DNA methylation by dimethyl sulfoxide and methionine sulfoxide triggered by hydroxyl radical and implications for epigenetic modifications

Methylsulfonylmethane: Applications and Safety of a Novel Dietary Supplement

Methylsulfonylmethane (MSM) has become a popular dietary supplement used for a variety of purposes, including its most common use as an anti-inflammatory agent. It has been well-investigated in animal models, as well as in human clinical trials and experiments. A variety of health-specific outcome measures are improved with MSM supplementation, including inflammation, joint/muscle pain, oxidative stress, and antioxidant capacity. Initial evidence is available regarding the dose of MSM needed to provide benefit, although additional work is underway to determine the precise dose and time course of treatment needed to provide optimal benefits. As a Generally Recognized As Safe (GRAS) approved substance, MSM is well-tolerated by most individuals at dosages of up to four grams daily, with few known and mild side effects. This review provides an overview of MSM, with details regarding its common uses and applications as a dietary supplement, as well as its safety for consumption.

Visible-light-induced and iron-catalyzed methylation of N-arylacrylamides with dimethyl sulphoxide: a convenient access to 3-ethyl-3-methyl oxindoles

An efficient synthesis of 3-ethyl-3-methyl oxindoles by visible-light promoted and iron-catalyzed difunctionalization of N-arylacrylamides with dimethyl sulphoxide was developed.

Free-radical initiated cascade methylation or trideuteromethylation of isocyanides with dimethyl sulfoxides

The methylation or trideuteromethylation reaction of isocyanides with dimethyl sulfoxides in a radical way is developed, which offers a low-cost, easy-operation cascade methylation strategy for the synthesis of phenanthridines or isoquinolines.

The mutagenic mechanism of oxygenated alkylhydrazones occurs through alkyl radicals and alkyldiazonium ions

Hydrazone hydroperoxides were formed by autoxidation and their mutagenicity was derived from the alkyldiazonium ion and the radical species.

Cryopreservation of testicular tissue or testicular cell suspensions: a pivotal step in fertility preservation

BACKGROUND

Germ cell depletion caused by chemical or physical toxicity, disease or genetic predisposition can occur at any age. Although semen cryopreservation is the first reflex for preserving male fertility, this cannot help out prepubertal boys. Yet, these boys do have spermatogonial stem cells (SSCs) that able to produce sperm at the start of puberty, which allows them to safeguard their fertility through testicular tissue (TT) cryopreservation. SSC transplantation (SSCT), TT grafting and recent advances in in vitro spermatogenesis have opened new possibilities to restore fertility in humans. However, these techniques are still at a research stage and their efficiency depends on the amount of SSCs available for fertility restoration. Therefore, maintaining the number of SSCs is a critical step in human fertility preservation. Standardizing a successful cryopreservation method for TT and testicular cell suspensions (TCSs) is most important before any clinical application of fertility restoration could be successful.

OBJECTIVE AND RATIONALE

This review gives an overview of existing cryopreservation protocols used in different animal models and humans. Cell recovery, cell viability, tissue integrity and functional assays are taken into account. Additionally, biosafety and current perspectives in male fertility preservation are discussed.

SEARCH METHODS

An extensive PubMED and MEDline database search was conducted. Relevant studies linked to the topic were identified by the search terms: cryopreservation, male fertility preservation, (immature)testicular tissue, testicular cell suspension, spermatogonial stem cell, gonadotoxicity, radiotherapy and chemotherapy.

OUTCOMES

The feasibility of fertility restoration techniques using frozen-thawed TT and TCS has been proven in animal models. Efficient protocols for cryopreserving human TT exist and are currently applied in the clinic. For TCSs, the highest post-thaw viability reported after vitrification is 55.6 ± 23.8%. Yet, functional proof of fertility restoration in the human is lacking. In addition, few to no data are available on the safety aspects inherent to offspring generation with gametes derived from frozen-thawed TT or TCSs. Moreover, clarification is needed on whether it is better to cryopreserve TT or TCS.

WIDER IMPLICATIONS

Fertility restoration techniques are very promising and expected to be implemented in the clinic in the near future. However, inter-center variability needs to be overcome and the gametes produced for reproduction purposes need to be subjected to safety studies. With the perspective of a future clinical application, there is a dire need to optimize and standardize cryopreservation and safety testing before using frozen-thawed TT of TCSs for fertility restoration.

