Lupus-inducing drugs alter the structure of supercoiled circular DNA domains

Diagnostic dilemma: drug-induced vasculitis versus systemic vasculitis

Drug-induced vasculitis can rarely cause inflammation and necrosis of blood vessel walls of both kidney and lung tissue. Diagnosis is challenging because of the lack of difference between systemic and drug-induced vasculitis in clinical presentation, immunological workup and pathological findings. Tissue biopsy guides diagnosis and treatment. Pathological findings must be correlated with clinical information to arrive at a presumed diagnosis of drug-induced vasculitis. We present a patient with hydralazine-induced antineutrophil cytoplasmic antibodies-positive vasculitis with a pulmonary-renal syndrome manifesting as pauci-immune glomerulonephritis and alveolar haemorrhage.

Comparative study of dG affinity vs. DNA methylation modulating properties of side chain derivatives of procainamide: insight into its DNA hypomethylating effect

Structural features of side-chains govern the association of procainamide and its derivatives with dG base of CpG rich DNA, which may differentially hinder the activity of DNMT-1, thereby they act as DNA hypomethylating agents.

Will DNA methylation inhibitors work in solid tumors? A review of the clinical experience with azacitidine and decitabine in solid tumors

The recent approval of azacitidine (Vidaza®), decitabine (Dacogen®) and vorinostat (Zolinza™) for myelodysplastic syndrome and cutaneous T-cell lymphoma has led to a wave of interest in epigenetic therapy. These DNA methylation inhibitors and the histone deacetylase inhibitor clearly have demonstrated activity in hematologic malignancies, but the future role of epigenetic therapy in solid tumors is still unknown. What is not commonly known is that azacitidine and decitabine were originally developed as cytotoxic nucleoside analogs and clinical trials were previously conducted in a variety of cancer types prior to the knowledge of their ability to inhibit DNA methylation. We review the experience of azacitidine and decitabine in early clinical trials and demonstrate the activity of epigenetic therapy in solid tumors.

Epigenetic events associated with breast cancer and their prevention by dietary components targeting the epigenome

Aberrant epigenetic alterations in the genome such as DNA methylation and chromatin remodeling play a significant role in breast cancer development. Since epigenetic alterations are considered to be more easily reversible compared to genetic changes, epigenetic therapy is potentially very useful in reversing some of these defects. Methylation of CpG islands is an important component of the epigenetic code, and a number of genes become abnormally methylated in breast cancer patients. Currently, several epigenetic-based synthetic drugs that can reduce DNA hypermethylation and histone deacetylation are undergoing preclinical and clinical trials. However, these chemicals are generally very toxic and do not have gene specificity. Epidemiological studies have shown that Asian women are less prone to breast cancer due to their high consumption of soy food than the Caucasian women of western countries. Moreover, complementary/and or alternative medicines are commonly used by Asian populations which are rich in bioactive ingredients known to be chemopreventive against tumorigenesis in general. Examples of such agents include dietary polyphenols, (-)-epigallocatechin-3-gallate (EGCG) from green tea, genistein from soybean, isothiocyanates from plant foods, curcumin from turmeric, resveratrol from grapes, and sulforaphane from cruciferous vegetables. These bioactive components are able to modulate epigenetic events, and their epigenetic targets are known to be associated with breast cancer prevention and therapy. This approach could facilitate the discovery and development of novel drugs for the treatment of breast cancer. In this brief review, we will summarize the epigenetic events associated with breast cancer and the potential of some of these bioactive dietary components to modulate these events and thus afford new therapeutic or preventive approaches.

DNA hypermethylation as a chemotherapy target

Epigenetics refers to partially reversible, somatically inheritable, but DNA sequence-independent traits that modulate gene expression, chromatin structure, and cell functions such as cell cycle and apoptosis. DNA methylation is an example of a crucial epigenetic event; aberrant DNA methylation patterns are frequently found in human malignancies. DNA hypermethylation and the associated expression silencing of tumor suppressor genes represent a hallmark of neoplastic cells. The cancer methylome is highly disrupted, making DNA methylation an excellent target for anti-cancer therapies. Several small synthetic and natural molecules, are able to reverse the DNA hypermethylation through inhibition of DNA methyltransferase (DNMT). DNMT is the enzyme catalyzing the transfer of methyl groups to cytosines in genomic DNA. These reagents are studied intensively in cell cultures, animal models, and clinical trials for potential anti-cancer activities. It was found that accompanying DNA demethylation is a dramatic reactivation of the silenced genes and inhibition of cancer cell proliferation, promotion of cell apoptosis, or sensitization of cells to other chemotherapeutic reagents. During the last few decades, an increasing number of DNMT inhibitors (DNMTi) targeting DNA methylation have been developed to increase efficacy with reduced toxicity. This review provides an update on new findings on cancer epigenetic mechanisms, the development of new DNMTi, and their application in the clinical setting. Current challenges, potential solutions, and future directions concerning the development of DNMTi are also discussed in this review.

