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The liver possesses a high regenerative capacity. Liver regeneration is a compensatory response overcoming disturbances of whole-body homeostasis provoked by organ defects. Here we show that a vagus-macrophage-hepatocyte link regulates acute liver regeneration after liver injury and that this system is critical for promoting survival. Hepatic Foxm1 is rapidly upregulated after partial hepatectomy (PHx). Hepatic branch vagotomy (HV) suppresses this upregulation and hepatocyte proliferation, thereby increasing mortality. In addition, hepatic FoxM1 supplementation in vagotomized mice reverses the suppression of liver regeneration and blocks the increase in post-PHx mortality. Hepatic macrophage depletion suppresses both post-PHx Foxm1 upregulation and remnant liver regeneration, and increases mortality. Hepatic Il-6 rises rapidly after PHx and this is suppressed by HV, muscarinic blockade or resident macrophage depletion. Furthermore, IL-6 neutralization suppresses post-PHx Foxm1 upregulation and remnant liver regeneration. Collectively, vagal signal-mediated IL-6 production in hepatic macrophages upregulates hepatocyte FoxM1, leading to liver regeneration and assures survival. The mechanisms underlying the regenerative capacity of the liver are not fully understood. Here, the authors show that the acute regenerative response to liver injury in mice is regulated by the communication involving the vagus nerve, macrophages, and hepatocytes, leading to hepatic FoxM1 activation and promotion of overall survival.

An animal-like cryptochrome derived from Chlamydomonas reinhardtii ( Cr aCRY) is a bifunctional flavoenzyme harboring flavin adenine dinucleotide (FAD) as a photoreceptive/catalytic center and functions both in the regulation of gene transcription and the repair of UV-induced DNA lesions in a light-dependent manner, using different FAD redox states. To address how Cr aCRY stabilizes the physiologically relevant redox state of FAD, we investigated the thermodynamic and kinetic stability of the two-electron reduced anionic FAD state (FADH − ) in Cr aCRY and related (6–4) photolyases. The thermodynamic stability of FADH − remained almost the same compared to that of all tested proteins. However, the kinetic stability of FADH − varied remarkably depending on the local structure of the secondary pocket, where an auxiliary chromophore, 8-hydroxy-7,8-didemethyl-5-deazariboflavin (8-HDF), can be accommodated. The observed effect of 8-HDF uptake on the enhancement of the kinetic stability of FADH − suggests an essential role of 8-HDF in the bifunctionality of Cr aCRY.

(6–4) Photolyases ((6–4) PLs) are ubiquitous photoenzymes that use the energy of sunlight to catalyze the repair of carcinogenic UV-induced DNA lesions, pyrimidine(6–4)pyrimidone photoproducts. To repair DNA, (6–4) PLs must first undergo so-called photoactivation, in which their excited flavin adenine dinucleotide (FAD) cofactor is reduced in one or two steps to catalytically active FADH − via a chain of three or four conserved tryptophan residues, transiently forming FAD •− /FADH − ⋯ TrpH •+ pairs separated by distances of 15 to 20 Å. Photolyases and related photoreceptors cryptochromes use a plethora of tricks to prevent charge recombination of photoinduced donor–acceptor pairs, such as chain branching and elongation, rapid deprotonation of TrpH •+ or protonation of FAD •− . Here, we address Arabidopsis thaliana (6–4) PL ( At 64) photoactivation by combining molecular biology, in vivo survival assays, static and time-resolved spectroscopy and computational methods. We conclude that At 64 photoactivation is astonishingly efficient compared to related proteins—due to two factors: exceptionally low losses of photoinduced radical pairs through ultrafast recombination and prevention of solvent access to the terminal Trp 3 H •+ , which significantly extends its lifetime. We propose that a highly conserved histidine residue adjacent to the 3rd Trp plays a key role in Trp 3 H •+ stabilization.

