Sildenafil Alleviates Murine Experimental Autoimmune Encephalomyelitis by Triggering Autophagy in the Spinal Cord.

Eduardo Duarte-Silva,Wilma Helena Oliveira,Amanda Pires Bonfanti,Christina Alves Peixoto,Deniele Bezerra Lós,Gabriela Peron,Livia De Lima Thomaz,Liana Verinaud,Shyrlene Meiry Da Rocha Araújo

doi:10.3389/fimmu.2021.671511

Abstract

Multiple Sclerosis (MS) is a neuroinflammatory and chronic Central Nervous System (CNS) disease that affects millions of people worldwide. The search for more promising drugs for the treatment of MS has led to studies on Sildenafil, a phosphodiesterase type 5 Inhibitor (PDE5I) that has been shown to possess neuroprotective effects in the Experimental Autoimmune Encephalomyelitis (EAE), an animal model of MS. We have previously shown that Sildenafil improves the clinical score of EAE mice via modulation of apoptotic pathways, but other signaling pathways were not previously covered. Therefore, the aim of the present study was to further investigate the effects of Sildenafil treatment on autophagy and nitrosative stress signaling pathways in EAE. 24 female C57BL/6 mice were divided into the following groups: (A) Control - received only water; (B) EAE - EAE untreated mice; (C) SILD - EAE mice treated with 25mg/kg of Sildenafil s.c. The results showed that EAE mice presented a pro-nitrosative profile characterized by high tissue nitrite levels, lowered levels of p-eNOS and high levels of iNOS. Furthermore, decreased levels of LC3, beclin-1 and ATG5, suggests impaired autophagy, and decreased levels of AMPK in the spinal cord were also detected in EAE mice. Surprisingly, treatment with Sildenafil inhibited nitrosative stress and augmented the levels of LC3, beclin-1, ATG5, p-CREB and BDNF and decreased mTOR levels, as well as augmented p-AMPK. In conclusion, we propose that Sildenafil alleviates EAE by activating autophagy via the eNOS-NO-AMPK-mTOR-LC3-beclin1-ATG5 and eNOS-NO-AMPK-mTOR-CREB-BDNF pathways in the spinal cord.

Highlights

Multiple Sclerosis (MS) is a chronic neurodegenerative disease of the Central Nervous System (CNS) with a strong immuneinflammatory component underpinning is etiopathogenesis [1]
To assess whether the prophylactic administration of Sildenafil could prevent the development of motor dysfunction in EAE mice or even prevent a severe motor dysfunction, we evaluated mice daily to observe any changes in the motor function
When in excess nitrosative stress can lead to protein misfolding and aggregation, which contributes to neurodegeneration [24, 25]

Summary

Introduction

Multiple Sclerosis (MS) is a chronic neurodegenerative disease of the Central Nervous System (CNS) with a strong immuneinflammatory component underpinning is etiopathogenesis [1]. A previous study by our group has shown that Sildenafil at a dose of 25 mg/kg s.c. has neuroprotective effects because it inhibits demyelination, neuroinflammation and apoptosis in the spinal cord of EAE mice, which is directly related to the motor dysfunction observed in EAE mice [9]. These different studies highlighted different aspects of the same pathology and contributed to our understanding of how the disease evolves and how it could be treated, since they highlighted different molecular targets. The aim of the present study was to further explore the signaling pathways underlying the mechanism of action of Sildenafil in EAE, focusing on nitrosative stress and autophagy pathways

Objectives

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Results

Conclusion