Carbon Monoxide (CO) Released from Tricarbonyldichlororuthenium (II) Dimer (CORM-2) in Gastroprotection against Experimental Ethanol-Induced Gastric Damage

Role of Gasotransmitters in Inflammatory Edema

Significance: Nitric oxide (NO), carbon monoxide (CO), and hydrogen sulfide (H2S) are, to date, the identified members of the gasotransmitter family, which consists of gaseous signaling molecules that play central roles in the regulation of a wide variety of physiological and pathophysiological processes, including inflammatory edema. Recent Advances: Recent studies show the potential anti-inflammatory and antiedematogenic effects of NO-, CO-, and H2S-donors in vivo. In general, it has been observed that the therapeutical effects of NO-donors are more relevant when administered at low doses at the onset of the inflammatory process. Regarding CO-donors, their antiedematogenic effects are mainly associated with inhibition of proinflammatory mediators (such as inducible NO synthase [iNOS]-derived NO), and the observed protective effects of H2S-donors seem to be mediated by reducing some proinflammatory enzyme activities. Critical Issues: The most recent investigations focus on the interactions among the gasotransmitters under different pathophysiological conditions. However, the biochemical/pharmacological nature of these interactions is neither general nor fully understood, although specifically dependent on the site where the inflammatory edema occurs. Future Directions: Considering the nature of the involved mechanisms, a deeper knowledge of the interactions among the gasotransmitters is mandatory. In addition, the development of new pharmacological tools, either donors or synthesis inhibitors of the three gasotransmitters, will certainly aid the basic investigations and open new strategies for the therapeutic treatment of inflammatory edema. Antioxid. Redox Signal. 40, 272-291.

Carbon monoxide (CO) derived from the CO-releasing molecule CORM-2 reduces peritoneal adhesion formation in a rat model

BACKGROUND

Although low-dose carbon monoxide (CO) administration has been shown to have an anti-fibrotic effect in various fibrotic diseases, its effects on peritoneal adhesion (PA), one of the postoperative complications, are not elucidated. In this study, the effect of CO-releasing tricarbonyldichlororuthenium (II) dimer (CORM-2) administration on the formation of PA and the underlying factors of its potential effect were investigated.

METHODS AND RESULTS

After the induction of PA, rats were divided into four groups with 8 rats in each group. The rats received either (i) dimethyl sulfoxide:saline solution (1:10) as a vehicle, (ii) 2.5 mg/kg CORM-2, (iii) 5 mg/kg CORM-2, or (iv) inactive (i) CORM (iCORM) intragastrically every day for a duration of 7 days. PA was not induced in rats (n = 8) designated as sham controls. Gross, histological, immunohistochemical and quantitative real-time polymerase chain reaction analyses were performed to evaluate the effectiveness of CORM-2 administration. Gross analysis showed that CORM-2 administration reduced PA formation compared to rats treated with vehicle. Histological and immunohistochemical examinations showed that increased collagen deposition, myofibroblast accumulation, microvessel density, and M1 macrophage count in the peritoneal fibrosis area of vehicle-treated rats decreased following CORM-2 treatments. PCR analyses showed that CORM-2 treatments decreased hypoxia-induced Hif1a, profibrotic Tgfb1, ECM components Col1a1 and Col3a1, collagen degradation suppressor Timp1, fibrinolysis inhibitor Serpine1, and pro-inflammatory Tnf mRNA expressions, while increasing the M2 macrophage marker Arg1 mRNA expression.

CONCLUSIONS

These results suggested that CORM-2 administration reduces PA formation by affecting adhesiogenic processes such as pro-inflammatory response, fibrinolytic system, angiogenesis and fibrogenesis.

Novel Toxicodynamic Model of Subcutaneous Envenomation to Characterize Snake Venom Coagulopathies and Assess the Efficacy of Site-Directed Inorganic Antivenoms

Venomous snake bite adversely affects millions of people yearly, but few animal models allow for the determination of toxicodynamic timelines with hemotoxic venoms to characterize the onset and severity of coagulopathy or assess novel, site-directed antivenom strategies. Thus, the goals of this investigation were to create a rabbit model of subcutaneous envenomation to assess venom toxicodynamics and efficacy of ruthenium-based antivenom administration. New Zealand White rabbits were sedated with midazolam via the ear vein and had viscoelastic measurements of whole blood and/or plasmatic coagulation kinetics obtained from ear artery samples. Venoms derived from Crotalus scutulatus scutulatus, Bothrops moojeni, or Calloselasma rhodostoma were injected subcutaneously, and changes in coagulation were determined over three hours and compared to samples obtained prior to envenomation. Other rabbits had ruthenium-based antivenoms injected five minutes after venom injection. Viscoelastic analyses demonstrated diverse toxicodynamic patterns of coagulopathy consistent with the molecular composition of the proteomes of the venoms tested. The antivenoms tested attenuated venom-mediated coagulopathy. A novel rabbit model can be used to characterize the onset and severity of envenomation by diverse proteomes and to assess site-directed antivenoms. Future investigation is planned involving other medically important venoms and antivenom development.

Potential effects of carbon monoxide donor and its nanoparticles on experimentally induced gastric ulcer in rats

The prevalence of gastric ulcers is increasing worldwide, especially those brought on by non-steroidal anti-inflammatory drugs (NSAIDS), so prevention is extremely crucial. The protective potential of carbon monoxide (CO) in several inflammatory disorders has been clarified. The goal of the current study was to investigate the gastroprotective effect of CO produced by its pharmacological donor (CORM2) and its nanoparticles (NPs) against indomethacin (INDO)-induced ulcers. Investigations on CORM2's dose-dependent effects were also conducted. For induction of gastric ulcer, 100 mg kg^-1 of INDO was given orally. Before ulcer induction, CORM2 (5, 10, and 15 mg kg^-1), CORM2 nanoparticles (5 mg kg^-1), or ranitidine (30 mg kg^-1) were given intraperitoneally for 7 days. Ulcer score, gastric acidity, gastric contents of malondialdehyde (MDA), nitric oxide (NO), heme oxygenase-1 (HO-1), and carboxyhemoglobin (COHb) blood content were estimated. Additionally, gene expression of nuclear factor erythroid 2-related factor 2 (NRF2) and immunohistochemical staining of cyclooxygenase-1 (COX-1) as well as cyclooxygenase-2 (COX-2) were analyzed. Results demonstrated a substantial dose-dependent decrease in ulcer score, pro-inflammatory indicators, and oxidative stress markers with CORM2 and its NPs. Furthermore, CORM2 and its NPs markedly increased NRF2, COX-1, and HO-1, but CORM2 NPs outperformed CORM2 in this regard. In conclusion, the CO released by CORM2 can protect against INDO-induced gastric ulcers dose dependently, and the highest used dose had no effect on COHb concentration.

Reassessing CORM-A1: redox chemistry and idiosyncratic CO-releasing characteristics of the widely used carbon monoxide donor

Redox activity and unreliable carbon monoxide production of CO donor, CORM-A1, presents new complications in its use for studying CO biology.

