis on Ulcerative Colitis.

Ulcerative colitis (UC) is a multifactorial disorder of the large intestine, especially the colon, and has become a challenge globally. Allopathic medicines are primarily available for the treatment and prevention of UC. However, their uses are limited due to several side effects. Hence, an alternative therapy is of utmost importance in this regard. Herbal medicines are considered safe and effective for managing human health problems. Chlorogenic acid (CGA), the herbal-derived bioactive, has been reported for pharmacological effects like antiinflammatory, immunomodulatory, antimicrobial, hepatoprotective, antioxidant, anticancer, etc. This review aims to understand the antiinflammatory and chemopreventive potential of CGA against UC. Apart from its excellent therapeutic potential, it has been associated with low absorption and poor oral bioavailability. In this context, colon-specific novel drug delivery systems (NDDS)are pioneering to overcome these problems. The pertinent literature was compiled from a thorough search on various databases such as ScienceDirect, PubMed, Google Scholar, etc., utilizing numerous keywords, including ulcerative colitis, herbal drugs, CGA, pharmacological activities, mechanism of actions, nanoformulations, clinical updates, and many others. Relevant publications accessed till now were chosen, whereas non-relevant papers, unpublished data, and non-original articles were excluded. The present review comprises recent studies on pharmacological activities and novel drug delivery systems of CGA for managing UC. In addition, the clinical trials of CGA against UC have been discussed.

Recent Insight into Herbal Bioactives-based Novel Approaches for Chronic Intestinal Inflammatory Disorders Therapy.

Inflammatory bowel disease (IBD) is a life-threatening complex disease. It causes chronic intestinal inflammation in GIT. IBD significantly affects people's lifestyles and carries a high risk of colon cancer. IBD involves the rectum, ileum, and colon, with clinical manifestations of bloody stools, weight loss, diarrhea, and abdominal pain. The prevalence of inflammatory disease is increasing dramatically worldwide. Over 16 million people are affected annually in India, with an economic burden of $6.8- $8.8 billion for treatment. Modern medicine can manage IBD as immunosuppressive agents, corticosteroids, tumor necrosis factor antagonists, integrin blockers, and amino-salicylates. However, these approaches are allied with limitations such as limited efficacy, drug resistance, undesired side effects, and overall cost, which cannot be ignored. Hence, the herbal bioactives derived from various plant resources can be employed in managing IBD. Science Direct, PubMed, Google, and Scopus databases have been searched for conclusively relevant herbal plant-based anti-inflammatory agent compositions. Studies were screened through analysis of previously published review articles. Eminent herbal bioactives, namely curcumin, resveratrol, ellagic acid, silybin, catechin, kaempferol, icariin, glycyrrhizin acid, berberine, quercetin, rutin, and thymol are reported to be effective against IBD. Herbal leads are promising treatment options for IBD; they have been shown to display antiinflammatory and antioxidant properties by targeting enzymes and regulating the expressions of various inflammatory mediators. Natural products have been reported to have anti-inflammatory properties in various clinical and preclinical studies, and some are available as herbal preparations. Herbal medicine would be promising in association with the implication of a novel drug delivery system for managing IBD.

Andrographis paniculata and Andrographolide - A Snapshot on Recent Advances in Nano Drug Delivery Systems against Cancer.

Cancer is one of the deadliest illnesses of the 21st century. Chemotherapy and radiation therapies both have considerable side effects. Antitumor antibiotics are one of them. Coughs, common colds, fevers, laryngitis, and infectious disorders have all been treated with Andrographis paniculata for centuries. Extracts of Andrographis effectively treat various ailments, as well as cancer. The most active molecule in Andrographis paniculata is andrographolide a, diterpene, and lactone. Andrographis paniculata and its derivatives have long been used to treat various ailments. Anti-inflammatory and cancerfighting characteristics have been observed in Andrographolide. Andrographolide, a diterpene lactone separated from Andrographis paniculata, has also been shown to have important criticalessential biological protective properties. It has also been suggested that it could be used to treat major human diseases like-rheumatoid like rheumatoid, colitis, and Parkinsons disease. This summary aims to highlight Andrographolide as a promising cancer treatment option. Several databases were searched for andrographolides cytotoxic/anti-cancer effects in pre-clinical and clinical research to serve this purpose. Several studies have shown that Andrographolide is helpful in cancer medication, as detailed in this review.

