Graphene quantum dots alleviate ROS-mediated gastric damage.

The gastrointestinal (GI) tract is one of the major sites for reactive oxygen species generation (ROS). Physiological ROS, lower than the threshold concentration, is beneficial for human physiology to preserve gut functional integrity. However, ROS generated in large quantities in presence of external stimuli overwhelms the cellular antioxidant defense mechanism and results in oxidative damage and associated physiological disorder. Graphene quantum dots (GQDs) are a class of carbon-based nanomaterials that have attracted tremendous attention not only for their tunable optical properties but also for their broad-spectrum antioxidant properties. In this report we have shown that GQDs are highly efficient in scavenging ROS and suppressing stress-induced gastric ulcers by targeting the MMP-9 pathway and reducing the inflammatory burden by suppressing excessive oxidative stress by inducing high caspase activity, overproduction of Bax, and downregulation of BCL2.

Melatonin rescues swim stress induced gastric ulceration by inhibiting matrix metalloproteinase-3 via down-regulation of inflammatory signaling cascade.

AIM: This study investigated the link between forced swim induced acute gastric ulceration, inflammation and MMP-3 along with the possible mechanism of protective efficacy of melatonin. MAIN METHODS: We distributed Balb/c mice into four different groups. Group 1 and 2 were given PBS gavage. Group 3 and 4 were given melatonin (60 mg/kg b.wt.) and omeprazole (25 mg/kg b.wt.), respectively, an hour prior to forced swim. Ulcer index, tissue histology, immunohistochemistry, protein carbonylation, lipid peroxidation, Myeloperoxidase, Zymography, Western blotting, reactive oxygen species (ROS), mitochondrial dehydrogenase, mitochondrial transmembrane potential and bioinformatical analysis were performed. KEY FINDINGS: Our data revealed that gastric ulceration due to forced swim stress is responsible for overproduction of ROS, which may be a prime reason for mitochondrial dysfunction and induction of apoptosis via activation of Caspase-3. ROS is also responsible for p38 phosphorylation which in turn increases the activity of MMP-3 in ulcerated milieu, along with the oxidation of proteins, peroxidation of lipids and altered expression patterns of heat shock protein (HSP)-70. Melatonin is shown to reduce the inflammatory burden in gastric milieu and offers gastroprotection by binding to the active site of MMP-3; thereby inhibiting its activity, as suggested by in silico studies. Melatonin also inhibits the downregulation of HSP-70 and activates p38 dephosphorylation and thereby, it rescues gastric mucosal cells from stress-induced ulceration. SIGNIFICANCE: Our findings suggest that, melatonin imparts its gastroprotective effect by down-regulating the activation of MAPK-ERK pathway along with binding to the active site of MMP-3.

Zymography and Reverse Zymography for Testing Proteases and Their Inhibitors.

Zymography is a powerful technique for the assay of different hydrolases that act upon any biological macromolecule. In particular, zymography is used to assay the activities of serine proteases, e.g., matrix metalloproteinases (MMPs), and reverse zymography is used for tissue inhibitors of metalloproteinases (TIMPs) in multifarious experimental samples. Zymography is a method of electrophoretic separation of proteases under non-reducing conditions in a polyacrylamide gel containing substrate. The resolved proteins are renatured by exchange of the anionic detergent with a nonionic one, and the gel is incubated in a specific buffer for the specific proteases. After staining the gel by Coomassie blue staining solution, the proteolytic activities are visualized as clear colorless bands against a dark background. In contrast, reverse zymography is a parallel technique to detect protease inhibitors. In addition to substrate gelatin, proteases (i.e., MMPs) are also incorporated in proper ratio into the polyacrylamide gel. After electrophoresis, during the developing step, the MMPs specifically digest the substrate in regions where TIMPs are absent. Thus, inhibitors/TIMP is represented as dark zones of inhibition against a transparent background after staining. In this chapter, common troubleshoots during sample preparation, running zymography, and data interpretation are discussed. Notes are specified to enhance the sensitivity of the methods. In conclusion, zymography could be crucial for enzyme assay at the nanogram level and for the improvement of new investigative techniques for diseases such as endometriosis, rheumatoid arthritis, osteoarthritis, tumor invasion, and inflammation.

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.

Triumph and tumult of matrix metalloproteinases and their crosstalk with eicosanoids in cancer.

Cancer development and metastasis are associated to perturbation in metabolic functions of tumor cells and surrounding inflammatory and stromal cell responses. Eicosanoids and lipid mediators, in this regard, attract potential attention during cancer development. Eicosanoids, which include prostaglandin, prostacyclin, thromboxane, and leukotriene, are synthesized from arachidonic acid when cells are stimulated by stress, cytokines, or other growth factors. However, the underlying mechanism of eicosanoids in cancer development, specially their interactions with proto-oncogene factors in tumor microenvironment, remain unexplored. On the other hand, matrix metalloproteinases (MMPs) are a group of zinc-dependent endopeptidases which are involved in degradation of different extracellular matrix (ECM) proteins. MMPs are associated with different physiological responses, including embryogenesis, vasculogenesis, and cellular remodeling, as well as different disease pathogenesis. Induced MMP responses are especially associated with cancer metastasis and secondary tumor development through proteolytic cleavage of several ECM and non-ECM proteins. Although both eicosanoids and MMPs are involved with cancer progression and metastasis, the interrelation between these two molecules are less explored. The present review discusses relevant studies that connect eicosanoids and MMPs and highlight the crosstalk between them offering novel therapeutic approach in cancer treatment.