Phosphodiesterase 5 inhibitor mirodenafil ameliorates Alzheimer-like pathology and symptoms by multimodal actions

Abstract

Background Alzheimer’s disease (AD) pathology is associated with complex interactions among multiple factors, involving an intertwined network of various signaling pathways. The polypharmacological approach is an emerging therapeutic strategy that has been proposed to overcome the multifactorial nature of AD by targeting multiple pathophysiological factors including amyloid-β (Aβ) and phosphorylated tau. We evaluated a blood-brain barrier penetrating phosphodiesterase 5 (PDE5) inhibitor, mirodenafil (5-ethyl-2-7-n-propyl-3,5-dihydrro-4H-pyrrolo[3,2-d]pyrimidin-4-one), for its therapeutic effects on AD with polypharmacological properties. Methods To evaluate the potential of mirodenafil as a disease-modifying AD agent, mirodenafil was administered to test its effects on the cognitive behaviors of the APP-C105 AD mouse model using the Morris water maze and passive avoidance tests. To investigate the mechanisms of action that underlie the beneficial disease-modifying effects of mirodenafil, human neuroblastoma SH-SY5Y cells and mouse hippocampal HT-22 cells were used to show mirodenafil-induced alterations associated with the cyclic guanosine monophosphate (cGMP)/cGMP-dependent protein kinase (PKG)/cAMP-responsive element-binding protein (CREB) pathway, apoptotic cell death, tau phosphorylation, amyloidogenesis, the autophagy-lysosome pathway, glucocorticoid receptor (GR) transcriptional activity, and the Wnt/β-catenin signaling. Results Here, mirodenafil is demonstrated to improve cognitive behavior in the APP-C105 mouse model. Mirodenafil not only reduced the Aβ and phosphorylated tau burdens in vivo, but also ameliorated AD pathology induced by Aβ through the modulation of the cGMP/PKG/CREB signaling pathway, glycogen synthase kinase 3β (GSK-3β) activity, GR transcriptional activity, and the Wnt/β-catenin signaling in neuronal cells. Interestingly, homodimerization and nuclear localization of GR were inhibited by mirodenafil, but not by other PDE5 inhibitors. In addition, only mirodenafil reduced the expression levels of the Wnt antagonist Dickkopf-1 (Dkk-1), thus activating the Wnt/β-catenin signaling. Conclusions These findings strongly suggest that the PDE5 inhibitor mirodenafil shows promise as a potential polypharmacological drug candidate for AD treatment, acting on multiple key signaling pathways involved in amyloid deposition, phosphorylated tau burden, the cGMP/PKG/CREB pathway, GSK-3β kinase activity, GR signaling, and the Wnt/β-catenin signaling. Mirodenafil administration to the APP-C105 AD mouse model also improved cognitive behavior, demonstrating the potential of mirodenafil as a polypharmacological AD therapeutic agent.

The Role of Tau Protein on Alzheimer’s Disease

“…The p-tax burden was also decreased by 16% [19]. Moreover, hydrogen peroxide-induced calcium ion spike in cells was remarkably decreased by treating with mirodenafil, which is also a meaningful discovery as the hydrogen peroxide is responsible for rising intracellular calcium ion levels that could induce contraction of brain pericytes [19].…”

“…It has been reported that mitochondrial depolarization enhances apoptosis in neurons [6]. Combined treatment with mirodenafil showed the ability to remarkably reduce the concentration of apoptotic markers like caspase-3, by which the neuronal survival rate raised compared with treating with A-beta42 alone [19]. The p-tax burden was also decreased by 16% [19].…”

“…Mirodenafil acts as phosphodiesterase 5 inhibitor, which has a variety of functions such as reducing p-tax burden, inhibiting apoptosis, and impeding several pathways to reduce pathological tau accumulation [19]. In the transgenic AD mice model, mice treated with mirodenafil got a 64%-time decline and a 44% distance decrease compared with mice with AD but without any treatment in water maze training, indicating the potential of mirodenafil in improving the cognitive ability in AD patients [19]. By shielding mitochondrial membrane potential, mirodenafil can also prevent neuronal unnatural death.…”

“…Combined treatment with mirodenafil showed the ability to remarkably reduce the concentration of apoptotic markers like caspase-3, by which the neuronal survival rate raised compared with treating with A-beta42 alone [19]. The p-tax burden was also decreased by 16% [19]. Moreover, hydrogen peroxide-induced calcium ion spike in cells was remarkably decreased by treating with mirodenafil, which is also a meaningful discovery as the hydrogen peroxide is responsible for rising intracellular calcium ion levels that could induce contraction of brain pericytes [19].…”

Neuroprotective Effect of NO-Delivery Dinitrosyl Iron Complexes (DNICs) on Amyloid Pathology in the Alzheimer’s Disease Cell Model

“…31 Inhibition of PDE-5 could ameliorate AD pathology and improve cognitive behavior in vivo by enhancing the NO-cGMP pathway. 32 Thus, targeting NO might be an effective therapy for AD. 33 However, NO has a short half-life under biological systems due to its reaction with O 2 .…”