Effect of retinoid X receptor-α nuclear export inhibition on apoptosis of neurons in vivo and in vitro

Progress and Promise of Nur77-based Therapeutics for Central Nervous System Disorders

Nur77 belongs to the NR4A subgroup of the nuclear receptor superfamily. Unlike other nuclear receptors, a natural ligand for Nur77 has not been identified yet. However, a few small molecules can interact with this receptor and induce a conformational change to mediate its activity. The expression and activation of Nur77 can be rapidly increased using various physiological and pathological stimuli. In vivo and in vitro studies have demonstrated its regulatory role in tissues and cells of multiple systems by means of participation in cell differentiation, apoptosis, metabolism, mitochondrial homeostasis, and other processes. Although research on Nur77 in the pathophysiology of the central nervous system (CNS) is currently limited, the present data support the fact that Nur77 is involved in many neurological disorders such as stroke, multiple sclerosis, Parkinson’s disease. This indicates that activation of Nur77 has considerable potential in treating these diseases. This review summarizes the regulatory mechanisms of Nur77 in CNS diseases and presents available evidence for its potential as targeted therapy, especially for cerebrovascular and inflammation-related CNS diseases.

The Differential Effect of Treadmill Exercise Intensity on Hippocampal Soluble Aβ and Lipid Metabolism in APP/PS1 Mice

Alzheimer's disease (AD) is characterized clinically by progressive impairments in learning and memory. Accumulating evidence suggests that regular exercise plays a neuroprotective role in aging-associated memory loss. Our previous study has confirmed that long-term treadmill exercise initiated either before or during the onset of β-amyloid (Aβ) pathology, was beneficial for reducing the levels of soluble Aβ and further improved cognition. In this study, in APP/PS1 mice, we assessed changes in soluble Aβ, and various blood biochemistry and molecular biological indices to assess whether exercise modulated lipid metabolism and thereby decelerated AD progression. Our results show that long-term treadmill exercise reduced the total cholesterol, triglyceride, and low-density lipoprotein cholesterol levels, and increased the level of high-density lipoprotein cholesterol. Exercise also decreased the levels of soluble Aβ1-40 and Aβ1-42, down-regulated retinoid X receptor expression, and up-regulated liver X receptor, Apolipoprotein E, Low density lipoprotein receptor, Low density lipoprotein receptor-related protein 1, and ATP-binding cassette transporter A1 expression. This indicates that long-term treadmill exercise alters the lipoprotein content, increases lipid metabolism and cholesterol transportation, reduces the soluble Aβ, and therein plays an important neuroprotective role and delays AD progression. We further show that medium exercise intensity (60%-70% of maximal oxygen uptake) was more efficacious in increasing lipid metabolism and reducing blood lipid levels and soluble Aβ levels, than low-intensity exercise (45-55% of maximal oxygen uptake). This research has broad prospects and implications, and offers a theoretical basis for the prevention of AD.

Bexarotent Attenuated Chronic Constriction Injury-Induced Spinal Neuroinflammation and Neuropathic Pain by Targeting Mitogen-Activated Protein Kinase Phosphatase-1

It is widely accepted that neuroinflammation in the spinal cord contributes to the development of central sensitization in neuropathic pain. Mitogen-activated protein kinase (MAPK) activation plays a vital role in the development of neuroinflammation in the spinal cord. In this study, we investigated the effect of bexarotene (bex), a retinoid X receptor agonist, on MAPKs activation in chronic constriction injury (CCI)-induced neuropathic pain. The data showed that daily treatment with bex 50 mg/kg significantly alleviated CCI-induced nociceptive hypersensitivity in rats. Bex 50 mg/kg/day inhibited CCI-induced MAPKs (p38MAPK, ERK1/2, and JNK) activation and upregulation of proinflammatory factors (IL-1β, tumor necrosis factor-α and IL-6). Bex also reversed CCI-induced microglia activation in the ipsilateral spinal cord. Furthermore, bex treatment significantly upregulated MKP-1 in the spinal cord. These effects were completely abrogated by MKP-1 inhibitor BCI. These results indicated that bex relieved CCI-induced neuroinflammation and neuropathic pain by targeting MKP-1. Therefore, bex might be a potential agent for the treatment of neuropathic pain. PERSPECTIVE: Bex could relieve neuropathic pain behaviors in animals by reversing MKP-1 downregulation and MAPKs activation in the spinal cord. Therapeutic applications of bex may be extended beyond cutaneous T-cell lymphoma.