Hepatocytes play important roles in the liver, but in culture, they immediately lose function and dedifferentiate into progenitor-like cells. Although this unique feature is well-known, the dynamics and mechanisms of hepatocyte dedifferentiation and the differentiation potential of dedifferentiated hepatocytes (dediHeps) require further investigation. Here, we employ a culture system specifically established for hepatic progenitor cells to study hepatocyte dedifferentiation. We found that hepatocytes dedifferentiate with a hybrid epithelial/mesenchymal phenotype, which is required for the induction and maintenance of dediHeps, and exhibit Vimentin-dependent propagation, upon inhibition of the Hippo signaling pathway. The dediHeps re-differentiate into mature hepatocytes by forming aggregates, enabling reconstitution of hepatic tissues in vivo. Moreover, dediHeps have an unexpected differentiation potential into intestinal epithelial cells that can form organoids in three-dimensional culture and reconstitute colonic epithelia after transplantation. This remarkable plasticity will be useful in the study and treatment of intestinal metaplasia and related diseases in the liver. Hepatocytes dedifferentiate into progenitor-like cells in culture. Here, authors elucidate the dynamics and mechanisms of hepatocyte dedifferentiation and find an unexpected differentiation potential of hepatocytes into intestinal epithelial cells.

Recent advances have enabled the direct induction of human tissue-specific stem and progenitor cells from differentiated somatic cells. However, it is not known whether human hepatic progenitor cells (hHepPCs) can be generated from other cell types by direct lineage reprogramming with defined transcription factors. Here, we show that a set of three transcription factors, FOXA3, HNF1A, and HNF6, can induce human umbilical vein endothelial cells to directly acquire the properties of hHepPCs. These induced hHepPCs (hiHepPCs) propagate in long-term monolayer culture and differentiate into functional hepatocytes and cholangiocytes by forming cell aggregates and cystic epithelial spheroids, respectively, under three-dimensional culture conditions. After transplantation, hiHepPC-derived hepatocytes and cholangiocytes reconstitute damaged liver tissues and support hepatic function. The defined transcription factors also induce hiHepPCs from endothelial cells circulating in adult human peripheral blood. These expandable and bipotential hiHepPCs may be useful in the study and treatment of human liver diseases. The conditions to induce human hepatic progenitor cells from other cell types are unclear. Here, the authors reprogram human endothelial cells to hepatic progenitor cells by expressing FOXA3, HNF1A and HNF6, capable of giving rise to hepatocytes and cholangiocytes that reconstitute damaged liver tissues on transplantation.

In mammalian global genomic nucleotide excision repair, UV-DDB plays a central role in recognizing DNA lesions, such as 6-4 photoproducts and cyclobutane pyrimidine dimers, within chromatin. In the present study, we perform cryo-electron microscopy analyses coupled with chromatin-immunoprecipitation to reveal that the cellular UV-DDB binds to UV-damaged DNA lesions in a chromatin unit, the nucleosome, at a position approximately 20 base-pairs from the nucleosomal dyad in human cells. An alternative analysis of the in vitro reconstituted UV-DDB-cyclobutane pyrimidine dimer nucleosome structure demonstrates that the DDB2 subunit of UV-DDB specifically recognizes the cyclobutane pyrimidine dimer lesion at this position on the nucleosome. We also determine the structures of UV-DDB bound to DNA lesions at other positions in purified cellular human nucleosomes. These cellular and reconstituted UV-DDB-nucleosome complex structures provide important evidence for understanding the mechanism by which UV lesions in chromatin are recognized and repaired in mammalian cells. UV-DDB is a protein that plays a key role in recognizing DNA lesions. Here, the authors determine the cryo-EM structure of UV-DDB bound to UV-damaged chromatin in human cells, identifying a nucleosome binding site.

