Linderane Attenuates Complete Freund's Adjuvant-Induced Pain and Anxiety in Mice by Restoring Anterior Cingulate Cortex Microglia M2 Polarization through Activating Cannabinoid 2 Receptor

Narirutin reduces microglia-mediated neuroinflammation by inhibiting the JAK2/STAT3 pathway in MPP+/MPTP-induced Parkinson's disease models

Parkinson's disease (PD) is one of the most common neurodegenerative disorders, characterized by the loss of dopaminergic neurons in the substantia nigra compacta (SNc). Although the detailed molecular mechanisms of PD remain unknown, microglia-mediated neuroinflammation undoubtedly plays a key role in disease progression. Narirutin (Nar), a major flavonoid naturally occurring in citrus fruits, has garnered considerable research attention due to its various therapeutic applications and low toxicity. However, its effects on PD remain unclear. In this study, we explored the protective effects of Nar in 1-methyl-4-phenyl-1,2,3,6-tetrahydro-pyridine (MPTP)-induced PD mouse model as well as in 1-methyl-4-phenyl-pyridinium (MPP+)-induced BV2 cells. Treatment with Nar (2.0, 10.0, and 50.0 mg/kg) reduced dopaminergic neuronal loss in a dose-dependent manner and ameliorated motor impairment in PD mice. Moreover, Nar administration inhibited microglia-mediated inflammation, evidenced by decreased microglial activation in SNc and BV2 cells, and lowered levels of pro-inflammatory cytokines (TNF-α, IL-1β, and IL-6) in the serum and cells. In addition, we found that Nar exerted anti-inflammatory effects by inhibiting the JAK2/STAT3 pathway. Importantly, using molecular docking and cellular thermal shift assay, we confirmed that JAK2 was a potential binding target of Nar. Overall, Nar attenuated MPTP/MPP+-induced neuroinflammation by inhibiting the JAK2/STAT3 pathway in activated microglia, thereby preventing dopaminergic neuron loss and improving motor disorders in PD mice. Our results provide new evidence supporting that Nar is promising for PD treatment and should be considered for further clinical development.

The role of cannabinoid-mediated signaling pathways and mechanisms in brain disorders

Cannabinoids play significant roles in the central nervous system (CNS), but cannabinoid-mediated physiopathological functions are not elaborated. Cannabinoid receptors (CBRs) mediate functions that include the regulation of neuroinflammation, oxidative stress, apoptosis, autophagy, and neurogenesis. Microglia are the primary immune cells responsible for mediating neuroinflammation in the CNS. Therefore, this article primarily focuses on microglia to summarize the inflammatory pathways mediated by cannabinoids in the CNS, including nuclear factor-κB (NF-κB), NOD-like receptor protein 3 (NLRP3) inflammasome, mitogen-activated protein kinase (MAPK), protein kinase B (Akt), and cAMP-dependent protein kinase (PKA) signaling pathways. Additionally, we provide a table summarizing the role of cannabinoids in various brain diseases. Medical use of cannabinoids has protective effects in preventing and treating brain diseases; however, excessive and repeated use can be detrimental to the CNS. We propose that cannabinoids hold significant potential for preventing and treating brain diseases, including ferroptosis, lactate metabolism, and mitophagy, providing new insights for further research on cannabinoids.

The endocannabinoid system in the brain undergoes long-lasting changes following neuropathic pain

The endocannabinoid system (ECS), which is composed of endocannabinoids (eCBs), cannabinoid receptors (CBRs), and associated signaling molecules, has been identified within the brain. In neuropathic pain animal models and patients, long-lasting alterations in the ECS have been observed. These changes of neurons and glial cells in the ECS contribute to the modulation of neuropathic pain. Intervention strategies such as the activation of CBRs, the enhancement of hydrolytic enzyme function, and the inhibition of synthetizing enzymes typically alleviate neuropathic pain through CBR-dependent mechanisms. Additionally, emotions such as fear, anxiety, and depression are frequently experienced with neuropathic pain. Exogenous cannabinoids can mitigate these mood disorders via CBR signaling pathways. Therefore, the targeting of long-lasting ECS alterations represents a potential therapeutic approach for both neuropathic pain and emotional disorders. In this review, the long-lasting variations in neurons and glial cells in the ECS related to neuropathic pain and the accompanying emotional comorbidities are elucidated. Furthermore, the cellular and molecular mechanisms underlying synaptic plasticity and neural circuit activities in the brain are reviewed.