Validation of Artificial Intelligence (AI)-Assisted Flow Cytometry Analysis for Immunological Disorders.

Flow cytometry is a vital diagnostic tool for hematologic and immunologic disorders, but manual analysis is prone to variation and time-consuming. Over the last decade, artificial intelligence (AI) has advanced significantly. In this study, we developed and validated an AI-assisted flow cytometry workflow using 379 clinical cases from 2021, employing a 3-tube, 10-color flow panel with 21 antibodies for primary immunodeficiency diseases and related immunological disorders. The AI software (DeepFlow™, version 2.1.1) is fully automated, reducing analysis time to under 5 min per case. It interacts with hematopatholoists for manual gating adjustments when necessary. Using proprietary multidimensional density-phenotype coupling algorithm, the AI model accurately classifies and enumerates T, B, and NK cells, along with important immune cell subsets, including CD4+ helper T cells, CD8+ cytotoxic T cells, CD3+/CD4-/CD8- double-negative T cells, and class-switched or non-switched B cells. Compared to manual analysis with hematopathologist-determined lymphocyte subset percentages as the gold standard, the AI model exhibited a strong correlation (r > 0.9) across lymphocyte subsets. This study highlights the accuracy and efficiency of AI-assisted flow cytometry in diagnosing immunological disorders in a clinical setting, providing a transformative approach within a concise timeframe.

IMP1/IGF2BP1 in human colorectal cancer extracellular vesicles.

Colorectal cancer (CRC) is a leading cause of cancer-related death. There is an urgent need for new methods of early CRC detection and monitoring to improve patient outcomes. Extracellular vesicles (EVs) are secreted, lipid-bilayer bound, nanoparticles that carry biological cargo throughout the body and in turn exhibit cancer-related biomarker potential. RNA binding proteins (RBPs) are posttranscriptional regulators of gene expression that may provide a link between host cell gene expression and EV phenotypes. Insulin-like growth factor 2 RNA binding protein 1 (IGF2BP1/IMP1) is an RBP that is highly expressed in CRC with higher levels of expression correlating with poor prognosis. IMP1 binds and potently regulates tumor-associated transcripts that may impact CRC EV phenotypes. Our objective was to test whether IMP1 expression levels impact EV secretion and/or cargo. We used RNA sequencing, in vitro CRC cell lines, ex vivo colonoid models, and xenograft mice to test the hypothesis that IMP1 influences EV secretion and/or cargo in human CRC. Our data demonstrate that IMP1 modulates the RNA expression of transcripts associated with extracellular vesicle pathway regulation, but it has no effect on EV secretion levels in vitro or in vivo. Rather, IMP1 appears to affect EV regulation by directly entering EVs in a transformation-dependent manner. These findings suggest that IMP1 has the ability to shape EV cargo in human CRC, which could serve as a diagnostic/prognostic circulating tumor biomarker.NEW & NOTEWORTHY This work demonstrates that the RNA binding protein IGF2BP1/IMP1 alters the transcript profile of colorectal cancer cell (CRC) mRNAs from extracellular vesicle (EV) pathways. IMP1 does not alter EV production or secretion in vitro or in vivo, but rather enters CRC cells where it may further impact EV cargo. Our work shows that IMP1 has the ability to shape EV cargo in human CRC, which could serve as a diagnostic/prognostic circulating tumor biomarker.

An Enriched Environment Alters DNA Repair and Inflammatory Responses After Radiation Exposure.

After the Fukushima Daiichi Nuclear Power Plant accident, there is growing concern about radiation-induced carcinogenesis. In addition, living in a long-term shelter or temporary housing due to disasters might cause unpleasant stress, which adversely affects physical and mental health. It's been experimentally demonstrated that "eustress", which is rich and comfortable, has beneficial effects for health using mouse models. In a previous study, mice raised in the enriched environment (EE) has shown effects such as suppression of tumor growth and enhancement of drug sensitivity during cancer treatment. However, it's not yet been evaluated whether EE affects radiation-induced carcinogenesis. Therefore, to evaluate whether EE suppresses a radiation-induced carcinogenesis after radiation exposure, in this study, we assessed the serum leptin levels, radiation-induced DNA damage response and inflammatory response using the mouse model. In brief, serum and tissues were collected and analyzed over time in irradiated mice after manipulating the raising environment during the juvenile or adult stage. To assess the radiation-induced DNA damage response, we performed immunostaining for phosphorylated H2AX which is a marker of DNA double-strand break. Focusing on the polarization of macrophages in the inflammatory reaction that has an important role in carcinogenesis, we performed analysis using tissue immunofluorescence staining and RT-qPCR. Our data confirmed that EE breeding before radiation exposure improved the responsiveness to radiation-induced DNA damage and basal immunity, further suppressing the chronic inflammatory response, and that might lead to a reduction of the risk of radiation-induced carcinogenesis.

