Gastroduodenal mucosal defense: an integrated protective response

Essential Oils: Chemistry and Pharmacological Activities-Part II

The importance of essential oils and their components in the industrial sector is attributed to their chemical characteristics and their application in the development of products in the areas of cosmetology, food, and pharmaceuticals. However, the pharmacological properties of this class of natural products have been extensively investigated and indicate their applicability for obtaining new drugs. Therefore, this review discusses the use of these oils as starting materials to synthesize more complex molecules and products with greater commercial value and clinic potential. Furthermore, the antiulcer, cardiovascular, and antidiabetic mechanisms of action are discussed. The main mechanistic aspects of the chemopreventive properties of oils against cancer are also presented. The data highlight essential oils and their derivatives as a strategic chemical group in the search for effective therapeutic agents against various diseases.

Total triterpenoids from the fruits of Chaenomeles speciosa exerted gastroprotective activities on indomethacin-induced gastric damage via modulating microRNA-423-5p-mediated TFF/NAG-1 and apoptotic pathways

Our previous studies have demonstrated that the total triterpenes from the fruits of Chaenomeles speciosa (CSTT) exhibit effective therapeutic effects on gastric ulcer patients and animals. The present aim is to further investigate the mechanisms involved. The results indicated that CSTT could ameliorate IND-induced gastric injury, which was related to promoting IND-damaged GES-1 cell proliferation and migration, improving the IND-damaged rat GBF, ulcer area, inhibition rate and pathologic changes of gastric mucous tissue, increasing the amount of adhered gastric mucus, attenuating the volume and total acidity of the gastric effluents, and augmenting the gastric pH; further studies showed that CSTT obviously downregulated miR-423-5p mRNA, NAG-1 mRNA and protein expression, Bax, Bad, cytosol cytochrome C, Apaf-1, cleaved-caspase-3, and cleaved-caspase-9 protein expression and cytosol cytochrome C concentration, and upregulated TFF1, TFF2 and TFF3 mRNA and protein expression, Bcl-2, Bcl-xl, pro-caspase-3, and pro-caspase-9 protein expression, mitochondrial viability, mitochondrial cytochrome C concentration and Bcl-2/Bax, Bcl-xl/Bad ratios. These findings demonstrated that CSTT protected against IND-induced gastric damage by depressing miR-423-5p expression and modulating the TFF/NAG-1 pathway, which in turn restrained mitochondrion-mediated apoptosis.

Anti-ulcer and anti-Helicobacter pylori potentials of the ethyl acetate fraction of Physalis alkekengi L. var. franchetii (Solanaceae) in rodent

ETHNOPHARMACOLOGICAL RELEVANCE

Physalis alkekengi L. var. franchetii (Solanaceae) has been widely used in Chinese folk medicine due to its wide distribution throughout the country, for the treatment of a wide range of diseases including heat and cold, sore throat, fever, fungal infection, inflammation, toothache, rheumatism, burn, analgesic, ulcer and urinary diseases. However, the effect of P. alkekengi var. franchetii on ulcer and Helicobacter pylori infection has not been reported to date.

AIM OF THE STUDY

This study was designed to investigate the anti-inflammatory, anti-ulcer, anti-Helicobacter pylori and analgesic properties of ethyl acetate fraction of the crude aqueous methanolic extract from the aerial parts of the plant P. alkekengi L. var. franchetii in rodents.

MATERIALS AND METHODS

Acute toxicity of the crude extract of P. alkekengi L. var. franchetii (PAF) was evaluated in rats. The petroleum ether fraction (PEF), butanol fraction (BF), ethyl acetate fraction (EAF) and aqueous fraction (AF) of crude aqueous methanolic extract from PAF were screened for anti-inflammatory and anti-ulcer potential at doses of 100, 250 and 500mg/kg (p.o.), using carrageenin-induced hind paw edema and ethanol-induced gastric lesions test in rats. In vitro anti-Helicobacter pylori activity of EAF was assayed subsequently. In addition, three doses of EAF were evaluated for analgesic activity using hot plate and writhing tests, respectively. Finally, we performed a phytochemical analysis of EAF.

