Adverse reactions are one of the most important issues in drug development, as well as in the therapeutic usage of drugs during the post-approval stage. Specifically, idiosyncratic adverse drug reactions (IDR) occur in only a small group of patients who are treated with certain drugs, and are unpredictable. It is widely accepted that drug-induced IDR is often associated with CYP-mediated bioactivation. Benzbromarone (BBR) is effective in the treatment of hyperuricemia, and has been used as an effective drug in Japan for a long time. However, BBR has been associated with hepatotoxicity, including fatal liver injury. We identified 2,6-dibromohydroquinone (DBH) and mono-debrominated catechol (CAT) as novel metabolites of BBR in human and rat liver microsomal systems, by comparison with chemically synthesized authentic compounds via ipso-substitution, which we previously discovered to be a unique metabolic reaction of substituted phenols by CYP. Furthermore, CAT, DBH and the oxidized form of DBH (DBBQ) were highly cytotoxic in human hepatocellular carcinoma cells, compared with BBR. We consider that the formation of these metabolites from BBR is linked to the mechanism involved in BBR-induced hepatotoxicity because catechols, hydroquinones, and their oxidized forms are known to be toxic.
The ability to metabolize xenobiotics in organisms has a wide degree of variation among organisms. This is caused by differences in the pattern of xenobiotic bioaccumulation among organisms, which affects their tolerance. It has been reported in the veterinary field that glucuronidation (UGT) activity in cats, acetylation activity in dogs and sulfation (SULT) activity in pigs are sub-vital in these species, respectively, and require close attention when prescribing the medicine. On the other hand, information about species differences in xenobiotics metabolism remains insufficient, especially in non-experimental animals. In the present study, we tried to elucidate xenobiotic metabolism ability, especially in phase II UGT conjugation of various non-experimental animals, by using newly constructed in vivo, in vitro and genomic techniques. The results indicated that marine mammals (Steller sea lion, northern fur seal, and Caspian seal) showed UGT activity as low as that in cats, which was significantly lower than in rats and dogs. Furthermore, UGT1A6 pseudogenes were found in the Steller sea lion and Northern fur seal; all Otariidae species are thought to have the UGT1A6 pseudogene as well. Environmental pollutants and drugs conjugated by UGT are increasing dramatically in the modern world, and their dispersal into the environment can be of great consequence to Carnivora species, whose low xenobiotic glucuronidation capacity makes them highly sensitive to these compounds.
Epigenetics has drawn much attention as a mechanism of transcriptional regulation involving modifications to genomic DNA and histone, without changes to nucleotide sequences. Epigenetics is related to various biological phenomena. We defined one of these phenomena as “epigenetic toxicity”, in which chemicals affect epigenetic regulation and result in undesirable effects on living organisms. We then detailed the importance of epigenetics and the need for intensive research. Epigenetics is a mechanism that might explain the long-lasting effects of chemicals in an organism, and the formation of a predisposition to various diseases. Recent significant technological advancement in the study of epigenetics could break through the barrier of the mysterious black box of epigenetic toxicity. However, at present it is difficult to say whether the epigenetic point of view is being fully utilized in the evaluation of chemical safety. In this review, we will first summarize the epigenetic toxicity research field, with examples of epigenetic toxicities and technologies for epigenetic analysis. Following that, we will point out some challenges in which an epigenetic viewpoint may be essential for the evaluation of chemical safety, and we will show some current approaches. We hope this review will trigger a discussion about epigenetic toxicity that will lead to encouraging research advancements.
Epigenetics is the study of heritable changes in gene expression that occur without alterations in the DNA sequence. Several studies have shown that environmental chemicals can alter epigenetic modifications, including histone modifications and DNA methylation. Environmental chemicals may show toxic effects via epigenetic mechanism-regulated changes in gene expression. Previously, we reported that zinc treatment rapidly decreased Lys(4)-trimethylated and Lys(9)-acetylated histone H3 in the metallothionein (MT) promoter, and also decreased total histone H3. The chromatin structure in the MT promoter may be locally disrupted by zinc-induced nucleosome removal. We also showed that chromium (VI) inhibited MT gene transcription by modifying the transcription potential of the co-activator p300. MT is a small cysteine-rich protein that is active in zinc homeostasis, cadmium detoxification, and protection against reactive oxygen species. Epigenetic changes might influence the cytoprotective function of the MT gene. In this review, I briefly summarize the results of previous studies and discuss the mechanisms and toxicological significance of metal-mediated epigenetic modifications.
