The increased gastroprotective effect of pioglitazone in cholestatic rats: role of nitric oxide and tumour necrosis factor alpha

Gastroprotective effects of extract of Jasminum grandiflorum L. flower in HCl/EtOH-induced gastric mucosal ulceration mice

Jasminum grandiflorum L. is a medicinal plant used to treat hepatitis and gastritis, but the mechanisms underlying its protective effects against gastrointestinal mucosal damage remain to be elucidated. In this study, we analyzed the effects of four different extracts and two compounds from the flower of J. grandiflorum in a mouse model of HCl/EtOH-induced gastric ulcer. The flower extracts alleviated gastric mucosal ulceration by increasing PGE2 production and the activity of antioxidant enzymes, along with the suppression of reactive oxygen species (ROS) generation, lipid peroxidation, apoptosis-related proteins, pro-inflammatory cytokines and nitric oxide (NO) production.

Taurine mitigates bile duct obstruction-associated cholemic nephropathy: effect on oxidative stress and mitochondrial parameters

AIM OF THE STUDY

Cholestasis is a serious complication affecting other organs such as the liver and kidney. Oxidative stress and mitochondrial impairment are proposed as the primary mechanisms for cholestasis-induced organ injury. Taurine (TAU) is the most abundant free amino acid in the human body, which is not incorporated in the structure of proteins. Several pharmacological effects have been attributed to TAU. It has been reported that TAU effectively mitigated oxidative stress and modulated mitochondrial function. The current study aimed to evaluate the impact of TAU on oxidative stress biomarkers and mitochondrial parameters in the kidney of cholestatic animals.

MATERIAL AND METHODS

Bile duct ligated (BDL) rats were used as an antioxidant model of cholestasis. Animals were treated with TAU (500 and 1000 mg/kg, oral) for seven consecutive days. Animals were anesthetized (thiopental 80 mg/kg, i.p.), and kidney and blood specimens were collected.

RESULTS

Severe elevation in serum and urine biomarkers of renal injury was evident in the BDL group. Significant lipid peroxidation, reactive oxygen species (ROS) formation, and protein carbonylation were detected in the kidney of BDL animals. Furthermore, depleted glutathione reservoirs and a significant decrease in the antioxidant capacity of renal tissue were detected in cholestatic rats. Renal tubular atrophy and interstitial inflammation were evident in BDL animals. Cholestasis also caused significant mitochondrial dysfunction in the kidney. TAU significantly prevented cholestasis-induced renal injury by inhibiting oxidative stress and mitochondrial impairment.

CONCLUSIONS

These data indicate TAU as a potential therapeutic agent in the management of cholestasis-induced renal injury.

Pioglitazone-Loaded Nanostructured Hybrid Material for Skin Ulcer Treatment

Pioglitazone, a popular antidiabetic drug, which was recently shown to be effective in the treatment of skin ulcers, was successfully encapsulated in polysaccharide nanoparticles and used as a bioactive component of the wound-dressing material based on modified bacterial nanocellulose. Alginate and hydroxypropyl cellulose were used as a matrix for the nanoparticulate drug-delivery system. The matrix composition and particles’ size, as well as drug encapsulation efficiency and loading, were optimized. Pioglitazone hydrochloride (PIO) loaded particles were coated with chitosan introduced into the crosslinking medium, and covalently attached to the surface of bacterial nanocellulose functionalized with carboxyl groups. PIO was released from the surface of the hybrid material in a controlled manner for 5 days. Preliminary cytotoxicity studies confirmed safety of the system at PIO concentrations as high as 20 mg/mL. The obtained hybrid system may have potential application in the treatment of skin ulcers e.g., in diabetic foot.

Acute exercise inhibits gastric emptying of liquids in rats: influence of the NO-cGMP pathway

