Table 1.

Curcumin and neuroprotective mechanisms.

Study type	Subjects	Dose/frequency	Outcome & Mechanisms	Reference
In vivo	Male Sprague–Dawley rats	300 mg/kg b.w.	Reducing oxidative stress levels in middle cerebral artery occlusion	(Wu et al., 2013)
			Increasing phospho-Akt, Nrf2, and NQO1 expression levels
			Upregulating Nrf2 activity
In vivo	Male Sprague–Dawley rats	5, 10 and 20 mg/kg /day for 30 days	Upregulating PI3K expression	(Yang et al., 2014)
			Activating the BDNF/TrkB-dependent pathway
			Increasing the contents of monoaminergic neurotransmitters
In vitro / In vivo	Primary hippocampus neurons/APP/PS1 transgenic mice	150 mg/kg /day for 4 weeks	Reducing the activation of microglia and astrocytes	(Liu et al., 2016)
			Inhibiting the NF-κB signaling pathway
			Increasing the transcriptional activity and protein levels of PPARγ
In vivo	Male Sprague–Dawley rats	5, 10 and 20 mg/kg /day for 30 days	Increasing levels of SOD and GSH-Px	(Song et al., 2016)
			Increasing levels of Dopamine and acetylcholine
			Upregulating of bFGF, NGF, and TrkA
In vivo	Male Wistar rats	100 mg/kg b.w. for 28 days	Modulating the PI3K/Akt/GSK3β neuronal survival pathway	(Srivastava et al., 2018)
			Increasing levels of pCaMKIIα/CaMKIIα and PSD95
			Increasing levels of pCREB/CREB
In vivo	Tg2576 mice	160 and 5000 mg/mL for 6 months	Immunomodulator of the TREM2-CD33-TyroBP hub	(Teter et al., 2019)
			Stimulating phagocytosis and altering inflammatory cytokines expression
			Reducing levels of miR-155
In vivo	Male Sprague Dawley rats	200 mg/kg b.w.	Attenuating autophagic activities through mediating the PI3K/Akt/mTOR pathway	(Huang et al., 2018)
			Suppressing an inflammatory reaction by regulating the TLR4/p38/MAPK pathway
In vivo	Male Sprague Dawley rats	100 mg/kg b.w.	Activating the Nrf2-ARE pathway	(Dai et al., 2018)