Background/objectivesIsothiocyanate (ITC) is formed via the hydrolysis of glucosinolates by myrosinase, found in cruciferous vegetables. Although myrosinase is inactivated by the cooking process, no studies have incorporated the effect of cooking into the estimation of dietary ITC intake or evaluated the validity. We evaluated the validity of dietary ITC intake estimated from a food frequency questionnaire (FFQ), and urinary ITC levels using 24 h urine samples or a WFR (weighed food record), and evaluated the reproducibility of dietary ITC in two FFQs administered at an interval of 1-year.Subjects/methodsThe JPHC-NEXT Protocol Area included a total of 255 middle-aged participants across Japan. We calculated dietary ITC intake from WFR and two FFQs by assuming that cooked cruciferous vegetables contain zero ITC. Urinary ITC excretion was measured at two points during summer and winter. The validity and reproducibility of dietary ITC intake estimated by FFQ were assessed using Spearman’s correlation coefficients.ResultsAlthough we observed a moderate correlation between dietary ITC intake derived from a 12-day WFR and urinary ITC excretion, notwithstanding the cooking process, the correlation between dietary ITC intake estimated by FFQ and mean urinary ITC excretion was low. However, the correlation was improved when we compared urinary ITC excretion and a 3-day WFR or FFQ collected during winter. Our FFQ showed good reproducibility.ConclusionAlthough seasonality is a critical factor, dietary ITC intake estimated using an FFQ showed moderate validity and reproducibility and can be used in future epidemiological studies.

Carcinogens often generate mutable DNA lesions that contribute to cancer and aging. However, the chemical structure of tumorigenic DNA lesions formed by acetaldehyde remains unknown, although it has long been considered an environmental mutagen in alcohol, tobacco, and food. Here, we identify an aldehyde-induced DNA lesion, forming an intrastrand crosslink between adjacent guanine bases, but not in single guanine bases or in other combinations of nucleotides. The GG intrastrand crosslink exists in equilibrium in the presence of aldehyde, and therefore it has not been detected or analyzed in the previous investigations. The newly identified GG intrastrand crosslinks might explain the toxicity and mutagenicity of acetaldehyde in DNA metabolism.

Background: Few studies have investigated the effects of Okinawan vegetable consumption on the risk of incident stroke and coronary heart disease. This study aimed to examine associations of vegetable, fruit, and Okinawan vegetable consumption with risk of incident stroke and coronary heart disease in the Japanese population of Okinawa. Methods: The study design was a prospective cohort study. During 1995–1998, a validated food frequency questionnaire was administered in two study areas to 16,498 participants aged 45–74 years. In 217,467 person-years of follow-up until the end of 2012, a total of 839 stroke cases and 197 coronary heart disease cases were identified. Results: No statistically significant association between total Okinawan vegetable consumption and risk of stroke and coronary heart disease was obtained: the multivariable adjusted hazard ratios for the highest versus lowest tertile of consumption were 1.09 (95% confidence interval, 0.93–1.29; P for trend = 0.289) in model 2. Total vegetable and fruit and specific Okinawan vegetable consumption were also not statistically significantly associated with risk of cardiovascular outcomes. Conclusions: This study demonstrated that consumption of total vegetable and fruit, total Okinawan vegetables, and specific Okinawan vegetables in Japanese residents of Okinawa was not associated with risk of incident stroke and coronary heart disease.

We aimed to validate a method for assessing trans-fatty acid (TFA) intake in the Japanese population using the FFQ developed in the 1990s from a prospective study that was based on the Japan Public Health Center-based Prospective Cohort Study. For FFQ validation, we included 565 participants (Cohort I: n 215, Cohort II: n 350) aged 40–69 years. We used a 28-d dietary record (DR) over 1 year and two FFQ administered before and after DR assessment. We calculated total TFA intake, TFA from industrial oils (i-TFA) and TFA from ruminants (r-TFA) considering a database of measurements obtained mainly from Japan. Spearman’s rank correlation coefficients (CC) were computed for validity and reproducibility. Energy adjustments were applied using two methods considering the TFA measurement: density method for TFA % of total energy and residual method for TFA g/d. The total TFA intake (% of the total energy intake) was 0·08–0·76 % (median, 0·27–0·37 %) in DR of both cohorts and was 0·00–1·13 % (median, 0·30–0·40 %) in FFQ. The i-TFA accounted for approximately 50 % of the total TFA intake in DR and approximately 40 % in FFQ. For total TFA (% of the total energy intake), CC were 0·54–0·69, and weighted κ coefficients were 0·88–0·92 for both cohorts. The de-attenuated CC was 0·46–0·62 for i-TFA (g/d) and 0·57–0·68 for r-TFA (g/d). Our study showed that the validity and reproducibility of TFA intake estimation using the FFQ were reasonable, suggesting its suitability among the Japanese population with low-TFA intake.