894 Circulation Research September 30, 2016 interaction between the protein targets and certain adapter molecules for LC3, such as p62/SQSTM1. For example, autophagy degrades dBruce, an inhibitor of apoptosis in flies11 and, in fibroblasts, the antioxidant catalase. 12 Second, the components of the autophagic or mitophagic machinery can directly affect cell survival and death through nonautophagic functions. Direct cross talk between autophagy-related (Atg) proteins and the death machinery has been reviewed previously. 13 Although the second scenario involves induction of cell death with autophagy, they may not involve induction of cell death by autophagy. Third, different forms of autophagy may affect the activities of one another. For example, suppression of generalized autophagy is cardioprotective in mouse models of type 1 diabetes mellitus by stimulating mitophagy. 14 If the reciprocal relationship also operates, it is possible that excessive activation of autophagy may inhibit mitophagy, thereby depriving the cell of the protection it entails. Thus, autophagy may be involved in death of cardiac myocytes through multiple mechanisms. In general, death of cardiac myocytes occurs when autophagy is activated in excess. The question then arises as to what are the morphological or biochemical features common in cell death induced by autophagy. Liu et al15 have introduced the concept of a novel form of cell death by autophagy, termed autosis, which is characterized by unique morphological features without features of apoptosis or necrosis. Autosis can be induced by TAT-Beclin1 and starvation in HeLa cells in vitro and in response to cerebral hypoxia–ischemia in hippocampal neurons in neonatal rats in vivo, whereas it is inhibited by knockdown of Atg13 or Atg14, as well as treatment with 3-methyladenine, an inhibitor of autophagy. 15 Cells dying by autosis exhibit 2 phases of morphological changes: phase 1 with gradual changes and phase 2 with abrupt changes, collapse, and death. In phase 1a, convoluted nuclei, dilated and fragmented ER, and increased numbers of autophagosomes, autolysosomes, and empty vacuoles are observed. In phase 1b, a swollen perinuclear space, which contains cytoplasmic materials and electron-dense mitochondria, is observed. In phase 2, the number of ER, autophagosomes, and autolysosomes is drastically decreased and focal nuclear concavity and focal ballooning of the PNS are observed. Currently, the molecular mechanism by which autosis induces death is not well understood. Importantly, however, Na+, K+-ATPase participates in regulating autosis, as cardiac glycosides, chemical inhibitors of the Na+, K+-ATPase, inhibit autosis and dramatically reduce brain damage in neonatal rats subjected to cerebral hypoxia–ischemia. 15 Moreover, knockdown of the Na+, K+-ATPase inhibits starvation-induced autosis in cultured cells. 15 To date, the presence of autosis has not been shown in cardiac myocytes. It should be noted that the α-subunit of the Na+, K+-ATPase expressed in the rodent heart is not inhibited by the classic cardiac glycoside drugs (eg, digoxin) used in humans. Thus, other approaches will need to be used to study autosis using mouse models. One important feature of autosis is that the death cannot be prevented in the presence of bafilomycin A1, a vacuolar proton ATPase inhibitor. Thus, stimulation of early stages of autophagosome formation, such as consumption of ER membranes as a source of autophagosomes, rather than massive destruction at lysosomes, may be the cause of cell death with the characteristic nuclear morphology. This raises the possibility that even strong …