Stimuli-Responsive Nanocapsules for the Spatiotemporal Release of Melatonin: Protection against Gastric Inflammation.

Melatonin is a secretory product of the pineal gland that regulates circadian rhythm. It is also well-known for its anti-inflammatory and antioxidant properties against the damaging influences of reactive oxygen species. To improve its therapeutic efficacy, a new formulation with melatonin loaded in a stimuli-responsive polymeric nanocapsule has been prepared following an inverse mini-emulsion technique. The colloidal stability of the melatonin-loaded nanocapsules (MNCs) is studied using dynamic light scattering, while the morphology of these MNCs is characterized using various electron microscopies. These MNCs have an inner diameter of 80-120 nm with a cell wall thickness of 29 ± 11 nm. The emission band maximum for melatonin appears at 350 nm following excitation at 305 nm (quantum yield, Φ350 = 0.13). The self-quenching nature of the entrapped melatonin molecules inside the nanocapsules attributes to a lower Φ350 value for the MNCs. The controlled release of melatonin from MNCs in an in vitro condition is achieved by inducing a rupture of the polymeric backbone through maintaining a certain media pH (∼2.0-4.0) as an external stimulus, and this accounts for a significant enhancement in its characteristic luminescence. The H,K-ATPase, an integral membrane protein, maintains this specific pH range in the interior of the gastrointestinal tract. This methodology is adopted for developing an efficient drug delivery process in the gastric environment. A significant improvement in the AGS cell survival under oxidative stress conditions is observed during preincubation with MNCs compared to free melatonin. In a murine model of the stress-induced gastric ulcer, MNCs outperformed free melatonin in terms of drug efficacy. The value for the gastric ulcer index is reduced from ∼30 to ∼15 by free melatonin and from ∼30 to ∼8 by MNCs treatments, respectively. Such formulation could be a step forward for developing more efficient melatonin-based gastroprotective supplements.

Neuro-protective role of nanocapsulated curcumin against cerebral ischemia-reperfusion induced oxidative injury.

Cerebral ischemia-reperfusion (CIR) accelerates the progression of neurodegeneration by causing mitochondrial dysfunction to overproduce reactive oxygen species (ROS). Curcumin shows protective effects against CIR-induced oxidative damage. Free curcumin (FC) is effective at high doses due to its poor bioavailability. Also the blood-brain barrier (BBB) limits the passage of substances from circulation into the cerebral region. Thus, formulation of curcumin within polyethylene glycol (PEG)-ylated polylactide-co-glycolide (PLGA) nanoparticles (NC) was applied orally to aged rats to explore its role against CIR injury. Mitochondrial damage was evaluated. The levels of pro-inflammatory cytokines and components of apoptotic pathway were studied. Unlike FC, NC pre-treatment exerted better neuro-protection by ameliorating ROS-mediated oxidative damage and prevented CIR-induced neuronal apoptosis. Therefore, curcumin incorporated PEGylated PLGA nanoparticles may be used as a suitable delivery vehicle to the brain as they can increase curcumin bioavalability and the released curcumin may confer protection to the neurons against CIR-induced oxidative damage.

Tamarixetin 3-O-ß-d-Glucopyranoside from Azadirachta indica Leaves: Gastroprotective Role through Inhibition of Matrix Metalloproteinase-9 Activity in Mice.

Neem (Azadirachta indica) is a well-known medicinal and insecticidal plant. Although previous studies have reported the antiulcer activity of neem leaf extract, the lead compound is still unidentified. The present study reports tamarixetin 3-O-ß-d-glucopyranoside (1) from a methanol extract of neem leaves and its gastroprotective activity in an animal model. Compound 1 showed significant protection against indomethacin-induced gastric ulceration in mice in a dose-dependent manner. Moreover, ex vivo and circular dichroism studies confirmed that 1 inhibited the enzyme matrix metalloproteinase-9 (MMP-9) activity with an IC50 value of ca. 50 µM. Molecular docking and dynamics showed the binding of 1 into the pocket of the active site of MMP-9, forming a coordination complex with the catalytic zinc, thus leading to inhibition of MMP-9 activity.

Bioprotective potential of bacteriocinogenic Enterococcus gallinarum strains isolated from some Nigerian fermented foods, and of their bacteriocins.

Enterococcus gallinarum strains isolated from some Nigerian fermented foods were found to produce bacteriocins. The bacteriocins had a broad spectrum of activity against both Gram-positive and negative bacteria. The effects of the bacteriocins and bacteriocinogenic organ- isms on Staphylococcus aureus infections in rats were evaluated. Sprague-Dawley rats were infected with S. aureus MTCC 737 and treated with E. gallinarum T71 and different concentrations of the bacteriocins from E. gallinarum W211 and T71. Staphylococcus aureus infection caused significant upregulation of aspartate aminotransferase and alanine aminotransferase levels in sera of the infected rats. Moreover, gelatin zymography revealed that infected gastric tissues showed elevated matrix metalloproteinase-9 activity. Bacteriocin treatments reduced the MMP-9 activity and inhibited the expressions of both Tumour Necrosis Factor Alpha (TNF-α) and Interleukin-1 Beta (IL-1ß) dose dependently, pointing to a potential role of the bacteriocins in attenuating inflammatory responses to Staphylococcus aureus infec- tion. Gastric and GIT damage caused by staphylococcal infection were reduced in the Enterococcus gallinarum T71 and bacteriocin-treated groups also dose dependently. We conclude that these bacteriocins may have useful biomedical applications.

