Sirtuin 1 Inhibiting Thiocyanates (S1th)—A New Class of Isotype Selective Inhibitors of NAD+ Dependent Lysine Deacetylases

Abstract

Sirtuin 1 (Sirt1) is a NAD + dependent lysine deacetylase associated with the pathogenesis of various diseases including cancer. In many cancer types Sirt1 expression is increased and higher levels have been associated with metastasis and poor prognosis. However, it was also shown, that Sirt1 can have tumor suppressing properties and in some instances even a dual role for the same cancer type has been reported. Increased Sirt1 activity has been linked to extension of the life span of cells, respectively, organisms by promoting DNA repair processes and downregulation of tumor suppressor proteins. This may have the downside of enhancing tumor growth and metastasis. In mice embryonic fibroblasts depletion of Sirt1 was shown to decrease levels of the DNA damage sensor histone H2AX. Impairment of DNA repair mechanisms by Sirt1 can promote tumorigenesis but also lower chemoresistance toward DNA targeting therapies. Despite many biological studies, there is currently just one small molecule Sirt1 inhibitor in clinical trials. Selisistat (EX-527) reached phase III clinical trials for treatment of Huntington's Disease. New small molecule Sirt1 modulators are crucial for further investigation of the contradicting roles of Sirt1 in cancer. We tested a small library of commercially available compounds that were proposed by virtual screening and docking studies against Sirt1, 2 and 3. A thienopyrimidone featuring a phenyl thiocyanate moiety was found to selectively inhibit Sirt1 with an IC 50 of 13 µM. Structural analogs lacking the thiocyanate function did not show inhibition of Sirt1 revealing this group as key for the selectivity and affinity toward Sirt1. Further analogs with higher solubility were identified through iterative docking studies and in vitro testing. The most active compounds (down to 5 µM IC 50) were further studied in cells. The ratio of phosphorylated γH2AX to unmodified H2AX is lower when Sirt1 is depleted or inhibited. Our new Sirtuin 1 inhibiting thiocyanates (S1th) lead to similarly lowered γH2AX/H2AX ratios in mouse embryonic fibroblasts as Sirt1 knockout and treatment with the reference inhibitor EX-527. In Wössner et al. Sirtuin 1 Inhibiting Thiocyanates (S1th) addition to that we were able to show antiproliferative activity, inhibition of migration and colony forming as well as hyperacetylation of Sirt1 targets p53 and H3 by the S1th in cervical cancer cells (HeLa). These results reveal thiocyanates as a promising new class of selective Sirt1 inhibitors.

A small molecule compound with an indole moiety inhibits the main protease of SARS-CoV-2 and blocks virus replication

“…8a ). The observed shifts of T m values to lower temperatures have reportedly been associated with an apparent destabilization of the protein by covalently-bound compounds 36 – 38 . Thus, these data corroborate that GRL-1720 forms a covalent bond with M pro .…”

“…Of note, the interpretation of a decreased T m in the case of lopinavir is complex. In general, destabilizers have been largely dismissed and removed from detailed investigations; however, all such destabilizers have been summarily placed into the non-specific binder category 36 – 38 . In conclusion, these thermal stability data suggest that GRL-1720 forms covalent interactions with M pro , while 5h likely forms reversible covalent interactions 35 with M pro .…”

SIRT1 and SIRT2 Activity Control in Neurodegenerative Diseases

“…The study came up with the novel amino acid coupled SIRT1 selective inhibitor. A phenyl thiocyanate was also found to be a selective inhibitor for SIRT1, as identified in a recent study (Wössner et al, 2020). As SIRT1 inhibition was focused on cancer treatment, the inhibitory thiocyanates (S1th) were tested for antiproliferative activity, inhibition of migration, and colony formation as well as hyperacetylation of Sirt1 targets p53 and H3 in cervical cancer cells (HeLa).…”

“…A randomized, double-blind placebo-controlled multicenter exploratory clinical trial with selisistat also established its safety and tolerability for the HD patients ( Süssmuth et al, 2015 ). Selisistat has currently reached phase III clinical trials for the treatment of HD ( Wössner et al, 2020 ). Sesame lignans (50 mg of sesamin/episesamin = 1/1) were also confirmed to be safe and tolerable in healthy subjects ( Tomimori et al, 2013 ).…”

The Role of Sirtuin-1 in Immune Response and Systemic Lupus Erythematosus

“…In a large-scale fluorimetric screening research, indole derivatives that are potential SIRT1 inhibitors have been found with IC50 values ranging from 60 to 100 nM ( 40 ). Other exogenous SIRT1 inhibitors such as EX-527, tetrahydrocarbazole, thiobarbiturates, thiocyanates, and phloroglucinol derivatives have also been intensively studied ( 9 , 41 ).…”