Ca2+ influx is not involved in acute cytotoxicity of arachidonic acid

Doroshenko, Nina; Doroshenko, P. A.

doi:10.1016/j.bcp.2003.10.005

Cited by 10 publications

(8 citation statements)

References 34 publications

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“…The mechanisms of AA toxicity appear to be complex and are not fully understood [16]. These include oxidative metabolism of AA to biologically active eicosanoids and/or reactive oxygen species [8,9,14], induction of the mitochondrial permeability transition [13,17], accumulation of cellular ceramides [10,11] and intracellular calcium regulation [12].…”

Section: Introductionmentioning

confidence: 99%

“…An increase of intracellular calcium may aggravate the mechanism of cell injury and accelerate the time of onset of the mitochondrial permeability transition [18,19], and activate Ca 2+ -dependent hydrolases such as calpain and phospholipase A2 [20]. The role of calcium in AA-induced cytotoxicity seems to depend on the experimental model under study, as increased release of calcium from intracellular stores was related to AA-dependent cell death in a neuronal cell line [12], but Ca 2+ influx was not involved in AA toxicity in PC12 cells [16].…”

Section: Introductionmentioning

confidence: 99%

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Role of intracellular calcium and phospholipase A2 in arachidonic acid-induced toxicity in liver cells overexpressing CYP2E1

Andrés¹,

Cederbaum²

2007

Archives of Biochemistry and Biophysics

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Liver cells (HepG2 and primary hepatocytes) overexpressing CYP2E1 and exposed to arachidonic acid (AA) were previously shown to lose viability together with enhanced lipid peroxidation. These events were blocked in cells pre-incubated with antioxidants (α -tocopherol, glutathione ethyl ester), or in HepG2 cells not expressing CYP2E1. The goal of the current study was to evaluate the role of calcium and calcium-activated hydrolases in these CYP2E1-AA interactions. CYP2E1-expressing HepG2 cells treated with AA showed an early increase in cytosolic calcium and partial depletion of ionomycin-sensitive calcium stores. These changes in calcium were blocked by α -tocopherol. AA activated phospholipase A2 (PLA2) in CYP2E1-expressing liver cells, and this was inhibited by PLA2 inhibitors or α -tocopherol. PLA2 inhibitors prevented the cell death caused by AA, without affecting CYP2E1 activity or lipid peroxidation. AA toxicity and PLA2 activation were inhibited in calcium-depleted cells, but not by removal of extracellular calcium alone. Removal of extracellular calcium inhibited the early increase in cytosolic calcium caused by AA. CYP2E1 overexpressing HepG2 cells exposed to AA showed a decrease in mitochondrial membrane potential, which was prevented by the PLA2 inhibitors. These results suggest that AA-induced toxicity to CYPE1-expressing cells: (i) is associated with release of Ca 2+ from intracellular stores that depends mainly on oxidative membrane damage; (ii) is associated with activation of PLA2 that depends on intracellular calcium and lipid peroxidation; iii) does not depend on increased influx of extracellular calcium, and iv) depends on the effect of converging events (lipid peroxidation, intracellular calcium, activation of PLA2) on mitochondria to induce bioenergetic failure and necrosis. These interactions may play a role in alcohol liver toxicity, which requires polyunsaturated fatty acids, and involves induction of CYP2E1.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Role of intracellular calcium and phospholipase A2 in arachidonic acid-induced toxicity in liver cells overexpressing CYP2E1

Andrés¹,

Cederbaum²

2007

Archives of Biochemistry and Biophysics

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“…The effect is enhanced in cells pretreated with buthionine sulfoximine an inhibitor of glutathione synthesis, and suppressed in cells that were treated with an antioxidant deferoxamine. The cytotoxicity of carmustine is mediated by the oxidative stress that results from the depletion of reduced glutathione following the inhibition of TrxR and Gor [137,167]. In contrast, other alkylating nitrogen mustards such as chlorambucil (4-[bis(2-chlorethyl)amino] benzenebutanoic acid, #305-03-3) and melphalan (2-amino-3-[4-[bis(2-chloroethyl)amino]phenyl]-propanoic acid, #148-82-3) efficiently inhibit TrxR but not Gor, and inhibition of the former enzyme is considered as a factor in the cytotoxicity observed in the clinical use of these drugs [137].…”

Section: Alkylating Agents That Target Disulfide Reductasesmentioning

confidence: 99%

“…(12)) and fotemustine (diethyl [1-{([2-chloroethyl][nitroso] carbanoyl)amino}ethyl]phosphonate, #92118-27-9, Fig. (13)) covalently deactivate thioredoxin reductase, glutathione reductase and ribonucleotide reductase by alkylating their thiolate active sites [137,167]. Since thioredoxin reductase and glutathione reductase function as alternative electron donors in the biosynthesis of deoxyribonucleotides, the inhibition of these electron transfer systems by the nitrosoureas would determine the cytostatic property of this homologous series of drugs.…”