What causes human cancer? Approaches from the chemistry of DNA damage

To prevent human cancers, environmental mutagens must be identified. A common mechanism of carcinogenesis is DNA damage, and thus it is quite possible that environmental mutagens can be trapped as adducts by DNA components. It is also important to identify new types of DNA damaging reactions and clarify their mechanisms. In this paper, I will provide typical examples of our efforts to identify DNA damage by environmental agents, from chemistry-based studies. 1) Oxidative DNA damage: 8-Hydroxydeoxyguanosine (8-OHdG, 8-oxodG) was discovered during a structural study of DNA modifications caused in vitro by heating glucose, which was used as a model of cooked foods. We found that various oxygen radical-forming agents induced the formation of 8-OHdG in DNA, in vitro and in vivo. Analyses of the urinary 8-OHdG levels are useful to assess the extent of oxidative DNA damage in a human population. 2) Lipid peroxide-derived DNA adducts: We searched for mutagens that react with deoxynucleosides, in model systems of lipid peroxidation. The reaction mixtures were analyzed by high performance liquid chromatography (HPLC), and we discovered various lipid peroxide-derived mutagens, including new mutagens. Some of these adducts were detected in human DNA. These mutagens may be involved in lipid peroxide-related cancers. 3) Methylation of cytosine by free radicals: Methylation of the cytosine C-5 position is an important mechanism of carcinogenesis, in addition to gene mutations. However, the actual mechanisms of de novo methylation in relation to environmental agents are not clear. We found that cytosine C-5 methylation occurred by a free radical mechanism. The possible role of this radical-induced DNA methylation in carcinogenesis will be discussed, in relation to the presently accepted concept of cancer epigenetics. In these studies, chemical analyses of the adducts formed in model reactions led to the discoveries of new mutagens and important types of DNA modifications, which seem to be involved in human carcinogenesis.

Radical trideuteromethylation with deuterated dimethyl sulfoxide in the synthesis of heterocycles and labelled building blocks

A selective introduction of trideuteromethyl groups for the synthesis of labelled compounds under radical reaction conditions is demonstrated.

Free radical-mediated cytosine C-5 methylation triggers epigenetic changes during carcinogenesis

The methylation of the C-5 position of deoxycytidine (dC) in the promoter regions of tumor suppressor genes is often observed in cancer cells. We found that various environmental agents, as well as endogenous compounds such as methionine sulfoxide (MetO), generate methyl radicals and modify dC to form 5-methyl-dC in DNA in vitro. We confirmed that both DNA methylation and cancer incidence in the liver were increased by the administration of MetO to oxidatively stressed mice. In this review, we summarize previous reports on methyl radical generation in vitro and in vivo and DNA modifications by methyl radicals, including our discoveries, as well as our recent experimental evidence suggesting that free radical-mediated dC methylation triggers epigenetic changes.

Synthetic polymeric variant of S-adenosyl methionine synthetase

Side-chain l-methionine containing polymers show the ability to donate a methyl group in the absence of a methyltransferase enzyme, which confirms their enzyme-like activity.

C-H methylation of heteroarenes inspired by radical SAM methyl transferase

A practical C–H functionalization method for the methylation of heteroarenes is presented. Inspiration from Nature’s methylating agent, S-adenosylmethionine (SAM), allowed for the design and development of zinc bis(phenylsulfonylmethanesulfinate), or PSMS. The action of PSMS on a heteroarene generates a (phenylsulfonyl)methylated intermediate that can be easily separated from unreacted starting material. This intermediate can then be desulfonylated to the methylated product or elaborated to a deuteriomethylated product, and can divergently access medicinally important motifs. This mild, operationally simple protocol that can be conducted in open air at room temperature is compatible with sensitive functional groups for the late-stage functionalization of pharmacologically relevant substrates.