Modulatory Role of Carbon Monoxide on the Inflammatory Response and Oxidative Stress Linked to Gastrointestinal Disorders

Significance: Carbon monoxide (CO) is an endogenous gaseous mediator that plays an important role in maintaining gastrointestinal (GI) tract homeostasis, acting in mucosal defense, and providing negative modulation of pathophysiological markers of clinical conditions. Recent Advances: Preclinical studies using animal models and/or cell culture show that CO can modulate the inflammatory response and oxidative stress in GI mucosal injuries and pathological conditions, reducing proinflammatory cytokines and reactive oxygen species, while increasing antioxidant defense mechanisms. Critical Issues: CO has potent anti-inflammatory and antioxidant effects. The defense mechanisms of the GI tract are subject to aggression by different chemical agents (e.g., drugs and ethanol) as well as complex and multifactorial diseases, with inflammation and oxidative stress as strong triggers for the deleterious effects. Thus, it is possible that CO acts on a variety of molecules involved in the inflammatory and oxidative signaling cascades, as well as reinforcing several defense mechanisms that maintain GI homeostasis. Future Directions: CO-based therapies are promising tools for the treatment of GI disorders, such as gastric and intestinal injuries, inflammatory bowel disease, and pancreatitis. Therefore, it is necessary to develop safe and selective CO-releasing agents and/or donor drugs to facilitate effective treatments and methods for analysis of CO levels that are simple and inexpensive. Antioxid. Redox Signal. 37, 98-114.

Carbon monoxide signaling and soluble guanylyl cyclase: Facts, myths, and intriguing possibilities

The endogenous signaling roles of carbon monoxide (CO) have been firmly established at the pathway level. For CO's molecular mechanism(s) of actions, hemoproteins are generally considered as possible targets. Importantly, soluble guanylyl cyclase (sGC) is among the most widely referenced molecular targets. However, the affinity of CO for sGC (K_d: 240 μM) is much lower than for other highly abundant hemoproteins in the body, such as myoglobin (K_d: 29 nM) and hemoglobin (K_d: 0.7 nM-4.5 μM), which serve as CO reservoirs. Further, most of the mechanistic studies involving sGC activation by CO were based on in-vitro or ex-vivo studies using CO concentrations not readily attenable in vivo and in the absence of hemoglobin as a competitor in binding. As such, whether such in-vitro/ex-vivo results can be directly extrapolated to in-vivo studies is not clear because of the need for CO to be transferred from a high-affinity binder (e.g., hemoglobin) to a low-affinity target if sGC is to be activated in vivo. In this review, we discuss literature findings of sGC activation by CO and the experimental conditions; examine the myths in the disconnect between the low affinity of sGC for CO and the reported activation of sGC by CO; and finally present several possibilities that may lead to additional studies to improve our understanding of this direct CO-sGC axis, which is yet to be convincingly established as playing generally critical roles in CO signaling in vivo.

Ameliorative effect of fluvoxamine against colon carcinogenesis via COX-2 blockade with oxidative and metabolic stress reduction at the cellular, molecular and metabolic levels

Fluvoxamine's (FLX's) anticancer potential was investigated in pre-clinical research utilizing a DMH-induced colorectal cancer (CRC) rat model. qRT-PCR and immunoblotting validated the mechanistic investigation. The CRC condition was induced in response to COX-2 and IL-6, however, following FLX therapy, the condition returned to normal. FLX's anti-CRC potential may be attributable to COX-2 inhibition since this molecular activity was more apparent for COX-2 than IL-6. FLX repaired the altered metabolites linked to CRC rats, according to ¹H-NMR analysis. FLX was shown to be similar to 5-FU in terms of tumor protection, which may be useful in future medication development.

"CO in a pill": Towards oral delivery of carbon monoxide for therapeutic applications

Along with the impressive achievements in understanding the endogenous signaling roles and mechanism(s) of action of carbon monoxide (CO), much research has demonstrated the potential of using CO as a therapeutic agent for treating various diseases. Because of CO's toxicity at high concentrations and the observed difference in toxicity profiles of CO depending on the route of administration, this review analyzes and presents the benefits of developing orally active CO donors. Such compounds have the potential for improved safety profiles, enhancing the chance for developing CO-based therapeutics. In this review, the difference between inhalation and oral administration in terms of toxicity, CO delivery efficiency, and the potential mechanism(s) of action is analyzed. The evolution from CO gas inhalation to oral administration is also extensively analyzed by summarizing published studies up to date. The concept of "CO in a pill" can be achieved by oral administration of novel formulations of CO gas or appropriate CO donors.

Malvidin Protects against and Repairs Peptic Ulcers in Mice by Alleviating Oxidative Stress and Inflammation

Peptic ulcer episodes cause damage to the stomach and intestine, with inflammatory cell infiltration and oxidative stress as the main players. In this study, we investigated the potential of anthocyanidin malvidin for preventive and curative peptic ulcer treatment. The anthocyanidin effects were examined in gastric ulcer mouse models induced by ethanol, non-steroidal anti-inflammatory drugs (NSAIDs), ischemia-reperfusion (IR), acetic acid and duodenal ulcer induced by polypharmacy. Expression levels of oxidative and inflammatory genes were measured to investigate the mechanism of anthocyanin activity. At a dose of 5 mg·kg⁻¹, Malvidin prevented gastric ulcer induction by ethanol, NSAID and repaired the tissue after 6 days of IR. Moreover, the anthocyanidin accelerated the healing of acetic acid-induced ulcer, increased the gene expression of EGF and COX-1, and downregulated MMP-9. Anthocyanin treatment mitigated the effect of polypharmacy on inflammation and oxidative stress observed in the intestine. Additionally, the compound downregulated cytokine expression and TLR4 and upregulated HMOX-1 and IL-10, exhibiting protective activity in the mouse gut. Malvidin thus prevented gastric and duodenal ulcers due to prominent anti-inflammatory and antioxidative effects on the gastrointestinal tract that were related to gene expression modulation and an increase in endogenous defense mechanisms.

Carbon Monoxide is an Inhibitor of HIF Prolyl Hydroxylase Domain 2

Hypoxia-inducible factor prolyl hydroxylase domain 2 (PHD2) is an important oxygen sensor in animals. By using the CO-releasing molecule-2 (CORM-2) as an in situ CO donor, we demonstrate that CO is an inhibitor of PHD2. This report provides further evidence about the emerging role of CO in oxygen sensing and homeostasis.

Organic carbon monoxide prodrug, BW-CO-111, in protection against chemically-induced gastric mucosal damage

Metal-based carbon monoxide (CO)-releasing molecules have been shown to exert anti-inflammatory and anti-oxidative properties maintaining gastric mucosal integrity. We are interested in further development of metal-free CO-based therapeutics for oral administration. Thus, we examine the protective effect of representative CO prodrug, BW-CO-111, in rat models of gastric damage induced by necrotic ethanol or aspirin, a representative non-steroidal anti-inflammatory drug. Treatment effectiveness was assessed by measuring the microscopic/macroscopic gastric damage area and gastric blood flow by laser flowmetry. Gastric mucosal mRNA and/or protein expressions of HMOX1, HMOX2, nuclear factor erythroid 2-related factor 2, COX1, COX2, iNos, Anxa1 and serum contents of TGFB1, TGFB2, IL1B, IL2, IL4, IL5, IL6, IL10, IL12, tumor necrosis factor α, interferon γ, and GM-CSF were determined. CO content in gastric mucosa was assessed by gas chromatography. Pretreatment with BW-CO-111 (0.1 mg/kg, i.g.) increased gastric mucosal content of CO and reduced gastric lesions area in both models followed by increased GBF. These protective effects of the CO prodrug were supported by changes in expressions of molecular biomarkers. However, because the pathomechanisms of gastric damage differ between topical administration of ethanol and aspirin, the possible protective and anti-inflammatory mechanisms of BW-CO-111 may be somewhat different in these models.

