Geetha Mathew

Silymarin liposomes improves oral bioavailability of silybin besides targeting hepatocytes, and immune cells

BACKGROUND Silymarin, a hepatoprotective agent, has poor oral bioavailability. However, the current dosage form of the drug does not target the liver and inflammatory cells selectively. The aim of the present study was to develop lecithin-based carrier system of silymarin by incorporating phytosomal-liposomal approach to increase its oral bioavailability and to make it target-specific to the liver for enhanced hepatoprotection. METHODS The formulation was prepared by film hydration method. Release of drug was assessed at pH 1.2 and 7.4. Formulation was assessed for in vitro hepatoprotection on Chang liver cells, lipopolysaccharide-induced reactive oxygen species (ROS) production by RAW 267.4 (murine macrophages), in vivo efficacy against paracetamol-induced hepatotoxicity and pharmacokinetic study by oral route in Wistar rat. RESULTS The formulation showed maximum entrapment (55%) for a lecithin-cholesterol ratio of 6:1. Comparative release profile of formulation was better than silymarin at pH 1.2 and pH 7.4. In vitro studies showed a better hepatoprotection efficacy for formulation (one and half times) and better prevention of ROS production (ten times) compared to silymarin. In in vivo model, paracetamol showed significant hepatotoxicity in Wistar rats assessed through LFT, antioxidant markers and inflammatory markers. The formulation was found more efficacious than silymarin suspension in protecting the liver against paracetamol toxicity and the associated inflammatory conditions. The liposomal formulation yielded a three and half fold higher bioavailability of silymarin as compared with silymarin suspension. CONCLUSIONS Incorporating the phytosomal form of silymarin in liposomal carrier system increased the oral bioavailability and showed better hepatoprotection and better anti-inflammatory effects compared with silymarin suspension.

6b,11b-Dihydroxy-6b,11b-dihydro-7H-indeno[1,2-b]naphtho[2,1-d]furan-7-one (DHFO), a small molecule targeting NF-κB, demonstrates therapeutic potential in immunopathogenic chronic inflammatory conditions.

6b,11b-Dihydroxy-6b,11b-dihydro-7H-indeno[1,2-b]naphtho[2,1-d]furan-7-one (DHFO), an easily synthesisable, orally bioavailable and relatively non-toxic small molecule synthesised in our lab, was previously reported to possess anti-oxidant, 5-lipoxygenase inhibitory, anti-inflammatory and peripheral analgesic activities. The present work deals with exploration of DHFOs efficacy in immunopathogenic chronic inflammatory conditions - arthritis and allergy. In carrageenan-induced inflammatory air pouch, which resembles the arthritic synovium, DHFO effectively reduced inflammatory redness and swelling and neutrophil infiltration. In complete Freunds adjuvant-induced arthritis, DHFO significantly decreased paw oedema and nitrite levels with efficacy comparable to diclofenac. DHFO inhibited neutrophil activation (observed as decreased myeloperoxidase levels), in both the in vivo models of inflammation. Interestingly, DHFO did not ulcerate the gastrointestinal tract, while diclofenac was observed to be extremely ulcerogenic. In antigen-induced active and passive anaphylaxis (allergy) models, DHFO dose-dependently prevented mesenteric mast cell (MC) degranulation with efficacy comparable to ketotifen. DHFO also inhibited compound 48/80 (C48/80)-induced paw oedema and peritoneal MC degranulation. DHFO stabilised p815 murine MCs stimulated by C48/80 and calcium ionophore-A23187, indicating an action downstream of calcium mobilisation. DHFOs anti-allergic mechanism could be two-pronged involving (1) inhibition of IgE production and/or (2) MC stabilisation. DHFO inhibited lipopolysaccharide (LPS)-induced pro-inflammatory mediator release (ROS, NO, IL-6 levels) and COX2 expression in RAW264.7 murine macrophages. Protein expression studies confirmed DHFOs ability to reduce nuclear levels of NF-κB in LPS-stimulated macrophages. Thus, DHFO is a promising non-ulcerogenic synthetic small molecule lead for immunopathogenic chronic inflammatory conditions.

