Osteoprotegerin production by human intestinal epithelial cells: a potential regulator of mucosal immune responses

Peptic ulcer disease, commonly called PUD, represents a multifaceted condition characterized by disruptions in the lining of the gastrointestinal (GI)  tract. Central to the protection of the gastrointestinal lining is the mucosal-bicarbonate barrier. This physiological defense mechanism is a formidable shield against the corrosive effects of gastric acid and pepsin secretion in the stomach. Its role is pivotal in maintaining the structural integrity of the stomach's inner lining. Bicarbonate,...

The gastric glands contain parietal cells that secrete hydrochloric acid (HCl) for digestion. The cells secrete HCl because it is highly corrosive and essential for breaking down food. To achieve this, they secrete hydrogen and chloride ions into the lumen of the gastric glands, which combine to form HCl.
Within parietal cells, carbonic acid is first formed through the reaction of water and carbon dioxide. The dissociation of carbonic acid releases bicarbonate and hydrogen ions. The bicarbonate...

The intestinal epithelial lining rapidly renews every 4 to 5 days. The renewal is facilitated by intestinal stem cells (ISCs) located at the base of the crypt– a gland located at the bottom of each villus. ISCs divide asymmetrically to form new stem cells and progenitor daughter cells. The daughter cells are called transit-amplifying (TA) cells which move upwards along the crypt and either differentiate into absorptive cells– the enterocytes or secretory cells– including the goblet,...

Notch signaling was first discovered in Drosophila melanogaster, where it is involved in cell lineage differentiation. Notch signaling regulates the maintenance and differentiation of intestinal stem cells or ISCs by controlling the expression of atonal homolog 1 or Atoh1. Atoh1 directs cells to differentiate into secretory cells.
Direct cell-to-cell contact is needed for the activation of Notch signaling. The signal is initiated when a notch ligand binds to a receptor on an adjacent cell, also...

The gastric mucosa produces prostaglandins E2 (PGE2) and prostacyclin (PGI2), crucial in maintaining gastric health. They exert cytoprotective effects, including increasing bicarbonate secretion, releasing protective mucin, reducing gastric acid output, and preventing harmful vasoconstriction. These effects are mediated through various receptors, such as EP1, EP2, EP3, and EP4.
Non-steroidal anti-inflammatory drugs (NSAIDs) can induce peptic ulcers by inhibiting cyclooxygenase, decreasing...

The skin and mucous membranes serve as the primary line of defense against pathogens by providing both physical and chemical protection. These barriers are essential in preventing the entry and establishment of microbes, thereby maintaining the integrity of the host.
The outer layer of the skin, the epidermis, is a robust barrier comprising layers of closely packed keratinized cells. This dense arrangement prevents microbes from penetrating the body. The periodic shedding of epidermal cells...