Role of Carbon Monoxide in Host-Gut Microbiome Communication

Nature is full of examples of symbiotic relationships. The critical symbiotic relation between host and mutualistic bacteria is attracting increasing attention to the degree that the gut microbiome is proposed by some as a new organ system. The microbiome exerts its systemic effect through a diverse range of metabolites, which include gaseous molecules such as H₂, CO₂, NH₃, CH₄, NO, H₂S, and CO. In turn, the human host can influence the microbiome through these gaseous molecules as well in a reciprocal manner. Among these gaseous molecules, NO, H₂S, and CO occupy a special place because of their widely known physiological functions in the host and their overlap and similarity in both targets and functions. The roles that NO and H₂S play have been extensively examined by others. Herein, the roles of CO in host-gut microbiome communication are examined through a discussion of (1) host production and function of CO, (2) available CO donors as research tools, (3) CO production from diet and bacterial sources, (4) effect of CO on bacteria including CO sensing, and (5) gut microbiome production of CO. There is a large amount of literature suggesting the "messenger" role of CO in host-gut microbiome communication. However, much more work is needed to begin achieving a systematic understanding of this issue.

Evidence for Cytoprotective Effect of Carbon Monoxide Donor in the Development of Acute Esophagitis Leading to Acute Esophageal Epithelium Lesions

Exposure to acidic gastric content due to malfunction of lower esophageal sphincter leads to acute reflux esophagitis (RE) leading to disruption of esophageal epithelial cells. Carbon monoxide (CO) produced by heme oxygenase (HMOX) activity or released from its donor, tricarbonyldichlororuthenium (II) dimer (CORM-2) was reported to protect gastric mucosa against acid-dependent non-steroidal anti-inflammatory drug-induced damage. Thus, we aimed to investigate if CO affects RE-induced esophageal epithelium lesions development. RE induced in Wistar rats by the ligation of a junction between pylorus and forestomach were pretreated i.g. with vehicle CORM-2; RuCl₃; zinc protoporphyrin IX, or hemin. CORM-2 was combined with NG-nitro-L-arginine (L-NNA), indomethacin, capsazepine, or capsaicin-induced sensory nerve ablation. Esophageal lesion score (ELS), esophageal blood flow (EBF), and mucus production were determined by planimetry, laser flowmetry, histology. Esophageal Nrf-2, HMOXs, COXs, NOSs, TNF-α and its receptor, IL-1 family and IL-1 receptor antagonist (RA), NF-κB, HIF-1α, annexin-A1, suppressor of cytokine signaling (SOCS3), TRPV1, c-Jun, c-Fos mRNA/protein expressions, PGE₂, 8-hydroxy-deoxyguanozine (8-OHdG) and serum COHb, TGF-β1, TGF-β2, IL-1β, and IL-6 content were assessed by PCR, immunoblotting, immunohistochemistry, gas chromatography, ELISA or Luminex platform. Hemin or CORM-2 alone or combined with L-NNA or indomethacin decreased ELS. Capsazepine or capsaicin-induced denervation reversed CORM-2 effects. COHb blood content, esophageal HMOX-1, Nrf-2, TRPV1 protein, annexin-A1, HIF-1α, IL-1 family, NF-κB, c-Jun, c-Fos, SOCS3 mRNA expressions, and 8-OHdG levels were elevated while PGE₂ concentration was decreased after RE. CO donor-maintained elevated mucosal TRPV1 protein, HIF-1 α, annexin-A1, IL-1RA, SOCS3 mRNA expression, or TGF-β serum content, decreasing 8-OHdG level, and particular inflammatory markers expression/concentration. CORM-2 and Nrf-2/HMOX-1/CO pathway prevent esophageal mucosa against RE-induced lesions, DNA oxidation, and inflammatory response involving HIF-1α, annexin-A1, SOCS3, IL-1RA, TGF-β-modulated pathways. Esophagoprotective and hyperemic CO effects are in part mediated by afferent sensory neurons and TRPV1 receptors activity with questionable COX/PGE₂ or NO/NOS systems involvement.

Oxidative gastric mucosal damage induced by ischemia/reperfusion and the mechanisms of its prevention by carbon monoxide-releasing tricarbonyldichlororuthenium (II) dimer

Endogenous gaseous mediators, such as nitric oxide, hydrogen sulfide or carbon monoxide (CO) are known to exert anti-inflammatory and anti-oxidative activity due to modulation of various molecular pahtways. Therefore, we aimed to investigate if CO released from tricarbonyldichlororuthenium (II) dimer (CORM-2) prevents gastric mucosa against ischemia/reperfusion (I/R)-induced injury in male Wistar rats. Animals were pretreated i.g. With vehicle (DMSO and saline, 1:10), CORM-2 (1, 5 or 10 mg/kg) or zinc protoporphyrin IX (ZnPP, 10 mg/kg i.p.), the HMOXs inhibitor. In separate series, rats were pretreated with CORM-2 (5 mg/kg) applied in combination with glibenclamide (10 mg/kg i.g.), N^G-nitro-l-arginine (L-NNA, 20 mg/kg i.p.), 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ, 10 mg/kg i.p.) or indomethacin (5 mg/kg i.p.). I/R-injuries were induced by clamping celiac artery for 30 min (I) followed by removal of the clamp to obtain R for 3 h. The macroscopic and microscopic area of gastric damage, mucus production and protein expression for HMOX-1/Nrf-2 was determined by planimetry, histology and immunohistochemistry, respectively. Gastric mucosal HMOX-1, HMOX-2, COX-1, COX-2, Kir6.1, Sur2, sGC-α1, sGC-α2, iNOS and eNOS mRNA expression was assessed by real-time PCR. COHb in blood and gastric mucosal CO concentration was analyzed by gas chromatography. Serum content of TGF-β1, TGF-β2, TGF-β3, IL-1α, IL-1β, IL-2, IL-4, IL-5, IL-6, IL-10, IL-12, TNF-α, IFN-γ, GM-CSF was evaluated using Luminex platform. PGE₂ concentration and 8-hydroxyguanozine (8-OHG) concentration in gastric mucosa was determined by ELISA. Exposure to I/R induced extensive hemorrhagic erosions in gastric mucosa pretreated with vehicle as compared with intact rats and the area of this gastric damage was reduced by pretreatment with CORM-2 (5 mg/kg i.g.). This effect of CO donor was accompanied by the increased PGE₂ content and a significant decrease in 8-OHG and expression of pro- and anti-inflammatory markers mRNA and proteins. Concurrent treatment of CORM-2 with glibenclamide, L-NNA, ODQ but not with indomethacin significantly increased the area of I/R-induced injury and significantly decreased GBF as compared with the group treated with CORM-2 alone. We conclude that CO releasing CORM-2 prevents gastric mucosal oxidative damage induced by I/R improving GBF, decreasing DNA oxidation and inflammatory response on systemic level. This CO-gastroprotection is mediated by the activity of sGC, NOS and K-ATP channels. CO delivered from its donor maintained physiological gastric mucosal PGE₂ concentration but the involvement of endogenous COX in beneficial activity of this gaseous mediator at least in this model is questionable.