Antidiabetic, Antihyperlipidemic and Antioxidant Effects of the Flavonoids

Environmental and lifestyle changes contribute to the increasing global incidence of metabolic pathologies. None of the available marketed drugs comprehensively tackle the complexities associated with the axis linking inflammation/insulin resistance with obesity/hyperlipidemia. Flavonoids, found ubiquitously in most edible vegetables and fruits and constituting a major portion of micronutrients in diet, have emerged as potential alternatives for treating diabetes, hyperlipidemia and oxidative stress, involving multiple signaling pathways. Active components in a flavonoid-rich diet act synergistically on different biochemical pathways, bringing about a comprehensive therapeutic effect. Clinical evidences support the usefulness of flavonoid-rich foods over supplementation with individual flavonoids in high doses. The pleiotropic nature of flavonoids demonstrates a strong basis for their multi-targeted action on metabolic pathology. As more and more drugs focusing on single targets are being withdrawn, possibly because they destabilize the delicate equilibrium in the complex metabolic network, research on flavonoids is pacing ahead towards targeting multiple pathways holistically, legitimizing the need for re-establishing the metabolic homeostasis.

Remedial effects of novel 2,3-disubstituted thiazolidin-4-ones in chemical mediated inflammation.

Three thiazolidin-4-one derivatives were synthesized, purified and characterized by chromatographic and spectroscopic methods. In the in vitro assays, these compounds inhibited reactive oxygen species (ROS), nitrite and cytokine generation in RAW 264.7 murine macrophages and whole blood. These derivatives attenuated carrageenan-induced acute inflammation in rats. The most effective compound 4C possessed identical anti-inflammatory action at two doses (50 and 100 mg/kg). Further, the effect of compound 4C on locally induced inflammatory mediators was investigated in carrageenan-induced air pouch inflammation in rats. In this model, compound 4C inhibited the cytokines, tumor necrosis factor (TNF)-α and interleukin (IL)-6 (systemic and local). Additionally, compound 4C was able to reduce locally elevated prostaglandin-E₂ (PGE₂). Inhibition of leukocyte infiltration by compound 4C was correlated with reduced locally released myeloperoxidase (MPO). To conclude, compound 4C corrected the inflammatory condition by negative effect on cytokine (TNF-α, IL-6) network and prostaglandin-E₂ generation.

Novel 2,5-disubstituted-1,3,4-oxadiazoles as anti-inflammatory drugs

Objective: 1,3,4-oxadiazole ring is a versatile moiety with a wide range of pharmacological properties. The present work deals with the synthesis and evaluation of the anti-inflammatory activity of two novel 2,5-disubstituted-1,3,4-oxadiazoles (OSD and OPD). Materials and Methods: Carrageenan-induced rat hind paw edema was employed as an acute model of inflammation. For evaluating sub-acute anti-inflammatory activity, carrageenan-induced inflammation in rat air pouch was employed. Complete Freunds adjuvant-induced arthritis in rats was used as a model of chronic inflammation. To evaluate in vitro anti-inflammatory activity, lipopolysaccharide (LPS)-stimulated RAW264.7 cells were used. Results: OSD (100 mg/kg) reduced carrageen-induced paw edema by 60%, and OPD (100 mg/kg) produced a modest 32.5% reduction. OSD also reduced leukocyte influx and myeloperoxidase in carrageenan-induced rat air pouch model. In complete Freunds adjuvant-induced arthritis model, both OSD and OPD (200 mg/kg for 14 days) reduced paw edema and NO levels. In LPS-stimulated RAW264.7 cells, OSD and OPD inhibited formation of nitric oxide and reactive oxygen species, with OPD showing a better activity in comparison to OSD. Conclusions: OSD was the better of the two compounds in in vivo models of inflammation. The o-phenol substitution at position 2 of oxadiazole ring in OSD may be responsible for its better in vivo anti-inflammatory activity. The ability of the compounds to inhibit LPS-induced pro-inflammatory mediator release suggests an anti-inflammatory mechanism targeting LPS-TLR4-NF-κB signalling pathway, which needs to be explored in detail. The disparate efficacy in vitro and in vivo also requires in-depth evaluation of the pharmacokinetics of these novel oxadiazoles.