Current Insight into Novel Delivery Approaches of Resveratrol for Improving Therapeutic Efficacy and Bioavailability with its Clinical Updates.

Resveratrol (RSV) is a polyphenolic phytoalexin, and belongs to the stilbene family. RSV has several therapeutic activities such as cardioprotective, anticancer, and antioxidant. Apart from its therapeutic benefits, its pharmacological uses are limited due to low solubility, poor bioavailability, and short biological halflife. A researcher continuously focuses on overcoming the limitations of RSV through nanotechnology platforms to get the optimum health benefits. In this context, nanocarriers are pioneering to overcome these drawbacks. Nanocarriers possess high drug loading capacity, thermal stability, low production cost, longer shelflife, etc. Fortunately, scientists were proficient in delivering resveratrol-based nanocarriers in the present scenario. Nanocarriers can deliver drugs to the target sites without compromising the bioavailability. Thus, this review highlights how the latest nanocarrier systems overcome the shortcomings of RSV, which will be good for improving therapeutic efficacy and bioavailability. Moreover, recent updates on resveratrol-based novel formulations and their clinical trials have been addressed to manage several health-related problems.

Recent Insights into Nanoparticulate Carrier Systems of Curcumin and its Clinical Perspective in the Management of Various Health Issues.

Curcumin is a potent bioactive compound of Curcuma longa. Curcumin comprises a broad spectrum of biological activities, including hepatoprotective, anticancer, antimicrobial, anti-inflammatory, antitumor, anti-oxidant, etc. However, its low aqueous solubility, rapid excretion, and poor bioavailability restricted its therapeutic uses. To resolve these issues, novel nano-systems have now been developed to increase the bioactivity and bioavailability of curcumin by lowering the particle size, altering the surface, and increasing the efficacy of its encapsulation with various nanocarriers. Nanotechnology-based treatments can broaden the outlook for individuals with critical conditions. This article explores curcumin-based nanoparticulate carrier systems that should be employed to overcome this natural ingredient's inherent limitations. These nanocarriers also provide physical and chemical stability by encapsulating the drug into the core or matrix of the lipids or polymers. Nanotechnologists developed curcumin-encapsulated various nanoparticulate systems, including solid lipidic nanoparticles, polymeric nanoparticles, nano-structured lipid carriers, polymer conjugates, etc., to improve curcumin bioavailability and boost the sustained release of curcumin to target cells.

A review on emerging targeted therapies for the management of metastatic colorectal cancers.

Colorectal cancers are among the most commonly found cancers over the world. In spite of the recent advancements in diagnosis and prognosis, the management of this metastatic condition remains a challenge. The utility of monoclonal antibodies in the healing of patients with colorectal cancer has opened a new chapter in the quest for newer therapies. The resistance to the standard treatment regimen made it mandatory to search for newer targets. Mutagenic alterations in the gene engaged in cellular differentiation and growth pathway have been the reason for resistance to treatment. The newer therapies target the various proteins and receptors involved in the signal transduction and down streaming pathways leading to cell proliferation. This review presents an insight into the newer targeted therapies for colorectal cancer involving tyrosine kinase blockers, epidermal growth factor receptors, vascular endothelial growth factor, immune checkpoint therapy, and BRAF inhibitors.

Recent Insight into UV-induced Oxidative Stress and Role of Herbal Bioactives in the Management of Skin Aging.

Skin is a defensive barrier that protects the body against sun rays and other harmful environmental elements. Sun rays contain ultraviolet rays, UVA (320-400 nm) and UVB (280-320 nm), which are highly harmful to the skin, leading to photoaging. Nowadays, sunscreen products are being utilized to protect the skin against photodamage. Conventional sunscreens are useful but cannot provide skin protection against UV rays for a longer period of time. Therefore, they need to be applied frequently. Aromatic compounds (ACs)-based sunscreens may filter out the UV rays but give rise to several side effects, like premature aging, stress, atopic dermatitis, keratinocytes (KCs) damage, genetic interruption, and malignant melanoma due to deposition of their toxic metabolites on the skin. The concept of natural medicines has become popular worldwide because of their safety and efficacy. Natural medicines have been proven to possess a wide array of biological properties, including antioxidant, antityrosinase, antielastase, antiwrinkle, antiaging, anti-inflammatory, anticancer, etc., against sun rays-mediated skin damage. The present review article is focused on UV-induced oxidative stress, and pathological and molecular targets with updates on herbal bioactives for the management of skin aging.

