Luteolin Exerts Neuroprotection via Modulation of the p62/Keap1/Nrf2 Pathway in Intracerebral Hemorrhage

Xin Tan,Jiasheng Ding,Jia He,Wanli Dong,Xiang Li,Yan Zhang,Yibin Chen,Jianguo Xu,Ruming Deng,Haiying Li,Peng Zhang,Yiguang Mao,Gang Chen,Haitao Shen,Yi Yang

doi:10.3389/fphar.2019.01551

Abstract

Upregulation of neuronal oxidative stress is involved in the progression of secondary brain injury (SBI) following intracerebral hemorrhage (ICH). In this study, we investigated the potential effects and underlying mechanisms of luteolin on ICH-induced SBI. Autologous blood and oxyhemoglobin (OxyHb) were used to establish in vivo and in vitro models of ICH, respectively. Luteolin treatment effectively alleviated brain edema and ameliorated neurobehavioral dysfunction and memory loss in vivo. Also, in vivo, we found that luteolin promoted the activation of the sequestosome 1 (p62)/kelch‐like enoyl-coenzyme A hydratase (ECH)‐associated protein 1 (Keap1)/nuclear factor erythroid 2-related factor 2 (Nrf2) pathway by enhancing autophagy and increasing the translocation of Nrf2 to the nucleus. Meanwhile, luteolin inhibited the ubiquitination of Nrf2 and increased the expression levels of downstream antioxidant proteins, such as heme oxygenase-1 (HO-1) and reduced nicotinamide adenine dinucleotide phosphate (NADPH): quinine oxidoreductase 1 (NQO1). This effect of luteolin was also confirmed in vitro, which was reversed by the autophagy inhibitor, chloroquine (CQ). Additionally, we found that luteolin inhibited the production of neuronal mitochondrial superoxides (MitoSOX) and alleviated neuronal mitochondrial injury in vitro, as indicated via tetrachloro-tetraethylbenzimidazol carbocyanine-iodide (JC-1) staining and MitoSOX staining. Taken together, our findings demonstrate that luteolin enhances autophagy and anti-oxidative processes in both in vivo and in vitro models of ICH, and that activation of the p62-Keap1-Nrf2 pathway, is involved in such luteolin-induced neuroprotection. Hence, luteolin may represent a promising candidate for the treatment of ICH-induced SBI.

Highlights

Intracerebral hemorrhage (ICH) is an important public health problem that has aroused worldwide concern due to its high mortality and morbidity rates (Qureshi et al, 2009)
We investigated the neuroprotective effects of luteolin in intracerebral hemorrhage (ICH)-induced secondary brain injury (SBI), including potential underlying mechanisms related to regulation of antioxidative processes and autophagy
We found that sham group vs. ICH group, Z = −4.077, P < 0.0001; ICH + vehicle group vs. ICH + 5 mg/kg luteolin group, Z = −0.390, P = 0.8471; ICH + vehicle group vs. ICH + 10 mg/kg luteolin group, FIGURE 2 | Luteolin ameliorates intracerebral hemorrhage (ICH)-induced neuronal injury

Summary

Introduction

Intracerebral hemorrhage (ICH) is an important public health problem that has aroused worldwide concern due to its high mortality and morbidity rates (Qureshi et al, 2009). In addition to primary brain injury that disrupts the physical structure of brain tissue, ICH-induced secondary brain injury (SBI) often leads to severe neurological deficits or even death (Xi et al, 2006). There are many pathophysiological changes that have been demonstrated to participate in the process of SBI, including hemoglobin-induced iron overload, oxidative stress, inflammation, cell apoptosis, autophagy, mitochondrial dysfunction, and blood−brain−barrier disruption (Zhou et al, 2014; Duan et al, 2016). Under conditions of oxidative stress, Nrf disassociates from Keap and translocates to the nucleus to activate the antioxidant response element (ARE), which leads to an increase in the expression of downstream protective proteins such as heme oxygenase-1 (HO1) and reduced nicotinamide adenine dinucleotide phosphate (NADPH):quinine oxidoreductase-1 (NQO1) (Wang et al, 2018a)

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