CO-Releasing Molecule-2 Induces Nrf2/ARE-Dependent Heme Oxygenase-1 Expression Suppressing TNF-α-Induced Pulmonary Inflammation

The upregulation of heme oxygenase-1 (HO-1) by the carbon monoxide-releasing molecule (CORM)-2 may be mediated through the activation of nicotinamide adenine dinucleotide phosphate (NADPH) oxidases [Nox] and reactive oxygen species (ROS) generation, which could provide cytoprotection against various cellular injuries. However, the detailed mechanisms of CORM-2-induced HO-1 expression in human pulmonary alveolar epithelial cells (HPAEpiCs) remain largely unknown. Therefore, we dissected the mechanisms underlying CORM-2-induced HO-1 expression in HPAEpiCs. We found that the administration of mice with CORM-2 attenuated the tumor necrosis factor-alpha (TNF-α)-induced intercellular adhesion molecule-1 (ICAM-1) expression and leukocyte count as revealed by immunohistochemical staining, western blot, real-time polymerase chain reaction (PCR), and cell count. Furthermore, TNF-α-induced ICAM-1 expression associated with monocyte adhesion to HPAEpiCs was attenuated by infection with adenovirus (adv)-HO-1 or incubation with CORM-2. These inhibitory effects of HO-1 were reversed by pretreatment with hemoglobin (Hb). Moreover, CORM-2-induced HO-1 expression was mediated via the phosphorylation of p47^phox, c-Src, epidermal growth factor receptor (EGFR), Akt, and NF-E2-related factor 2 (Nrf2), which were inhibited by their pharmacological inhibitors, including diphenyleneiodonium (DPI) or apocynin (APO), ROS [N-acetyl-L-cysteine (NAC)], PP1, AG1478, PI3K (LY294002), or Akt (SH-5), and small interfering RNAs (siRNAs). CORM-2-enhanced Nrf2 expression, and anti-oxidant response element (ARE) promoter activity was also inhibited by these pharmacological inhibitors. The interaction between Nrf2 and AREs was confirmed with a chromatin immunoprecipitation (ChIP) assay. These findings suggest that CORM-2 increases the formation of the Nrf2 and AREs complex and binds with ARE-binding sites via Src, EGFR, and PI3K/Akt, which further induces HO-1 expression in HPAEpiCs. Thus, the HO-1/CO system might suppress TNF-α-mediated inflammatory responses and exert a potential therapeutic strategy in pulmonary diseases.

Time-dependent course of gastric ulcer healing and molecular markers profile modulated by increased gastric mucosal content of carbon monoxide released from its pharmacological donor

BACKGROUND AND PURPOSE

Besides hydrogen sulfide (H₂S) and nitric oxide (NO), carbon monoxide (CO) contributes to the maintenance of gastric mucosal integrity. We investigated increased CO bioavailability effects on time-dependent dynamics of gastric ulcer healing mediated by particular growth factors, anti-inflammatory and molecular pathways.

EXPERIMENTAL APPROACH

Wistar rats with gastric ulcers induced by serosal acetic acid application (day 0) were treated i.g. throughout 3, 6 or 14 days with vehicle or CO-releasing tricarbonyldichlororuthenium (II) dimer (CORM-2, 2.5 mg/kg). Gross and microscopic alterations in gastric ulcer size and gastric blood flow (GBF) at ulcer margin were determined by planimetry, histology and laser flowmetry, respectively. Gastric mRNA/protein expressions of platelet derived growth factors (PDGFA-D), insulin-like growth factor (IGF-1), epidermal growth factor (EGF), hepatocyte growth factor (HGF), vascular endothelial growth factor (VEGFA) and their receptors, heme oxygenases (HMOX), nuclear factor (erythroid-derived 2)-like 2 (Nrf-2), cyclooxygenase (COX-2), hypoxia inducible factor (HIF)-1α, anti-inflammatory annexin-1 and transforming growth factor (TGF-β1) were assessed by real-time PCR or Western blot. TGF-β1-3 and IL-10 plasma concentration were measured using Luminex platform. Prostaglandin E₂ content at ulcer margin was assessed by ELISA.

KEY RESULTS

CORM-2 decreased ulcer area and increased GBF after 6 and 14 days of treatment comparing to vehicle. CO donor upregulated HGF, HGFr, VEGFR1, VEGFR2, TGF-β1, annexin-1 and maintained increased IGF-1, PDGFC and EGF expression at various time-intervals of ulcer healing. TGF-β3 and IL-10 plasma concentration were significantly increased after COMR-2 vs. vehicle.

CONCLUSIONS

CO time-dependently accelerates gastric ulcer healing and raises GBF at ulcer margin by mechanism involving subsequent upregulation of anti-inflammatory, growth promoting and angiogenic factors response, not observed physiologically.

Alterations in Gastric Mucosal Expression of Calcitonin Gene-Related Peptides, Vanilloid Receptors, and Heme Oxygenase-1 Mediate Gastroprotective Action of Carbon Monoxide against Ethanol-Induced Gastric Mucosal Lesions

Carbon monoxide (CO) has been reported to contribute to the maintenance of gastric mucosal integrity, gastroprotection, and ulcer healing. However, involvement of transient receptor potential vanilloid receptor type 1 (TRPV1) located on afferent sensory fibers endings and sensory neuropeptide calcitonin gene-related peptide (CGRP) in CO-mediated gastroprotection against ethanol-induced gastric damage has not been explored. Male Wistar rats with and without denervation of afferent sensory neurons induced by capsaicin (total dose 125 mg/kg within 3 days) were pretreated with vehicle, CO donor tricarbonyldichlororuthenium (II) dimer (CORM-2, 5 mg/kg i.g.), administered alone or with CGRP-α (10 μg/kg i.p.) or TRPV1 antagonist capsazepine (5 mg/kg i.g.), followed 30 min later by intragastric (i.g.) administration of 75% ethanol. The area of gastric damage and gastric blood flow (GBF) were assessed planimetrically and by laser flowmetry, respectively. Microscopic evaluation of ethanol-induced gastric lesions was performed after haematoxylin/eosin (H&E) or alcian blue/periodic acid-Schiff/alcian blue (AB/PAS) staining. Gastric mucosal mRNA fold change for heme oxygenase (HMOX)-1, HMOX-2, CGRP-α, CGRP-β, inducible nitric oxide synthase (iNOS), endothelial (e)NOS, neuronal (n)NOS, cyclooxygenase (COX)-1, COX-2, and protein expression for HMOX-1 and TRPV1 was determined by real-time PCR or Western blot, respectively. Pretreatment with CORM-2 combined or not with CGRP reduced ethanol-induced gastric lesions and elevated GBF. Capsaicin-denervation or co-treatment with capsazepine or CGRP and CORM-2 in capsaicin-denervated animals failed to affect these beneficial effects of CO donor. In rats with intact sensory nerves, CORM-2 increased gastric mRNA level for HMOX-1 and CGRP-α. In capsaicin-denervated rats, CORM-2 increased eNOS mRNA fold change and TRPV1 protein expression while capsaicin denervation itself decreased HMOX-1 protein expression and eNOS mRNA level. We conclude that CO prevents gastric mucosa from ethanol-induced lesions due to activation of TRPV1/CGRP-α system and accompanying increase in gastric microcirculation but independently on afferent sensory nerve activity despite the stimulation of TRPV1 protein and CGRP-α mRNA expression.

An Overview of the Potential Therapeutic Applications of CO-Releasing Molecules

Carbon monoxide (CO) has long been known as the “silent killer” owing to its ability to form carboxyhemoglobin—the main cause of CO poisoning in humans. Its role as an endogenous neurotransmitter, however, was suggested in the early 1990s. Since then, the biological activity of CO has been widely examined via both the direct administration of CO and in the form of so-called “carbon monoxide releasing molecules (CORMs).” This overview will explore the general physiological effects and potential therapeutic applications of CO when delivered in the form of CORMs.