We previously found that acute exercise inhibited the gastric emptying of liquid in awake rats by causing an acid-base imbalance. In the present study, we investigated the involvement of the nitric oxide-cyclic guanosine monophosphate (NO-cGMP) pathway, vasoactive intestinal peptide (VIP), and corticotropin-releasing factor (CRF) peptide in this phenomenon. Male rats were divided into exercise or sedentary group and were subjected to a 15-min swim session against a load (2.5 or 5% b.w.). The rate of gastric emptying was evaluated after 5, 10, or 20 min postprandially. Separate groups of rats were treated with vehicle (0.9% NaCl, 0.1 mL/100 g, ip) or one of the following agents: atropine (1.0 mg/kg, ip), the NO non-selective inhibitor Nω-nitro-L-arginine methyl ester hydrochloride (L-NAME; 10.0 mg/kg, ip), or the selective cGMP inhibitor 1H-(1,2,4)oxadiazole[4,3-a]quinoxalin-1-one (ODQ; 5.0 mg/kg, ip), the i-NOS non-specific inhibitor (aminoguanidine; 10.0 mg/kg, ip), the corticotropin-releasing factor receptor antagonist (astressin; 100 µg/kg, ip), or the vasoactive intestinal peptide (VIP) receptor antagonist Lys¹, Pro^2,5, Arg^3,4, Tyr⁶ (100 µg/kg, ip). Compared to sedentary rats, both the 2.5 and 5% exercise groups exhibited higher (P<0.05) values of blood lactate and fractional gastric dye recovery. Corticosterone and NO levels increased (P<0.05) in the 5% exercised rats. Pretreatment with astressin, VIP antagonist, atropine, L-NAME, and ODQ prevented the increase in gastric retention caused by exercise in rats. Acute exercise increased gastric retention, a phenomenon that appears to be mediated by the NO-cGMP pathway, CRF, and VIP receptors.

Mitigation of stress from gastric mucosal injuries by mulberry extract may occur via nitric oxide synthase signaling in mice

Acute gastric mucosal injuries are serious clinical problems worldwide and are principally found with different types of stresses in animals. A constant challenge is to find original plant products that can combat stress. In the present study, we examined the effects of big-leaf mulberry extracts on stomach injury, and the activity of nitric oxide synthases (NOS) and total antioxidant activity (TAO) in the gastric mucosae of mice during water immersion and restraint stress (WIRS). Our data showed that WIRS-exposed mice produced several injuries and showed an enhanced iNOS, reduced eNOS activity, and decreased TAO activity in the stomach, whereas pretreatment with big-leaf mulberry extracts increased TAO activitiy. The data from our immunohistochemical study indicated that both iNOS and eNOS were expressed in parietal cells and blood vessels, while nNOS was only weakly expressed in parietal cells. In conclusion, our findings suggested that big-leaf mulberry mitigated WIRS-induced stomach injuries, and NOS signaling may play important roles in the mouse stomach during the recovery process.

The gastroprotective effect of nobiletin against ethanol-induced acute gastric lesions in mice: impact on oxidative stress and inflammation

CONTEXT

Gastric ulcer is a common gastrointestinal disorder with increasing incidence and prevalence attributed to loss of balance between aggressive and protective factors. Nobiletin (NOB), a major component of polymethoxyflavones in citrus fruits, has a broad spectrum of health beneficial properties including anti-inflammatory and anti-tumor activities. Although NOB was originally shown to possess anti-inflammatory activity, its effects on gastric ulcer were rarely explored previously.

OBJECTIVE

The aim of the present study was to investigate the anti-ulcerogenic activity of NOB on ethanol-induced gastric ulcer in mice and to elucidate the underlying mechanisms.

METHODS

Seventy-two male Kunming mice administered with absolute ethanol (0.2 ml/animal) were pretreated with NOB (5, 10 or 20 mg/kg), cimetidine (100 mg/kg), or vehicles by intragastric administration in different experimental groups for three days, and animals were euthanized 3 h after ethanol ingestion. Gross and microscopic lesions, immunological and biochemical parameters were taken into consideration.

RESULTS

The results showed that ethanol induced gastric injury, increased malondialdehyde (MDA) levels, decreased glutathione (GSH) content, superoxide dismutase (SOD) activity, and prostaglandin E₂ (PGE₂) levels, increased pro-inflammatory cytokines tumor necrosis factor-alpha (TNF-α) and interleukin-6 (IL-6) levels and myeloperoxidase (MPO) activity, as well as the expression MAPK signaling pathway. Pretreatment with NOB significantly attenuated the gastric lesions as compared to the ethanol group.

CONCLUSIONS

These findings suggest that the gastroprotective activity is attribute to the improvement of antioxidant activities, the stimulation of PGE₂, and the reduction of pro-inflammatory cytokines through the MAPK pathway.

Cirrhosis-induced morphological changes in the retina: possible role of endogenous opioid

AIM

To investigate the impact of cirrhosis on retinal morphology and to evaluate the role of endogenous opioids as a mediator in cirrhosis induced retinal change.

