Cocaine induces astrocytosis through ER stress-mediated activation of autophagy

Abstract

Cocaine is known to induce inflammation, thereby contributing in part, to the pathogenesis of neurodegeneration. A recent study from our lab has revealed a link between macroautophagy/autophagy and microglial activation. The current study was aimed at investigating whether cocaine could also mediate activation of astrocytes and, whether this process involved induction of autophagy. Our findings demonstrated that cocaine mediated the activation of astrocytes by altering the levels of autophagy markers, such as BECN1, ATG5, MAP1LC3B-II, and SQSTM1 in both human A172 astrocytoma cells and primary human astrocytes. Furthermore, cocaine treatment resulted in increased formation of endogenous MAP1LC3B puncta in human astrocytes. Additionally, astrocytes transfected with the GFP-MAP1LC3B plasmid also demonstrated cocaine-mediated upregulation of the green fluorescent MAP1LC3B puncta. Cocaine-mediated induction of autophagy involved upstream activation of ER stress proteins such as EIF2AK3, ERN1, ATF6 since blockage of autophagy using either pharmacological or gene-silencing approaches, had no effect on cocaine-mediated induction of ER stress. Using both pharmacological and gene-silencing approaches to block either ER stress or autophagy, our findings demonstrated that cocaine-induced activation of astrocytes (measured by increased levels of GFAP) involved sequential activation of ER stress and autophagy. Cocaine-mediated-increased upregulation of GFAP correlated with increased expression of proinflammatory mediators such as TNF, IL1B, and IL6. In conclusion, these findings reveal an association between ER stress-mediated autophagy and astrogliosis in cocaine-treated astrocytes. Intervention of ER stress and/or autophagy signaling would thus be promising therapeutic targets for abrogating cocaine-mediated neuroinflammation.

Cocaine and HIV‐1 Tat disrupt cholesterol homeostasis in astrocytes: Implications for HIV‐associated neurocognitive disorders in cocaine user patients

“…This study demonstrated that although SREBP2 activation and HMGCR levels were increased, HMGCR activity was reduced by 70% under ER stress, which led to decreased cholesterol synthesis. There are a number of reports of ER stress induced by cocaine or Tat contributing to neurotoxicity (Desai et al 2010; Fan and He 2016; Ma et al 2016; Periyasamy et al 2016). Therefore, it is possible that ER stress may be an upstream event mediating cholesterol dysregulation following cocaine and Tat exposure.…”

“…In fact, cocaine use is a major risk factor for becoming infected with HIV and together, HIV and cocaine synergize to increase cellular dysfunction in astrocytes in the brain (Buch et al 2012; Cai et al 2016; Dahal et al 2015; Hauser and Knapp 2014; Reynolds et al 2006; Yang et al 2016). Likewise, HIV infection and cocaine use are associated with myelin loss and synaptodendritic damage (Dash et al 2011; Fitting et al 2013; Kim et al 2003; Periyasamy et al 2016), suggesting that dysregulation in CNS cholesterol metabolism may be involved in the progression of neurocognitive impairment. Several studies report toxic synergy between cocaine and HIV proteins such as Tat on cells of the CNS, including astrocytes (Gandhi et al 2010; Wayman et al 2015).…”

Morphine-Mediated Brain Region-Specific Astrocytosis Involves the ER Stress-Autophagy Axis

“…1 μg of total RNA was used for the synthesis of complementary DNA as described previously [37]. The reverse transcribed RNA was analyzed with the 7500 Fast Real-Time PCR System (Applied Biosystems, Grand Island, NY) with the RT 2 SYBR Green Fluor qPCR Mastermix (Qiagen, 330510).…”

“…Several studies have also implicated the regulatory role of PERK in ER stress-mediated autophagy [49,46]. Drugs of abuse such as cocaine under various experimental conditions have been shown to mediate ER stress, which in turn, regulates the expression of different genes involved in microglial and astrocyte autophagy [50,37]. Morphine-mediated autophagy has also been reported in various cell types, such as bone marrow-derived macrophages [51], neuroblastoma cell line [52], primary hippocampal neurons [43], and microglia [53].…”

Crosstalk between autophagy and intracellular radiation response (Review)

“…Autophagy initiation begins with the membrane distention from either the ER or Golgi complex, followed by formation of autophagosome, a cup shaped double-membrane structure which sequesters cellular components. Subsequently, autophagosome fuses with the lysosome to form an autolysosome which is the site for degradation of the sequestered cargo by the action of the lysosomal hydrolytic enzymes (2).…”