An alternative therapy for idiopathic pulmonary fibrosis by doxycycline through matrix metalloproteinase inhibition.

BACKGROUND: Idiopatiic pulmonary fibrosis (IPF) is a disease of dysregulated fibrogenesis with abnormal matrix metalloproteinase (MMPs) activity, angiogenesis, and profibrotic milieu wherein MMPs inhibition appears to be target-based therapy. We evaluated the role of doxycycline as a nonspecific inhibitor of MMPs in IPF patients. MATERIALS AND METHODS: Patients of IPF diagnosed on the basis of ATS-ERS consensus criteria were put on oral doxycycline in an open prospective trial. They were followed up for long term with spirometry, 6 min walk test (6MWT), St. Georges respiratory questionnaire (SGRQ), forced vital capacity (FVC), and repeat bronchoscopy while on doxycycline monotherapy for over 24 weeks. Both the initial and follow-up broncho alveolar lavage fluids (BALF) from IPF patients (n = 6) and control subjects (n = 6) were looked for MMP-9, -3, tissue inhibitor of metalloproteinase (TIMP)-1 and vascular endothelial growth factor (VEGF) expression. Additionally, doxycycline's action on MMP activities in vitro was tested in BALF of IPF patients. RESULTS: Doxycycline intervention showed significant improvement in IPF patients in terms of change in 6MWT, SGRQ, FVC, and quality of life. The level of MMP-9, -3, TIMP-1 and VEGF in the BALF were found significantly higher in the IPF patients compared to the controls while doxycycline therapy reduced those parameters nearer to control value. Doxycycline also showed a significant dose-dependent reduction in the in vitro MMPs activities in BALF. CONCLUSION: Doxycycline shows significant prospect in the treatment of IPF through its anti MMPs activities. This is the first report on a case series of long-term doxycycline monotherapy in IPF patients.

Curcumin arrests endometriosis by downregulation of matrix metalloproteinase-9 activity.

Curcumin, a polyphenol derived from turmeric (Curcuma longa) possesses diverse pharmacological properties including antioxidant, anti-inflammatory and antiproliferative activities. Endometriosis is a gyneocological disorder characterized by growth of endometrial tissues outside uterus that involves aberrant matrix remodeling. In this study the effect of curcumin was studied on surgically developed endometriosis in mice. Endometriosis with varying severity was developed in mice by peritoneal implantation of uterine fragments. The changes in matrix metalloproteinase (MMP)-9 and tissue inhibitor of metalloprotease (TIMP)-1 were investigated in endometriotic tissues following curcumin pre- and posttreatment. Results showed that MMP-9 activity increased gradually in endometriotic tissues with severity and curcumin treatment reversed the MMP-9 activity near to control value. Curcumin administered either post- or pre-endometriosis arrested endometriosis in a dose-dependent manner. It inhibited both MMP-9 activity and its expression at the level of secretion, during regression of endometriotic lesion. In addition, the attenuated activity of MMP-9 was associated with decreased expression of tumor necrosis factor-alpha (TNF-alpha) during healing, suggesting the anti-inflammatory property of curcumin. Moreover, curcumin pretreatment prevented lipid peroxidation and protein oxidation in endometriotic tissues. We reported here for the first time the anti-endometriotic property of curcumin via MMP-9 dependent pathway that may lead to new therapeutic intervention.

Hydrogen peroxide-mediated downregulation of matrix metalloprotease-2 in indomethacin-induced acute gastric ulceration is blocked by melatonin and other antioxidants.

Gastric mucosal damage is directly associated with extracellular matrix degradation in which matrix metalloproteinases (MMPs) play a crucial role. Remodeling of connective tissues and loss of tissue integrity due to the action of MMPs are reported in several inflammatory diseases, including gastric ulcer. Indomethacin-induced gastric ulceration involves the generation of reactive oxygen species (ROS) and a reduction in MMP-2 transcription and translation. Our aim was to identify the mechanism for suppression of MMP-2 activity by ROS during acute ulceration and further to examine the possible actions of antioxidants, especially melatonin, during healing. Melatonin (N-acetyl-5-methoxytryptamine) blocked hydroxyl radical and nitrite anion generation, protein oxidation, mucosal cell disruption, and MMP-2 downregulation. In addition, suppression of MMP-2 activity by H2O2 in a dose- and time-dependent manner in vitro is blocked by melatonin, omeprazole, and curcumin. We observed that melatonin and other antioxidants (e.g., curcumin and omeprazole) offered gastroprotection in vivo by upregulation of suppressed MMP-2 expression and activity at the level of secretion and synthesis. Moreover, antioxidants reversed the suppression of MMP-2 expression by upregulation of MT1-MMP and downregulation of TIMP-2. Hence, we hypothesize that antioxidants exerted protection against H2O2-mediated inactivation and downregulation of MMP-2 expression during onset of indomethacin-induced ulceration.