RESULTS

Four fractions of crude extract from PAF significantly reduced the paw volume in carrageenin-induced hind paw edema model at different doses (100, 250 and 500mg/kg, p.o.). The fraction EAF at a dose of 500mg/kg exhibited the highest (75.92%) (0.150 ± 0.045***, ***p < 0.001) anti-inflammatory potential, which is similar to indomethacin (***P < 0.001)（0.120 ± 0.014***, 80.74% inhibition of inflammation） at 5mg/kg. Pretreatment with EAF (500mg/kg, p.o.) significantly reduced the intensity of gastric mucosal damage and showed higher gastroprotective activity (90.6%) when compared to the standard drug famotidine (84.6%). In addition, EAF fraction also showed a moderate (P < 0.05) anti-Helicobacter pylori activity with a minimal inhibition concentration (MIC) of 500μg/ml. Furthermore, pain sensation was effectively inhibited at 500mg/kg, p.o. of EAF as manifested by an increase (p < 0.001) of latency time in hot plate from 30 to 90min and a decrease (p < 0.001) in count of writhing induced by acetic acid. By HPLC, we determined some steroid, terpenoid and flavonoids (four compounds): kaempferol, quercetin, Blumenol A and physalindicanols A, which were isolated from the ethyl acetate fraction and identified using ¹H NMR and ¹³C NMR spectra analysis.

CONCLUSION

This study demonstrated the anti-inflammatory, anti-ulcer, anti-Helicobacter pylori and analgesic properties of EAF of the crude extract from PAF thus justifying its traditional usage.

Protective Factors of the Gastric and Duodenal Mucosa: An Overview

The structural and functional integrity of the gastric and duodenal mucosa represents equilibrium between aggressive factors and protective mechanisms. Mucus-buffers-phospholipid layer as pre-epithelial barrier, enhanced by prostaglandins and epidermal growth factor, remains a vanguard of mucosal protection. It maintains a neutral pH at the surface epithelial luminal interface, facing luminal pH dropping to 1.0, i.e., hydrogen ion concentration gradient equal 1,000,000. The surface epithelial cells, elaborating mucins, buffers, phospholipids, prostaglandins, trefoil peptides, peptide growth factor and their receptors, heat shock proteins, cathelicidins, and β-defensins form the second line of defense. Endothelium exerts mucosal protection through production of potent vasodilators like nitric oxide and prostacyclins and through release of angiogenic growth factors, securing adequate blood flow and representing the third and an ultimate line of mucosal protection. This microcirculation is instrumental for supply of oxygen, nitric oxide, hydrogen sulfide and removal of ad hoc generated toxic substances as well as for continuous mucosal cell renewal from progenitor cells, secured by growth factors accompanied by survivin preventing early apoptosis.

Gastro protective properties of the novel prostone SPI-8811 against acid-injured porcine mucosa

AIM: To evaluate the protective properties of novel prostone ClC-2 agonist SPI-8811 in porcine model of gastric acid injury.

METHODS: Porcine gastric mucosa was mounted in Ussing chambers and injured by bathing mucosal tissues in an HCl Ringer’s solution (pH = 1.5) with or without SP1-8811 (1 μmol/L), cystic fibrosis transmembrane conductance regulator (CFTR) inhibitor (inhibitor 172, 10 μmol/L, apical) and ClC-2 inhibitor ZnCl₂, 300 μmol/L, apical), on the apical surface of tissues. Transepithelial resistance and mucosal-to-serosal ³H-mannitol fluxes were measured over a 90-min period. Tissues were analyzed by morph metric techniques, Immunofluorescence and by western blots.

RESULTS: Compared with control tissues, acid exposure decreased transepithelial electrical resistance (TER) and increased ³H-mannitol flux. Pretreatment of gastric mucosa with SPI-8811 was protective against acid-induced decreases in TER (TER, 50 Ω.cm²vs 100 Ω.cm²) and abolished increases in flux (³H-mannitol flux, 0.10 μmol/L.cm²vs 0.04 μmol/L.cm²). Evidence of histological damage in the presence of acid was markedly attenuated by SPI-0811. Immunofluorescence and western analysis for occludin revealed enhanced localization to the region of the tight junction (TJ) after treatment with SPI-8811. Pretreatment with the ClC-2 inhibitor ZnCl₂, but not the selective CFTR inhibitor 172, attenuated SPI-8811-mediated mucosal protection, suggesting a role for ClC-2. Prostone may serve both protective and reparative roles in injured tissues.

CONCLUSION: ClC-2 agonist SPI-8811 stimulated enhancement of mucosal barrier function by protecting TJ protein occludin in porcine gastric mucosa and thus protected the gastric acid injury in porcine stomach.

