Cytosolic-free calcium increases to greater than 100 micromolar in ATP-depleted proximal tubules.

Weinberg, Joel M.; Davis, Julie; Venkatachalam, Manjeri A.

doi:10.1172/jci119584

Cited by 47 publications

(35 citation statements)

References 55 publications

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“…That this same profile was observed with maleate toxicity further underscores the similarity of these two forms of renal damage. Fourth, cytosolic Ca 2ϩ overload, evoked by a failure of mitochondrial sequestration, is a known determinant of hypoxic/ ATP depletion-mediated tubular cell death (39,40). That an chelator mitigated maleate toxicity again implies commonality between maleate and hypoxic injury pathways.…”

Section: Discussionmentioning

confidence: 99%

Maleate nephrotoxicity: mechanisms of injury and correlates with ischemic/hypoxic tubular cell death

Zager¹,

Johnson²,

Naito³

et al. 2008

American Journal of Physiology-Renal Physiology

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Maleate injection causes dose-dependent injury in proximal tubular cells. This study sought to better define underlying pathogenic mechanisms and to test whether maleate toxicity recapitulates critical components of the hypoxic/ischemic renal injury cascade. CD-1 mice were injected with maleate or used as a source for proximal tubule segments (PTS) for in vitro studies. Maleate induced dose-dependent PTS injury [lactate deydrogenase (LDH) release, ATP reductions, nonesterified fatty acid (NEFA) accumulation]. These changes were partially dependent on maleate metabolism (protection conferred by metabolic inhibitors: succinate, acetoacetate). Maleate toxicity reproduced critical characteristics of the hypoxia/ATP depletion-induced injury cascade: 1) glutathione (GSH) conferred protection, but due to its glycine, not cysteine (antioxidant), content; 2) ATP reductions reflected decreased production, not Na-K-ATPase-driven increased consumption; 3) cell death was completely blocked by extracellular acidosis (pH 6.6); 4) intracellular Ca2+ chelation (BAPTA) mitigated cell death; 5) maleate and hypoxia each caused plasma membrane cholesterol shedding and in both instances, this was completely glycine suppressible; 6) maleate + hypoxia caused neither additive NEFA accumulation nor LDH release, implying shared pathogenic pathways; and 7) maleate, like ischemia, induced renal cortical cholesterol loading; increased HMG CoA reductase (HMGCR) activity (statin inhibitable), increased HMGCR mRNA levels, and increased RNA polymerase II recruitment to the HMGCR locus (chromatin immunoprecipitation, ChIP, assay) were involved. These results further define critical determinants of maleate nephrotoxicity and suggest that it can serve as a useful adjunct for studies of ischemia/ATP depletion-induced, proximal tubule-specific, cell death.

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Section: Discussionmentioning

confidence: 99%

Maleate nephrotoxicity: mechanisms of injury and correlates with ischemic/hypoxic tubular cell death

Zager¹,

Johnson²,

Naito³

et al. 2008

American Journal of Physiology-Renal Physiology

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“…The incubation medium was pregassed with 95% N 2 /5% CO 2 . EC Oxyrase, a biocatalytic oxygen reducing agent, was added at 1.2 units/ml to the medium to consume residual O2 and maximize the degree of hypoxia (Weinberg et al, 1997). Glycine was included at 5 mM in the medium to simulate glycine contents of tissues in vivo (Nissim and Weinberg, 1996;Duran et al, 1990), and thus prevent early necrotic injury during hypoxic incubation (Venkatachalam and Weinberg, 1993).…”

Section: Discussionmentioning

confidence: 99%

Role of hypoxia-induced Bax translocation and cytochrome c release in reoxygenation injury

et al. 1998

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We investigated mechanisms of cell death during hypoxia/reoxygenation of cultured kidney cells. During glucose-free hypoxia, cell ATP levels declined steeply resulting in the translocation of Bax from cytosol to mitochondria. Concurrently, there was cytochrome c release and caspase activation. Cells that leaked cytochrome c underwent apoptosis after reoxygenation. ATP depletion induced by a mitochondrial uncoupler resulted in similar alterations even in the presence of oxygen. Moreover, inclusion of glucose during hypoxia prevented protein translocations and reoxygenation injury by maintaining intracellular ATP. Thus, ATP depletion, rather than hypoxia per se, was the cause of protein translocations. Overexpression of Bcl-2 prevented cytochrome c release and reoxygenation injury without ameliorating ATP depletion or Bax translocation. On the other hand, caspase inhibitors did not prevent protein translocations, but inhibited apoptosis during reoxygenation. Nevertheless, they could not confer long-term viability, since mitochondria had been damaged. Omission of glucose during reoxygenation resulted in continued failure of ATP production, and cell death with necrotic morphology. In contrast, cells expressing Bcl-2 had functional mitochondria and remained viable during reoxygenation even without glucose. Therefore, Bax translocation during hypoxia is a molecular trigger for cell death during reoxygenation. If ATP is available during reoxygenation, apoptosis develops; otherwise, death occurs by necrosis. By preserving mitochondrial integrity, BCL-2 prevents both forms of cell death and ensures cell viability.