Adenoviral transduction of EGFR into pregnancy-adapted uterine artery endothelial cells remaps growth factor induction of endothelial dysfunction.

During pregnancy, uterine vascular vasodilation is enhanced through adapted Ca2+ signaling, facilitated through increased endothelial connexin 43 (Cx43) gap junctional communication (GJC). In preeclampsia (PE), this adaptive response is missing. Of note, the angiogenic factor VEGF can also act via Src and ERK to close Cx43 gap junctions. While VEGFR2 is necessary for such closure, a role VEGFR1 is less clear. We reasoned if VEGFR2 is acting alone, then substituting another growth factor receptor with VEGFR2-like signaling should have the same effect. In uterine artery endothelial cells derived from pregnant sheep (P-UAEC), endogenous EGFR expression is very low. When we used adenovirus to raise EGFR, we also dose-dependently induced EGF-sensitive Cx43 phosphorylation mainly via ERK, and corresponding loss of Ca2+ bursts, but eliminated VEGF effects on phosphorylation of Cx43 or loss of Ca2+ bursting. This surprising observation suggests that while activated EGFR may indeed substitute for VEGFR2, it also sequesters a limited pool of effector molecules needed for VEGFR2 to phosphorylate Cx43. Thus, low endogenous EGFR expression in P-UAEC may be a necessary strategy to allow VEGFR-2 control of GJC, a first step in initiating angiogenesis in healthy pregnancy. Of further note, trophoblasts are rich in EGFR, and we have demonstrated shed PLAP+/EGFR + extracellular vesicles in maternal circulation in first trimester plasma samples using nanoscale high resolution flow cytometry. Collectively our data suggest that placenta derived exosomes positive for EGFR should be further considered as a possible cause of endothelial dysfunction in women with PE.

Tumor necrosis factor receptor-associated factor 6 is required to inhibit foreign body giant cell formation and activate osteoclasts under inflammatory and infectious conditions.

Osteoclasts and foreign body giant cells (FBGCs) are derived from common progenitors and share properties such as multi-nucleation capacity induced by cell-cell fusion; however, mechanisms underlying lineage determination between these cells remain unclear. Here we show that, under inflammatory conditions, osteoclasts are stimulated in a manner similar to M1 macrophages, while formation of FBGCs, which exhibit M2-like phenotypes, is inhibited in a manner similar to that seen in M1/M2 macrophage polarization. FBGC/osteoclast polarization was inhibited by conditional knockout of tumor necrosis factor receptor associated factor 6 (Traf6) in adults in vivo and in vitro. Traf6-null mice were previously reported to die soon after birth, but we found that Traf6 deletion in adults did not cause lethality but rather inhibited osteoclast activation and prevented FBGC inhibition under inflammatory conditions. Accordingly, basal osteoclastogenesis was significantly inhibited by Traf6 deletion in vivo and in vitro and accompanied by increased bone mass. Lipopolysaccharide-induced osteoclast formation and osteolysis were significantly inhibited in Traf6 conditional knockout mice. Our results suggest that Traf6 plays a crucial role in regulating M1 osteoclast and M2 FBGC polarization and is a potential therapeutic target in blocking FBGC inhibition, antagonizing osteolysis in inflammatory conditions, and increasing bone mass without adverse effects in adults.

Extracellular Signals of a Human Epithelial Colorectal Adenocarcinoma (Caco-2) Cell Line Facilitate the Penetration of Pseudomonas aeruginosa PAO1 Strain through the Mucin Layer.