Gastroprotective activity of the hydroalcoholic extract obtained from Polygala paniculate L. in rats

The possible gastroprotective effects of the hydroalcoholic extract of Polygala paniculata in rats have been evaluated. We have investigated the effects of this hydroalcoholic extract on acute lesions induced by ethanol (70%, p.o.) and indometacin (20 mg kg−1, s.c). Its influence on mucus secretion was investigated, measured as the amount of Alcian blue dye estimated by colorimetry, and antisecretory effects were assessed in the pylorus ligature model. The treatment of rats with a crude hydroalcoholic extract of P. paniculata (HEPP; 30, 100, 300 mg kg−1, p.o., or 3, 10 and 30 mg kg−1, i.p.) decreased the ulcer index, and maintained the gastric mucus production in acute gastric lesions caused by ethanol 70%. In addition, the extract partially protected the mucosa against indometacin-induced lesions. The extract did not change the volume and acidity of gastric secretion in the pylorus-ligated rat. An additional antioxidant activity of the extract and its isolated flavonoid compound rutin, in the DPPH free radical scavenging assay, was observed. In conclusion, HEPP exhibited marked gastroprotection; these effects may have involved prostaglandins and be related to cytoprotective factors, such as antioxidant activity and maintenance of mucus production.

Molecular defense mechanisms of Barrett's metaplasia estimated by an integrative genomics

Barrett's esophagus is characterized by the replacement of squamous epithelium with specialized intestinal metaplastic mucosa. The exact mechanisms of initiation and development of Barrett's metaplasia remain unknown, but a hypothesis of "successful adaptation" against noxious reflux components has been proposed. To search for the repertoire of adaptation mechanisms of Barrett's metaplasia, we employed high-throughput functional genomic and proteomic methods that defined the molecular background of metaplastic mucosa resistance to reflux. Transcriptional profiling was established for 23 pairs of esophageal squamous epithelium and Barrett's metaplasia tissue samples using Affymetrix U133A 2.0 GeneChips and validated by quantitative real-time polymerase chain reaction. Differences in protein composition were assessed by electrophoretic and mass-spectrometry-based methods. Among 2,822 genes differentially expressed between Barrett's metaplasia and squamous epithelium, we observed significantly overexpressed metaplastic mucosa genes that encode cytokines and growth factors, constituents of extracellular matrix, basement membrane and tight junctions, and proteins involved in prostaglandin and phosphoinositol metabolism, nitric oxide production, and bioenergetics. Their expression likely reflects defense and repair responses of metaplastic mucosa, whereas overexpression of genes encoding heat shock proteins and several protein kinases in squamous epithelium may reflect lower resistance of normal esophageal epithelium than Barrett's metaplasia to reflux components. Despite the methodological and interpretative difficulties in data analyses discussed in this paper, our studies confirm that Barrett's metaplasia may be regarded as a specific microevolution allowing for accumulation of mucosal morphological and physiological changes that better protect against reflux injury.

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Gastroduodenal mucosal defense: role of endogenous mediators

PURPOSE OF REVIEW

The remarkable resistance of the mucosal lining of the upper gastrointestinal tract to concentrated gastric acid remains one of the biggest unsolved mysteries of upper gastrointestinal physiology. In the past year, there have been prominent findings regarding prostaglandin subtypes, growth factors, proteinase-activated receptors, peroxisome proliferator-activated receptors, and nitric oxide releasing nonsteroidal antiinflammatory agents.

RECENT FINDINGS

The prostaglandin I receptor subtype is involved with the mucosal acid-sensing neural circuit termed the capsaicin pathway. Proteinase-activated receptors and peroxisome proliferator activated receptor-gamma are important components of host defense against acid injury. Nitric oxide releasing nonsteroidal antiinflammatory agents have potential usefulness in subjects with mucosal injury related to the use of nonsteroidal antiinflammatory agents and may be an important alternative to selective cyclooxygenase-2 inhibitors for patients who need aspirin cotherapy for the prevention of arterial thrombus formation.

SUMMARY

Peptic ulcer disease, although declining in prevalence, appears to be increasing in virulence, perhaps because of the overall aging of the population and improved care in the intensive care unit. Although Helicobacter pylori and nonsteroidal antiinflammatory agents have been identified as key pro-ulcerogenic factors, many ulcers may also result from a deficiency of other, unknown host protective factors. A more detailed understanding of the host factors involved in mucosal protection will thus help identify novel therapeutic targets aimed at the prevention and treatment of upper gastrointestinal tract mucosal injury.