Cytoprotective and Neuroinductive Effects of Thiol-Containing Simple Signaling Molecules

Abstract

ABSTRACTAround 20 million Americans, mostly young adults, have suffered from a peripheral nerve injury due to trauma or a medical condition. However, prevailing treatments, including those that employ exogenous growth factors, often exhibit drawbacks outweighing their benefits, highlighting the need for novel solutions. Non-complex agents that govern bioactivity, termed simple signaling molecules (SSMs), offer an exciting alternative when compared to traditional approaches due to their small size, ready availability, and influence on cellular pathways. This study explores the cytoprotective and neuroinductive effects of three thiol-containing SSMs: hydrogen sulfide (H2S), n-acetyl cysteine (NAC), and glutathione (GSH). Neural stem cells (NE-4Cs) were exposed to toxic levels of hydrogen peroxide (H2O2) while supplemented with different concentrations of H2S, NAC, or GSH to assess their cytoprotective effects. To study the neuroinductivity of H2S, NAC, and GSH with NE-4Cs, immunofluorescence microscopy for an early neuronal marker, β3-tubulin, was employed to determine stem cell neural differentiation. Significant cytoprotection was found for NAC (2 - 8 mM) and GSH (2 - 12 mM), while H2S showed limited protective effects. Interestingly, the opposite result was observed for neuroinductivity as only H2S (7.75 - 125 μM) achieved a desirable effect while NAC and GSH had minimal impact on neural differentiation. This research establishes therapeutic concentration ranges of H2S, NAC, and GSH for future drug delivery systems targeting neural regeneration, especially for peripheral nerve injuries.LAY SUMMARYApproximately 20 million Americans, mainly young adults, suffer from peripheral nerve injuries, necessitating new effective treatments. Currently emerging approaches, including growth factor-based therapies, unfortunately face considerable limitations. This study explores the potential of simple signaling molecules (SSMs) - small, readily available agents - specifically hydrogen sulfide (H2S), n-acetyl cysteine (NAC), and glutathione (GSH) for their potential to be used to address issues underlying peripheral nerve injuries. Our findings reveal NAC and GSH have cytoprotective effects, whereas H2S is neuroinductive. This research identifies optimal concentrations for future drug delivery targeting neural regeneration, especially beneficial for peripheral nerve injuries.FUTURE WORKSUpcoming investigation will concentrate on exploiting the potential of novel SSM-releasing monomers within degradable polymeric systems. This involves defining therapeutic windows and optimizing polymer chemistry to induce desired cytoprotective and neuroinductive effects in neural stem cells, crucial for peripheral nerve injury repair. Emphasizing controlled release, this approach holds promise for developing advanced therapeutic strategies utilizing H2S, NAC, and/or GSH in nerve guidance conduits.GRAPHICAL ABSTRACT