Inducing mitophagy in diabetic platelets protects against severe oxidative stress

Abstract

Diabetes mellitus (DM) is a growing international concern. Considerable mortality and morbidity associated with diabetes mellitus arise predominantly from thrombotic cardiovascular events. Oxidative stress‐mediated mitochondrial damage contributes significantly to enhanced thrombosis in DM. A basal autophagy process has recently been described as playing an important role in normal platelet activation. We now report a substantial mitophagy induction (above basal autophagy levels) in diabetic platelets, suggesting alternative roles for autophagy in platelet pathology. Using a combination of molecular, biochemical, and imaging studies on human DM platelets, we report that platelet mitophagy induction serves as a platelet protective mechanism that responds to oxidative stress through JNK activation. By removing damaged mitochondria (mitophagy), phosphorylated p53 is reduced, preventing progression to apoptosis, and preserving platelet function. The absence of mitophagy in DM platelets results in failure to protect against oxidative stress, leading to increased thrombosis. Surprisingly, this removal of damaged mitochondria does not require contributions from transcription, as platelets lack a nucleus. The considerable energy and resources expended in “prepackaging” the complex mitophagy machinery in a short‐lived normal platelet support a critical role, in anticipation of exposure to oxidative stress.

Hypoxic mitophagy regulates mitochondrial quality and platelet activation and determines severity of I/R heart injury

“…A collection of fresh blood and isolation of washed mouse platelets were conducted as described previously (Lee et al, 2016; Feng et al, 2014; Ouseph et al, 2015). Briefly, the Fundc1 fl/fl ::Pf4 Cre+ mice (8 to 10 weeks old) and their Fundc1 fl/fl ::Pf4 Cre- littermates were anesthetized with pentobarbital (70 mg/kg, i.p.).…”

“…Platelets were prepared as described previously (Lee et al, 2016; Feng et al, 2014; Ouseph et al, 2015). Washed mouse platelets (3 × 10 8 /ml) resuspended in modified tyrode buffer (MTB) were lysed in 2 × platelet lysis buffer (1 mM dithiothreitol, 0.15 M NaCl, 0.1 M Tris, 2% Triton X-100 and 0.01 M EGTA, pH 7.4) containing E64 (0.1 mM), 1/100 aprotinin and phenylmethylsulfonyl fluoride (PMSF, 1 mM), at a volume ratio of 1:1 on ice for 0.5 hr.…”

“…It is unclear whether dysfunctional mitochondria are the cause or consequence of these diseases. General autophagy occurs in platelets in response to starvation in an ATG5-dependent fashion (Lee et al, 2016; Feng et al, 2014; Cao et al, 2015; Ouseph et al, 2015); however, the physiological relevance of autophagy in platelets is unclear. A recent report suggests that mitophagy in diabetic platelets protects against severe oxidative stress (Lee et al, 2016).…”

“…General autophagy occurs in platelets in response to starvation in an ATG5-dependent fashion (Lee et al, 2016; Feng et al, 2014; Cao et al, 2015; Ouseph et al, 2015); however, the physiological relevance of autophagy in platelets is unclear. A recent report suggests that mitophagy in diabetic platelets protects against severe oxidative stress (Lee et al, 2016). Platelet activation is a major (patho-)physiological mechanism that underlies atherosclerosis, myocardial infarction acute coronary syndromes and ischemia/reperfusion (I/R)-related damage, and thus anti-platelet therapy is important for managing many cardiovascular diseases (Nagareddy and Smyth, 2013; Gawaz et al, 2005; Antithrombotic Trialists' Collaboration, 2002; Du, 2007; Ruggeri, 2002; Li et al, 2015).…”

Establishment and characterization of a radiation‐induced dermatitis rat model

“…13,14 Similarly, p53 activation induces irreversible G1/S or G2/M cell-cycle arrest, senescence, and apoptosis 15,16 but can also activate the energy sensor AMPK pathway, inhibit the mammalian target of rapamycin (mTOR) pathway, and transactivate multiple genes with pro-autophagic effects. 21 Recent studies have shown that ROS could act as cellular signalling molecules to initiate autophagosome formation and autophagic degradation, 22 whereas autophagy can reduce oxidative damage and ROS levels through removal of protein aggregates and damaged organelles such as mitochondria. 21 Recent studies have shown that ROS could act as cellular signalling molecules to initiate autophagosome formation and autophagic degradation, 22 whereas autophagy can reduce oxidative damage and ROS levels through removal of protein aggregates and damaged organelles such as mitochondria.…”