Pseudomonas aeruginosa can penetrate the layer of mucus formed by host intestinal epithelial cells, often resulting in sepsis in immunocompromised patients. We have previously demonstrated that P. aeruginosa can penetrate the mucin layer by flagellar motility and the degradation of the mucin layer. However, it remains unclear how P. aeruginosa initially recognizes epithelial cells. Using the human epithelial colorectal adenocarcinoma (Caco-2) cell line, we investigated extracellular signaling that could facilitate the penetration of P. aeruginosa through the mucin layer. The supernatant from Caco-2 cell cultures increased penetration of P. aeruginosa through an artificial mucin layer. The Caco-2 cell supernatant increased bacterial flagella-dependent swarming motility, but it did not influence P. aeruginosa growth or protease activity. Filtering of the Caco-2 cell supernatant indicated that proteins weighing <10 kDa increased mucin penetration, swarming motility, and, based on a tethered cell assay, induced acceleration of the flagellar filament rotational rate. Furthermore, a capillary assay showed that <10 kDa proteins in the Caco-2 cell supernatant attracted P. aeruginosa cells. Finally, we identified that growth-regulated oncogene-α (GRO-α) secreted by Caco-2 cells was a factor facilitating flagellar filament rotation and swarming motility, although it did not attract the bacteria. We conclude that penetration of the mucin layer by P. aeruginosa is facilitated by small proteins (<10 kDa) secreted by Caco-2 cells, both by inducing acceleration of flagellar motility and increasing chemotaxis.

Elevation of pro-inflammatory cytokine levels following anti-resorptive drug treatment is required for osteonecrosis development in infectious osteomyelitis.

Various conditions, including bacterial infection, can promote osteonecrosis. For example, following invasive dental therapy with anti-bone resorptive agents, some patients develop osteonecrosis in the jaw; however, pathological mechanisms underlying these outcomes remain unknown. Here, we show that administration of anti-resorptive agents such as the bisphosphonate alendronate accelerates osteonecrosis promoted by infectious osteomyelitis. Potent suppression of bone turnover by these types of agents is considered critical for osteonecrosis development; however, using mouse models we found that acceleration of bone turnover by teriparatide injection did not prevent osteonecrosis but rather converted osteoclast progenitors to macrophages expressing inflammatory cytokines, which were required for osteonecrosis development. In fact, we demonstrate that TNFα-, IL-1α/ß- or IL-6-deficient mice as well as wild-type mice administered a TNFα-inhibitor were significantly resistant to development of osteonecrosis accompanying infectious myelitis, even under bisphosphonate treatment. Our data provide new insight into mechanisms underlying osteonecrosis and suggest new ways to prevent it.

Selective estrogen receptor modulators and the vitamin D analogue eldecalcitol block bone loss in male osteoporosis.

Rapid increases in the number of elderly people have dramatically increased the number of female and male osteoporosis patients. Osteoporosis often causes bone fragility fractures, and males exhibit particularly poor prognosis after these fractures, indicating that control of osteoporosis is crucial to maintain quality of men's lives. However, osteoporosis therapies available for men have lagged behind advances available for women. Here, we show that three selective estrogen receptor modulators (SERMs), namely, raloxifene, bazedoxifene, and tamoxifen, plus the vitamin D analogue ED71, also called eldecalcitol, completely block orchiectomy-induced, testosterone-depleted bone loss in male mice in vivo. Patients treated with hormone deprivation therapy for prostate cancer also exhibit male osteoporosis, and bone management is critical for these patients. Given that androgen replacement therapy is not an option for these patients, our results represent a novel approach potentially useful to control male osteoporosis.

A serum metabolomics-based profile in low bone mineral density postmenopausal women.

Osteoporosis is characterized as a metabolic disorder of bone tissue, and various metabolic markers are now available to support its diagnosis and evaluate treatment effects. Substances produced as end products of metabolomic activities are the correlated factors to the biological or metabolic status, and thus, metabolites are considered highly sensitive markers of particular pathological states, including osteoporosis. Here we undertook comprehensive serum metabolomics analysis in postmenopausal women with or without low bone mineral density (low BMD vs controls) for the first time using capillary electrophoresis/mass spectrometry. Among the metabolites tested, 57 were detected in sera. Levels of hydroxyproline, Gly-Gly and cystine, differed significantly between groups, with Gly-Gly and cystine significantly lower in the low BMD group and hydroxyproline, a reported marker of osteoporosis, significantly higher. Levels of TRACP5b, a bone resorption marker, were significantly higher in the low BMD group, supporting the study's validity. Taken together, our findings represent novel metabolomic profiling in low BMD in postmenopausal women.

The onset risk of carcinoma in patients continuing tacrolimus topical treatment for oral lichen planus: a case report.