AMPK activation promotes gastroprotection through mutual interaction with the gaseous mediators H2S, NO, and CO

Activation of 5' adenosine monophosphate-activated protein kinase (AMPK) stimulates production of the gaseous mediators nitric oxide (NO) and carbon monoxide (CO), which are involved in mucosal defense and gastroprotection. As AMPK itself has gastroprotective effects against several gastric ulcer etiologies, in the present study, we aimed to elucidate whether AMPK may also prevent ethanol-induced injury and play a key role in the associated gastroprotection mediated by hydrogen sulfide (H₂S), NO, and CO. Mice were pretreated with AICAR (20 mg/kg, an AMPK activator) alone or with 50% ethanol. Other groups were pretreated with respective gaseous mediator inhibitors PAG, l-NAME, or ZnPP IX 30 min prior to AICAR, or with gaseous mediator donors NaHS, Lawesson's reagent and l-cysteine (H₂S), SNP, l-Arginine (NO), Hemin, or CORM-2 (CO) 30 min prior to ethanol with or without compound C (10 mg/kg, a non-selective AMPK inhibitor). H₂S, nitrate/nitrite (NO₃^-/NO₂^-), bilirubin levels, GSH and MDA concentration were evaluated in the gastric mucosa. The gastric mucosa was also collected for histopathological analysis and AMPK expression assessment by immunohistochemistry. Pretreatment with AICAR attenuated the ethanol-induced injury and increased H₂S and bilirubin levels but not NO₃^-/NO₂^- levels in the gastric mucosa. In addition, inhibition of H₂S, NO, or CO synthesis exacerbated the ethanol-induced gastric damage and inhibited the gastroprotection by AICAR. Pretreatment with compound C reversed the gastroprotective effect of NaHS, Lawesson's reagent, l-cysteine, SNP, l-Arginine, CORM-2, or Hemin. Compound C also reversed the effect of NaHS on H₂S production, SNP on NO₃^-/NO₂^- levels, and Hemin on bilirubin levels. Immunohistochemistry revealed that AMPK is present at basal levels mainly in the gastric mucosa cells, and was increased by pretreatment with NaHS, SNP, and CORM-2. In conclusion, our findings indicate that AMPK activation exerts gastroprotection against ethanol-induced gastric damage and mutually interacts with H₂S, NO, or CO to facilitate this process.

Mechanisms of curcumin-induced gastroprotection against ethanol-induced gastric mucosal lesions

BACKGROUND

Curcumin, a pleiotropic substance used for centuries in traditional medicine, exhibits antioxidant, anti-inflammatory and antiproliferative efficacy against various tumours, but the role of curcumin in gastroprotection is little studied. We determined the effect of curcumin against gastric haemorrhagic lesions induced by 75% ethanol and alterations in gastric blood flow (GBF) in rats with cyclooxygenase-1 (COX-1) and COX-2 activity inhibited by indomethacin, SC-560 or rofecoxib, inhibited NO-synthase activity, capsaicin denervation and blockade of TRPV1 receptors by capsazepine.

METHODS

One hour after ethanol administration, the gastric mucosal lesions were assessed by planimetry, the GBF was examined by H2 gas clearance, plasma gastrin was determined by radioimmunoassay, and the gastric mucosal mRNA expression of Cdx-2, HIF-1α, HO-1 and SOD 2 was analysed by RT-PCR.

RESULTS

Curcumin, in a dose-dependent manner, reduced ethanol-induced gastric lesions and significantly increased GBF and plasma gastrin levels. Curcumin-induced protection was completely reversed by indomethacin and SC-560, and significantly attenuated by rofecoxib, L-NNA, capsaicin denervation and capsazepine. Curcumin downregulated Cdx-2 and Hif-1α mRNA expression and upregulated HO-1 and SOD 2, and these effects were reversed by L-NNA and further restored by co-treatment of L-NNA with L-arginine.

CONCLUSIONS

Curcumin-induced protection against ethanol damage involves endogenous PG, NO, gastrin and CGRP released from sensory nerves due to activation of the vanilloid TRPV1 receptor. This protective effect can be attributed to the inhibition of HIF-1α and Cdx-2 expression and the activation of HO-1 and SOD 2 expression.

Novel 1,3,4-thiadiazoles inhibit colorectal cancer via blockade of IL-6/COX-2 mediated JAK2/STAT3 signals as evidenced through data-based mathematical modeling

We attempted a preclinical study using DMH-induced CRC rat model to evaluate the antitumor potential of our recently synthesized 1,3,4-thiadiazoles. The molecular insights were confirmed through ELISA, qRT-PCR and western blot analyses. The CRC condition was produced in response to COX-2 and IL-6 induced activation of JAK2/STAT3 which, in turn, was due to the enhanced phosphorylation of JAK2 and STAT3. The treatment with 1,3,4-thiadiazole derivatives (VR24 and VR27) caused the significant blockade of this signaling pathway. The behavior of STAT3 populations in response to IL-6 and COX-2 stimulations was further confirmed through data-based mathematical modeling using the quantitative western blot data. Finally, VR24 and VR27 restored the perturbed metabolites associated to DMH-induced CRC as evidenced through ¹H NMR based serum metabolomics. The tumor protecting ability of VR24 and VR27 was found comparable or to some degree better than the marketed chemotherapeutics, 5-flurouracil.

Gastroprotective Effects of Sulphated Polysaccharides from the Alga Caulerpa mexicana Reducing Ethanol-Induced Gastric Damage

The development of the gastric lesion is complex and the result of the imbalance between aggressive and protective factors, involving the generation of free radicals and disturbance in nitric oxide (NO) production. Sulphated polysaccharides (SP), from marine algae, are widely used in biotechnological and pharmaceutical areas. In this study, we evaluated the effects of SP from the green marine alga Caulerpa mexicana (Cm-SP) in ethanol-induced gastric damage models in mice. Cm-SP (2, 20, or 200 mg/kg), administered p.o., significantly reduced gastric damage, and these effects were inhibited through pretreatment with indomethacin. Cm-SP (200 mg/kg) prevented the ethanol-induced decline in glutathione and restored its normal level. Moreover, it was able to normalize the elevated thiobarbituric acid reactive substance levels. However, Cm-SP did not show any significant effects on NO₂/NO₃ level, when compared to the ethanol group. The pretreatment with L- NAME induced gastric mucosal damage and did not inhibit the gastroprotective effect of Cm-SP (200 mg/kg). In conclusion, the gastroprotective effects of Cm-SP in mice involve prostaglandins and reduction in the oxidative stress and are independent of NO.

Nitric oxide, afferent sensory nerves, and antioxidative enzymes in the mechanism of protection mediated by tricarbonyldichlororuthenium(II) dimer and sodium hydrosulfide against aspirin-induced gastric damage

BACKGROUND

Aspirin exerts side effects within the gastrointestinal tract. Hydrogen sulfide (H₂S) and carbon monoxide (CO) have been implicated in gastroprotection but the mechanism of beneficial action of these gaseous mediators against aspirin-induced damage has not been fully studied. We determined the involvement of afferent sensory neurons, calcitonin-gene-related peptide (CGRP), lipid peroxidation, and nitric oxide (NO) biosynthesis in gastroprotection of H₂S-releasing NaHS and CO-releasing tricarbonyldichlororuthenium(II) dimer (CORM-2) against aspirin-induced injury.

METHODS

Wistar rats with or without capsaicin-induced denervation of sensory neurons were pretreated with vehicle, CORM-2 (5 mg/kg intragastrically), or NaHS (5 mg/kg intragastrically) with or without capsazepine (5 mg/kg intragastrically) or N ^G-nitro-L-arginine (L-NNA, 20 mg/kg intraperitoneally). The areas of aspirin-induced lesions and gastric blood flow (GBF) were assessed by planimetry and laser flowmetry respectively. Gastric mucosal messenger RNA and/or protein expression of CGRP, heme oxygenase 1, inducible nitric oxide synthase, cyclooxygenase 2, interleukin-1β, glutathione peroxidase 1 (GPx-1), and superoxide dismutase was determined by real-time PCR or Western blot. Malondialdehyde (MDA) and 4-hydroxynonenal (4-HNE) content was determined by colorimetric assay.

