Comparative In Vitro Toxicology of Novel Cytoprotective Short-Chain Naphthoquinones

Abstract

Short-chain quinones (SCQs) have been identified as potential drug candidates against mitochondrial dysfunction, which largely depends on the reversible redox characteristics of the active quinone core. We recently identified 11 naphthoquinone derivatives, 1–11, from a library of SCQs that demonstrated enhanced cytoprotection and improved metabolic stability compared to the clinically used benzoquinone idebenone. Since the toxicity properties of our promising SCQs were unknown, this study developed multiplex methods and generated detailed toxicity profiles from 11 endpoint measurements using the human hepatocarcinoma cell line HepG2. Overall, the toxicity profiles were largely comparable across different assays, with simple standard assays showing increased sensitivity compared to commercial toxicity assays. Within the 11 naphthoquinones tested, the L-phenylalanine derivative 4 consistently demonstrated the lowest toxicity across all assays. The results of this study not only provide useful information about the toxicity features of SCQs but will also enable the progression of the most promising drug candidates towards their clinical use.

The Anti-Obesity Compound Asperuloside Reduces Inflammation in the Liver and Hypothalamus of High-Fat-Fed Mice

“…Since the safety properties of ASP were unknown, this study aimed to assess the effects of the natural compound on cellular viability using the human hepatocarcinoma cell line HepG2. This cell line is widely used for toxicity studies due to its high phenotypic stability for robust and reproducible outcomes, although HepG2 cells are less metabolically active compared with primary hepatocytes and other cell lines such as C3A or HepaRG [36].…”

Bioactivity Profiles of Cytoprotective Short-Chain Quinones

“…This study aimed to characterize the in vitro bioactivities of a library of 103 recently described short-chain naphthoquinones (SCQs) [ 22 , 24 , 26 ] to investigate the underlying mechanism(s) of SCQ-dependent cytoprotection. For this purpose, the current study employed not only the previously reported endpoints of cytoprotection and normalization of cellular ATP levels [ 26 ], but also assessed additional bioactivities of quinones that are indicative of mitochondrial function, compound bioactivation, expression or activities of cytoprotective proteins (Lin28A, Hsp70, HDAC6), oxidative damage and DNA damage.…”

“…At present, the only synthetic quinone clinically approved for a single mitochondrial disease is the benzoquinone idebenone [ 18 ], which showed some activity to protect against vision loss and restored visual acuity and color vision in LHON patients [ 19 , 20 , 21 ]. Although idebenone is safe and well tolerated in vitro (IC 50 = 151.7 μM, 24 h) [ 22 ] and in vivo (2250 mg/d, 14 d) [ 23 ], it is not an ideal drug as it shows low solubility (logP = 1.24, logD = 3.57) and more importantly is characterized by very low metabolic stability in vitro ( t 1/2 = 2 h, 40 μM) [ 24 ] and in vivo ( t 1/2 = 3 h, 150 mg) [ 25 ], which significantly restrict its therapeutic potential.…”

“…To overcome these significant limitations, we previously described a class of short-chain quinones (SCQs), which centers around a 2,3-disubstituted naphthoquinone core with an amide linkage on the alkyl side chain [ 26 ]. Some of these SCQs showed significantly higher cytoprotective activity [ 26 ], higher metabolic stability [ 24 ] and/or lower cytotoxicity [ 22 ] in the human hepatocarcinoma cell line HepG2. This cell line, widely employed in in vitro studies, represents a robust testing platform to offer reproducible outcomes due to its phenotypic stability and unlimited availability [ 27 ].…”

Short-Chain Naphthoquinone Protects Against Both Acute and Spontaneous Chronic Murine Colitis by Alleviating Inflammatory Responses

“…Recently, more than 148 novel naphthoquinones derivatives of short-chain quinones (SCQs) have been synthesised and screened in vitro for their cytoprotective activity against mitochondrial dysfunction ( Woolley et al, 2019 ). Among them, 16 amide-linked naphthoquinones showed high metabolic stability, low toxicity, and better cytoprotection in vitro ( Woolley et al, 2019 ; Feng et al, 2020a ; Feng et al, 2020b ). Indeed, one of the newly synthesised naphthoquinones (UTA77) restored vision loss in vivo in mitochondrial dysfunction-related pathology, i.e., diabetic retinopathy ( Daniel et al, 2021 ).…”