The first step in “drug” discovery is to find compounds binding to a potential drug target. In modern medicinal chemistry, the screening of a chemical library, structure-based drug design, and ligand-based drug design, or a combination of these methods, are generally used for identifying the desired compounds. However, they do not necessarily lead to success and there is no infallible method for drug discovery. Therefore, it is important to explore medicinal chemistry based on not only the conventional methods but also new ideas. So far, we have found various compounds as drug candidates. In these studies, some strategies based on organic chemistry have allowed us to find drug candidates, through 1) construction of a focused library using organic reactions and 2) rational design of enzyme inhibitors based on chemical reactions catalyzed by the target enzyme. Medicinal chemistry based on organic chemical reactions could be expected to supplement the conventional methods. In this review, we present drug discovery with the help of organic chemistry showing examples of our explorative studies on histone deacetylase inhibitors and lysine-specific demethylase 1 inhibitors.
8-Oxo-2′-deoxyguanosine (8-oxo-dG) is a representative of nucleoside damage, which is generated by the reaction of the 8 position of dG with reactive oxygen species. Abundant 8-oxo-dG in DNA exhibits genotoxicity and has been linked to aging and disease, such as cancer. As the metabolism of cancer cells is much faster than that of normal cells, the oxidized product of the oligonucleotides and the nucleotide pool produces 8-oxo-dG and 8-oxo-2′-deoxyguanosine triphosphate (8-oxo-dGTP), respectively. Human oxoguanine glycosylase (hOGG1) shows base excision activity for 8-oxo-dG in duplex DNA. On the other hand, human mutT homologue protein (hMTH1, also known as NUDT1) is important for oxidized nucleotide removal including 8-oxo-dGTP, and it is reported that the presence of hMTH1 is not essential for normal cells but is required for the survival of cancer cells. Therefore, we designed and synthesized 8-halogenated 7-deaza-2′-deoxyguanosine triphosphate (8-halo-7-deaza-dGTP) derivatives as mimics of 8-oxo-dGTP in order to interact with hMTH1. The 8-halo-7-deaza-dGTP derivatives were poor substrates for but strong binders to hMTH1. Interestingly, they exhibited strong competitive inhibition of hMTH1 in the hydrolysis of 8-oxo-dGTP. This inhibitory effect is caused by the slower rate of hydrolysis due to possible small enzyme structural changes. Although the detailed inhibition mechanism of the hydrolysis activity of hMTH1 is unknown, this result is the first to demonstrate the potential of nucleoside triphosphate derivatives as antitumor agents.
Acrolein, a highly toxic α, β-unsaturated aldehyde, occurs as pollutant in the environment (e.g., tobacco smoke and exhaust gas) and is ubiquitously generated in biosystems (e.g., the lipid peroxidation process and metabolism of polyamine or amino acids). High accumulation of acrolein in biosystems is often linked pathologically with several oxidative stress-related diseases, including cancer and Alzheimer's disease. Accordingly, acrolein holds great potential as a key biomarker in oxidative stress-related diseases, and direct measurement of acrolein in biological samples is important to provide information for diagnostic and therapeutic purposes. Recently, we have serendipitously discovered the unrecognized reactivity of phenyl azide to acrolein. Phenyl azide can rapidly and selectively react with acrolein in a “click” manner to provide 4-formyl-1,2,3-triazoline through 1,3-dipolar cycloaddition. We have successfully utilized the acrolein-azide click reaction as a simple but robust method for detecting and visualizing acrolein generated by live cells in the context of oxidative stress processes. In addition, we also serendipitously discovered novel cycloaddition reactions of N-alkyl-α,β-unsaturated imines derived from acrolein and biogenic amines (e.g., polyamines, norepinephrine, and sphingosine), to yield 8-membered cyclic compounds. We then examined the biological functions of the cyclic products and revealed for the first time their roles in the oxidative stress mechanism and inhibition of amyloid β(1-40) fibrillization.
Sudden illness while driving has been identified as a major cause of vehicle collisions, accounting for approximately 1 in 10 collisions. Because most drivers who experience sudden illnesses while driving do not perform avoidance maneuvers, the improvement of drivers' health is being promoted as a traffic safety strategy. Although stroke, heart disease, and epilepsy are common causes of sudden illness, common symptoms, such as abdominal cramps, vertigo, and syncope can also cause problems during driving. We found that regular referral to physicians was significantly less common among drivers who experienced health-related vehicle collisions or incidents. Inadequate control of chronic disease might lead to unusual symptoms and the onset of major attacks. Medications are prescribed to patients to relieve their symptoms and/or bring their diseases under control. However, pharmacists and doctors should ensure that patients are treated with appropriate medications to avoid drivers being distracted due to adverse reactions to medications. The author suggests that it is important to keep drivers in good health and administer appropriate medications if necessary. Both pharmacists and doctors should warn drivers that sudden illness or medication-associated distractions can cause vehicle collisions. Such interventions might contribute to reducing the frequency of sudden illness-related vehicle collisions.
