Selective Targeting of Non-nuclear Estrogen Receptors with PaPE-1 as a New Treatment Strategy for Alzheimer’s Disease

Abstract

Alzheimer’s disease (AD) is a multifactorial and severe neurodegenerative disorder characterized by progressive memory decline, the presence of Aβ plaques and tau tangles, brain atrophy, and neuronal loss. Available therapies provide moderate symptomatic relief but do not alter disease progression. This study demonstrated that PaPE-1, which has been designed to selectively activate non-nuclear estrogen receptors (ERs), has anti-AD capacity, as evidenced in a cellular model of the disease. In this model, the treatment of mouse neocortical neurons with Aβ (5 and 10 μM) induced apoptosis (loss of mitochondrial membrane potential, activation of caspase-3, induction of apoptosis-related genes and proteins) accompanied by increases in levels of reactive oxygen species (ROS) and lactate dehydrogenase (LDH) as well as reduced cell viability. Following 24 h of exposure, PaPE-1 inhibited Aβ-evoked effects, as shown by reduced parameters of neurotoxicity, oxidative stress, and apoptosis. Because PaPE-1 downregulated Aβ-induced Fas/FAS expression but upregulated that of Aβ-induced FasL, the role of PaPE-1 in controlling the external apoptotic pathway is controversial. However, PaPE-1 normalized Aβ-induced loss of mitochondrial membrane potential and restored the BAX/BCL2 ratio, suggesting that the anti-AD capacity of PaPE-1 particularly relies on inhibition of the mitochondrial apoptotic pathway. These data provide new evidence for an anti-AD strategy that utilizes the selective targeting of non-nuclear ERs with PaPE-1.

Posttreatment Strategy Against Hypoxia and Ischemia Based on Selective Targeting of Nonnuclear Estrogen Receptors with PaPE-1

“…Furthermore, in the present study, PaPE-1-evoked neuroprotection was mediated through a reduction in ROS formation and enhancement of cellular metabolic activity that was dysregulated in the course of hypoxia and ischemia. Previously, we showed that PaPE-1 has the ability to reduce ROS formation and to prevent apoptosis through the restoration of the mitochondrial membrane potential and BAX/BCL2 ratio as well as the downregulation of Fas/ FAS expression (Wnuk et al 2020a), which concurs with the results of the present research. Interestingly, estrogen deficiency appeared to predispose brain neurons to apoptosis following cerebral ischemia (Guo et al 2017), which supports essential roles of estrogen-based compounds such as PaPE-1 in pharmacotherapy of stroke and perinatal asphyxia.…”

“…However, similar to E2, PaPE-1 strongly activates the MAPK and mTOR pathways. The neuroprotective capacity of PaPE-1 against Amyloid β (Aβ)-induced neurotoxicity and apoptosis has already been evidenced by our group (Wnuk et al 2020a). We showed that following 24 h of exposure, PaPE-1 inhibited Aβ-evoked effects, as shown by reduced parameters of neurotoxicity, oxidative stress, and apoptosis.…”

“…Newly synthesized PaPE-1 selectively activates membrane (nonnuclear/extranuclear) estrogen receptors (ERs), namely, mERα, and mERβ, and has been shown to evoke neuroprotection in a cellular model of AD and in a mouse model of stroke, specifically transient middle cerebral artery occlusion (tMCAO). PaPE-1 appeared to inhibit both Aβ-induced neurotoxicity in mouse primary neurons in in vitro cultures and tMCAO-evoked infarction and leukocyte infiltration into the ischemic mouse brain (Wnuk et al 2020a;Selvaraj et al 2018). However, until recently, PaPE-1's effectiveness in protecting brain tissue against hypoxia/ischemia has been verified only in a pretreatment paradigm, namely, PaPE-1 was administered 24 h before inducing brain lesions via tMCAO.…”

“…Primary neocortical cultures were prepared from CD-1 ® IGS Swiss mouse embryos at 15 days of gestation (Charles River, Germany) as previously described (Kajta et al 2006;Wnuk et al 2020a, b). The cortices were mechanically and then enzymatically fragmented with 0.1% trypsin for 15 min at 37 °C.…”

“…During reoxygenation, cells were cultured in a humidified incubator (New Brunswick Scientific, NJ, USA). PaPE-1 was dissolved in DMSO, not exceeding a concentration of 0.1% in the culture medium, as previously described (Wnuk et al 2020a).…”