The lysine derivative aminoadipic acid, a biomarker of protein oxidation and diabetes-risk, induces production of reactive oxygen species and impairs trypsin secretion in mouse pancreatic acinar cells.

We have examined the effects of α-aminoadipic acid, an oxidized derivative from the amino acid lysine, on the physiology of mouse pancreatic acinar cells. Changes in intracellular free-Ca2+ concentration, the generation of reactive oxygen species, the levels of carbonyls and thiobarbituric-reactive substances, cellular metabolic activity and trypsin secretion were studied. Stimulation of mouse pancreatic cells with cholecystokinin (1 nM) evoked a transient increase in [Ca2+]i. In the presence of α-amoniadipic acid increases in [Ca2+]i were observed. In the presence of the compound, cholecystokinin induced a Ca2+ response that was smaller compared with that observed when cholecystokinin was applied alone. Stimulation of cells with cholecystokinin in the absence of Ca2+ in the extracellular medium abolished further mobilization of Ca2+ by α-aminoadipic acid. In addition, potential pro-oxidant conditions, reflected as increases in ROS generation, oxidation of proteins and lipids, were noted in the presence of α-aminoadipic acid. Finally, the compound impaired trypsin secretion induced by the secretagogue cholecystokinin. We conclude that the oxidized derivative from the amino acid lysine induces pro-oxidative conditions and the impairment of enzyme secretion in pancreatic acinar cells. α-aminoadipic acid thus creates a situation that could potentially lead to disorders in the physiology of the pancreas.

The melatonin receptor antagonist luzindole induces Ca2+ mobilization, reactive oxygen species generation and impairs trypsin secretion in mouse pancreatic acinar cells.

BACKGROUND: In this work we studied the effects of the melatonin receptor-antagonist luzindole (1 µM-50 µM) on isolated mouse pancreatic acinar cells. METHODS: Changes in intracellular free-Ca2+ concentration, reactive oxygen species production and trypsin secretion were analyzed. RESULTS: Luzindole induced increases in [Ca2+]i that diminished CCK-8 induced Ca2+ mobilization, compared with that observed when CCK-8 was applied alone. Treatment of cells with thapsigargin (1 µM), in the absence of Ca2+ in the extracellular medium, evoked a transient increase in [Ca2+]i. The additional incubation of cells with luzindole (10 µM) failed to induce further mobilization of Ca2+. In the presence of luzindole a concentration-dependent increase in ROS generation was observed that decreased in the absence of Ca2+ or by pretreatment of cells with melatonin (100 µM). Incubation of pancreatic acinar cells with luzindole (10 µM) impaired CCK-8-induced trypsin secretion. Melatonin was unable to revert the effect of luzindole on CCK-8-induced trypsin secretion. CONCLUSION: The melatonin receptor-inhibitor luzindole induces Ca2+-mediated pro-oxidative conditions and impairment of enzyme secretion, which creates a situation in pancreatic acinar cells that might compromise their function. GENERAL SIGNIFICANCE: The effects of luzindole that we have observed, might be unspecific and could mislead the observations when it is used to study the actions of melatonin on the gland. Another possibility is that melatonin receptors exhibit a basal or agonist-independent activity in pancreatic acinar cells, which might be modulated by melatonin or luzindole.