RESULTS

Aspirin caused gastric lesions, decreased GBF, and raised MDA content, but pretreatment with NaHS and CORM-2 reduced these effects. Capsaicin-induced denervation or co-treatment with capsazepine reversed the gastroprotective and vasodilatory effects of NaHS but not those of CORM-2. L-NNA reversed NaHS-induced gastroprotection and partly reduced CORM-2-induced gastroprotection. NaHS and CORM-2 decreased MDA and 4-HNE content, restoring GPx-1 protein expression.

CONCLUSIONS

We conclude that H₂S- but not CO-mediated gastroprotection against aspirin-induced injury involves afferent sensory nerves and partly NO activity. NaHS and CORM-2 prevented aspirin-induced gastric mucosal lipid peroxidation via restoration of microcirculation and antioxidative GPx-1 protein expression.

Cross-talk between hydrogen sulfide and carbon monoxide in the mechanism of experimental gastric ulcers healing, regulation of gastric blood flow and accompanying inflammation

Hydrogen sulfide (H₂S) and carbon monoxide (CO) exert gastroprotection against acute gastric lesions. We determined the cross-talk between H₂S and CO in gastric ulcer healing process and regulation of gastric blood flow (GBF) at ulcer margin. Male Wistar rats with acetic acid-induced gastric ulcers were treated i.g. throughout 9 days with vehicle (control), NaHS (0.1-10 mg/kg) +/- zinc protoporphyrin (ZnPP, 10 mg/kg), d,l-propargylglycine (PAG, 30 mg/kg), CO-releasing CORM-2 (2.5 mg/kg) +/- PAG. GBF was assessed by laser flowmetry, ulcer area was determined by planimetry/histology. Gastric mucosal H₂S production was analysed spectrophotometrically. Protein and/or mRNA expression at ulcer margin for vascular endothelial growth factor (VEGF)A, epidermal growth factor receptor (EGFr), cystathionine-γ-lyase (CSE), cystathionine-β-synthase (CBS), 3-mercaptopyruvate sulfurtransferase (3-MST), heme oxygenases (HOs), nuclear factor (erythroid-derived 2)-like 2 (Nrf-2), cyclooxygenase (COX)-2, inducible nitric oxide synthase (iNOS), IL-1β, TNF-α and hypoxia inducible factor (HIF)-1α were determined by real-time PCR or western blot. IL-1α, IL-1β, IL-2, IL-4, IL-5, IL-6, IL-10, IL-12, IL-13, IFN-γ, TNF-α, GM-CSF plasma concentration was assessed using Luminex platform. NaHS dose-dependently decreased ulcer area and increased GBF but ZnPP attenuated these effects. PAG decreased H₂S production but failed to affect CORM-2-mediated ulcer healing and vasodilation. NaHS increased Nrf-2, EGFr, VEGFA and decreased pro-inflammatory markers expression and IL-1β, IL-2, IL-13, TNF-α, GM-CSF plasma concentration. CORM-2 decreased IL-1β and GM-CSF plasma levels. We conclude that NaHS accelerates gastric ulcer healing increasing microcirculation and Nrf-2, EGFr, VEGFA expression. H₂S-mediated ulcer healing involves endogenous CO activity while CO does not require H₂S. NaHS decreases systemic inflammation more effectively than CORM-2.

Gaseous Mediators in Gastrointestinal Mucosal Defense and Injury

Of the numerous gaseous substances that can act as signaling molecules, the best characterized are nitric oxide, carbon monoxide and hydrogen sulfide. Contributions of each of these low molecular weight substances, alone or in combination, to maintenance of gastrointestinal mucosal integrity have been established. There is considerable overlap in the actions of these gases in modulating mucosal defense and responses to injury, and in some instances they act in a cooperative manner. Each also play important roles in regulating inflammatory and repair processes throughout the gastrointestinal tract. In recent years, significant progress has been made in the development of novel anti-inflammatory and cytoprotective drugs that exploit the beneficial activities of one or more of these gaseous mediators.

Carbon monoxide released from its pharmacological donor, tricarbonyldichlororuthenium (II) dimer, accelerates the healing of pre-existing gastric ulcers

BACKGROUND AND PURPOSE

Carbon monoxide (CO), a gaseous mediator produced by haem oxygenases (HOs), has been shown to prevent stress-, ethanol-, aspirin- and alendronate-induced gastric damage; however, its role in gastric ulcer healing has not been fully elucidated. We investigated whether CO released from tricarbonyldichlororuthenium (II) dimer (CORM-2) can affect gastric ulcer healing and determined the mechanisms involved in this healing action.

EXPERIMENTAL APPROACH

Gastric ulcers were induced in Wistar rats by serosal application of acetic acid. Animals received 9 days of treatment with RuCl₃ [2.5 mg·kg^-1 intragastrically (i.g.)], haemin (5 mg·kg^-1 i.g.), CORM-2 (0.1-10 mg·kg^-1 i.g.) administered alone or with zinc protoporphyrin IX (ZnPP, 10 mg·kg^-1 i.g.), 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ, 5 mg·kg^-1 i.g.), N^G -nitro-l-arginine (l-NNA, 15 mg·kg^-1 i.g.), indomethacin (5 mg·kg^-1 i.g.) or glibenclamide (10 mg·kg^-1 i.g.). Gastric ulcer area and gastric blood flow (GBF) were assessed planimetrically, microscopically and by laser flowmeter respectively. Gastric mRNA/protein expressions of EGF, EGF receptors, VEGFA, HOs, nuclear factor (erythroid-derived 2)-like 2 (Nrf2), COX-2, hypoxia-inducible factor (HIF)-1α and pro-inflammatory iNOS, IL-1β and TNF-α were determined by real-time PCR or Western blots.

KEY RESULTS

CORM-2 and haemin but not RuCl₃ or ZnPP decreased ulcer size while increasing GBF. These effects were reduced by ODQ, indomethacin, l-NNA and glibenclamide. CORM-2 significantly decreased the expression of pro-inflammatory markers, Nrf2/HO1 and HIF-1α, and up-regulated EGF.

CONCLUSIONS AND IMPLICATIONS

CO released from CORM-2 or endogenously produced by the HO1/Nrf2 pathway accelerates gastric ulcer healing via an increase in GBF, an up-regulation in EGF expression and down-regulation of the inflammatory response.

Arachidonic Acid Induces ARE/Nrf2-Dependent Heme Oxygenase-1 Transcription in Rat Brain Astrocytes

Arachidonic acid (AA) is a major product of phospholipid hydrolysis catalyzed by phospholipase A₂ during neurodegenerative diseases. AA exerts as a second messenger to regulate various signaling components which may be involved in different pathophysiological processes. Astrocytes are the main types of CNS resident cells which maintain and support the physiological function of brain. AA has been shown to induce ROS generation through activation of NADPH oxidases (Noxs) which may play a key role in the expression of heme oxygenase-1 (HO-1). Therefore, this study was designed to investigate the mechanisms underlying AA-induced HO-1 expression in rat brain astrocytes (RBA-1). We found that AA induced HO-1 protein and mRNA expression and promoter activity in RBA-1, which was mediated through the synthesis of 15-deoxy-Δ12,14-prostaglandin D₂-activated peroxisome proliferator-activated receptor-γ (PPARγ) receptors. This note was confirmed by transfection with PPARγ small interfering RNAs (siRNA) which attenuated the AA-mediated responses. AA-induced HO-1 expression was mediated through Nox/ROS generation, which was inhibited by Nox inhibitors (diphenyleneiodonium and apocynin) and ROS scavengers (N-acetyl cysteine). Moreover, AA-induced HO-1 expression was mediated through phosphorylation of Src, Pyk2, platelet-derived growth factor, PI3K/Akt, and ERK1/2 which were inhibited by the pharmacological inhibitors including PP1, PF431396, AG1296, LY294002, and U0126 or by transfection with respective siRNAs. AA-enhanced Nrf2 expression and HO-1 promoter activity was inhibited by transfection with Nrf2 siRNA or by these pharmacological inhibitors. Furthermore, chromatin immunoprecipitation assay confirmed that Nrf2 and PPARγ were associated with the proximal antioxidant response element (ARE)-binding site on HO-1 promoter, suggesting that Nrf2/PPARγ are key transcription factors modulating HO-1 expression. AA-induced ARE promoter activity was also reduced by these pharmacological inhibitors. These findings suggested that AA increases formation of Nrf2 and PPARγ complex and binding with ARE1 binding site through Src, Pyk2, PI3K/Akt, and ERK1/2, which further induced HO-1 expression in RBA-1 cells.