Antidiabetic activity of 3-hydroxyflavone analogues in high fructose fed insulin resistant rats.

Synthetic 3-hydroxyflavone analogues (JY-1, JY-2, JY-3, JY-4), were tested for antidiabetic activity in high-fructose-diet-fed (66 %, for 6 weeks) insulin-resistant Wistar rats (FD-fed rats). The fasting blood glucose, insulin, creatinine and AGEs were decreased to near normal upon treatment with test compounds. Insulin resistance markers such as HOMA-IR, K-ITT, plasma triglycerides, lipids, endogenous antioxidant defense and glycogen were restored in FD-fed rats after treatment with 3-hydroxyflavones. It is known that insulin resistance is partly because of oxidative stress and hence antioxidant activity was determined. They exhibited significant in vitro DPPH and ABTS radical scavenging activity (IC50: 10.66-66.63 µM). Test compounds inhibited ROS and NO production in RAW 264.7 cells (IC50: 10.39–42.63 µM) and they were found as potent as quercetin. Further, the test compounds inhibited lipid peroxidation at low concentrations (IC50: 99.61-217.47 µM). All test compounds at concentrations 100-200 µM protected calf thymus DNA-damage by Fenton reaction. In addition, test compounds inhibited protein glycation in different in vitro antiglycation assays. JY-2 showed maximum potency in all the stages of glycation which was comparable to the standard quercetin and aminoguanidine. Test compounds also enhanced the glucose uptake by L6 myotubes at an EC50 much lower than that of quercetin. Thus the synthetic 3-hydroxyflavones were found to have good antidiabetic activity by pleotropic and multimodal suppression of insulin resistance and enhancement of glucose uptake by skeletal muscles. These compounds are non-toxic at the doses tested. Further, the combined antioxidant and antiglycation activities of these molecules have complementary benefits in management of diabetes.

Multi-target drugs to address multiple checkpoints in complex inflammatory pathologies: evolutionary cues for novel “first-in-class” anti-inflammatory drug candidates: a reviewer’s perspective

Abstract Inflammation is a complex, metabolically expensive process involving multiple signaling pathways and regulatory mechanisms which have evolved over evolutionary timescale. Addressing multiple targets of inflammation holistically, in moderation, is probably a more evolutionarily viable strategy, as compared to current therapy which addresses drug targets in isolation. Polypharmacology, addressing multiple targets, is commonly used in complex ailments, suggesting the superior safety and efficacy profile of multi-target (MT) drugs. Phenotypic drug discovery, which generated successful MT and first-in-class drugs in the past, is now re-emerging. A multi-pronged approach, which modulates the evolutionarily conserved, robust and pervasive cellular mechanisms of tissue repair, with AMPK at the helm, regulating the complex metabolic/immune/redox pathways underlying inflammation, is perhaps a more viable strategy than addressing single targets in isolation. Molecules that modulate multiple molecular mechanisms of inflammation in moderation (modulating TH cells toward the anti-inflammatory phenotype, activating AMPK, stimulating Nrf2 and inhibiting NFκB) might serve as a model for a novel Darwinian “first-in-class” therapeutic category that holistically addresses immune, redox and metabolic processes associated with inflammatory repair. Such a multimodal biological activity is supported by the fact that several non-calorific pleiotropic natural products with anti-inflammatory action have been incorporated into diet (chiefly guided by the adaptive development of olfacto-gustatory preferences over evolutionary timescales) rendering such molecules, endowed with evolutionarily privileged molecular scaffolds, naturally oriented toward multiple targets.