Chemical regulation of epigenetic modifications: opportunities for new cancer therapy

Epigenetics is concerned about heritable changes in gene expression without alteration of the coding sequence. Epigenetic modification of chromatin includes methylation of genomic DNA as well as post-translational modification of chromatin-associated proteins, in particular, histones. The spectrum of histone and non-histone modifications ranges from the addition of relatively small groups such as methyl, acetyl and phosphoryl groups to the attachment of larger moieties such as poly(ADP-ribose) and small proteins ubiquitin or small ubiquitin-like modifier (SUMO). The combinatorial nature of DNA methylation and histone modifications constitutes a significant pathway of epigenetic regulation and considerably extends the information potential of the genetic code. Chromatin modification has emerged as a new fundamental mechanism for gene transcriptional activity control associated with many cellular processes like proliferation, growth, and differentiation. Also it is increasingly recognized that epigenetic modifications constitute important regulatory mechanisms for the pathogenesis of malignant transformations. We review here the recent progress in the development of chemical inhibitors/activators that target different chromatin modifying enzymes. Such potent natural or synthetic modulators can be utilized to establish the quantitative contributions of epigenetic modifications in DNA regulated pathways including transcription, replication, recombination and repair, as well as provide leads for developing new cancer therapeutics.

Drug-induced vasculitis

PURPOSE OF REVIEW

This review aims to draw attention to the features that distinguish drug-induced vasculitis and drug-induced lupus-like disease from those of idiopathic autoimmune syndromes, first and foremost primary vasculitides and systemic lupus erythematosus. Drug-induced vasculitis and drug-induced lupus-like disease are seen in patients treated long term with a drug, and close to 100 drugs representing all pharmacologic classes have been assumed capable of inducing such syndromes. The clinical phenotypes vary from single tissue or organ involvement to severe systemic inflammatory disease dominated by vasculitis and sometimes organ failure.

RECENT FINDINGS

The recent discovery of antineutrophil cytoplasm antibodies in a large serological subset of drug-induced vasculitis/drug-induced lupus-like disease caused by long-term antithyroid drug treatment has opened new avenues for differential diagnostics. Antineutrophil cytoplasm antibodies with specificity to more than one lysosomal antigen, combined with presence of antibodies to histones and beta-2 glycoprotein 1 constitute a unique serological profile for drug-induced vasculitis/drug-induced lupus-like disease.

SUMMARY

Rational use of laboratory marker profiles is likely to aid in distinguishing drug-induced from idiopathic syndromes. Hence, the use of antineutrophil cytoplasm antibodies and other autoantibodies as biomarkers of different phenotypes of drug-induced vasculitis/drug-induced lupus-like disease is the main focus of this review.

Procainamide is a specific inhibitor of DNA methyltransferase 1

CpG island hypermethylation occurs in most cases of cancer, typically resulting in the transcriptional silencing of critical cancer genes. Procainamide has been shown to inhibit DNA methyltransferase activity and reactivate silenced gene expression in cancer cells by reversing CpG island hypermethylation. We report here that procainamide specifically inhibits the hemimethylase activity of DNA methyltransferase 1 (DNMT1), the mammalian enzyme thought to be responsible for maintaining DNA methylation patterns during replication. At micromolar concentrations, procainamide was found to be a partial competitive inhibitor of DNMT1, reducing the affinity of the enzyme for its two substrates, hemimethylated DNA and S-adenosyl-l-methionine. By doing so, procainamide significantly decreased the processivity of DNMT1 on hemimethylated DNA. Procainamide was not a potent inhibitor of the de novo methyltransferases DNMT3a and DNMT3b2. As further evidence of the specificity of procainamide for DNMT1, procainamide failed to lower genomic 5-methyl-2'-deoxycytidine levels in HCT116 colorectal cancer cells when DNMT1 was genetically deleted but significantly reduced genomic 5-methyl-2'-deoxycytidine content in parental HCT116 cells and in HCT116 cells where DNMT3b was genetically deleted. Because many reports have strongly linked DNMT1 with epigenetic alterations in carcinogenesis, procainamide may be a useful drug in the prevention of cancer.