A Snapshot of Current Updates and Future Prospects of 3D Printing in Medical and Pharmaceutical Science.

3D printing in other fields, such as aviation, is quite old, but in the pharmaceutical area, it is an emerging technique. 3D printing is used to formulate various drug delivery systems and dosage forms with complex geometry. It allows large and fast production of products according to the need of the patient. Today, it is the widely used manufacturing technique in the healthcare field for the engineering of tissues and tissue models, production of medicines and medical devices, organ and tissue bioprinting, implant manufacturing, and production of polypills, vaginal rings, orodispersible films, etc. It allows the production of various dosage forms with complex release profiles containing multiple active ingredients. It is used for manufacturing medicines according to the need of individual patients focusing on the concept of personalized medicines. The idea of customized medicines allows change of dosage and design of the product as per individual and with decreased side effects. This review details various techniques of 3D printing used, such as stereolithography, fused deposition modeling, inkjet printing, etc., and applications and dosage forms developed with the latest patents. The significant challenges in the emergence of the 3D printing technique are the involvement of complex combinations to achieve desired properties, and also, the bioprinter involved provides slow and less resolution. The materials prepared by this technique are both biocompatible and printable, due to which additive manufacturing is increasing in the field of medicine.

DNA Nanobots - Emerging Customized Nanomedicine in Oncology.

Cancer is one of the most lethal diseases of the twenty-first century. Many medicines, including antitumor antibiotics, deliver tedious and severe chemotherapy and radiation treatment, both of which have significant side effects. DNA nanorobots, as an alternative, might be used as a cancer treatment method that is both safer and more precise than current treatments. DNA nanobots are being praised as a major milestone in medical research. The major goal of these nanobots is to find and destroy malignant cells in the human body. A unique strand of DNA is folded into the systematic form to create these nanobots. DNA origami has magnified passive tumor-targeting and prolonged properties at the tumor location. The triangle-like DNA origami, in particular, shows excellent accumulation on passive targeting of the tumor. Self-built DNA origami nanostructures were utilized to deliver the anticancer drug doxorubicin into tumors, and the approach was found to be highly successful in vivo. In another demonstration, a robot was made with the help of DNA origami and aptamer for folding a 90nm long tube-like apparatus. It was carried out to transport the blood coagulation protease thrombin in the interior portion guarded against blood plasma protein and circulating platelets. The robot unfolded once the aptamer was identified and attached to its tumor-specific target molecule, delivering thrombin to the circulation, stimulating coagulation of the regional malignant cells, and proceeding to tumor necrosis and tumor growth inhibition. Various studies revealed the effectiveness of DNA nanobots in cancer therapy.

Sodium alginate-guar gum and carbopol based methotrexate loaded mucoadhesive microparticles for colon delivery: An in vitro evaluation

Methotrexate (MTX) is famous for its therapeutic potential against different cancers including colorectal cancer. Goal of the present investigation was to formulate MTX loaded mucoadhesive microparticles for colon targeting. The optimized formulation (MTX-MS2) was composed of mucoadhesive polymers (sodium alginate, guar gum and carbopol 940) in an appropriate ratio. MTXMS2 was developed by ionic-gelation method. The suitable particle size and zeta potential were found to be 21.10 ± 0.18 µm and 3.01 ± 0.16 mV for MTX-MS2 respectively. The % yield (98.60 ± 2.12), % entrapment efficiency (97.98 ± 1.22) and % drug loading (1.04 ± 0.03) were estimated for MTXMS2. The swelling index (0.99 ± 0.04 θ) and mucoadhesion (97.29 ± 4.61%) were significantly (***P ˂ 0.01) achieved with MTX-MS2 as compared to other formulations. The optimum drug release (96.07 ± 4.52%) was significantly achieved with MTX-MS2 at simulated gastric fluid (pH 7.4) for 36 h in a sustained manner. This profile may be attributed towards excellent mucoadhesivness of the polymers used in the formulation. Therefore, the current investigation suggests that mucoadhesive carrier system could be promising approach for colon delivery. Thus, the proposed work would be helpful for the treatment of colorectal canc

Breast cancer: An insight into its inflammatory, molecular, pathological and targeted facets with update on investigational drugs.