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“…Furthermore, glycine appears to be a key component in storage/ perfusion solutions employed for liver transplantation, protecting against hepatic ischemia-reperfusion injury (1,4,19,27). In kidney tubules, glycine affords protection against a variety of insults that deplete energy stores and elevate [Ca 2ϩ ] i (38,40). Interestingly, in the presence of glycine, ATP-depleted renal proximal tubule cells can survive and subsequently proliferate despite loss of ion concentration gradients and sustained increases in [Ca 2ϩ ] i to values between 10 and 100 M (8).…”

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confidence: 99%

Blockade of maitotoxin-induced endothelial cell lysis by glycine and l-alanine

Estacion

Weinberg

Sinkins

et al. 2003

American Journal of Physiology-Cell Physiology

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]i), which is followed by the biphasic uptake of vital dyes. The initial phase of dye entry reflects activation of large pores and correlates with surface membrane bleb formation; the second phase reflects cell lysis. In the present study, the effect of the cytoprotective amino acid glycine was examined. Glycine had no effect on MTX-induced change in [Ca 2ϩ ]i or on the first phase of vital dye uptake but produced a concentration-dependent (EC50 ϳ1 mM) inhibition of the second phase of dye uptake. No cytoprotective effect was observed with L-valine, L-proline, or D-alanine, whereas L-alanine was equieffective to glycine. Furthermore, glycine had no effect on MTX-induced bleb formation. To test the hypothesis that glycine specifically blocks formation of a lytic "pore," the loss of fluorescence from BAECs transiently expressing GFP and concatemers of GFP ranging in size from 27 to 162 kDa was examined using time-lapse videomicroscopy. MTX-induced loss of GFP was rapid, correlated with the second phase of dye uptake, and was relatively independent of molecular size. The MTXinduced loss of GFP from BAECs was completely blocked by glycine. The data suggest that the second "lytic" phase of MTX-induced endothelial cell death reflects formation of a novel permeability pathway that allows macromolecules such as GFP or LDH to escape, yet can be prevented by the cytoprotective agents glycine and L-alanine. necrosis; vital dyes; membrane blebs; time-lapse videomicroscopy; fura 2 BECAUSE OF ITS UNIQUE LOCATION and varied function, the vascular endothelium plays an active role in the development or progression of various cardiovascular diseases including atherosclerosis, hypertension, and ischemic-reperfusion injury. Specifically, endothelial cell function may be compromised in disease states as a result of oxidative stress arising, for example, from activation of leukocytes, the products of drug metabolism, uptake of oxidized lipoproteins, and/or the reduction of molecular oxygen (3,20,28,29). Such cellular insults, which ultimately lead to either apoptotic or necrotic (oncotic) cell death, share a common feature; i.e., they appear to trigger a rise in cytosolic free Ca 2ϩ concentration ([Ca 2ϩ ] i ) (26,29,34). Although the immediate downstream molecular events linking a rise in [Ca 2ϩ ] i to oncosis and/or apoptosis remain largely unknown, defining the biochemical steps in the cell death cascade may be essential to our understanding of vascular disease and the ultimate design of effective therapeutic interventions.Natural products such as cholera toxin, pertussis toxin, tetrodotoxin, digitalis, ryanodine, and thapsigargin have proved extremely useful for the identification and characterization of specific biochemical pathways important for cell signaling. Maitotoxin (MTX), isolated from the dinoflagellate Gambierdiscus toxicus, is the most potent marine toxin known and a major causative agent of ciguatera seafood poisoning. The reported LD 50 value in mice is 0.2 g/kg (33). When added to cells at subnanomolar con...

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Cytosolic-free calcium increases to greater than 100 micromolar in ATP-depleted proximal tubules.

Cited by 47 publications

References 55 publications

Maleate nephrotoxicity: mechanisms of injury and correlates with ischemic/hypoxic tubular cell death

Maleate nephrotoxicity: mechanisms of injury and correlates with ischemic/hypoxic tubular cell death

Role of hypoxia-induced Bax translocation and cytochrome c release in reoxygenation injury

Blockade of maitotoxin-induced endothelial cell lysis by glycine and l-alanine

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