Analysis of N1‐acetyl‐N2‐formyl‐5‐methoxykynuramine/N1‐acetyl‐5‐methoxy‐kynuramine formation from melatonin in mice

Abstract: The interactions of melatonin, a potent endogenous antioxidant, with reactive oxygen species generate several products that include N¹‐acetyl‐N²‐formyl‐5‐methoxykynuramine (AFMK) and N¹‐acetyl‐5‐methoxy‐kynuramine (AMK). The physiological or pathological significance of AFMK/AMK formation during the process of melatonin metabolism in mammals has not been clarified. Using a metabolomic approach in the current study, the AFMK/AMK pathway was thoroughly investigated both in mice and humans. Unexpectedly, AFMK and AMK were not identified in the urine of humans nor in the urine, feces or tissues (including liver, brain, and eyes) in mice under the current experimental conditions. Metabolomic analysis did identify novel metabolites of AMK, i.e. hydroxy‐AMK and glucuronide‐conjugated hydroxy‐AMK. These two newly identified metabolites were, however, not found in the urine of humans. In addition, oxidative stress induced by acetaminophen in the mouse model did not boost AFMK/AMK formation. These data suggest that AFMK/AMK formation is not a significant pathway of melatonin disposition in mice, even under conditions of oxidative stress.     

Effect of genipin on cholestasis induced by estradiol‐17β‐glucuronide and lithocholate‐3‐O‐glucuornide in rats

Aim: Genipin is reported to stimulate the insertion of multidrug resistance protein 2 (Mrp2) in the bile canalicular membrane, thereby causing choleresis by the increased the biliary excretion of glutathione, which has been considered to be a substrate of Mrp2. In the present study, we examined the effect of genipin on cholestasis induced by estradiol‐17β‐glucuronide and lithocholate‐3‐O‐glucuronide, Mrp2 substrates, in rats. Further, the effect of genipin on the biliary excretion of substrates of P‐glycoprotein (P‐gp), vinblastine and erythromycin, was also studied. Methods: The effect of genipin infusion at the rate of 0.5 µmol/min/100 g on cholestasis induced by estradiol‐17β‐glucuronide (0.075 µmol/min/100 g for 20 min) and lithocholate‐3‐O‐glucuronide (0.15 µmol/min/100 g for 40 min) was studied. The effect of genipin infusion on the biliary excretion of a tracer dose of vinblastine and erythromycin infused at the rate of 0.1 µmol/min/100 g was also studied. Results: Genipin relieved estradiol‐17β‐glucuronide‐induced cholestasis, and cumulative biliary estradiol‐17β‐glucuronide excretion for 120 min was increased from 50 ± 20%–81 ± 20% dose. In contrast, genipin had no effect on lithocholate‐3‐O‐glucuronide‐induced cholestasis. Biliary excretion of a tracer dose of vinblastine and the maximum biliary excretion of erythromycin were significantly decreased by genipin. Conclusions: Genipin protected estradiol‐17β‐glucuronide‐induced cholestasis. The mechanism of the protection of cholestasis by genipin is unknown, but it is speculated to be due to a conformational change of P‐gp by genipin, in addition to the stimulation of Mrp2 insertion into the bile canaliculi.     

Encephalitis caused by human herpesvirus‐6B in pancreas‐after‐kidney transplantation

Human herpesvirus‐6 (HHV‐6) is a common pathogen among children, classically presenting with fever and rash that resolves without specific therapy. HHV‐6 can be reactivated in the immunosuppressed patient. After bone marrow and solid organ transplantation, HHV‐6 has been linked to various clinical syndromes, including undifferentiated febrile illness, encephalitis, myelitis, hepatitis, pneumonitis, and bone marrow suppression. However, HHV‐6 encephalitis after pancreatic transplant has rarely been reported. Early diagnosis and treatment of HHV‐6 encephalitis may be important for affected patients. We report the case of a 53‐year‐old pancreas‐after‐kidney transplant recipient who initially presented with high fever and confusion 3 weeks after operation. We managed to save the patient's life and preserve the pancreas graft function. We also review previously reported cases of HHV‐6B encephalitis in solid organ transplant recipients.     

The melatonin metabolite N1‐acetyl‐5‐methoxykynuramine facilitates long‐term object memory in young and aging mice

Melatonin (MEL) has been reported to enhance cognitive processes, making it a potential treatment for cognitive decline. However, the role of MEL’s metabolites, N1‐acetyl‐N2‐formyl‐5‐methoxykynuramine (AFMK) and N1‐acetyl‐5‐methoxykynuramine (AMK), in these effects are unknown. The current study directly investigated the acute effects of systemic MEL, AFMK, and AMK on novel object recognition. We also analyzed MEL, AFMK, and AMK levels in hippocampus and temporal lobe containing the perirhinal cortex following systemic MEL and AMK treatment. AMK administered post‐training had a more potent effect on object memory than MEL and AFMK. AMK was also able to rescue age‐associated declines in memory impairments when object memory was tested up to 4 days following training. Results from administering AMK at varying times around the training trial and the metabolism time course in brain tissue suggest that AMK’s memory‐enhancing effects reflect memory consolidation. Furthermore, inhibiting the MEL‐to‐AMK metabolic pathway disrupted object memory at 24 hours post‐training, suggesting that endogenous AMK might play an important role in long‐term memory formation. This is the first study to report that AMK facilitates long‐term object memory performance in mice, and that MEL crosses the blood‐brain barrier and is immediately converted to AMK in brain tissue. Overall, these results support AMK as a potential therapeutic agent to improve or prevent memory decline.     