Cancer is a heterogeneous disease, occurs due to transcriptional changes in genetic and epigenetic including numerous genes and proteins. Worldwide, breast cancer (BC) is the life-threatening malignancies in women, is characterized by the occurrence of more than one molecular alteration. The incidence and mortality of BC are growing every day because of the adoption of western living standards, metropolitanization, and more life expectancy. Even though many modern approaches are available for the detection and treatment of BC, despite of these, it remains the topmost cause of death in women. This review highlights various approaches, including the importance of clinical, pathological, and molecular aspects of BC. Moreover, risk factors, biomarkers, immunotherapy, investigational drugs, and their role through tumor targets and immune systems have been discussed for management of BC. Furthermore, various targeting approaches for tumors through nanocarriers and their clinical trials have been elaborated in BC challenges and future perspectives.

Bridging the Gap of Drug Delivery in Colon Cancer: The Role of Chitosan and Pectin Based Nanocarriers System.

Colon cancer is one of the most prevalent diseases, and traditional chemotherapy has not been proven beneficial in its treatment. It ranks second in terms of mortality due to all cancers for all ages. Lack of selectivity and poor biodistribution are the biggest challenges in developing potential therapeutic agents for the treatment of colon cancer. Nanoparticles hold enormous prospects as an effective drug delivery system. The delivery systems employing the use of polymers, such as chitosan and pectin as carrier molecules, ensure the maximum absorption of the drug, reduce unwanted side effects and also offer protection to the therapeutic agent from quick clearance or degradation, thus allowing an increased amount of the drug to reach the target tissue or cells. In this systematic review of published literature, the author aimed to assess the role of chitosan and pectin as polymer-carriers in colon targeted delivery of drugs in colon cancer therapy. This review summarizes the various studies employing the use of chitosan and pectin in colon targeted drug delivery systems.

Exciting Potential of Nanoparticlized Lipidic System for Effective Treatment of Breast Cancer and Clinical Updates: A Translational Prospective.

Breast cancer (BC) is a multifactorial disease and becoming a major health issue in women throughout the globe. BC is a malignant type of cancer which results from transcriptional changes in proteins and genes. Besides the availability of modern medicines and detection tools, BC has become a topmost deadly disease and its cure still remains challenging. Nanotechnology based approaches are being employed for the diagnosis and treatment of BC at clinical stages. Nanosystems have a significant role in the study of the interaction of malignant cells with their microenvironment through receptor-based targeted approach. Nowadays, lipid-based nanocarriers are being popularized in the domain of pharmaceutical and medical biology for cancer therapy. Lipidic nanoparticlized systems (LNPs) have proven to have high loading efficiency, less toxicity, improved therapeutic efficacy, enhanced bioavailability and stability of the bioactive compounds compared to traditional drug delivery systems. In the present context, several LNPs based formulations have been undertaken in various phases of clinical trials in different countries. This review highlights the importance of chemotherapeutics based lipidic nanocarriers and their anticipated use for the treatment of BC. Furthermore, the clinical trials and future prospective of LNPs have been widely elaborated.

Phagocytic uptake of oxidized heme polymer is highly cytotoxic to macrophages.