Oral lichen planus is a chronic inflammatory mucocutaneous disease. Topical use of steroids and other immuno-modulating therapies have been tried for this intractable condition. Nowadays, tacrolimus ointment is used more commonly as a choice for treatment. However, a number of discussions have taken place after tacrolimus was reported to be carcinogenic. This report describes a patient who applied tacrolimus ointment to the lower lip after being diagnosed with oral lichen planus in 2008, and whose lesion developed squamous cell carcinoma in 2010. Since the relationship between tacrolimus and cancer development has been reported in only a few cases, including this case report, the clinician must be careful selecting tacrolimus as a second-line treatment for oral lichen planus.

Selective Estrogen Receptor Modulators Suppress Hif1α Protein Accumulation in Mouse Osteoclasts.

Anti-bone resorptive drugs such as bisphosphonates, the anti-RANKL antibody (denosumab), or selective estrogen receptor modulators (SERMs) have been developed to treat osteoporosis. Mechanisms underlying activity of bisphosphonates or denosumab in this context are understood, while it is less clear how SERMs like tamoxifen, raloxifene, or bazedoxifene inhibit bone resorption. Recently, accumulation of hypoxia inducible factor 1 alpha (Hif1α) in osteoclasts was shown to be suppressed by estrogen in normal cells. In addition, osteoclast activation and decreased bone mass seen in estrogen-deficient conditions was found to require Hif1α. Here, we used western blot analysis of cultured osteoclast precursor cells to show that tamoxifen, raloxifene, or bazedoxifene all suppress Hif1α protein accumulation. The effects of each SERM on osteoclast differentiation differed in vitro. Our results suggest that interventions such as the SERMs evaluated here could be useful to inhibit Hif1α and osteoclast activity under estrogen-deficient conditions.

Smad4 is required to inhibit osteoclastogenesis and maintain bone mass.

Bone homeostasis is maintained as a delicate balance between bone-resorption and bone-formation, which are coupled to maintain appropriate bone mass. A critical question is how bone-resorption is terminated to allow bone-formation to occur. Here, we show that TGFßs inhibit osteoclastogenesis and maintain bone-mass through Smad4 activity in osteoclasts. We found that latent-TGFß1 was activated by osteoclasts to inhibit osteoclastogenesis. Osteoclast-specific Smad4 conditional knockout mice (Smad4-cKO) exhibited significantly reduced bone-mass and elevated osteoclast formation relative to controls. TGFß1-activation induced expression of Irf8 and Bcl6, both of which encode factors inhibiting osteoclastogenesis, by blocking their negative regulator, Prdm1, in osteoclasts in a Smad4-dependent manner. Reduced bone-mass and accelerated osteoclastogenesis seen in Smad4-cKO were abrogated by Prdm1 deletion. Administration of latent-TGFß1-Fc to wild-type mice antagonized LPS-induced bone destruction in a model of activated osteoclast-mediated bone destruction. Thus, latent-TGFß1-Fc could serve as a promising new therapeutic agent in bone diseases marked by excessive resorption.

Methotrexate inhibits osteoclastogenesis by decreasing RANKL-induced calcium influx into osteoclast progenitors.

The increasing number of osteoporosis patients is a pressing issue worldwide. Osteoporosis frequently causes fragility fractures, limiting activities of daily life and increasing mortality. Many osteoporosis patients take numerous medicines due to other health issues; thus, it would be preferable if a single medicine could ameliorate osteoporosis and other conditions. Here, we screened 96 randomly selected drugs targeting various diseases for their ability to inhibit differentiation of osteoclasts, which play a pivotal role in development of osteoporosis, and identified methotrexate (MTX), as a potential inhibitor. MTX is currently used to treat sarcomas or leukemic malignancies or auto-inflammatory diseases such as rheumatoid arthritis (RA) through its anti-proliferative and immunosuppressive activities; however, a direct effect on osteoclast differentiation has not been shown. Here, we report that osteoclast formation and expression of osteoclastic genes such as NFATc1 and DC-STAMP, which are induced by the cytokine RANKL, are significantly inhibited by MTX. We found that RANKL-dependent calcium (Ca) influx into osteoclast progenitors was significantly inhibited by MTX. RA patients often develop osteoporosis, and osteoclasts are reportedly required for joint destruction; thus, MTX treatment could have a beneficial effect on RA patients exhibiting high osteoclast activity by preventing both osteoporosis and joint destruction.

Auraptene Acts as an Anti-Inflammatory Agent in the Mouse Brain.

