Alcohol, pancreatic muscarinic receptors and acute pancreatitis

Multiple roles for cholinergic signaling in pancreatic diseases

Cholinergic nerves are widely distributed throughout the human body and participate in various physiological activities, including sensory, motor, and visceral activities, through cholinergic signaling. Cholinergic signaling plays an important role in pancreatic exocrine secretion. A large number of studies have found that cholinergic signaling overstimulates pancreatic acinar cells through muscarinic receptors, participates in the onset of pancreatic diseases such as acute pancreatitis and chronic pancreatitis, and can also inhibit the progression of pancreatic cancer. However, cholinergic signaling plays a role in reducing pain and inflammation through nicotinic receptors, but enhances the proliferation and invasion of pancreatic tumor cells. This review focuses on the progression of cholinergic signaling and pancreatic diseases in recent years and reveals the role of cholinergic signaling in pancreatic diseases.

Pain in chronic pancreatitis: a salutogenic mechanism or a maladaptive brain response?

Pain in chronic pancreatitis is frequently refractory to medical and even surgical treatment. This refractoriness leads us to believe that a pancreas-independent, brain-mediated mechanism must be responsible. If so, several scenarios are worth considering. First, chronic pain could be the consequence of undesirable neuroplastic changes, by which pathology becomes established and causes disability. Alternatively, pain may be linked to the salutogenic (from salutogenesis, the Latin word for health and well-being) central nervous system response (we defined 'salutogenic response' as the specific modulation of the immune system induced by brain activity changes) to promote healing of the injured viscera. If so, chronic pain could index the ongoing nervous system attempt to promote healing. In this review, we discuss (1) the mechanisms of pain in chronic pancreatitis; (2) potential brain-related salutogenic mechanisms, and (3) the potential relationship of these two factors to the disease status. Furthermore, we consider these aspects in light of a new approach to treat visceral pain: transcranial magnetic stimulation, a noninvasive method of brain stimulation.

Is an elevated concentration of acinar cytosolic free ionised calcium the trigger for acute pancreatitis?

The pathogenesis of acute pancreatitis is poorly understood, despite well-recognised precipitating factors. Current evidence suggests that the earliest abnormalities of acute pancreatitis arise within acinar cells, but the key intracellular trigger has yet to be identified. Within the pancreas, physiological concentrations of secretagogues bind to G-protein-linked cell-surface receptors on acinar cells, evoking short, oscillatory spikes of acinar cytosolic-free ionised calcium ([Ca2+]i), an ubiquitous intracellular messenger. Specific effects within acinar cells include initiation of enzyme release through the phosphorylation cascades of stimulus-secretion coupling. Low resting levels of [Ca2+]i are restored by Ca(2+)-ATPase, which pumps calcium into the endoplasmic reticulum and out of the cell. If high concentrations of [Ca2+]i persist, toxicity results, intracellular signalling is disrupted, and cell damage occurs. Sustained elevations in acinar [Ca2+]i result from exposure to high concentrations of secretagogues, high doses of which also induce acute pancreatitis. Similarly, sustained elevations of [Ca2+]i may result from ductal hypertension, alcohol, hypoxia, hypercalcaemia, hyperlipidaemia, viral infection, and various drugs--all factors known to precipitate acute pancreatitis. We suggest that these factors precipitate acute pancreatitis by causing either excessive release of acinar [Ca2+]i, or damage to the integrity of mechanisms that restore low resting levels of [Ca2+]i, and that the consequent calcium toxicity is the key trigger in the pathogenesis of acute pancreatitis.