Apoptosis in macrophages is responsible for immune-depression and pathological effects during malaria. Phagocytosis of PRBC causes induction of apoptosis in macrophages through release of cytosolic factors from infected cells. Heme polymer or ß-hematin causes dose-dependent death of macrophages with LC50 of 132 µg/ml and 182 µg/ml respectively. The toxicity of hemin or heme polymer was amplified several folds in the presence of non-toxic concentration of methemoglobin. ß-hematin uptake in macrophage through phagocytosis is crucial for enhanced toxicological effects in the presence of methemoglobin. Higher accumulation of ß-hematin is observed in macrophages treated with ß-hematin along with methemoglobin. Light and scanning electron microscopic observations further confirm accumulation of ß-hematin with cellular toxicity. Toxicological potentiation of pro-oxidant molecules toward macrophages depends on generation of H2O2 and independent to release of free iron from pro-oxidant molecules. Methemoglobin oxidizes ß-hematin to form oxidized ß-hematin (ßH*) through single electron transfer mechanism. Pre-treatment of reaction mixture with spin-trap Phenyl-N-t-butyl-nitrone dose-dependently reverses the ß-hematin toxicity, indicates crucial role of ßH* generation with the toxicological potentiation. Acridine orange/ethidium bromide staining and DNA fragmentation analysis indicate that macrophage follows an oxidative stress dependent apoptotic pathway to cause death. In summary, current work highlights mutual co-operation between methemoglobin and different pro-oxidant molecules to enhance toxicity towards macrophages. Hence, methemoglobin peroxidase activity can be probed for subduing cellular toxicity of pro-oxidant molecules and it may in-turn make up for host immune response against the malaria parasite.

Highly selective probe detects Cu2+ and endogenous NO gas in living cell.

The rapid and highly sensitive detection of extremely short-lived nitric oxide (NO) gas generated in vivo by a water-soluble fluorescein derivative is developed. This assay system comprises of indole-3-carboxaldehyde functionalized fluorescein hydrazone (FI) assay which displays a typically high absorption at 492 and 620 nm in the presence of Cu2+ and also shows FRET induced fluorescence turn-on exclusively with Cu2+. FI selectively detects Cu2+ in vivo and in vitro by the "turn-on" mechanism followed by fluorescence "turn-off" with NO gas generated by the lipopolysaccharide (LPS) action. The in vivo experiment performed in the cellular system indicates that FI loaded RAW264.7 cells showed bright fluorescence in the presence of Cu2+, while other metals did not influence the FI fluorescence. In addition, the fluorescence of FI-Cu2+ was efficiently quenched by NO generated in macrophages through LPS stimulation. FI demonstrates characteristic "turn-on" behavior in the presence of Cu2+ via spirolactom ring-opening, while other metals such as Na+, K+, Ca2+, Cr3+, Mn2+, Fe3+, Fe2+, Co2+, Ni2+, Zn2+, Cd2+, Hg2+, and Ag+ did not influence FI fluorescence even at very high concentration. Further, the FI-Cu2+ complex fluorescence was not quenched with any anions or amino acids but totally quenched by NO and the paramagnetic nature of Cu2+ ion converted into the diamagnetic nature when reduced to Cu1+. FI and the FI-Cu2+ complex are nontoxic to the cellular system and have high potential for biomedical applications.

Pro-stimulatory role of methemoglobin in inflammation through hemin oxidation and polymerization.

Inflammation or vascular occlusion by parasitized red blood cell contributes to the pathogenesis of cerebral malaria. The current study aimed to characterize the role of major pro-oxidant factor methemoglobin present in the malaria culture supernatant contributing in inflammation during malaria. Heme and heme polymer stimulate macrophage to secrete large amount of reactive oxygen species into the external micro-environment. The addition of methemoglobin along with heme or heme polymer amplifies production of ROS from macrophages several folds. Methemoglobin mediated stimulatory effect is not due to release of iron, enhanced production of H2O2 or mutual interaction of reaction components. Spectroscopic studies show that methemoglobin accepts heme as a substrate and oxidizes it through a single electron transfer mechanism. Heme oxidation product is a heme polymer with similar chemical and structural properties to synthetic ß-hematin. Phenyl N-t-butylnitrone inhibits heme polymerization (IC50=30 nM) and indicates the absolute necessity of heme oxidation and heme free radical generation for heme polymerization. Methemoglobin produced heme polymer is a potent pro-inflammatory factor to release ROS into external microenvironment. Interestingly, methemoglobin not only produces pro-inflammatory heme polymer, but it also amplifies the potential of heme or preformed heme polymer (haemozoin or ß-hematin) to produce several folds high ROS production from macrophages. This study illustrates the pro-inflammatory effect of methemoglobin, the underlying novel mechanism by which this occurs and a possible clinical intervention. Based on the results, we recommend methemoglobin directed peroxidase inhibitors as an adjuvant therapy during malaria.