Oxidant-impaired intracellular Ca²⁺ signaling in pancreatic acinar cells: role of the plasma membrane Ca²⁺-ATPase

Abstract

Pancreatitis is an inflammatory disease of pancreatic acinar cells whereby intracellular calcium concentration ([Ca(2+)](i)) signaling and enzyme secretion are impaired. Increased oxidative stress has been suggested to mediate the associated cell injury. The present study tested the effects of the oxidant, hydrogen peroxide, on [Ca(2+)](i) signaling in rat pancreatic acinar cells by simultaneously imaging fura-2, to measure [Ca(2+)](i), and dichlorofluorescein, to measure oxidative stress. Millimolar concentrations of hydrogen peroxide increased cellular oxidative stress and irreversibly increased [Ca(2+)](i), which was sensitive to antioxidants and removal of external Ca(2+), and ultimately led to cell lysis. Responses were also abolished by pretreatment with (sarco)endoplasmic reticulum Ca(2+)-ATPase inhibitors, unless cells were prestimulated with cholecystokinin to promote mitochondrial Ca(2+) uptake. This suggests that hydrogen peroxide promotes Ca(2+) release from the endoplasmic reticulum and the mitochondria and that it promotes Ca(2+) influx. Lower concentrations of hydrogen peroxide (10-100 muM) increased [Ca(2+)](i) and altered cholecystokinin-evoked [Ca(2+)](i) oscillations with marked heterogeneity, the severity of which was directly related to oxidative stress, suggesting differences in cellular antioxidant capacity. These changes in [Ca(2+)](i) also upregulated the activity of the plasma membrane Ca(2+)-ATPase in a Ca(2+)-dependent manner, whereas higher concentrations (0.1-1 mM) inactivated the plasma membrane Ca(2+)-ATPase. This may be important in facilitating "Ca(2+) overload," resulting in cell injury associated with pancreatitis.

The platinum (II) complex [Pt(O,O′-acac)(γ-acac)(DMS)] alters the intracellular calcium homeostasis in MCF-7 breast cancer cells

“…efflux [39]. PMCA is a very sensitive target for oxidative stress as occurs in pancreatic acinar cells [40] and in neuronal and liver membranes [41,42]. We have noticed that addition of [Pt(O,O'-acac)(γ-acac)(DMS) to MCF-7 cells induces rapid production of ROS ( Fig.…”

Oxidant-induced inhibition of the plasma membrane Ca2+-ATPase in pancreatic acinar cells: role of the mitochondria

“…Dye-loaded cells were allowed to adhere to a glass coverslip that formed the base of a gravity-fed perfusion chamber, continually perfused with HEPES-PSS with automatic valves for rapid switching of solutions (Harvard Apparatus, Kent, UK). All fluorescence imaging experiments were performed using an identical microscope and imaging system as previously described (1,9). Briefly, this comprised a Nikon TE2000S microscope equipped with a CoolSNAP HQ CCD camera (Roper Scientific Photometrics, Tucson, AZ), and Cairn monochromator (Cairn Research, Kent, UK) controlled by MetaFluor imaging software (Molecular Devices, Downington, PA).…”

“…We have previously reported that increased oxidative stress (H 2 O 2 ) profoundly altered the normal pattern of cholecystokinin (CCK)-evoked [Ca 2ϩ ] i signaling and resulted in an irreversible Ca 2ϩ overload response in an increasing proportion of cells as H 2 O 2 concentration was increased (9). This H 2 O 2 -induced Ca 2ϩ overload also corresponded to a marked inhibition of the plasma membrane Ca 2ϩ -ATPase (PMCA), suggesting that this may, at least in part, be responsible for the oxidant-induced Ca 2ϩ overload response (9). The aim of the present study was to further explore the mechanism of this oxidant-impaired inactivation of the PMCA, focusing on the role of the mitochondria.…”

Plasma membrane Ca2+-ATPases: Targets of oxidative stress in brain aging and neurodegeneration

“…A number of studies have indeed addressed this issue and investigated the effects of neurotoxins, excitotoxic insults, and reactive oxygen species (ROS) on the PMCAs present in neurons [40,[52][53][54][55][56] , and in non-neuronal cells [57][58][59] . Acute exposure of cerebrocortical neurons to N-methyl D-aspartate (NMDA), kainate, α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid, okadaic acid or maitotoxin results in accelerated cell death, which correlates with the activation of the Ca 2+ -dependent protease calpain and subsequent PMCA proteolysis [54] .…”