Regulatory mechanism of acid secretion in the damaged stomach: role of endogenous nitric oxide

Gastroprotective and Antioxidant Activity of Kalanchoe brasiliensis and Kalanchoe pinnata Leaf Juices against Indomethacin and Ethanol-Induced Gastric Lesions in Rats

Kalanchoe brasiliensis and Kalanchoe pinnata are used interchangeably in traditional medicine for treating peptic ulcers and inflammatory problems. In this context, this study aims to characterize the chemical constituents and evaluate the gastroprotective activity of the leaf juices of the two species in acute gastric lesions models. Thin Layer Chromatography (TLC) and Ultra High Performance Liquid Chromatography coupled to Mass Spectrometer (UHPLC-MS) were performed for chemical characterization. Wistar rats were pre-treated orally with leaf juices (125, 250 and 500 mg/kg) or ranitidine (50 mg/kg). The peaks observed in the chromatogram of K. brasiliensis showed similar mass spectra to flavonoid glycosides derived from patuletin and eupafolin, while K. pinnata showed mass spectra similar to compounds derived from quercetin, patuletin, eupafolin and kaempferol. K. brasiliensis at all doses and K. pinnata at doses of 250 mg/kg and 500 mg/kg significantly reduced the lesions in the ethanol induction model. In the indomethacin induction model, both species showed significant results at doses of 250 and 500 mg/kg. Also, the pre-treatment with leaf juices increased the antioxidant defense system, glutathione (GSH), whereas malondialdehyde (MDA), myeloperoxidase (MPO), interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α) levels were significantly decreased. Treatment with leaf juices led to the upregulation of zone occludes-1 (ZO-1) and the downregulation of inducible nitric oxide synthase (iNOS) and factor nuclear-κβ transcription (NF-κB-p65), while also showing a cytoprotective effect and maintaining mucus production. These findings show that the leaf juices of the two species showed gastroprotective effects on ethanol and gastric indomethacin injury which were a consequence of gastric inflammation suppression, antioxidant activity and the maintenance of cytoprotective defenses and mucosal structure architecture.

Capsaicin and gastric ulcers

In recent years, infection of the stomach with the organism Helicobacter Pylori has been found to be the main cause of gastric ulcers, one of the common ailments afflicting humans. Excessive acid secretion in the stomach, reduction in gastric mucosal blood flow, constant intake of non-steroid anti-inflammatory drugs (NSAIDS), ethanol, smoking, stress etc. are also considered responsible for ulcer formation. The prevalent notion among sections of population in this country and perhaps in others is that "red pepper" popularly known as "Chilli," a common spice consumed in excessive amounts leads to "gastric ulcers" in view of its irritant and likely acid secreting nature. Persons with ulcers are advised either to limit or avoid its use. However, investigations carried out in recent years have revealed that chilli or its active principle "capsaicin" is not the cause for ulcer formation but a "benefactor." Capsaicin does not stimulate but inhibits acid secretion, stimulates alkali, mucus secretions and particularly gastric mucosal blood flow which help in prevention and healing of ulcers. Capsaicin acts by stimulating afferent neurons in the stomach and signals for protection against injury causing agents. Epidemiologic surveys in Singapore have shown that gastric ulcers are three times more common in the "Chinese" than among Malaysians and Indians who are in the habit of consuming more chillis. Ulcers are common among people who are in the habit of taking NSAIDS and are infected with the organism "Helicobacter Pylori," responsible for excessive acid secretion and erosion of the mucosal layer. Eradication of the bacteria by antibiotic treatment and avoiding the NSAIDS eliminates ulcers and restores normal acid secretion.

Mucosal acid challenge activates nitrergic neurons in myenteric plexus of rat stomach

We tested the hypothesis that intrinsic neurons of the rat gastric myenteric plexus can be activated by an acid (HCl) challenge of the mucosa. Activated neurons were visualized by immunohistochemical detection of c-Fos, a marker for neuronal excitation. The neurochemical identity of the neurons activated by the HCl challenge was determined by colocalizing c-Fos with a marker for excitatory pathways, choline acetyltransferase (ChAT), and a marker for inhibitory pathways, nitric oxide synthase (NOS). Two hours after intragastric administration of HCl or saline, stomachs were removed and immunofluorescence triple labeling of myenteric neurons was carried out on whole mount preparations. Treatment with 0.35, 0.5, and 0.7 M HCl induced c-Fos in 8%, 56%, and 64%, respectively, of NOS-positive but not ChAT-positive neurons. c-Fos was also seen in glial cells of HCl-treated rats, whereas in saline-treated animals c-Fos was absent from the myenteric plexus. HCl treatment did not change the proportion of ChAT- and NOS-immunoreactive neurons in the myenteric ganglia. It is concluded that gastric acid challenge concentration-dependently stimulates a subpopulation of nitrergic, but not cholinergic, myenteric plexus neurons, which may play a role in muscle relaxation, vasodilatation, and/or secretion.

Gastroduodenal mucosal defense

The gastroduodenal mucosa is a model system of defense with several structural levels and biologic strategies that are closely interrelated with each other to cope with the harmful ingredients of ingested food and the potentially deleterious effects of gastric acid and pepsin. Experimental and clinical research carried out during the review period added to the understanding of each component of the multiple mechanisms of gastroduodenal mucosal protection. In the first place, mucosal integrity is defended by the mucus gel barrier, the epithelial cell barrier, and the immune barrier. The properties of these barriers are maintained by adequate regulation of mucus production, bicarbonate secretion, mucosal microcirculation, and motor activity. These regulatory systems are alarmed by nociceptive neurons and the mucosal immune system which includes chemokine-secreting epithelial cells. The ultimate defense system is rapid repair of the injured mucosa under the control of several growth factors. Progressing insight into the network of mucosal defense not only will improve existing therapies of inflammation and ulceration but also will provide new leads for the management of functional diseases in the gastroduodenal region.