Calculating the etiology of systemic lupus erythematosus

Objective was to clarify the etiology and pathogenesis of systemic lupus erythematosus (SLE). Drug-induced lupus (DIL) and SLE are both found in humans, are exacerbated by the same viruses or drugs, and they are both more common in slow acetylators. Thus, DIL can be used as a model for SLE and the Adhami equation of DIL can be applied to SLE. Polyamines are the only possible link between the viral and amine hypotheses of SLE pathogenesis. Based on the Adhami equation, polyamines can explain the actual annual incidence of SLE in the general population. Putrescine is a very weak SLE-causing agent, while spermine and spermidine contribute equally in triggering SLE. The positively charged polyamines bind to negatively charged internucleosomal DNA and change its conformation from B (non-immunogenic) to Z (immunogenic). This is the major contribution of polyamines in triggering SLE. The other effects of polyamines are only secondary. Apoptosis is a necessary step in SLE pathogenesis, because it causes the internucleosomal fragmentation of DNA and exposes Z-DNA to the immune system (due to cell death). The next step is the production of anti-DNA antibodies, followed by other SLE phenomena. Polyamines not only cause SLE, but they are also important in sustaining the disease. Other endogenous and exogenous amines have additive effects with polyamines and may contribute in exacerbating SLE. When SLE is in the active phase, polyamine levels are higher as compared to remissions. Fluctuations in polyamine levels due to diet, metabolic factors, infections, intestinal flora, etc. or the presence of other amines may explain the course of SLE, characterized by remissions and exacerbations. Acetylcysteine is a drug that can be completely metabolized to acetyl groups. As such, this drug is proposed as the ideal acetyl donor for the acetylation of polyamines and other SLE-triggering compounds. Clinical trials will be necessary to test the role of acetylcysteine in the etiologic treatment of SLE.

CONCLUSIONS

Changes in DNA conformation by polyamines are the first step in SLE pathogenesis. Many genetic and environmental factors may increase or decrease the effects or levels of polyamines, causing SLE exacerbations or remissions. Viruses and other infectious agents may cause SLE by producing polyamines or by increasing the levels of endogenous polyamines. The major autoimmune diseases are characterized by remissions and exacerbations and not by a continuously progressive course, as commonly believed. Consequently, they are not sustained by internal vicious cycles, but by the initial triggering agent(s). While the conventional treatment of autoimmune disorders is important in minimizing tissue damage, the neutralization of their etiology may be important in curing and preventing autoimmunity.

Intra- and intermolecular triplex DNA formation in the murine c-myb proto-oncogene promoter are inhibited by mithramycin

Mithramycin inhibits transcription by binding to G/C-rich sequences, thereby preventing regulatory protein binding. However, it is also possible that mithramycin inhibits gene expression by preventing intramolecular triplex DNA assembly. We tested this hypothesis using the DNA triplex adopted by the murine c-myb proto-oncogene. The 5'-regulatory region of c-myb contains two polypurine:polypyrimidine tracts with imperfect mirror symmetry, which are highly conserved in the murine and human c-myb sequences. The DNA binding drugs mithramycin and distamycin bind to one of these regions as determined by DNase I protection assay. Gel mobility shift assays, nuclease and chemical hypersensitivity and 2D-gel topological analyses as well as triplex-specific antibody binding studies confirmed the formation of purine*purine:pyrimidine inter- and pyrimidine*purine:pyrimidine intra-molecular triplex structures in this sequence. Mithramycin binding within the triplex target site displaces the major groove-bound oligonucleotide, and also abrogates the supercoil-dependent H-DNA formation, whereas distamycin binding had no such effects. Molecular modeling studies further support these observations. Triplex-specific antibody staining of cells pretreated with mithramycin demonstrates a reversal of chromosomal triplex structures compared to the non-treated and distamycin-treated cells. These observations suggest that DNA minor groove-binding drugs interfere with gene expression by precluding intramolecular triplex formation, as well as by physically preventing regulatory protein binding.

