Antoniella S. Gomes

Hydrogen sulfide prevents ethanol-induced gastric damage in mice: role of ATP-sensitive potassium channels and capsaicin-sensitive primary afferent neurons.

The aim of this study was to evaluate the protective effect of hydrogen sulfide (H2S) on ethanol-induced gastric lesions in mice and the influence of ATP-sensitive potassium (KATP) channels, capsaicin-sensitive sensory afferent neurons, and transient receptor potential vanilloid (TRPV) 1 receptors on such an effect. Saline and l-cysteine alone or with propargylglycine, sodium hydrogen sulfide (NaHS), or Lawessons reagent were administrated for testing purposes. For other experiments, mice were pretreated with glibenclamide, neurotoxic doses of capsaicin, or capsazepine. Afterward, mice received l-cysteine, NaHS, or Lawessons reagent. After 30 min, 50% ethanol was administrated by gavage. After 1 h, mice were sacrificed, and gastric damage was evaluated by macroscopic and microscopic analyses. l-Cysteine, NaHS, and Lawessons reagent treatment prevented ethanol-induced macroscopic and microscopic gastric damage in a dose-dependent manner. Administration of propargylglycine, an inhibitor of endogenous H2S synthesis, reversed gastric protection induced by l-cysteine. Glibenclamide reversed l-cysteine, NaHS, or Lawessons reagent gastroprotective effects against ethanol-induced macroscopic damage in a dose-dependent manner. Chemical ablation of sensory afferent neurons by capsaicin reversed gastroprotective effects of l-cysteine or H2S donors (NaHS or Lawessons reagent) in ethanol-induced macroscopic gastric damage. Likewise, in the presence of the TRPV1 antagonist capsazepine, the gastroprotective effects of l-cysteine, NaHS, or Lawessons reagent were also abolished. Our results suggest that H2S prevents ethanol-induced gastric damage. Although there are many mechanisms through which this effect can occur, our data support the hypothesis that the activation of KATP channels and afferent neurons/TRPV1 receptors is of primary importance.

Sildenafil prevents indomethacin-induced gastropathy in rats: role of leukocyte adherence and gastric blood flow

Nitric oxide (NO) is an important mediator of gastric mucosal defense. Sildenafil (SILD), a cyclic GMP‐specific phosphodiesterase inhibitor, promotes an increase in cGMP concentrations in the gastrointestinal tract. cGMP mediates many of the biological actions of NO. We tested the hypothesis that SILD could increase mucosal defense against indomethacin‐induced gastropathy in rats. SILD (1, 4 or 10 mg kg−1, p.o.) pretreatment significantly reduced (P<0.01) the gastric damage and the increase in gastric myeloperoxidase (MPO) activity elicited by indomethacin (20 mg kg−1 p.o.), with the maximal effect at the dose of 10 mg kg−1. L‐NAME (3, 10 or 20 mg kg−1, i.p.) dose dependently reversed the protective effects of SILD, an effect not seen when L‐arginine (L‐ARG) (200 mg kg−1, i.p.) was co‐administered with L‐NAME. Indomethacin‐induced leukocyte adhesion, assessed by intravital microscopy, was decreased (P<0.01) by SILD, and this effect was reversed by L‐NAME cotreatment. Indomethacin elicited a decrease in gastric blood flow and in gastric PGE2 levels. SILD was able to prevent the decrease in gastric blood flow (P<0.01), without diminishing the inhibitory effect of indomethacin on prostaglandin synthesis. These results indicate that SILD, acting via NO‐dependent mechanisms, prevents indomethacin‐induced gastropathy, possibly through a reduction of leukocyte adhesion and maintenance of gastric blood flow.

Inhaled 1,8-Cineole Reduces Inflammatory Parameters in Airways of Ovalbumin-Challenged Guinea Pigs

Eucalyptol, also known as 1,8-cineole, is a monoterpene traditionally used to treat respiratory disorders due to its secretolytic properties. In addition to its myorelaxant effects, it also has anti-inflammatory actions in vitro. In this study, we aimed to evaluate the efficacy of acute treatment with 1,8-cineole on reducing airway inflammatory parameters. Ovalbumin (OVA)-sensitized guinea pigs were submitted to antigenic challenge (OVA) with or without pre-treatment with a single dose of 1,8-cineole administered by inhalation. Airway inflammatory parameters were reduced or absent in 1,8-cineole-treated animals as compared with untreated guinea pigs. Acute treatment with 1,8-cineole impaired the development of airway hyperresponsiveness to carbachol in isolated tracheal rings. Levels of the pro-inflammatory cytokines TNFα and IL-1β was lower in bronchoalveolar lavage fluid (BALF) of 1,8-cineol-treated guinea pigs than in untreated animals. 1,8-Cineole impaired the OVA-induced increase of the myeloperoxidase activity in BALF. 1,8-Cineole also prevented the reduction of the mucociliary clearance induced by the antigen presentation. The present investigation provides evidence that inhaled 1,8-cineole prevents hyperresponsiveness and inhibits inflammation in airways of ovalbumin-challenged guinea pigs.