Synthesis and biological evaluation of Germanium(IV)-polyphenol complexes as potential anti-cancer agents

Germanium (Ge) is considered to play a key role in the pharmacological effects of some medicinal plants. Here, two new Ge(IV)-polyphenol complexes were synthesized and measured for their potential biological activities. The results indicated that these Ge(IV)-polyphenol complexes possessed great anti-oxidative activities, both showing stronger hydroxyl scavenging effects than their corresponding ligands. We also demonstrated the strong intercalating abilities of Ge(IV)-polyphenol complexes into calf thymus-DNA molecules. In addition, these two Ge(IV)-polyphenol complexes showed strong proliferative inhibition effect on HepG2 cancer cells. Moreover, the morphological changes in HepG2 cells induced by Ge(IV)-polyphenol complexes were detected by atomic force microscopy. All these results collectively suggested that Ge(IV)-polyphenol complexes could be served as promising pharmacologically active substances against cancer treatment.

Direct analysis of 5-methylcytosine and 5-methyl-2'-deoxycytidine in human urine by isotope dilution LC-MS/MS: correlations with N-methylated purines and oxidized DNA lesions

Recent evidence suggests that active DNA demethylation involves base excision repair (BER) and nucleotide excision repair (NER) pathways. We hypothesized that the resulting excision products could be further excreted and present in urine. A highly specific and sensitive liquid chromatography-tandem mass spectrometric (LC-MS/MS) method was first developed for simultaneously measuring urinary 5-methylcytosine (5-meC) and 5-methyl-2'-deoxycytidine (5-medC). With the use of isotope internal standards and online solid-phase extraction (SPE), the detection limits of 5-meC and 5-medC were estimated to be 1.2 and 0.3 pg, respectively. This method was applied to measure urinary samples of 376 healthy males. Urinary samples were also measured for methylated and oxidized DNA lesions, namely, N7-methylguanine (N7-meG), N3-methyladenine (N3-meA), 8-oxo-7,8-dihydroguanine (8-oxoGua), and 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG), using reported online SPE LC-MS/MS methods. Results showed that mean urinary levels of 5-meC and 5-medC were 28.4 ± 14.3 and 7.04 ± 7.2 ng/mg creatinine, respectively, supporting the possible presence of DNA demethylation through BER and NER mechanisms. Urinary levels of 5-meC were significantly positively correlated with N7-meG, N3-meA, and 8-oxodG. Good correlations between 5-meC and methylated and oxidized DNA lesions may have implied the underlying linkage between genetic (DNA lesions) and epigenetic (DNA methylation) alterations derived from exogenous exposure and/or from endogenous cellular processes in human and require further investigation.

The redox basis of epigenetic modifications: from mechanisms to functional consequences

Epigenetic modifications represent mechanisms by which cells may effectively translate multiple signaling inputs into phenotypic outputs. Recent research is revealing that redox metabolism is an increasingly important determinant of epigenetic control that may have significant ramifications in both human health and disease. Numerous characterized epigenetic marks, including histone methylation, acetylation, and ADP-ribosylation, as well as DNA methylation, have direct linkages to central metabolism through critical redox intermediates such as NAD(+), S-adenosyl methionine, and 2-oxoglutarate. Fluctuations in these intermediates caused by both normal and pathologic stimuli may thus have direct effects on epigenetic signaling that lead to measurable changes in gene expression. In this comprehensive review, we present surveys of both metabolism-sensitive epigenetic enzymes and the metabolic processes that may play a role in their regulation. To close, we provide a series of clinically relevant illustrations of the communication between metabolism and epigenetics in the pathogenesis of cardiovascular disease, Alzheimer disease, cancer, and environmental toxicity. We anticipate that the regulatory mechanisms described herein will play an increasingly large role in our understanding of human health and disease as epigenetics research progresses.

Reactive oxygen species (ROS)--induced genetic and epigenetic alterations in human carcinogenesis

Cancer is a multistage and complex process characterized by molecular alterations that underlie all three phases of its development: (i) initiation, (ii) promotion and (iii) progression. Some of these molecular events include alterations in gene expression that are regulated by both genetic and epigenetic mechanisms. On the other hand, "oxidative stress" implies a cellular state where ROS production exceeds the cell's ability to metabolize them resulting in excessive accumulation of ROS that overwhelms cellular defenses. Such state has been shown to regulate both genetic and epigenetic cascades underlying altered gene expression in human disease including cancer. Throughout this manuscript, we review the current state of knowledge on the role of ROS-induced oxidative stress in altering the genetic and epigenetic involvement during human carcinogenesis.