Sleepiness is known as one of the side effects of antihistamines, and impaired performance caused by these drugs has become problematic. Among the 13 second-generation antihistamines causing sleepiness to some extent, the package inserts of 8 drugs prohibit driving, 3 stress driving with care, and 2 give no driving-related warning. It was confirmed that the description did not necessarily reflect the results of the standard deviation of lateral position measurement study, which is considered the most effective study for evaluating the effects of drugs on automobile driving. Do these descriptions reflect actual patients' sleepiness? According to a questionnaire survey involving 2000 individuals taking second-generation antihistamines, 7.3% of respondents answered that they had always become sleepy after taking antihistamines (3.1-12.5% according to the type of antihistamine), 32.8% (27.8-45.8%) had become sleepy sometimes, 9.1% (3.1-15.8%) had previously become sleepy but not anymore, and 40.9% (27.1-49.1%) had never become sleepy. In addition, 10.3% (2.4-21.1%) reported intolerable sleepiness. Patients who had experience of receiving pharmaceutical education from pharmacists numbered 1296 (64.8%), and 80.2% of them had also received driving-related explanations, which included the prohibition of driving (32.8%), stressing the need to drive with care (54.7%), and the prohibition of medication before driving (12.0%). Concerning these explanations, the proportion who paid attention on a daily basis, paid slight attention, and paid no attention was 36.7, 31.2, and 32.1%, respectively. To provide effective and safe pharmacotherapy for the increasing number of patients taking antihistamines, pharmacists should ideally improve pharmaceutical education.
In 2013, the Ministry of Health, Labour, and Welfare issued a notification regarding drugs that influence driving. Afterward, a questionnaire survey of these drugs was conducted involving health insurance pharmacies in Tokyo and Shiga Prefectures. As a result, 503 (Tokyo) and 116 (Shiga) pharmacies provided completed questionnaires. The notification was sufficiently and slightly recognized by 20% and 44% of the surveyed pharmacies, respectively, and drugs with a driving-related warning were recognized by 31% of the pharmacies. In addition, 23% of the pharmacies reported that they always asked patients whether they drive. The influence on driving of antianxiety drugs, hypnotics, antiepileptics, and smoking-cessation drugs was always explained to patients by 74%, 72%, 64%, and 40% of the pharmacies, respectively. Concerning responses to the prescription of drugs influencing driving, the proportion of surveyed pharmacies in Tokyo and Shiga Prefectures that directed patients not to drive was 71% and 53%, respectively, and that directed patients to stop driving on developing any symptom was 32% and 49%. Tokyo and Shiga Prefectures showed a significant difference in the reason for not prohibiting driving; the proportion of pharmacies that regarded strict medication adherence as of major importance to treat patients' primary diseases was 22% and 43%, respectively. This difference might have been attributable to a high percentage of patients (80%) driving to pharmacies in Shiga Prefecture. To facilitate the prescription of drugs influencing driving, it is recommended to design drug-specific pharmaceutical education manuals that also give consideration to patients' QOL.
In November 2013, the Japanese Ministry of Health, Labour and Welfare issued a directive that required the revision of the package inserts of 13 substances whose consumption carries risks associated with driving and the operation of machinery due to their side effects, such as dizziness. Medical personnel are required to remind patients taking these drugs about the risks, but the abovementioned directive did not apply to any antidiabetic drugs at that point. In January 2014, it was decided that patients should “pay attention while driving and at the workplace” when taking any antidiabetic drugs. This point is mentioned in the “important precautions” section of the drugs' package inserts. Since the revised Road Traffic Law was enacted in June 2014, the penalty for car accidents caused by a lack of awareness of hypoglycemia has increased. It has therefore become essential for medical personnel to instruct diabetic patients how to avoid falling unconscious due to hypoglycemia during driving. Patients taking antidiabetic drugs that are categorized as high-risk drugs are required to take an extra set of precautions and these are important for preventing severe hypoglycemia as well as reducing patients' cardiovascular risk. For more than 20 years, my pharmacy has been giving annual intensive counseling on hypoglycemia to diabetic patients. This counseling includes reminding patients about preventative measures, the risks associated with driving, and the need to keep a source of sugar in their cars. Only about 10% of diabetic patients keep a source of sugar in their cars.