METHODS

Thirty-six male rats were divided into 3 main groups; the common bile duct ligated (BDL) group, the sham-operated (Sham) group and the unoperated (Unop) group. Then each of these three main groups was divided into two subgroups; the first subgroup received daily injection of naltrexone hydrochloride (NTX) and the second group was injected with normal saline (Saline) daily. After 28d, rats were anesthetized and their right eyes were enucleated and assessed for histological changes. The thickness of the rod and cons layer, outer nuclear layer, outer plexiform layer, inner nuclear layer, inner plexiform layer and ganglion cell layer for each eye were measured in micrometers by light microscope.

RESULTS

Ganglion cell layer showed significant increase in thickness in the BDL group (P<0.05). This increase was eliminated in the group where BDL rats received daily intraperitoneal injection of naltrexone hydrochloride (20 mg/kg). No other histological changes were detected in the other 5 layers we measured.

CONCLUSION

The morphological change we detected in the retina of cirrhotic rats is probably due to opioids increased tone in cirrhosis since the increase in thickness in the ganglion cell layer was almost eliminated when naltrexone hydrochloride was injected. These results suggest a possible role for endogenous opioids in the morphological retinal changes detected in cirrhotic rats.

Protective role of ellagitannins from Eucalyptus citriodora against ethanol-induced gastric ulcer in rats: impact on oxidative stress, inflammation and calcitonin-gene related peptide

The gastroprotective activity of an ellagitannin-rich fraction obtained from Eucalyptus citriodora (ECF) was investigated against ethanol-induced gastric ulceration in rats. The rats were pretreated with ECF (25, 50 and 100mg/kg) 1h before the administration of absolute ethanol to induce acute gastric ulceration. The gastric lesions were significantly reduced by all doses of ECF. Notably, pre-treatment with ECF (100mg/kg) conferred 99.6% gastroprotection, which is significantly higher than that produced by omeprazole. Moreover, ECF administration markedly increased the mucin content in a dose-dependent manner. The potent gastroprotective effect of ECF could be partly mediated by attenuating ethanol-induced oxidative stress. ECF-pre-treatment markedly increased the depleted GSH and SOD levels in a dose-dependent manner. Moreover, ECF significantly decreased the elevated MDA tissue levels induced by ethanol administration. The results demonstrated that ECF administration exerted a powerful anti-inflammatory activity as evidenced by the reduction in the pro-inflammatory markers; IL-1β, TNF-α, 5-LO and COX-2. Additionally, the caspase-3 tissue levels were significantly reduced in the groups pre-treated with ECF. These results suggest that ECF could exert a beneficial gastroprotective effect through their antioxidant, anti-inflammatory and anti-apoptotic properties. Furthermore, ECF pre-treatment significantly attenuated the ethanol-induced decrease in CGRP expression, which has a protective role against gastric ulceration. Histopathological examination revealed intact mucosal layer, absence of hemorrhage and necrosis in groups treated with ECF. Ellagitannins were identified as the major active constituents responsible for the marked antioxidant and gastroprotective properties of ECF. The HPLC-PDA-ESI/MS/MS technique was employed to identify the ellagitannins of E. citriodora.

Pioglitazone normalizes insulin signaling in the diabetic rat retina through reduction in tumor necrosis factor α and suppressor of cytokine signaling 3

Dysfunctional insulin signaling is a key component of type 2 diabetes. Little is understood of the effects of systemic diabetes on retinal insulin signaling. A number of agents are used to treat patients with type 2 diabetes to normalize glucose levels and improve insulin signaling; however, little has been done to investigate the effects of these agents on retinal insulin signal transduction. We hypothesized that pioglitazone, a peroxisome proliferator-activated receptor γ (PPARγ) agonist, would normalize retinal insulin signal transduction through reduced tumor necrosis factor α (TNFα) and suppressor of cytokine signaling 3 (SOCS3) activities in whole retina and retinal endothelial cells (REC) and Müller cells. To test this hypothesis, we used the BBZDR/Wor type 2 diabetic rat model, as well as REC and Müller cells cultured in normoglycemia and hyperglycemic conditions, to investigate the effects of pioglitazone on TNFα, SOCS3, and downstream insulin signal transduction proteins. We also evaluated pioglitazone's effects on retinal function using electroretinogram and markers of apoptosis. Data demonstrate that 2 months of pioglitazone significantly increased electroretinogram amplitudes in type 2 diabetic obese rats, which was associated with improved insulin receptor activation. These changes occurred in both REC and Müller cells treated with pioglitazone, suggesting that these two cell types are key to insulin resistance in the retina. Taken together, these data provide evidence of impaired insulin signaling in type 2 diabetes rats, which was improved by increasing PPARγ activity. Further investigations of PPARγ actions in the retina may provide improved treatment options.