Modulatory effects of sesamol in dinitrochlorobenzene-induced inflammatory bowel disorder in albino rats

BACKGROUND Inflammatory bowel disease (IBD) is a chronic inflammatory condition of gastrointestinal tract of immune, genetic and environmental origin. In the present study, we examined the effect of sesamol (SES), the main anti-oxidative constituent of Sesamum indicum (sesame seed) Linn. in the dinitrochlorobenzene (DNCB)-induced model for IBD in rats. METHODS The groups were divided into normal control, DNCB control, SES and sulfasalazine (SS). On day 24, the rats were killed, colon removed and the macroscopic, biochemical and histopathological evaluations were performed. RESULTS The levels of MPO, TBARS and nitrite increased significantly (p < 0.05) in the DNCB group, whereas reduced significantly in the SES, SS treated groups. Serum nitrite levels were found to be insignificant between the different groups. IL-6 and TNF-α levels were significantly high in the DNCB group. CONCLUSIONS We conclude the mucosal protective effect of SES on colon due to its potent antioxidant actions. Further investigation is required in a chronic model of different rodent strain for its role involved in the cytokine pathway.

In vivo Evaluation of Two Thiazolidin-4-one Derivatives in High Sucrose Diet Fed Pre-diabetic Mice and Their Modulatory Effect on AMPK, Akt and p38 MAP Kinase in L6 Cells.

We had previously demonstrated the anti-diabetic potential and pancreatic protection of two thiazolidin-4-one derivatives containing nicotinamide moiety (NAT-1 and NAT-2) in STZ-induced diabetic mice. However, due to the limitations of the STZ model, we decided to undertake a detailed evaluation of anti-diabetic potential of the molecules on a high sucrose diet (HSD) fed diabetic mouse model. Further, in vitro mechanistic studies on the phosphorylation of AMPK, Akt and p38 MAP kinase in L6 myotubes and anti-inflammatory studies in RAW264.7 mouse monocyte macrophage cells were performed. 15 months of HSD induced fasting hyperglycaemia and impaired glucose tolerance in mice. Treatment with NAT-1 and NAT-2 (100 mg/kg) for 45 days significantly improved the glucose tolerance and lowered fasting blood glucose levels compared to untreated control. An improvement in the elevated triglycerides and total cholesterol levels, and favorable rise in HDL cholesterol were also observed with test drug treatment. Also, no major changes were observed in the liver (albumin, AST and ALT) and kidney (creatinine and urea) parameters. This was further confirmed in their respective histology profiles which revealed no gross morphological changes. In L6 cells, significant phosphorylation of Akt and p38 MAP kinase proteins were observed with 100 μM of NAT-1 and NAT-2 with no significant changes in phosphorylation of AMPK. The molecules failed to exhibit anti-inflammatory activity as observed by their effect on the generation of ROS and nitrite, and nuclear levels of NF-κB in LPS-stimulated RAW264.7 cells. In summary, the molecules activated Akt and p38 MAP kinase which could have partly contributed to their anti-hyperglycaemic and hypolipidemic activities in vivo.

Dose-related antihyperglycemic and hypolipidemic effects of two novel thiazolidin-4-ones in a rodent model of metabolic syndrome.

The replacement of the thiazolidinedione moiety with a thiazolidinone may yield antidiabetic compounds with similar pleiotropic effects. Hence, the aim of the present study was to explore the dose‐related antihyperglycemic and hypolipidemic effects of two synthesized novel thiazolidin‐4‐one derivatives, one with a nicotinamide and the other with a p‐chlorophenoxyacetamide substitution at the N3 position of the thiazolidinone ring (NAT1 and PAT1, respectively), in a rodent model of metabolic syndrome (MetS).