Xanthotoxin and umbelliferone attenuate cognitive dysfunction in a streptozotocin-induced rat model of sporadic Alzheimer's disease: The role of JAK2/STAT3 and Nrf2/HO-1 signalling pathway modulation.

The aim of the present study was to assess the neuroprotective effects of xanthotoxin and umbelliferone in streptozotocin (STZ)-induced cognitive dysfunction in rats. Animals were injected intracerebroventricularly (ICV) with STZ (3 mg/kg) once to induce a sporadic Alzheimer's disease (SAD)-like condition. Xanthotoxin or umbelliferone (15 mg/kg, i.p.) were administered 5 hr after ICV-STZ and daily for 20 consecutive days. Xanthotoxin or umbelliferone prevented cognitive deficits in the Morris water maze and object recognition tests. In parallel, xanthotoxin or umbelliferone reduced hippocampal acetylcholinestrase activity and malondialdehyde level. Moreover, xanthotoxin or umbelliferone increased glutathione content. These coumarins also modulated neuronal cell death by reducing the level of proinflammatory cytokines (tumour necrosis factor-alpha and interleukin-6), inhibiting the overexpression of inflammatory markers (nuclear factor κB [NF-κB] and cyclooxygenase II), and upregulating the expression of NF-κB inhibitor (IκB-α). Interestingly, xanthotoxin diminished phosphorylated JAK2 and phosphorylated STAT3 protein expression, while umbelliferone markedly replenished nuclear factor erythroid-derived 2-like 2 (Nrf2) and haem oxygenase-1 (HO-1) levels. The current study provides evidence for the protective effect of xanthotoxin and umbelliferone in STZ-induced cognitive dysfunction in rats. This effect may be attributed, at least in part, to inhibiting acetylcholinestrase and attenuating oxidative stress, neuroinflammation and neuronal loss.

Repositioning of baricitinib for management of memory impairment in ovariectomized/D-galactose treated rats: A potential role of JAK2/STAT3-PI3K/AKT/mTOR signaling pathway.

AIMS: Neuroinflammation plays a pivotal role in amyloid ß (Aß) plaques formation which is among the hallmarks of Alzheimer's disease (AD). The present study investigated the potential therapeutic effects of baricitinib (BAR), a selective JAK2/ STAT3 inhibitor, in ovariectomized/ D-galactose (OVX/D-gal) treated rats as a model for AD. MAIN METHODS: To induce AD, adult female rats (130-180 g) underwent bilateral ovariectomy and were injected daily with 150 mg/kg, i.p. D-gal for 8 consecutive weeks. BAR (10 and 50 mg/kg/day) was then given orally for 14 days. KEY FINDINGS: BAR in a dose-dependent effect mitigated OVX/D-gal-induced aberrant activation of JAK2/STAT3 signaling pathway resulting in significant decreases in the expression of p-JAK 2, and p-STAT3 levels, along with deactivating AKT/PI3K/mTOR signaling as evidenced by deceased protein expression of p-AKT, p-PI3K, and p-mTOR. As a result, neuroinflammation was diminished as evidenced by decreased NF-κß, TNF-α, and IL-6 levels. Moreover, oxidative stress biomarkers levels as iNOS, and MDA were reduced, whereas GSH was increased by BAR. BAR administration also succeeded in reverting histopathological alterations caused by OVX/D-gal, increased the number of intact neurons (detected by Nissl stain), and diminished astrocyte hyperactivity assessed as GFAP immunoreactivity. Finally, treatment with BAR diminished the levels of Aß. These changes culminated in enhancing spatial learning and memory in Morris water maze, and novel object recognition test. SIGNIFICANCE: BAR could be an effective therapy against neuroinflammation, astrogliosis and cognitive impairment induced by OVX/ D-gal where inhibiting JAK2/STAT3- AKT/PI3K/mTOR seems to play a crucial role in its beneficial effect.