Anti-Bcl-2 family members, zfBcl-xL and zfMcl-1a, prevent cytochrome c release from cells undergoing betanodavirus-induced secondary necrotic cell death

Benzo(a)pyrene-7,8-diol-9,10-epoxide (BPDE) is a highly reactive DNA damage agent and can induce cell death through both p53-independent and -dependent pathways. However, little is known about the molecular mechanisms of p53-independent pathways in BPDE-induced cell death. To understand the p53-independent mechanisms, we have now examined BPDE-induced cytotoxicity in p53-deficient baby mouse kidney (BMK) cells. The results showed that BPDE could induce Bax and Bak activation, cytochrome c release, caspases activation, and necrotic cell death in the BMK cells. Bax and Bak, two key molecules of mitochondrial permeability transition pore, were interdependently activated by BPDE, with Bax and Bak translocation to and Bax/Bak homo-oligomerization in mitochondria, release of cytochrome c was induced. Importantly, cytochrome c release and necrotic cell death were diminished in BMK cells (Bax−/−), BMK cells (Bak−/−), and BMK cells (Bax−/−/Bak−/−). Furthermore, overexpression of Bcl-2 could ameliorate BPDE-induced cytochrome c release and necrosis. Together the findings suggested that BPDE-induced necrosis was modulated by the p53-independent pathway, which was related to the translocation of Bax and Bak to mitochondria, release of cytochrome c, and activation of caspases.

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Abstract 15546: Loss of Mitochondrial UCP3-Cytochrome c Oxidase Complexes Underlies Maladaptive Autophagy and Cardiac Failure in Anthracycline Cardiotoxicity

Circulation ◽

10.1161/circ.130.suppl_2.15546 ◽

2014 ◽

Vol 130 (suppl_2) ◽

Author(s):

Rimpy Dhingra ◽

Victoria Margulets ◽

Davindar Jassal ◽

Gerald Dorn ◽

Lorrie A Kirshenbaum

Keyword(s):

Cell Death ◽

Cytochrome C ◽

Cytochrome C Oxidase ◽

Cardiac Failure ◽

Uncoupling Protein ◽

Mitochondrial Morphology ◽

Necrotic Cell Death ◽

Mitochondrial Targeting ◽

Necrotic Cell ◽

Anthracycline Cardiotoxicity

Doxorubicin is known for its cardiotoxic effects and inducing cardiac failure. Herein we demonstrate a novel signaling pathway that functionally links activation and preferential mitochondrial targeting of Bnip3 to doxorubicin cardiotoxicity. Perturbations to mitochondria including increased calcium, ROS, loss of αΨm and mPTP opening were observed in cardiac myocytes treated with doxorubicin. This coincided with a decline in maximal respiratory capacity, loss of respiratory chain complexes of uncoupling protein 3 (UCP3) and cytochrome c oxidase complex IV subunit 1, (COX) and cell viability. Impaired mitochondrial function was accompanied by an accumulated increase in autophagosomes and necrosis demonstrated by increase release of LDH, cTnT and loss of nuclear High Mobility Group Protein 1 (HMGB-1) immunoreactivity. Interestingly, pharmacological or genetic inhibition of autophagy with 3-methyl adenine (3-MA), or Atg7 knock-down suppressed necrotic cell death induced by doxorubicin. Conversely, loss of function of Bnip3 or mutations of Bnip3 defective for mitochondrial targeting restored UCP3-COX complexes, mitochondrial respiratory integrity and suppressed necrotic cell death induced by doxorubicin. Finally, mice germ-line deficient for Bnip3 were resistant to the cytotoxic effects of doxorubicin displaying mitochondrial morphology, cardiac function and survival rates comparable to vehicle treated control mice. To our knowledge the findings of the present study provide the first direct evidence that doxorubicin triggers maladaptive autophagy and necrotic cell death of ventricular myocytes by a mechanism mutually dependent and obligatorily linked to Bnip3. Hence, therapeutic interventions to selectively inhibit Bnip3 may prove beneficial in suppressing mitochondrial injury and heart failure in cancer patients undergoing doxorubicin treatment.

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Abstract 24: Bnip3 Provokes ROS Production and Maladaptive Autophagy by Displacing Uncoupling Protein3 (UCP3) From Cytochrome c Oxidase of Respiration Chain Complex in Cardiotoxicity

Circulation Research ◽

10.1161/res.117.suppl_1.24 ◽

2015 ◽

Vol 117 (suppl_1) ◽

Author(s):

Rimpy Dhingra ◽

Victoria Margulets ◽

Davinder Jassal ◽

Gerald Dorn II ◽

Lorrie A. Kirshenbaum

Keyword(s):

Cell Death ◽

Cytochrome C ◽

Cytochrome C Oxidase ◽

Cardiac Myocytes ◽

Mitochondrial Function ◽

Uncoupling Protein ◽

Mitochondrial Morphology ◽

Necrotic Cell Death ◽

Ros Production ◽

Necrotic Cell

Doxorubicin is known for its cardiotoxic effects and inducing cardiac failure, however, the underlying mechanisms remain cryptic. Earlier we established the inducible - death protein, Bcl-2-like Nineteen- Kilodalton- Interacting - Protein 3 (Bnip3) to be crucial for disrupting mitochondrial function and inducing cell death of cardiac myocytes. Whether Bnip3 underlies cardiotoxic effects of doxorubicin toxicity is unknown. Herein we demonstrate a novel signaling pathway that functionally links activation and preferential mitochondrial targeting of Bnip3 to the cardiotoxic properties of doxorubicin. Perturbations to mitochondria including increased calcium loading, ROS, loss of αΨm and mPTP opening were observed in cardiac myocytes treated with doxorubicin. In mitochondria, Bnip3 forms strong association with Cytochrome c oxidase subunit1 (COX1) of respiratory chain and displaces uncoupling protein 3 (UCP3) resulting in increased ROS production, decline in maximal and reserved respiration capacity and cell viability. Impaired mitochondrial function was accompanied by an accumulated increase in autophagosomes and necrosis demonstrated by increase release of LDH, cTnT and loss of nuclear High Mobility Group Protein 1 (HMGB-1) immunoreactivity. Interestingly, pharmacological or genetic inhibition of autophagy with 3-methyl adenine (3-MA), or Atg7 knock-down suppressed necrotic cell death induced by doxorubicin. Loss of function of Bnip3 restored UCP3-COX complexes, mitochondrial respiratory integrity and abrogated necrotic cell death induced by doxorubicin. Mice germ-line deficient for Bnip3 were resistant to doxorubicin cardiotoxicity displaying normal mitochondrial morphology, cardiac function and survival rates comparable to vehicle treated mice. The findings of the present study demonstrate that doxorubicin provokes maladaptive autophagy and necrotic cell death of ventricular myocytes that is mutually dependent and obligatorily linked to Bnip3.

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