Section: Alkylating Agents That Target Disulfide Reductasesmentioning

confidence: 99%

Inhibition of Disulfide Reductases as a Therapeutic Strategy

Kaakoush¹,

Mendz

2009

CEI

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Disulfide reductases are involved in many functions in the cell, in particular, maintaining the intracellular redox balance. Many classes of these enzymes exist, and their inhibition has served as an effective therapy against different types of human diseases. The involvement of disulfide reductases in various cellular processes is reviewed, and therapeutic strategies against pathogenic bacteria, parasitic infections, and human diseases based on their inhibition are discussed.

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“…For this purpose, we utilized a monoclonal antibody with the highest affinity for the conformation that calpain can acquire following association with calpastatin (37). As an experimental model, we used Jurkat cells stimulated with arachidonate, known to commit Jurkat cells to apoptosis through a transient early phase not involving appreciable changes in intracellular free [Ca 2ϩ ] (60,61). To elevate intracellular [Ca 2ϩ ], cells were stimulated with the Ca 2ϩ ionophore A23187.…”

Section: Effect Of Phosphorylation Of Calpastatin On Its Interaction mentioning

confidence: 99%

Association of Calpastatin with Inactive Calpain

Melloni¹,

Averna²,

Stifanese³

et al. 2006

Journal of Biological Chemistry

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It is generally accepted that the Ca 2؉ -dependent interaction of calpain with calpastatin is the most relevant mechanism involved in the regulation of Ca 2؉ -induced proteolysis. We now report that a calpain-calpastatin association can occur also in the absence of Ca 2؉ or at very low Ca 2؉ concentrations, reflecting the physiological conditions under which calpain retains its inactive conformational state. The calpastatin binding region is localized in the non-inhibitory L-domain containing the amino acid sequences encoded by exons 4 -7. This calpastatin region recognizes a calpain sequence located near the end of the DIIdomain. Interaction of calpain with calpastatins lacking these sequences becomes strictly Ca 2؉ -dependent because, under these conditions, the transition to an active state of the protease is an obligatory requirement. The occurrence of the molecular association between Ca 2؉ -free calpain and various recombinant calpastatin forms has been demonstrated by the following experimental results. Addition of calpastatin protected calpain from trypsin digestion. Calpain was coprecipitated when calpastatin was immunoprecipitated. The calpastatin molecular size increased following exposure to calpain. The two proteins comigrated in zymogram analysis. Furthermore, calpain-calpastatin interaction was perturbed by protein kinase C phosphorylation occurring at sites located at the exons involved in the association. At a functional level, calpain-calpastatin interaction at a physiological concentration of Ca 2؉ represents a novel mechanism for the control of the amount of the active form of the protease potentially generated in response to an intracellular Ca 2؉ influx.Several reports have indicated that calpain can acquire different conformational states depending on the presence of low or high [Ca 2ϩ ] (1-9). Binding of Ca 2ϩ to sites present in both the large and small calpain subunits induces a conformational switch, which ultimately results in the rearrangement of the two catalytic subdomains into a functionally active catalytic site (3)(4)(5)(6)(7)(8).This conformational modification is the limiting step in the calpain activation process and may be followed by an autoproteolytic degradation that removes the N-terminal region of domains I and V, stabilizing a low Ca 2ϩ -requiring form of the protease. The active enzyme form is regulated by the endogenous proteinaceous inhibitor calpastatin (10 -12), which has a peculiar molecular structure consisting of one N-terminal region (L-domain) and four repetitive inhibitory units (13-21), each containing three highly conserved regions called A, B, and C (22, 23). Sequence B contains the calpain consensus sequence; sequences A and C do not seem to be required for expression of the inhibitory activity, as indicated by experiments showing that a 27-residue peptide derived from sequence B can interact and inhibit calpain (23-25). Although not required for inhibition, sequences A and C can exert other functions such as interaction with domains IV and VI in the p...

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Ca2+ influx is not involved in acute cytotoxicity of arachidonic acid

Cited by 10 publications

References 34 publications

Role of intracellular calcium and phospholipase A2 in arachidonic acid-induced toxicity in liver cells overexpressing CYP2E1

Role of intracellular calcium and phospholipase A2 in arachidonic acid-induced toxicity in liver cells overexpressing CYP2E1

Inhibition of Disulfide Reductases as a Therapeutic Strategy

Association of Calpastatin with Inactive Calpain

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