Ameliorative effects of pyrazinoic acid against oxidative and metabolic stress manifested in rats with dimethylhydrazine induced colonic carcinoma

Pyrazinoic acid (PA) is structurally similar to nicotinic acid which acts on G-protein-coupled receptor (GPR109A). GPR109A expresses in colonic and intestinal epithelial sites, and involves in DNA methylation and cellular apoptosis. Therefore, it may be assumed that PA has similar action like nicotinic acid and may be effective against colorectal carcinoma (CRC). CRC was produced via subcutaneous injection of dimethylhydrazine (DMH) at 40 mg/kg body weight once in a week for 4 weeks. After that, PA was administered orally at 2 doses of 10 and 25 mg/kg daily for 15 d to observe the antiproliferative effect. Various physiologic, oxidative stress, molecular parameters, histopathology, RT-PCR and NMR based metabolomics were performed to evaluate the antiproliferative potential of PA. Our results collectively suggested that PA reduced body weight, tumor volume and incidence no. to normal. It restored various oxidative stress parameters and normalized IL-2, IL-6, and COX-2 as compared with carcinogen control. In molecular level, overexpressed IL-6 and COX-2 genes became normal after PA administration. Again, normal tissue architecture was prominent after PA administration. Score plots of PLS-DA models exhibited that PA treated groups were significantly different from CRC group. We found that CRC rat sera have increased levels of acetate, glutamine, o-acetyl-glycoprotein, succinate, citrulline, choline, o-acetyl choline, tryptophan, glycerol, creatinine, lactate, citrate and decreased levels of 3-hydroxy butyrate, dimethyl amine, glucose, maltose, myoinositol. Further the PA therapy has ameliorated the CRC-induced metabolic alterations, signifying its antiproliferative properties. In conclusion, our study provided the evidence that PA demonstrated good antiproliferative effect on DMH induced CRC and thus demonstrated the potential of PA as a useful drug for future anticancer therapy.

Biological signaling by carbon monoxide and carbon monoxide-releasing molecules

Carbon monoxide (CO) is continuously produced in mammalian cells during the degradation of heme. It is a stable gaseous molecule that reacts selectively with transition metals in a specific redox state, and these characteristics restrict the interaction of CO with defined biological targets that transduce its signaling activity. Because of the high affinity of CO for ferrous heme, these targets can be grouped into heme-containing proteins, representing a large variety of sensors and enzymes with a series of diverse function in the cell and the organism. Despite this notion, progress in identifying which of these targets are selective for CO has been slow and even the significance of elevated carbonmonoxy hemoglobin, a classical marker used to diagnose CO poisoning, is not well understood. This is also due to the lack of technologies capable of assessing in a comprehensive fashion the distribution and local levels of CO between the blood circulation, the tissue, and the mitochondria, one of the cellular compartments where CO exerts its signaling or detrimental effects. Nevertheless, the use of CO gas and CO-releasing molecules as pharmacological approaches in models of disease has provided new important information about the signaling properties of CO. In this review we will analyze the most salient effects of CO in biology and discuss how the binding of CO with key ferrous hemoproteins serves as a posttranslational modification that regulates important processes as diverse as aerobic metabolism, oxidative stress, and mitochondrial bioenergetics.

Exogenous and Endogenous Hydrogen Sulfide Protects Gastric Mucosa against the Formation and Time-Dependent Development of Ischemia/Reperfusion-Induced Acute Lesions Progressing into Deeper Ulcerations

Hydrogen sulfide (H₂S) is an endogenous mediator, synthesized from l-cysteine by cystathionine γ-lyase (CSE), cystathionine β-synthase (CBS) or 3-mercaptopyruvate sulfurtransferase (3-MST). The mechanism(s) involved in H₂S-gastroprotection against ischemia/reperfusion (I/R) lesions and their time-dependent progression into deeper gastric ulcerations have been little studied. We determined the effect of l-cysteine, H₂S-releasing NaHS or slow H₂S releasing compound GYY4137 on gastric blood flow (GBF) and gastric lesions induced by 30 min of I followed by 3, 6, 24 and 48 h of R. Role of endogenous prostaglandins (PGs), afferent sensory nerves releasing calcitonin gene-related peptide (CGRP), the gastric expression of hypoxia inducible factor (HIF)-1α and anti-oxidative enzymes were examined. Rats with or without capsaicin deactivation of sensory nerves were pretreated i.g. with vehicle, NaHS (18–180 μmol/kg) GYY4137 (90 μmol/kg) or l-cysteine (0.8–80 μmol/kg) alone or in combination with (1) indomethacin (14 μmol/kg i.p.), SC-560 (14 μmol/kg), celecoxib (26 μmol/kg); (2) capsazepine (13 μmol/kg i.p.); and (3) CGRP (2.5 nmol/kg i.p.). The area of I/R-induced gastric lesions and GBF were measured by planimetry and H₂-gas clearance, respectively. Expression of mRNA for CSE, CBS, 3-MST, HIF-1α, glutathione peroxidase (GPx)-1, superoxide dismutase (SOD)-2 and sulfide production in gastric mucosa compromised by I/R were determined by real-time PCR and methylene blue method, respectively. NaHS and l-cysteine dose-dependently attenuated I/R-induced lesions while increasing the GBF, similarly to GYY4137 (90 μmol/kg). Capsaicin denervation and capsazepine but not COX-1 and COX-2 inhibitors reduced NaHS- and l-cysteine-induced protection and hyperemia. NaHS increased mRNA expression for SOD-2 and GPx-1 but not that for HIF-1α. NaHS which increased gastric mucosal sulfide release, prevented further progression of acute I/R injury into deeper gastric ulcers at 6, 24 and 48 h of R. We conclude that H₂S-induced gastroprotection against I/R-injury is due to increase in gastric microcirculation, anti-oxidative properties and afferent sensory nerves activity but independent on endogenous prostaglandins.

