Effects of Bilirubin Molecular Species on Membrane Dynamic Properties of Human Erythrocyte Membranes: A Spin Label Electron Paramagnetic Resonance Spectroscopy Study

Brito, Maria Alexandra; Brondino, Carlos D.; Moura, José J. G.; Brites, Dora

doi:10.1006/abbi.2000.2210

Cited by 35 publications

(20 citation statements)

References 42 publications

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“…Moreover, since perturbation of the mitochondrial membrane induced by UCB decreases from C-7 to C-16, it is conceivable that this gradient results from a secondary effect to the superficial accommodation of UCB. This scenario, although in agreement with results obtained using an erythrocyte model [42], does not exclude a possible interaction of UCB with even more external regions of the leaflet. To this end, kinetic and thermodynamic studies on the movement of UCB between intracellular membranes have suggested that UCB is associated with phospholipid bilayers at the membrane-water interface [43].…”

Section: Discussionsupporting

confidence: 89%

“…The increased permeability of the mitochondrial membrane induced by UCB as described above is also supported by the observation that UCB augments the mobility of the 4-maleimido-TEMPO spin label, indicating disruption of the protein order structure and increased membrane fluidity much above control values. As a final note, UCB appears to interact with mitochondrial membrane lipids in a fashion similar to that described in a recent study using erythrocyte membranes but, nevertheless, higher UCB concentrations [42], thus suggesting a more generic perturbation.…”

Section: Discussionsupporting

confidence: 69%

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Bilirubin directly disrupts membrane lipid polarity and fluidity, protein order, and redox status in rat mitochondria

Rodrigues¹,

Solá²,

Brito³

et al. 2002

Journal of Hepatology

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Background/Aims: Unconjugated bilirubin (UCB) impairs crucial aspects of cell function and induces apoptosis in primary cultured neurones. While mechanisms of cytotoxicity begin to unfold, mitochondria appear as potential primary targets.Methods: We used electron paramagnetic resonance spectroscopy analysis of isolated rat mitochondria to test the hypothesis that UCB physically interacts with mitochondria to induce structural membrane perturbation, leading to increased permeability, and subsequent release of apoptotic factors.Results: Our data demonstrate profound changes on mitochondrial membrane properties during incubation with UCB, including modified membrane lipid polarity and fluidity (P , 0:01), as well as disrupted protein mobility (P , 0:001). Consistent with increased permeability, cytochrome c was released from the intermembrane space (P , 0:01), perhaps uncoupling the respiratory chain and further increasing oxidative stress (P , 0:01). Both ursodeoxycholate, a mitochondrial-membrane stabilising agent, and cyclosporine A, an inhibitor of the permeability transition, almost completely abrogated UCB-induced perturbation.Conclusions: UCB directly interacts with mitochondria influencing membrane lipid and protein properties, redox status, and cytochrome c content. Thus, apoptosis induced by UCB may be mediated, at least in part, by physical perturbation of the mitochondrial membrane. These novel findings should ultimately prove useful to our evolving understanding of UCB cytotoxicity. q

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Section: Discussionsupporting

confidence: 89%

Section: Discussionsupporting

confidence: 69%

Bilirubin directly disrupts membrane lipid polarity and fluidity, protein order, and redox status in rat mitochondria

Rodrigues¹,

Solá²,

Brito³

et al. 2002

Journal of Hepatology

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“…The loss of inner-located phospholipids induced the externalization of phosphatidylserine (Brito et al, 2002). This membrane perturbation was increased by acidosis, indicating that the UCB species interacting with the membrane is the uncharged diacid (Brito et al, 2001).…”

mentioning

confidence: 99%

“…This binding is greatly increased at UCB/albumin molar ratios higher than 1.0 (Kaufmann et al, 1967), leading to morphologic changes, cell lysis, and loss of membrane lipids (Brito et al, 2000). Alterations of membrane dynamic properties of erythrocytes were accompanied by the release of phospholipids and cholesterol (Brito et al, 2001). The loss of inner-located phospholipids induced the externalization of phosphatidylserine (Brito et al, 2002).…”

mentioning

confidence: 99%

Bilirubin: An Endogenous Product of Heme Degradation with Both Cytotoxic and Cytoprotective Properties: Fig. 1

Kapitulnik¹

2004

Mol Pharmacol

216

180

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“…Further, since perturbation of the mitochondrial membrane induced by hydrophobic bile salts decreased with increasing depth of the leaflet from C-7 to C-16, it is conceivable that this gradient may result from an effect secondary to the superficial accommodation of toxic bile salts. This scenario is not without precedent, since similar effects have been described for other membrane-disturbing agents [40,41]. Finally, exposure to bile salt concentrations greater than 200 µM resulted in increased perturbation sensed by all spin labels ; this was, however, proportionally greater in deeper regions, probably reflecting lipid solubilization due to detergent effects.…”

Section: Discussionmentioning

confidence: 73%

Membrane structural changes support the involvement of mitochondria in the bile salt-induced apoptosis of rat hepatocytes

et al. 2002

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A B S T R A C TThe accumulation of toxic bile salts within the hepatocyte plays a key role in organ injury during liver disease. Deoxycholate (DC) and glycochenodeoxycholate (GCDC) induce apoptosis in vitro and in vivo, perhaps through direct perturbation of mitochondrial membrane structure and function. In contrast, ursodeoxycholate (UDC) and its taurine-conjugated form (TUDC) appear to be protective. We show here that hydrophobic bile salts induced apoptosis in cultured rat hepatocytes, without modulating the expression of pro-apoptotic Bax protein, and caused cytochrome c release in isolated mitochondria. Co-incubation with UDC and TUDC prevented cell death and efflux of mitochondrial factors. Using spin-labelling techniques and EPR spectroscopy analysis of isolated rat liver mitochondria, we found significant structural changes at the membrane-water surface in mitochondria exposed to hydrophobic bile salts, including modified lipid polarity and fluidity, altered protein order and increased oxidative injury. UDC, TUDC and cyclosporin A almost completely abrogated DC-and GCDC-induced membrane perturbations. We conclude that the toxicity of hydrophobic bile salts to hepatocytes is mediated by cytochrome c release, through a mechanism associated with marked direct effects on mitochondrial membrane lipid polarity and fluidity, protein order and redox status, without modulation of pro-apoptotic Bax expression. UDC and TUDC can directly suppress disruption of mitochondrial membrane structure, which may represent an important mechanism of hepatoprotection by these bile salts.

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Effects of Bilirubin Molecular Species on Membrane Dynamic Properties of Human Erythrocyte Membranes: A Spin Label Electron Paramagnetic Resonance Spectroscopy Study

Cited by 35 publications

References 42 publications

Bilirubin directly disrupts membrane lipid polarity and fluidity, protein order, and redox status in rat mitochondria

Bilirubin directly disrupts membrane lipid polarity and fluidity, protein order, and redox status in rat mitochondria

Bilirubin: An Endogenous Product of Heme Degradation with Both Cytotoxic and Cytoprotective Properties: Fig. 1

Membrane structural changes support the involvement of mitochondria in the bile salt-induced apoptosis of rat hepatocytes

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