Role of inducible nitric oxide synthase pathway on methotrexate-induced intestinal mucositis in rodents

BackgroundMethotrexate treatment has been associated to intestinal epithelial damage. Studies have suggested an important role of nitric oxide in such injury. The aim of this study was to investigate the role of nitric oxide (NO), specifically iNOS on the pathogenesis of methotrexate (MTX)-induced intestinal mucositis.MethodsIntestinal mucositis was carried out by three subcutaneous MTX injections (2.5 mg/kg) in Wistar rats and in inducible nitric oxide synthase knock-out (iNOS-/-) and wild-type (iNOS+/+) mice. Rats were treated intraperitoneally with the NOS inhibitors aminoguanidine (AG; 10 mg/Kg) or L-NAME (20 mg/Kg), one hour before MTX injection and daily until sacrifice, on the fifth day. The jejunum was harvested to investigate the expression of Ki67, iNOS and nitrotyrosine by immunohistochemistry and cell death by TUNEL. The neutrophil activity by myeloperoxidase (MPO) assay was performed in the three small intestine segments.ResultsAG and L-NAME significantly reduced villus and crypt damages, inflammatory alterations, cell death, MPO activity, and nitrotyrosine immunostaining due to MTX challenge. The treatment with AG, but not L-NAME, prevented the inhibitory effect of MTX on cell proliferation. MTX induced increased expression of iNOS detected by immunohistochemistry. MTX did not cause significant inflammation in the iNOS-/- mice.ConclusionThese results suggest an important role of NO, via activation of iNOS, in the pathogenesis of intestinal mucositis.

Gastroprotective effect of heme-oxygenase 1/biliverdin/CO pathway in ethanol-induced gastric damage in mice.

Our objective was to evaluate the role of heme-oxygenase 1 (HO-1)/biliverdin/CO pathway in gastric defense against ethanol-induced gastric damage in mice. Mice were pre-treated with saline, hemin (HO-1 inducer), biliverdin (HO-1 product), dimanganese decacarbonyl (DMDC, CO donor) or zinc protoporphyrin IX (ZnPP IX, HO-1 antagonist). Another group received soluble guanylate cyclase (sGC) inhibitor (ODQ) 30 min before hemin, biliverdin or DMDC. After 30 min, gastric damage was induced by ethanol. After one hour, rats were sacrificed. Gastric lesions were measured using a computer planimetry program, and gastric corpus pieces were assayed for malonylaldehyde (MDA), glutathione (GSH) or bilirubin. HO-1 expression was determined after saline or ethanol administration by polymerase chain reaction (PCR) or immunohistochemistry. Ethanol (25% or 50%) induced gastric damage, increased MDA levels and reduced GSH in the gastric tissue. Ethanol 50% increased HO-1 mRNA transcripts, HO-1 immunoreactivity, and bilirubin concentration in gastric mucosa. Pre-treatment with hemin reduced gastric damage and MDA formation and increased GSH concentration in the gastric mucosa. ZnPP IX amplified the ethanol-induced gastric lesion, increased MDA formation and decreased GSH concentration in gastric mucosa. Biliverdin and DMDC reduced gastric damage and MDA formation and increased GSH concentration in the gastric tissue. ODQ completely abolished the DMDC protective gastric effect. However, effects of hemin or biliverdin did not change with ODQ treatment. Our results suggest that HO-1/biliverdin/CO pathway plays a protective role against ethanol-induced gastric damage through mechanisms that can be dependent (CO) or independent (biliverdin) of sGC activation.

The enteric glia: identity and functions.

