The pharmacological regulation of cellular mitophagy

Small molecules are pharmacological tools of considerable value for dissecting complex biological processes and identifying potential therapeutic interventions. Recently, the cellular quality-control process of mitophagy has attracted considerable research interest; however, the limited availability of suitable chemical probes has restricted our understanding of the molecular mechanisms involved. Current approaches to initiate mitophagy include acute dissipation of the mitochondrial membrane potential (ΔΨm) by mitochondrial uncouplers (for example, FCCP/CCCP) and the use of antimycin A and oligomycin to impair respiration. Both approaches impair mitochondrial homeostasis and therefore limit the scope for dissection of subtle, bioenergy-related regulatory phenomena. Recently, novel mitophagy activators acting independently of the respiration collapse have been reported, offering new opportunities to understand the process and potential for therapeutic exploitation. We have summarized the current status of mitophagy modulators and analyzed the available chemical tools, commenting on their advantages, limitations and current applications

Attenuation of doxorubicin-induced cardiotoxicity by mdivi-1: a mitochondrial division/mitophagy inhibitor

Doxorubicin is one of the most effective anti-cancer agents. However, its use is associated with adverse cardiac effects, including cardiomyopathy and progressive heart failure. Given the multiple beneficial effects of the mitochondrial division inhibitor (mdivi-1) in a variety of pathological conditions including heart failure and ischaemia and reperfusion injury, we investigated the effects of mdivi-1 on doxorubicin-induced cardiac dysfunction in naïve and stressed conditions using Langendorff perfused heart models and a model of oxidative stress was used to assess the effects of drug treatments on the mitochondrial depolarisation and hypercontracture of cardiac myocytes. Western blot analysis was used to measure the levels of p-Akt and p-Erk 1/2 and flow cytometry analysis was used to measure the levels p-Drp1 and p-p53 upon drug treatment. The HL60 leukaemia cell line was used to evaluate the effects of pharmacological inhibition of mitochondrial division on the cytotoxicity of doxorubicin in a cancer cell line. Doxorubicin caused a significant impairment of cardiac function and increased the infarct size to risk ratio in both naïve conditions and during ischaemia/reperfusion injury. Interestingly, co-treatment of doxorubicin with mdivi-1 attenuated these detrimental effects of doxorubicin. Doxorubicin also caused a reduction in the time taken to depolarisation and hypercontracture of cardiac myocytes, which were reversed with mdivi-1. Finally, doxorubicin caused a significant elevation in the levels of signalling proteins p-Akt, p-Erk 1/2, p-Drp1 and p-p53. Co-incubation of mdivi-1 with doxorubicin did not reduce the cytotoxicity of doxorubicin against HL-60 cells. These data suggest that the inhibition of mitochondrial fission protects the heart against doxorubicin-induced cardiac injury and identify mitochondrial fission as a new therapeutic target in ameliorating doxorubicin-induced cardiotoxicity without affecting its anti-cancer properties

Hydrogen sulfide ameliorates hyperhomocysteinemia-associated chronic renal failure

Elevated level of homocysteine (Hcy), known as hyperhomocysteinemia (HHcy), is associated with end-stage renal diseases. Hcy metabolizes in the body to produce hydrogen sulfide (H2S), and studies have demonstrated a protective role of H2S in end-stage organ failure. However, the role of H2S in HHcy-associated renal diseases is unclear. The present study was aimed to determine the role of H2S in HHcy-associated renal damage. Cystathionine-β-synthase heterozygous (CBS+/−) and wild-type (WT, C57BL/6J) mice with two kidney (2-K) were used in this study and supplemented with or without NaHS (30 μmol/l, H2S donor) in the drinking water. To expedite the HHcy-associated glomerular damage, uninephrectomized (1-K) CBS(+/−) and 1-K WT mice were also used with or without NaHS supplementation. Plasma Hcy levels were elevated in CBS(+/−) 2-K and 1-K and WT 1-K mice along with increased proteinuria, whereas, plasma levels of H2S were attenuated in these groups compared with WT 2-K mice. Interestingly, H2S supplementation increased plasma H2S level and normalized the urinary protein secretion in the similar groups of animals as above. Increased activity of matrix metalloproteinase (MMP)-2 and -9 and apoptotic cells were observed in the renal cortical tissues of CBS(+/−) 2-K and 1-K and WT 1-K mice; however, H2S prevented apoptotic cell death and normalized increased MMP activities. Increased expression of desmin and downregulation of nephrin in the cortical tissue of CBS(+/−) 2-K and 1-K and WT 1-K mice were ameliorated with H2S supplementation. Additionally, in the kidney tissues of CBS(+/−) 2-K and 1-K and WT 1-K mice, increased superoxide (O2•−) production and reduced glutathione (GSH)-to-oxidized glutathione (GSSG) ratio were normalized with exogenous H2S supplementation. These results demonstrate that HHcy-associated renal damage is related to decreased endogenous H2S generation in the body. Additionally, here we demonstrate with evidence that H2S supplementation prevents HHcy-associated renal damage, in part, through its antioxidant properties