Polyamine involvement in the cell cycle, apoptosis, and autoimmunity

The polyamines: putrescine, spermidine and spermine, are ubiquitous polycations which have numerous, unique interactions in eukaryotic cells. Polyamines are essential for cell growth, with the bulk of polyamine expression co-ordinated with the cell cycle. The length, charge, and charge distribution of polyamines permit them to interact with large anionic molecules such as DNA, RNA, and phospholipids. Here, a mechanism is proposed whereby cell cycle expression of polyamines at the start of S phase leads to disruption of transcription and splicing, giving priority to DNA and histone synthesis. Inappropriate initiation of this process in non-viable cells leads to apoptosis and may be an underlying cause of autoimmunity.

Hydralazine induces Z-DNA conformation in a polynucleotide and elicits anti(Z-DNA) antibodies in treated patients

We studied the effect of hydralazine, an antihypertensive drug with lupus-inducing side effects, on the conformation of poly(dG-m5dC).poly(dG-m5dC) and a plasmid with a 23 bp insert of (dG-dC)n.(dG-dC)n sequences. Using an e.l.i.s.a. with a monoclonal anti-(Z-DNA) antibody Z22, we found that hydralazine provoked the Z-DNA conformation in poly(dG-m5dC).poly(dG-m5dC) at 250-500 microM concentration. The supercoiled form of hydralazine-treated plasmid bound to Z22 in a gel-retardation assay. To examine further whether Z-DNA could act as an inciting agent in anti-nuclear antibody production in patients, we analysed 65 sera from 25 hypertensive patients taking hydralazine and found anti-(Z-DNA) antibodies in 82% of these sera. Sera from age-matched normal controls showed no binding to Z-DNA. Data on sera drawn sequentially from four hypertensive patients showed that antibodies were present after the drug treatment. These data demonstrate the presence of a high incidence of anti-(Z-DNA) antibodies in patients treated with hydralazine and suggest that a possible mechanism for the production of autoantibodies in drug-related lupus might involve the induction and stabilization of Z-DNA by drugs.

Diversity and origin of rheumatologic autoantibodies

A hallmark of sera from patients with systemic rheumatic diseases is the presence of circulating autoantibodies directed against nuclear antigens. The identification of the antigens binding to these antibodies has provided the cell biologist and the immunologist with important tools to study cell structure, cell function, and the processes underlying the immune response. Through the elucidation of autoantibody specificities, the clinician has been provided with a better appreciation of the diagnostic and prognostic significance of autoantibodies. Many autoantigens, including those directed against components in the nuclear matrix, chromosomes, Golgi apparatus, and other intracellular antigens, are not yet characterized nor is their clinical significance established. The mechanisms leading to the breakdown of tolerance and the appearance of autoantibodies are not fully understood. Molecular mimicry at an interspecies or an intracellular level may be involved in altering immune tolerance. On the other hand, studies of epitopes on human autoantigens has provided compelling evidence that most autoantibody responses seen in systemic rheumatic diseases are driven by endogenous antigen.

5-Methylcytosine content of DNA in blood, synovial mononuclear cells and synovial tissue from patients affected by autoimmune rheumatic diseases

The percentage of 5-methylcytosine (m5Cyt) has been determined in peripheral blood, synovial mononuclear cells and synovial tissue from patients affected by various rheumatic autoimmune diseases. The determination was performed by reversed-phase high-performance liquid chromatography. Fifteen controls were compared to twenty-one patients affected by rheumatoid arthritis and to nine patients affected by systemic lupus erythematosus. The mean percentage of m5Cyt in normal individuals was significantly higher than in the rheumatoid arthritis and systemic lupus erythematosus patients. In addition, patients with active disease showed lower values than patients in remission. This finding is in agreement with the hypothesis that DNA hypomethylation may play a role in the pathogenesis of the autoimmune diseases, resulting in altered oncogene expression. Therapy with cyclosporin A led to a decrease in the percentage of m5Cyt in three rheumatoid arthritis patients, but a rebound was observed when the cyclosporin A was suspended. The percentage of m5Cyt in the DNA of synovial tissue from four rheumatoid arthritis patients and five patients with osteoarthritis was similar; this observation confirms that, in addition to disease-specific and disease activity-specific variations, the percentage of m5Cyt may also show tissue-specific variations.