The anti-inflammatory activity of auraptene (AUR), a citrus coumarin, in peripheral tissues is well-known, and we previously demonstrated that AUR exerts anti-inflammatory effects in the ischemic brain; the treatment of mice with AUR for eight days immediately after ischemic surgery suppressed demise and neuronal cell death in the hippocampus, possibly through its anti-inflammatory effects in the brain. We suggested that these effects were at least partly mediated by the suppression of inflammatory mediators derived from astrocytes. The present study showed that (1) AUR, as a pretreatment for five days before and another three days after ischemic surgery, suppressed microglial activation, cyclooxygenase (COX)-2 expression in astrocytes, and COX-2 mRNA expression in the hippocampus; (2) AUR suppressed the lipopolysaccharide-induced expression of COX-2 mRNA and the mRNA of pro-inflammatory cytokines in cultured astrocytes; (3) AUR was still detectable in the brain 60 min after its intraperitoneal administration. These results support our previous suggestion that AUR directly exerts anti-inflammatory effects on the brain.

Bcl6 promotes osteoblastogenesis through Stat1 inhibition.

Bone mass is tightly controlled by a balance between osteoclast and osteoblast activities. Although these cell types mature via different pathways, some factors reportedly regulate differentiation of both. Here, in a search for factors governing osteoblastogenesis but also expressed in osteoclasts to control both cell types by one molecule, we identified B cell lymphoma 6 (Bcl6) as one of those factors and show that it promotes osteoblast differentiation. Bcl6 was previously shown to negatively regulate osteoclastogenesis. We report that lack of Bcl6 results in significant inhibition of osteoblastogensis in vivo and in vitro and in defects in secondary ossification center formation in vivo. Signal transducer and activator of transcription 1 (Stat1) reportedly attenuates osteoblast differentiation by inhibiting nuclear translocation of runt-related transcription factor 2 (Runx2), which is essential for osteoblast differentiation. We found that lack of Bcl6 resulted in significant elevation of Stat1 mRNA and protein expression in osteoblasts and showed that Stat1 is a direct target of Bcl6 using a chromatin immune-precipitation assay. Mice lacking both Bcl6 and Stat1 (DKO) exhibited significant rescue of bone mass and osteoblastic parameters as well as partial rescue of secondary ossification center formation compared with Bcl6-deficient mice in vivo. Altered osteoblastogenesis in Bcl6-deficient cells was also restored in DKO in vitro. Thus, Bcl6 plays crucial roles in regulating both osteoblast activation and osteoclast inhibition.

Interleukin-1 receptor-associated kinase-4 (IRAK4) promotes inflammatory osteolysis by activating osteoclasts and inhibiting formation of foreign body giant cells.

Formation of foreign body giant cells (FBGCs) occurs following implantation of medical devices such as artificial joints and is implicated in implant failure associated with inflammation or microbial infection. Two major macrophage subpopulations, M1 and M2, play different roles in inflammation and wound healing, respectively. Therefore, M1/M2 polarization is crucial for the development of various inflammation-related diseases. Here, we show that FBGCs do not resorb bone but rather express M2 macrophage-like wound healing and inflammation-terminating molecules in vitro. We also found that FBGC formation was significantly inhibited by inflammatory cytokines or infection mimetics in vitro. Interleukin-1 receptor-associated kinase-4 (IRAK4) deficiency did not alter osteoclast formation in vitro, and IRAK4-deficient mice showed normal bone mineral density in vivo. However, IRAK4-deficient mice were protected from excessive osteoclastogenesis induced by IL-1ß in vitro or by LPS, an infection mimetic of Gram-negative bacteria, in vivo. Furthermore, IRAK4 deficiency restored FBGC formation and expression of M2 macrophage markers inhibited by inflammatory cytokines in vitro or by LPS in vivo. Our results demonstrate that osteoclasts and FBGCs are reciprocally regulated and identify IRAK4 as a potential therapeutic target to inhibit stimulated osteoclastogenesis and rescue inhibited FBGC formation under inflammatory and infectious conditions without altering physiological bone resorption.

Mycobacterium tuberculosis promotes arthritis development through Toll-like receptor 2.

