Hydrogen Sulfide Inhibits Amyloid Formation

Abstract

Amyloid fibrils are large aggregates of misfolded proteins, which are often associated with various neurodegenerative diseases such as Alzheimer’s, Parkinson’s, Huntington’s, and vascular dementia. The amount of hydrogen sulfide (H2S) is known to be significantly reduced in the brain tissue of people diagnosed with Alzheimer’s disease relative to that of healthy individuals. These findings prompted us to investigate the effects of H2S on the formation of amyloids in vitro using a model fibrillogenic protein hen egg white lysozyme (HEWL). HEWL forms typical β-sheet rich fibrils during the course of 70 min at low pH and high temperatures. The addition of H2S completely inhibits the formation of β-sheet and amyloid fibrils, as revealed by deep UV resonance Raman (DUVRR) spectroscopy and ThT fluorescence. Nonresonance Raman spectroscopy shows that disulfide bonds undergo significant rearrangements in the presence of H2S. Raman bands corresponding to disulfide (RSSR) vibrational modes in the 550–500 cm–1 spectral range decrease in intensity and are accompanied by the appearance of a new 490 cm–1 band assigned to the trisulfide group (RSSSR) based on the comparison with model compounds. The formation of RSSSR was proven further using a reaction with TCEP reduction agent and LC-MS analysis of the products. Intrinsic tryptophan fluorescence study shows a strong denaturation of HEWL containing trisulfide bonds. The presented evidence indicates that H2S causes the formation of trisulfide bridges, which destabilizes HEWL structure, preventing protein fibrillation. As a result, small spherical aggregates of unordered protein form, which exhibit no cytotoxicity by contrast with HEWL fibrils.

Dietary restriction transforms the protein sulfhydrome in a tissue-specific and cystathionine γ-lyase-dependent manner

“…As sulfhydration offers a protective barrier on protein cysteine residues from irreversible oxidative modifications (Filipovic et al, 2018), it first protects the proteome from unwanted oxidative stress and prevents the need to synthesize new proteins to replace those that have been damaged. It also offers neuroprotection by preventing protein misfolding and amyloid formation linked to a number of neurodegenerative diseases (Rosario-Alomar et al, 2015). Most importantly, it enhances the anti-aging and cytoprotective activities of longevity and metabolism associated proteins such as, but not limited to, glyceraldehyde phosphate dehydrogenase (GAPDH) (Gao et al, 2015;Mustafa et al, 2009), nuclear factor κB (NF-κB) (Sen et al, 2012), endothelial ATP-sensitive potassium channels (Mustafa et al, 2011), sirtuin 1 (SIRT1) (Du et al, 2019), and the E3 ubiquitin ligase parkin (Vandiver et al, 2013).…”

Exploring the structure and formation mechanism of amyloid fibrils by Raman spectroscopy: a review

“…Rosario-Alomar et al investigated the nature of H 2 S interactions with disulfide bonds using NR spectroscopy. 70 It was found that the sulfur atom of H 2 S becomes endogenously incorporated in protein disulfide bonds, which lead to the formation of trisulfides (SSS).…”

“…DUVRR spectra (C) of native HEWL (red), HEWL fibrils (blue) and spherical aggregates formed in the presence of H 2 S (black); spectra were normalized using the aromatic amino acid Raman band around 1600 cm −1 for comparison 70. …”

Nanoscale Discrimination between Toxic and Nontoxic Protein Misfolded Oligomers with Tip‐Enhanced Raman Spectroscopy

“…In order to rule out intensity biases due to local fluctuations in the enhancement factor as well as in surface density and local molecular orientation of the samples, which could influence the signal measured from the type A and type B samples, we normalized the intensity of the main peaks in the 1000–1030 and 1500–1680 cm −1 regions with respect to the corresponding intensity of the Phe mode at 1003 cm −1 ( I / I 1003 , Figure ) on a spectrum‐by‐spectrum basis. This latter mode (as well as the 1027 cm −1 mode), in fact, is poorly affected by the environment and frequently used as “internal” reference for the analysis of biological samples . We note that the amide I as well as the amide II modes exhibit almost overlapping I / I 1003 interval values in both type A and type B oligomers and their average values approach the Phe mode at 1003 cm −1 .…”

“…This latter mode (as well as the 1027 cm −1 mode), in fact, is poorly affected by the environment and frequently used as "internal" reference for the analysis of biological samples. [49,50] We note that the amide I as well as the amide II modes exhibit almost overlapping I/I 1003 interval values in both type A and type B oligomers and their average values approach the Phe mode at 1003 cm −1 . Conversely, the other modes appear largely more intense in type A than in type B spectra.…”