Global SUMOylation facilitates the multimodal neuroprotection afforded by quercetin against the deleterious effects of oxygen/glucose deprivation and the restoration of oxygen/glucose

Abstract

The putative neuroprotective properties of various flavonoids have long been reported. Amongst this class of chemicals, quercetin, a major flavone/flavonol naturally occurring in plants, deserves focused attention because of the myriad of beneficial effects observed in various in vitro and in vivo models of central nervous system damage/degeneration. However, the mechanisms governing the beneficial outcomes mediated by quercetin remain to be elucidated. In an effort to define the underlying molecular mechanisms, our study employed human/rat neuroblastoma cell lines (SHSY5Y and B35 rat respectively) and E18 derived rat primary cortical neurons upon which the effects of various flavonoids were examined. Of note, increases in levels of global SUMOylation, a post-translational modification with the Small Ubiquitin-like MOdifier (SUMO) were pronounced. Quercetin treatment increased SUMOylation levels in both SHSY5Y cells and rat cortical neurons in a dose and time-dependent manner, possibly via the direct inactivation of certain SENPs (SUMO-specific isopeptidases). Of particular interest, cells treated with quercetin displayed increased tolerance to OGD (oxygen-glucose deprivation) exposure, an in vitro model of ischemia. SHSY5Y cells treated with quercetin also increased the expression of Nrf2 (via a decrease in the levels of Keap1), heme oxygenase-1 (HO-1), and nitric oxide synthase 1 (NOS1), which provide further protection from oxidative stress. In addition, the increased SUMOylation of HIF-1α was noted and deemed to be significant. We hypothesize that SUMOylated HIF-1α plays a fundamental role in the protection afforded and may underlie some of quercetin’s ability to protect cells from OGD-induced cell death, via an upregulation of HO-1 and NOS1, which ultimately leads to the induction of pro-life NOS1/PKG signaling.

Increased SUMO-2/3-ylation mediated by SENP3 degradation is protective against cadmium-induced caspase 3–dependent cytotoxicity

“…There is an increasing body of evidence suggesting that SENP3 is a key regulator of stress responses (Huang et al, 2009;Han et al, 2010;Yan et al, 2010;Wang et al, 2012;Wei et al, 2012;Guo et al, 2013Guo et al, , 2017Yang et al, 2015aYang et al, , 2015bYu et al, 2015;Lee et al, 2016;Guo and Henley, 2014). This study adds to previous reports by demonstrating that loss of SENP3 and the consequent increase in SUMOylation plays a protective role in cadmium-induced toxicity, but that this effect is cell-type specific.…”

“…SUMOylation has been strongly implicated in response to ischaemic stress (Lee et al, 2007(Lee et al, , 2016Yang et al, 2008;Datwyler et al, 2011), so we next investigated if protein SUMOylation levels were altered in PC12 cells in response to cadmium toxicity. As expected, the total SUMO2/3-conjugated protein was increased after exposure to cadmium (Fig.…”

“…We, and others, have shown that global increases in SUMO-2/3 conjugation are a cellular protective response to severe ischaemic stress (Datwyler et al, 2011;Cimarosti et al, 2012;Lee et al, 2016;Lee et al, 2007). The unfolded protein response (UPR) mediates protective responses that allow cell adaptation and survival (Hetz, 2012).…”

“…RNAi knockdown of SENP3 protects cells from reoxygenation-induced cell death via a mechanism that requires Drp1 SUMOylation (Guo et al, , 2017Anderson and Blackstone, 2013;Schuldt, 2013). This represents a novel adaptive pathway to extreme cell stress in which dynamic changes in SENP3 stability and regulation of Drp1 by SUMO-2/3 are crucial determinants of cell fate, opening up possibilities of developing new drug targets and therapeutic strategies (Lee et al, 2016;Wei et al, 2012;Yang et al, 2015aYang et al, , 2015bYu et al, 2015).…”

Neuron-specific SUMO knockdown suppresses global gene expression response and worsens functional outcome after transient forebrain ischemia in mice

“…Further, it is widely appreciated that the post-ischemic activation of SUMO conjugation is a protective stress response that shields neurons from injury, as evidenced in in vitro and in vivo studies (Lee et al, 2007, 2009, 2011, 2016; Datwyler et al, 2011). However, the effect of SUMO conjugation on post-ischemic neurologic function has not yet been investigated.…”