Hybrid ubiquinone: novel inhibitor of mitochondrial complex I

AbstractWe synthesized novel ubiquinone analogs by hybridizing the natural ubiquinone ring (2,3-dimethoxy-5-methyl-1,4-benzoquinone) and hydrophobic phenoxybenzamide unit, and named them hybrid ubiquinones (HUs). The HUs worked as electron transfer substrates with bovine heart mitochondrial succinate–ubiquinone oxidoreductase (complex II) and ubiquinol–cytochrome c oxidoreductase (complex III), but not with NADH–ubiquinone oxidoreductase (complex I). With complex I, they acted as inhibitors in a noncompetitive manner against exogenous short-chain ubiquinones irrespective of the presence of the natural ubiquinone ring. Elongation of the distance between the ubiquinone ring and the phenoxybenzamide unit did not recover the electron accepting activity. The structure/activity study showed that high structural specificity of the phenoxybenzamide moiety is required to act as a potent inhibitor of complex I. These findings indicate that binding of the HUs to complex I is mainly decided by some specific interaction of the phenoxybenzamide moiety with the enzyme. It is of interest that an analogous bulky and hydrophobic substructure can be commonly found in recently registered synthetic pesticides the action site of which is mitochondrial complex I

Medical Treatment of Echinococcus multilocularis and New Horizons for Drug Discovery: Characterization of Mitochondrial Complex II as a Potential Drug Target

As an efficient drug for alveolar echinococcosis (AE) is still not available, new chemotherapy targets are necessary. The mitochondrial respiratory chain may be a good drug candidate because parasite respiratory chains are quite different from those of mammalian hosts. For example, Ascaris suum possesses an NADH‐fumarate reductase system (fumarate respiration) that is highly adapted to anaerobic environments such as the small intestine. It is composed of mitochondrial complex I (NADH‐ubiquinone reductase), complex II (succinate‐ubiquinone reductase), and rhodoquinone. We previously demonstrated that fumarate respiration is also essential in E. multilocularis. Quinazoline, a complex I inhibitor, inhibited growth of E. multilocularis larvae in vitro. These results indicate that fumarate respiration could be a target for E. multilocularis therapy. In the current chapter, we focused on complex II, which is another component of this system, because quinazoline exhibited strong toxicity to mammalian mitochondria. We evaluated the molecular and biochemical characterization of E. multilocularis complex II as a potential drug target. In addition, we found that ascofuranone, a trypanosome cyanide‐insensitive alternative oxidase inhibitor, inhibited E. multilocularis complex II at the nanomolar order. Our findings demonstrate the potential development of targeted therapy against Echinococcus complex II

Fumarate respiration of Fasciola flukes as a potential drug target

Fascioliasis is a neglected tropical zoonotic disease caused by liver flukes belonging to the genus Fasciola. The emergence of resistance to triclabendazole, the only World Health Organization-recommended drug for this disease, highlights the need for the development of new drugs. Helminths possess an anaerobic mitochondrial respiratory chain (fumarate respiration) which is considered a potential drug target. This study aimed to evaluate the occurrence of fumarate respiration in Fasciola flukes. We analyzed the properties of the respiratory chain of Fasciola flukes in both adults and newly excysted juveniles (NEJs). Fasciola flukes travel and mature through the stomach, bowel, and abdominal cavity to the liver, where oxygen levels gradually decline. High fumarate reductase activity was observed in the mitochondrial fraction of adult Fasciola flukes. Furthermore, rhodoquinone-10 (RQ10 Em’= −63 mV), a low-potential electron mediator used in fumarate respiration was found to be predominant in adults. In contrast, the activity of oxygen respiration was low in adults. Rotenone, atpenin A5, and ascochlorin, typical inhibitors of mitochondrial enzymes in complexes I, II, and III, respectively, inhibit the activity of each enzyme in the adult mitochondrial fraction. These inhibitors were then used for in vitro viability tests of NEJs. Under aerobic conditions, NEJs were killed by rotenone or ascochlorin, which inhibit aerobic respiration (complex I–III), whereas atpenin A5, which inhibits complex II involved in fumarate respiration, did not affect NEJs. Moreover, ubiquinone-10 (UQ10 Em’= +110 mV), which is used in oxidative respiration, was detected in NEJs, in addition to RQ10. In contrast, under anaerobic conditions, rotenone and atpenin A5, which inhibit fumarate respiration (complex I–II), were crucial for NEJs. These findings demonstrate that NEJs have active hybrid respiration, in which they can properly use both oxygen and fumarate respiration, depending on oxygen availability. Thus, fumarate respiration is a promising drug target for Fasciola flukes, because it plays an essential role in both adults and NEJs

Sex-inducing effects toward planarians widely present among parasitic flatworms

Summary Various parasitic flatworms infect vertebrates for sexual reproduction, often causing devastating diseases in their hosts. Consequently, flatworms are of great socioeconomic and biomedical importance. Although the cessation of parasitic flatworm sexual reproduction is a major target of anti-parasitic drug design, little is known regarding bioactive compounds controlling flatworm sexual maturation. Using the planarian Dugesia ryukyuensis, we observed that sex-inducing substances found in planarians are also widespread in parasitic flatworms, such as monogeneans and flukes (but not in tapeworms). Reverse-phase HPLC analysis revealed the sex-inducing substance(s) eluting around the tryptophan retention time in the fluke Calicophoron calicophorum, consistent with previous studies on the planarian Bipalium nobile, suggesting that the substance(s) is likely conserved among flatworms. Moreover, six of the 18 ovary-inducing substances identified via transcriptome and metabolome analyses are involved in purine metabolism. Our findings provide a basis for understanding and modifying the life cycles of various parasitic flatworms.journal articl