Rheumatoid arthritis (RA) is a multifactorial disease caused by genetic and environmental factors: however, precise molecular mechanisms underlying its pathogenesis remain largely unknown. Treatment of RA patients with disease-modifying biological agents occasionally promotes Mycobacterium tuberculosis infection or recurrence of M. tuberculosis, although how infection promotes arthritis has not been characterized. Here, we found that arthritis phenotypes in a collagen-induced mouse model were evident only when killed M. tuberculosis was co-administered. Treatment of cultured macrophages with killed M. tuberculosis promoted production of IL-6, a major inflammatory cytokine in RA patients, while similar treatment of TLR2-deficient macrophages failed to induce IL-6 expression. Arthritis scores, joint destruction, and serum IL-6 levels were all significantly ameliorated in TLR2-deficient compared with wild-type mice, even in animals treated with killed M. tuberculosis. These results suggest that M. tuberculosis infection enhances arthritis development and that TLR2 could serve as a therapeutic target for some forms of the disease.

In situ modification of cell-culture scaffolds by photocatalytic decomposition of organosilane monolayers.

We demonstrate a novel application of TiO2 photocatalysis for modifying the cell affinity of a scaffold surface in a cell-culture environment. An as-deposited octadecyltrichlorosilane self-assembled monolayer (OTS SAM) on TiO2 was found to be hydrophobic and stably adsorbed serum albumins that blocked subsequent adsorption of other proteins and cells. Upon irradiation of ultraviolet (UV) light, OTS molecules were decomposed and became permissive to the adhesion of PC12 cells via adsorption of an extracellular matrix protein, collagen. Optimal UV dose was 200 J cm(-2) for OTS SAM on TiO2. The amount of collagen adsorption decreased when excessive UV light was irradiated, most likely due to the surface being too hydrophilic to support its adsorption. This UV-induced modification required TiO2 to be present under the SAM and hence is a result of TiO2 photocatalysis. The UV irradiation for surface modification can be performed before cell plating or during cell culture. We also demonstrate that poly(ethylene glycol) SAM can also be patterned with this method, indicating that it is applicable to both hydrophobic and hydrophilic SAMs. This method provides a unique tool for fabricating cell microarrays and studying dynamical properties of living cells.

3,5,6,7,8,3',4'-Heptamethoxyflavone, a citrus flavonoid, on protection against memory impairment and neuronal cell death in a global cerebral ischemia mouse model.

The present study evaluated the effects of treatment with the citrus flavonoid, 3,5,6,7,8,3',4'-heptamethoxyflavone (HMF) on protection against memory impairment and neuronal death in a global cerebral ischemia mouse model. The results showed that HMF, administrated for three days immediately after ischemic surgery, protected against ischemia-induced memory dysfunction, rescued neuronal cell death in the CA1 cell layer, increased the production of BDNF, stimulated the autophosphorylation of CaMK II and suppressed microglial activation in the hippocampus. These results suggest that HMF has a neuroprotective effect after brain ischemia by inducing BDNF production and anti-inflammatory effects.

Chimeric mice with a humanized liver as an animal model of troglitazone-induced liver injury.

Troglitazone (Tro) is a thiazolidinedione antidiabetic drug that was withdrawn from the market due to its association with idiosyncratic severe liver injury. Tro has never induced liver injury in experimental animals in vivo. It was assumed that the species differences between human and experimental animals in the pharmaco- or toxicokinetics of Tro might be associated with these observations. In this study, we investigated whether a chimeric mouse with a humanized liver that we previously established, whose replacement index with human hepatocytes is up to 92% can reproduce Tro-induced liver injury. When the chimeric mice were orally administered Tro for 14 or 23 days (1000mg/kg/day), serum alanine aminotransferase (ALT) was significantly increased by 2.1- and 3.6-fold, respectively. Co-administration of l-buthionine sulfoximine (10mM in drinking water), an inhibitor of glutathione (GSH) synthesis, unexpectedly prevented the Tro-dependent increase of ALT, which suggests that the GSH scavenging pathway will not be involved in Tro-induced liver injury. To elucidate the mechanism of the onset of liver injury, hepatic GSH content, the level of oxidative stress markers and phase I and phase II drug metabolizing enzymes were determined. However, these factors were not associated with Tro-induced liver injury. An immune-mediated reaction may be associated with Tro-induced liver toxicity in vivo, because the chimeric mouse is derived from an immunodeficient SCID mouse. In conclusion, we successfully reproduced Tro-induced liver injury using chimeric mice with a humanized liver, which provides a new animal model for studying idiosyncratic drug-induced liver injury.