To prevent onset and proliferation of public health/hygiene hazards arising from adverse reactions to drugs, physicians and pharmacists in Japan are now required to provide sufficient explanation of precautions when prescribing or dispensing drugs with package inserts indicating that the patient should not drive, or should take precautions when driving, while taking the drug. Additionally, to ensure proper use of drugs dispensed in accordance with the prescriptions issued by physicians or dentists, the Law for Partial Amendment of the Pharmaceutical Affairs Law (Law No. 103 of 2013) mandates that pharmacists must provide necessary pharmacological research-supported information and guidance to the person receiving the prescribed drug. Under such circumstances, at the Ehime University Hospital Division of Pharmacy we have recently standardized our system for in-person explanation of precautions and necessary guidance to be practiced by pharmacists at our hospital's pharmacy with outpatients being prescribed any drug that requires driving caution. We present concrete examples to support that such standardization of the explanation and guidance system at our hospital has reduced the burden placed on pharmacists in their provision of routine clinical services.
Growing evidence indicates that serotonergic neurons play a crucial role in brain function and dysfunction, such as in major depressive disorder. However, the complexity of serotonergic projections severely hampers the elucidation of their precise mechanisms. Here we summarize our recent studies on the effects of ketamine and olanzapine, which have been reported to be effective in treatment-resistant depression, on dorsal raphe nucleus serotonergic neurons, using microdialysis, electrophysiology experiments, and slice cultures. Furthermore, we discuss the results of our recent approach using viral vectors, in particular, HIV-1 based lentiviral vectors.
In recent years, plant polyphenols have attracted great attention due to their wide range of biological activities. Certain kinds of polyphenols have complex structures; therefore, it is difficult to elucidate their total structure, including stereochemistry. In this study, we reinvestigated the stereostructures of two major C-glycosidic ellagitannins contained in Quercus plants, vescalagin and castalagin, and revised their stereostructures based on theoretical calculations of spectroscopic data. We also determined the structures of quercusnins A and B, isolated from the sapwood of Quercus crispula, based on theoretical calculations of NMR data. The oxidation mechanism of polyphenols has not been entirely elucidated. Therefore, we have also studied the oxidation mechanism of tea catechins during black tea production. Our investigation of the oxidation mechanism of black tea pigment theaflavins revealed that the difference in the position of the galloyl ester affords different oxidation products of theaflavins. In addition, oxidation products of pyrogallol-type catechins could be classified into three types—dehydrotheasinensins, theacitrins, and proepitheaflagallins; their detailed production and degradation mechanisms were also examined.
Respiratory medicine physicians prescribe many different kinds of medications depending on patient's condition. To examine an outside pharmacy's ability to meet the demand of our respiratory prescription services, we developed a questionnaire for all the patients who came to our outpatient department from November 1, 2015 to January 31, 2016. A total of 298 of 330 patients answered the questionnaire. Overall, 169 patients mainly went to the pharmacy near our hospital, whereas 64 patients mainly went to another pharmacy. Specifically, 23 of 219 patients who answered the question “When you went to the pharmacy with prescription, have you ever been not immediately given medication?”, were not immediately given medication by the pharmacy. The results show that the other pharmacy significantly delayed medication compared with the one near our hospital. Interestingly, there were many types of inhaler cases that were out of stock in both pharmacies. Also, we found that 9 of 11 patients who were not provided medication on the spot acquired the medication within 1 or 2 d. Further, 10 of 20 patients who were not provided medication on the spot were only able to obtain the medication once. We did not observe any changes in patients' physical condition due to the delay in medication.
Local venous pain caused by dacarbazine (DTIC) injection is due to its photodegradation product 5-diazoimidazole-4-carboxamide (Diazo-IC). The production of Diazo-IC can be decreased by protecting the drug from light. Furthermore, the production of Diazo-IC reportedly increases with time; however, there are no studies reporting the association between the injection preparation time and local venous pain caused by the DTIC injection. We evaluated the efficacy of the following: (1) method used to shorten the injection preparation time and (2) method used to change the diluting solution for DTIC. We found that shortening the injection preparation time tended to decrease the local venous pain expression due to DTIC, and Veen F decreased the production of Diazo-IC compared with the normal saline and 5% glucose solution. These results indicate that shortening the injection preparation time may be effective in preventing the local venous pain caused by the DTIC injection; moreover, using Veen F for DTIC may also reduce the pain.