Melatonin enhances L‐DOPA therapeutic effects,helps to reduce its dose,and protects dopaminergic neurons in 1‐methyl‐4‐phenyl‐1,2,3,6‐tetrahydropyridine‐induced parkinsonism in mice

L‐3,4‐dihydroxyphenylalanine (L‐DOPA) reduces symptoms of Parkinson's disease (PD), but suffers from serious side effects on long‐term use. Melatonin (10–30 mg/kg, 6 doses at 10 hr intervals) was investigated to potentiate L‐DOPA therapeutic effects in 1‐methyl‐4‐phenyl‐1,2,3,6‐tetrahydropyridine (MPTP)‐induced parkinsonism in mice. Striatal tyrosine hydroxylase (TH) immunoreactivity, TH, and phosphorylated ser 40 TH (p‐TH) protein levels were assayed on 7th day. Nigral TH‐positive neurons stereology was conducted on serial sections 2.8 mm from bregma rostrally to 3.74 mm caudally. MPTP caused 39% and 58% decrease, respectively, in striatal fibers and TH protein levels, but 2.5‐fold increase in p‐TH levels. About 35% TH neurons were lost between 360 and 600 μm from 940 μm of the entire nigra analyzed, but no neurons were lost between 250 μm rostrally and 220 μm caudally. When L‐DOPA in small doses (5–8 mg/kg) failed to affect MPTP‐induced akinesia or catalepsy, co‐administration of melatonin with L‐DOPA attenuated these behaviors. Melatonin administration significantly attenuated MPTP‐induced loss in striatal TH fibers (82%), TH (62%) and p‐TH protein (100%) levels, and nigral neurons (87–100%). Melatonin failed to attenuate MPTP‐induced striatal dopamine depletion. L‐DOPA administration (5 mg/kg, once 40 min prior to sacrifice, p.o.) in MPTP‐ and melatonin‐treated mice caused significant increase in striatal dopamine (31%), as compared to L‐DOPA and MPTP‐treated mice. This was equivalent to 8 mg/kg L‐DOPA administration in parkinsonian mouse. Therefore, prolonged, effective use of L‐DOPA in PD with lesser side effects could be achieved by treating with 60% lower doses of L‐DOPA along with melatonin.     

Innovative technologies for point‐of‐care testing of viral hepatitis in low‐resource and decentralized settings

According to the Global Burden of Diseases, chronic viral hepatitis B and C are one of the most challenging global health conditions that rank among the first causes of morbidity and mortality worldwide. Low‐ and middle‐income countries are particularly affected by the health burden associated with HBV or HCV infection. One major gap in efficiently addressing the issue of viral hepatitis is universal screening. However, the costs and chronic lack of human resources for using traditional screening strategies based on serology and molecular biology preclude any scaling‐up. Point‐of‐care tests have been deemed a powerful potential solution to fill the current diagnostics gap in low‐resource and decentralized settings. Despite high interest resulting from their development in recent years, very few point‐of‐care devices have reached the market. Scaling down and automating all testing steps in 1 single device (eg, sample preparation, detection and readout) is indeed challenging. But innovations in multiple disciplines such as nanotechnologies, microfluidics, biosensors and synthetic biology have led to the creation of chip‐sized laboratory systems called “lab‐on‐a‐chip” devices. This review aims to explain how these innovations can overcome technological barriers that usually arise for each testing step while developing integrated point‐of‐care tests. Point‐of‐care test prototypes rarely meet the requirements for mass production, which also hinders their large‐scale production. In addition to logistical hurdles, legal and economic constraints specific to the commercialization of in vitro diagnostics, which have also participated in the low transfer of innovative point‐of‐care tests to the field, are discussed.     

Validation of a disease‐specific quality‐of‐life questionnaire in a large sample of Dutch achalasia patients

SUMMARY. The aim of this study was to validate a translated version of an achalasia‐specific quality‐of‐life questionnaire (achalasia‐DSQoL) by examining its psychometric properties in a Dutch cohort of achalasia patients. The achalasia‐DSQoL was administered to 171 treated achalasia patients together with a clinical symptom score and the RAND‐36. Validation methods included factor analysis, known‐group techniques, Cronbach's alpha and Spearman rank correlation with other questionnaires and feasibility. About 72.5% of the achalasia patients completed the questionnaires. The achalasia‐DSQoL showed evidence of an underlying construct and seems reliable with a Cronbach's alpha of 0.77. The question concerning heartburn did not correlate with the other items on the questionnaire. Known‐group techniques demonstrated that the achalasia‐DSQoL discriminates between achalasia patients in clinical remission and patients who are not. There was a moderate correlation between the achalasia‐DSQoL and the RAND‐36 subscales. The questionnaire was easy in use. The translated version of the achalasia‐DSQoL is a valid and reliable instrument to compare groups of achalasia patients although the question concerning heartburn should be excluded.