Interaction between endogenous carbon monoxide and hydrogen sulfide in the mechanism of gastroprotection against acute aspirin-induced gastric damage

Acetylsalicylic acid (ASA) is mainly recognized as painkiller or anti-inflammatory drug. However, ASA causes serious side effects towards gastrointestinal (GI) tract which limits its usefulness. Carbon monoxide (CO) and hydrogen sulfide (H₂S) have been described to act as important endogenous messengers and mediators of gastroprotection but whether they can interact in gastroprotection against acute ASA-induced gastric damage remains unknown. In this study male Wistar rats were pretreated with 1) vehicle (saline, i.g.), 2) tricarbonyldichlororuthenium (II) dimer (CORM-2, 5mg/kg i.g.), 3) sodium hydrosulfide (NaHS, 5mg/kg i.g.), 4) zinc protoporphyrin (ZnPP, 10mg/kg i.p.), 5) D,L-propargylglycine (PAG, 30mg/kg i.g.), 6) ZnPP combined with NaHS, 7) PAG combined with CORM-2 or 8) 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ, 10mg/kg i.p.) combined with CORM-2 or NaHS and 30min later ASA was administered i.g. in a single dose of 125mg/kg. After 1h, gastric blood flow (GBF) was determined by H₂ gas clearance technique and gastric lesions were assessed by planimetry and histology. CO content in gastric mucosa and COHb concentration in blood were determined by gas chromatography and H₂S production was assessed in gastric mucosa using methylene blue method. Protein and/or mRNA expression for cystathionine-γ-lyase (CSE), cystathionine-β-synthase (CBS), 3-mercaptopyruvate sulfurtransferase (3-MST), heme oxygenase (HO)-1, HO-2, hypoxia inducible factor-alpha (HIF)-1α, nuclear factor (erythroid-derived 2)-like 2 (Nrf-2), cyclooxygenase (COX)-1 and COX-2, inducible nitric oxide synthase (iNOS) and interleukin (IL)-1β were determined by Western blot or real-time PCR, respectively. ASA caused hemorrhagic gastric mucosal damage and significantly decreased GBF, H₂S production, CO content, mRNA or protein expression for CSE, 3-MST, HO-2 and increased mRNA and/or protein expression for CBS, HO-1, Nrf-2, HIF-1α, iNOS, IL-1β, COX-2 in gastric mucosa and COHb concentration in blood. Pretreatment with CORM-2 or NaHS but not with PAG decreased ASA-damage and increased GBF. ZnPP reversed protective and hyperemic effect of NaHS but PAG failed to affect CORM-2-induced gastroprotection. CORM-2 elevated CO content, mRNA or protein expression for HO-1, Nrf-2, and decreased expression of CBS, HIF-1α, COX-2, IL-1β, iNOS, the H₂S production in gastric mucosa and COHb concentration in blood. NaHS raised mRNA or protein expression for CSE, COX-1 and decreased mRNA expression for IL-1β and COHb level in blood. We conclude that CO is involved in gastroprotection induced by H₂S while beneficial protective action of CO released from CORM-2 in gastric mucosa seems to be H₂S-independent. In contrast to H₂S, CO ameliorates hypoxia, regulates Nrf-2 expression but similarly to H₂S acts on sGC-dependent manner to restore gastric microcirculation and exhibit anti-inflammatory activity in gastric mucosa compromised by ASA.

Prevention of colitis by controlled oral drug delivery of carbon monoxide

Carbon monoxide (CO) is an endogenous signal transmitter involved in numerous physiological processes including the gastrointestinal (GI) homeostasis. CO has been recognized as potential new therapeutic agent for motility related and inflammatory disorders of the GI tract. A therapeutic use, however, is challenged by inappropriate drug delivery modes. Here we describe a micro scale Oral Carbon Monoxide Release System (M-OCORS) designed for localized and controlled exposure of the GI tract with in situ generated CO. M-OCORS allowed for controlled release profiles lasting for several minutes or up to almost one day. These in vitro release profiles translated into a large pharmacokinetic design space following oral administration in mice and measured as CO-hemoglobin (CO-Hb) formation. M-OCORS with a release profile featuring exposure of the intestine was profiled in two independently performed studies demonstrating preventive effects in chemically induced colitis. M-OCORS significantly reduced damage scores and prevented upregulation of colitis biomarkers.

The Protective Role of Carbon Monoxide (CO) Produced by Heme Oxygenases and Derived from the CO-Releasing Molecule CORM-2 in the Pathogenesis of Stress-Induced Gastric Lesions: Evidence for Non-Involvement of Nitric Oxide (NO)

Carbon monoxide (CO) produced by heme oxygenase (HO)-1 and HO-2 or released from the CO-donor, tricarbonyldichlororuthenium (II) dimer (CORM-2) causes vasodilation, with unknown efficacy against stress-induced gastric lesions. We studied whether pretreatment with CORM-2 (0.1-10 mg/kg oral gavage (i.g.)), RuCl₃ (1 mg/kg i.g.), zinc protoporphyrin IX (ZnPP) (10 mg/kg intraperitoneally (i.p.)), hemin (1-10 mg/kg i.g.) and CORM-2 (1 mg/kg i.g.) combined with N(G)-nitro-l-arginine (l-NNA, 20 mg/kg i.p.), 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ, 10 mg/kg i.p.), indomethacin (5 mg/kg i.p.), SC-560 (5 mg/kg i.g.), and celecoxib (10 mg/kg i.g.) affects gastric lesions following 3.5 h of water immersion and restraint stress (WRS). Gastric blood flow (GBF), the number of gastric lesions and gastric CO and nitric oxide (NO) contents, blood carboxyhemoglobin (COHb) level and the gastric expression of HO-1, HO-2, hypoxia inducible factor 1α (HIF-1α), tumor necrosis factor α (TNF-α), cyclooxygenase (COX)-2 and inducible NO synthase (iNOS) were determined. CORM-2 (1 mg/kg i.g.) and hemin (10 mg/kg i.g.) significantly decreased WRS lesions while increasing GBF, however, RuCl₃ was ineffective. The impact of CORM-2 was reversed by ZnPP, ODQ, indomethacin, SC-560 and celecoxib, but not by l-NNA. CORM-2 decreased NO and increased HO-1 expression and CO and COHb content, downregulated HIF-1α, as well as WRS-elevated COX-2 and iNOS mRNAs. Gastroprotection by CORM-2 and HO depends upon CO's hyperemic and anti-inflammatory properties, but is independent of NO.

Hydrogen Sulfide and Carbon Monoxide Protect Gastric Mucosa Compromised by Mild Stress Against Alendronate Injury

BACKGROUND

Alendronate is an inhibitor of osteoclast-mediated bone resorption, but its clinical utility is limited due to gastrointestinal complications including bleeding erosions.

AIMS

We studied whether potent vasodilators hydrogen sulfide (H₂S) and carbon monoxide (CO) can protect against alendronate-induced gastric lesions in rats exposed to mild stress.

METHODS

Three series (A, B, and C) of Wistar rats received alendronate (150-700 mg/kg i.g., series A) with or without NaHS (5 mg/kg), H₂S donor or CORM-2 (5 mg/kg) releasing CO administered i.g. 30 min before alendronate administration (series B) in rats exposed for 3 days before alendronate administration to mild stress (series C). The area of gastric lesions was assessed by planimetry, the gastric blood flow (GBF) was determined by H₂-gas clearance technique, and H₂S production via CSE/CBS/3-MST activity and the gastric expression of HO-1, HO-2, HIF-1α, NF-κB, iNOS, COX-2, IL-1β, TNF-α, GPx-1 and SOD-2 were analyzed by qPCR or Western blot.

RESULTS

Alendronate dose-dependently produced gastric mucosal lesions and significantly decreased GBF, and these effects were exacerbated by mild stress. NaHS and CORM-2 significantly reduced the alendronate-induced gastric lesions in non-stressed and stressed animals, but only NaHS but not CORM-2 raised H₂S production. NaHS and CORM-2 inhibited gastric expression of HIF-1α protein and HO-1, HIF-1α, NF-κB, COX-2, iNOS, IL-1β, TNF-α mRNAs but failed to affect those of HO-2, GPx-1, and SOD-2.

CONCLUSION

Both H₂S and CO released from their donors, NaHS and CORM-2, protect gastric mucosa compromised by stress against alendronate-induced gastric damage via mechanism involving downregulation of HIF-1α, NF-κB and proinflammatory factors COX-2, iNOS, IL-1β, and TNF-α.