Hydrogen sulfide signalling as an additional factor to sex-related differences in ALS progression

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative and devastating disorder characterized by the death of motor neurons in spinal cord, brain stem and motor cortex, with still no convincing therapy. Several etiologic factors, including genetic and environmental ones, can contribute to such neurodegeneration. Despite the underlying causes of motor neuron death remain largely unknown, a scenario of strong oxidative stress (OS) and mitochondrial dysfunction (MD) has long been associated with ALS[1]. Recent evidence points out that this dysregulation may act as real driver of neurodegeneration worthy of greater importance than previously recognized [2]. In this perspective, a disruption of hydrogen sulfide (H₂S) metabolism has been proposed as contributor to ALS pathogenesis. Harmful H2S concentrations have been shown in a mouse model of familial ALS (fALS), SOD1G93A, in primary spinal cord cultures prepared from fALS transgene [3,4], as well as in a cohort of ALS patients compared to other neurological disorders [5]. ALS women exhibit higher levels than men do, as do SOD1G93A female mice compared to males, with increased production correlating to disease progression from early to late symptomatic stages [6].The mechanisms driving this alteration is still elusive.

Therefore, the overall goal of the current study is to shed light on this still hidden H2S-ALS crosstalk, particularly by examining gender differences in ALS.

Label free proteomics analysis was performed on spinal cord tissues (total extracts and mitochondrial enriched fractions) prepared from female and male ALS SOD1G93A and SODWT mice. Dedicated mass spectrometry-based proteomics analysis have been developed to quantify the expression of enzymes involved in both H₂S synthesis (CBS, CSE, 3MST) and catabolism (ETHE1 and SQR) to elucidate the origin of such alteration in ALS. In addition, the enrichment and mapping of cysteine-persulfides was performed.Peptide identification and quantification were carried out by Peaks and MaxQuant softwares respectively; bioinformatics analysis was performed by Ingenuity Pathway analysis (Quiagen). An altered expression of H2S producing enzymes was shown in ALS tissues, particularly in female groups. Moreover, site-specific identification and quantification of cysteine persulfides highlighted a different profile in SOD1G93A compared to SODWT especially for those proteins related to mitochondrial quality control complexes.

This investigation provides a comprehensive mapping of the redox scenario in ALS, revealing hitherto unexplored molecular features.

References:

[1] Greco, V. et al. In Mitochondria in Health and in Sickness; Springer, 2019; pp. 71–82.

[2] Jagaraj, C. et al Front. Cell. Neurosci., 2021

[3] Davoli, A.; Greco, V. et al. Ann. Neurol. 2015, 77, 697–709.

[4] Greco, V. et al. Antioxidants 2018, 7, 87.

[5] Greco, V. et al. Metabolites 2021, 11

[6] Spalloni, A.; Greco, V.; et al. Int. J. Mol. Sci. 2019, 20, 2550.