Stromal micropapillary pattern predominant lung adenocarcinoma - a report of two cases

Generally, adenocarcinomas with micropapillary pattern, featuring small papillary tufts lacking a central fibrovascular core, are thought to have poor prognosis. This pattern has been described in various organs. However, tumor cells with micropapillary pattern of lung adenocarcinoma are more often seen to float within alveolar spaces (aerogenous micropapillary pattern, AMP) than in fibrotic stroma like other organs (stromal micropapillary pattern, SMP) and SMP predominant lung adenocarcinoma (SMPPLA) has not been well described yet. We presented two cases of SMPPLA which were found in the last four years. Both the cases showed more than 50% of SMP in the tumor area. The majority of the stromal micropapillary clusters expressed MUC1 and epithelial membrane antigen along the outer surface of cell membrane. On the other hand, connective tissues surrounding stromal micropapillary clusters showed no reactivity for epithelial markers (thyroid transcription factor-1 and cytokeratin) or endothelial marker (D2-40 and CD34). It means clusters of SMP do not exist within air space or lymphatic or vessel lumens. The tumors with SMP often presented lymphatic permeation and vessel invasion, and intriguingly, one of the two cases showed metastasis to the mediastinal lymph node. Additionally, both the cases showed EGFR point mutations of exon 21. These results suggest that SMPPLA might be associated with poor prognosis and effective for EGFR tyrosine kinase inhibitors

呼吸鎖酵素における合成ユビキノン類の構造と機能に関する研究

京都大学0048新制・課程博士博士(農学)甲第7899号農博第1057号新制||農||779(附属図書館)学位論文||H11||N3262(農学部図書室)UT51-99-G493京都大学大学院農学研究科農芸化学専攻(主査)教授 岩村 俶, 教授 上野 民夫, 教授 林 力丸学位規則第4条第1項該当Doctor of Agricultural ScienceKyoto UniversityDA

Liposteroid and methylprednisolone combination therapy for a case of idiopathic lung hemosiderosis

Idiopathic pulmonary hemosiderosis (IPH) is a rare disease in children, with unknown etiology. The classical clinical triad is hemoptysis, hypochromic anemia and diffuse parenchymal infiltrations on chest X-ray. Liposteroid dexamethasone palmitate, which was developed in Japan, has shown good efficacy for IPH. We present the case of a patient with IPH, who suffered from a life-threatening respiratory dysfunction, and was rescued by a trial administration of liposteroid with methylprednisolone (mPSL).A 6-year-old girl was admitted to our hospital for repeated dyspnea and blood-stained sputum. She was diagnosed with IPH at the age of three-months by iron staining of gastric fluid and sputum studies. Her cumulative dose of steroids (equivalent to prednisolone (PSL)) was 1062 mg/kg. However, she could not achieve remission. We decided to initiate liposteroid therapy. We administered an infusion of liposteroid 0.8 mg/kg intravenously, for three consecutive days as a therapy for acute bleeding. After administration of liposteroid, she developed high fever with CRP elevation. We suspected that the inflammation was caused by palmitate, which is present as a lipo base in liposteroid. Hence, we added 2 mg/kg mPSL per day for 1 week. As a maintenance treatment, a single infusion of liposteroid was administered followed by mPSL administration for 6 days in every week. Her respiratory condition slowly improved. Tracheostomy was performed for airway management. She was shifted out of the ICU on the 34th day.Steroid is a key therapy for hemosiderosis. When IPH is diagnosed, oral prednisone therapy is initiated. Although this is effective, there are limitations due to significant adverse effects. Maintaining drug therapy is very important for IPH patients to keep the disease under control. Liposteroid has the same mechanism of action as dexamethasone. It has a Lipo-base, palmitate, which could induce pro-inflammatory cytokine activation. We used mPSL to inhibit the inflammation following liposteroid administration. This was effective. A combination of liposteroid and mPSL administration was useful method of treatment for the patient. Keywords: Idiopathic pulmonary hemosiderosis, Liposteroi

Combined use of a two-channel endoscope and a flexible tip catheter for difficult biliary cannulation

A 69-year-old woman with jaundice was referred to our hospital. After a final diagnosis of pancreatic cancer with liver metastasis, we performed transpapillary biliary drainage with a covered self-expandable metal stent (SEMS). Three months later, we also placed an uncovered duodenal stent for duodenal stricture in a side-to-end fashion. Another month later, for biliary SEMS obstruction, we attempted a transpapillary approach. A duodenoscope was advanced and a guidewire was passed through the mesh of the duodenal stent into the bile duct with a flexible tip catheter, but the catheter was not. Thus, we exchanged the duodenoscope for a forward-viewing two-channel endoscope and used the left working channel with a flexible tip catheter. By adjusting the axis, we finally succeeded biliary cannulation and accomplished balloon cleaning for recanalization of the SEMS. This is the first case with successful biliary cannulation by combined use of a two-channel endoscope and a flexible tip catheter