Enteric glial cells were first described at the end of the 19th century, but they attracted more interest from researchers only in the last decades of the 20th. Although, they have a different embryological origin, the enteric GLIA share many characteristics with astrocytes, the main glial cell type of the central nervous system (CNS), such as in their expression of the same markers and in their functions. Here we review the construction of the enteric nervous system (ENS), with a focus on enteric glia, and also the main studies that have revealed the action of enteric glia in different aspects of gastrointestinal tract homeostasis, such as in the intestinal barrier, in communications with neurons, and in their action as progenitor cells. We also discuss recent discoveries about the roles of enteric glia in different disorders that affect the ENS, such as degenerative pathologies including Parkinsons and prion diseases, and in cases of intestinal diseases and injury. GLIA 2015;63:921–935

Experimental Model of Zymosan-Induced Arthritis in the Rat Temporomandibular Joint: Role of Nitric Oxide and Neutrophils

Aims. To establish a new model of zymosan-induced temporomandibular joint (TMJ) arthritis in the rat and to investigate the role of nitric oxide. Methods. Inflammation was induced by an intra-articular injection of zymosan into the left TMJ. Mechanical hypernociception, cell influx, vascular permeability, myeloperoxidase activity, nitrite levels, and histological changes were measured in TMJ lavages or tissues at selected time points. These parameters were also evaluated after treatment with the nitric oxide synthase (NOS) inhibitors L-NAME or 1400 W. Results. Zymosan-induced TMJ arthritis caused a time-dependent leucocyte migration, plasma extravasation, mechanical hypernociception, and neutrophil accumulation between 4 and 24 h. TMJ immunohistochemical analyses showed increased inducible NOS expression. Treatment with L-NAME or 1400 W inhibited these parameters. Conclusion. Zymosan-induced TMJ arthritis is a reproducible model that may be used to assess both the mechanisms underlying TMJ inflammation and the potential tools for therapies. Nitric oxide may participate in the inflammatory temporomandibular dysfunction mechanisms.

S-nitrosoglutathione decreases inflammation and bone resorption in experimental periodontitis in rats.

BACKGROUND S-nitrosoglutathione (GSNO) is a nitric oxide donor that may exert antioxidant, anti-inflammatory, and microbicidal actions and is thus a potential drug for the topical treatment of periodontitis. In this study, the effect of intragingival injections of GSNO-containing polyvinylpyrrolidone (PVP) formulations is evaluated in a rat model of periodontitis. METHODS Periodontal disease was induced by placing a sterilized nylon (000) thread ligature around the cervix of the second left upper molar of the animals, which received intragingival injections of PVP; saline; or PVP/GSNO solutions which corresponded to GSNO doses of 25, 100, and 500 nmol; 1 hour before periodontitis induction, and thereafter, daily for 11 days. RESULTS PVP/GSNO formulations at doses of 25 and/or 100, but not 500 nmol caused significant inhibition of alveolar bone loss, increase of bone alkaline phosphatase, decrease of myeloperoxidase activity, as well as significant reduction of inflammatory and oxidative stress markers when compared to saline and PVP groups. These effects were also associated with a decrease of matrix metalloproteinases 1 and 8, inducible nitric oxide synthase, and nuclear factor-κB immunostaining in the periodontium. CONCLUSION Local intragingival injections of GSNO reduces inflammation and bone loss in experimental periodontal disease.

Glutamine depletion potentiates leucocyte‐dependent inflammatory events induced by carrageenan or Clostridium difficile toxin A in rats

This research investigated the effect of glutamine (Gln) depletion on leucocyte‐dependent inflammatory events. Rats were treated intraperitoneally, 16 hr prior to the peak of every parameter evaluated, with either 0·9% NaCl, methionine‐sulphoximine (MSO, an inhibitor of endogenous Gln synthesis, 25 mg/kg) or with MSO + Gln (MSO as above plus Gln 3 g/kg in three doses). MSO‐induced Gln depletion increased paw oedema induced both by carrageenan (Cg) and by Clostridium difficile toxin A (TxA) (66·2% and 45·5%, respectively; P < 0·05). In dextran‐injected animals, oedema and myeloperoxidase (MPO) activity were not modified by Gln depletion. In Cg‐treated paws, Gln depletion increased MPO activity by 44% (P < 0·05), interleukin‐1β (IL‐1β) and tumour necrosis factor‐α (TNF‐α) concentrations by 47% and 52%, respectively (P < 0·05), and immunostaining for TNF‐α in paw tissue. In TxA‐injected paws, Gln depletion increased MPO activity (46%; P < 0·05). Gln depletion increased Cg‐ and TxA‐induced neutrophil migration to subcutaneous air pouches by 56% and 77% (P < 0·05), respectively, but did not affect migration induced by N‐formyl‐methionyl‐leucyl‐phenylalanine (fMLP). Gln infusions reversed all the effects of MSO. Leucocyte counts did not differ between groups. Gln depletion potentiates acute inflammation, possibly by increasing neutrophil migration through resident cell activation and production of IL‐1β and TNF‐α. Gln supplementation reverses these effects and may be useful during inflammatory catabolic stress.