Whole blood transcriptome analysis for age- and gender-specific gene expression profiling in Japanese individuals.

Whole blood transcriptome analysis is a valuable approachin medical research, primarily due to the ease of sample collection and the richness of the information obtained. Since the expression profile of individual genes in the analysis is influenced by medical traits and demographic attributes such as age and gender, there has been a growing demand for a comprehensive database for blood transcriptome analysis. Here, we performed whole blood RNA sequencing (RNA-seq) analysis on 576 participants stratified by age (20-30s and 60-70s) and gender from cohorts of the Tohoku Medical Megabank (TMM). A part of female segment included pregnant women. We did not exclude the globin gene family in our RNA-seq study, which enabled us to identify instances of hereditary persistence of fetal hemoglobin based on the HBG1 and HBG2 expression information. Comparing stratified populations allowed us to identify groups of genes associated with age-related changes and gender differences. We also found that the immune response status, particularly measured by neutrophil-to-lymphocyte ratio (NLR), strongly influences the diversity of individual gene expression profiles in whole blood transcriptome analysis. This stratification has resulted in a data set that will be highly beneficial for future whole blood transcriptome analysis in the Japanese population.

Detection and Correction of Sample Misidentifications in a Biobank Using the MassARRAY System and Genomic Information.

With the number of samples increasing in many biobanks, one of the most pressing tasks is recording the correct relationships between information and the specimens. Genomic information is useful in determining the identity of these specimens. The Tohoku Medical Megabank Organization is running one of the largest biobanks in Japan. Here, we introduce a management system, which includes the development of a new probe set for the MassARRAY system for use during the production of proliferating T cells (T cells) and lymphoblastoid cell lines (LCLs). We selected single nucleotide variants that could be detected by next-generation sequencing and showed high resolution with ∼0.5 minor allele frequencies. After checking the set of probes against 96 samples from 48 people, we obtained no contradictory results in comparison with our genome sequence information. When we applied the set to our 3035 LCLs and 2256 T cells, the result showed 98.93% consistency with the corresponding genomic information. We surveyed the handling records of the 1.07% of samples that showed inconsistencies, and found that most had resulted from human errors (ID swapping between samples) during manual operations. After improving a few error-prone protocols, the error rate dropped to 0.47% for LCLs and 0% for T cells. Overall, the system that we developed shows high accuracy with easy and fast operability, and provides a good opportunity to improve the validation procedure to facilitate high-quality banking, especially in cases involving genomic information.

Construction of a trio-based structural variation panel utilizing activated T lymphocytes and long-read sequencing technology.

Long-read sequencing technology enable better characterization of structural variants (SVs). To adapt the technology to population-scale analyses, one critical issue is to obtain sufficient amount of high-molecular-weight genomic DNA. Here, we propose utilizing activated T lymphocytes, which can be established efficiently in a biobank to stably supply high-grade genomic DNA sufficiently. We conducted nanopore sequencing of 333 individuals constituting 111 trios with high-coverage long-read sequencing data (depth 22.2x, N50 of 25.8 kb) and identified 74,201 SVs. Our trio-based analysis revealed that more than 95% of the SVs were concordant with Mendelian inheritance. We also identified SVs associated with clinical phenotypes, all of which appear to be stably transmitted from parents to offspring. Our data provide a catalog of SVs in the general Japanese population, and the applied approach using the activated T-lymphocyte resource will contribute to biobank-based human genetic studies focusing on SVs at the population scale.

Stress-activated leukocyte 12/15-lipoxygenase metabolite enhances struggle behaviour and tocotrienols relieve stress-induced behaviour alteration.

Stress induces emotional arousal causing anxiety, irritability, exaggerated startle behaviour, and hypervigilance observed in patients with trauma and stress-related mental disorders, including acute stress disorder and post-traumatic stress disorder. Central norepinephrine release promotes stress-induced emotional arousal. However, the regulator of emotional arousal remains unknown. Here, we show that the arachidonate-derived metabolite produced by stress-activated leukocyte 12/15-lipoxygenase is remarkably elevated in the plasma and upregulates the central norepinephrine release, resulting in the enhancement of the struggle behaviour (= escape behaviour) in the tail suspension test. Struggle behaviour is mimicking a symptom of emotional arousal. This stress-induced struggle behaviour was absent in 12/15-lipoxygenase deficient mice; however, intravenous administration of a 12/15-lipoxygenase metabolite to these mice after stress exposure rekindled the struggle behaviour. Furthermore, tocotrienols and geranylgeraniol reduced stress-induced 12/15-lipoxygenase metabolite production and suppressed the struggle behaviour. Our findings indicate that arachidonate-derived 12/15-lipoxygenase metabolite is involved in the regulation of stress-enhanced central norepinephrine release and struggle behaviour. In addition, we propose 12/15-lipoxygenase as a potential therapeutic target for the treatment of emotional arousal observed in stress-related mental disorders.

Hepatic resistance to cold ferroptosis in a mammalian hibernator Syrian hamster depends on effective storage of diet-derived α-tocopherol.

Mammalian hibernators endure severe and prolonged hypothermia that is lethal to non-hibernators, including humans and mice. The mechanisms responsible for the cold resistance remain poorly understood. Here, we found that hepatocytes from a mammalian hibernator, the Syrian hamster, exhibited remarkable resistance to prolonged cold culture, whereas murine hepatocytes underwent cold-induced cell death that fulfills the hallmarks of ferroptosis such as necrotic morphology, lipid peroxidation and prevention by an iron chelator. Unexpectedly, hepatocytes from Syrian hamsters exerted resistance to cold- and drug-induced ferroptosis in a diet-dependent manner, with the aid of their superior ability to retain dietary α-tocopherol (αT), a vitamin E analog, in the liver and blood compared with those of mice. The liver phospholipid composition is less susceptible to peroxidation in Syrian hamsters than in mice. Altogether, the cold resistance of the hibernator's liver is established by the ability to utilize αT effectively to prevent lipid peroxidation and ferroptosis.

Identification of Dominant Transcripts in Oxidative Stress Response by a Full-Length Transcriptome Analysis.

Our body responds to environmental stress by changing the expression levels of a series of cytoprotective enzymes/proteins through multilayered regulatory mechanisms, including the KEAP1-NRF2 system. While NRF2 upregulates the expression of many cytoprotective genes, there are fundamental limitations in short-read RNA sequencing (RNA-Seq), resulting in confusion regarding interpreting the effectiveness of cytoprotective gene induction at the transcript level. To precisely delineate isoform usage in the stress response, we conducted independent full-length transcriptome profiling (isoform sequencing; Iso-Seq) analyses of lymphoblastoid cells from three volunteers under normal and electrophilic stress-induced conditions. We first determined the first exon usage in KEAP1 and NFE2L2 (encoding NRF2) and found the presence of transcript diversity. We then examined changes in isoform usage of NRF2 target genes under stress conditions and identified a few isoforms dominantly expressed in the majority of NRF2 target genes. The expression levels of isoforms determined by Iso-Seq analyses showed striking differences from those determined by short-read RNA-Seq; the latter could be misleading concerning the abundance of transcripts. These results support that transcript usage is tightly regulated to produce functional proteins under electrophilic stress. Our present study strongly argues that there are important benefits that can be achieved by long-read transcriptome sequencing.

Quantification of the Flavor and Taste of Gonads from the Sea Urchin Mesocentrotus nudus Using GC-MS and a Taste-Sensing System.

Sea urchin gonads are a delicious seafood item of high commercial value. Our past studies have revealed that the gonads of the sea urchin Mesocentrotus nudus fed the basal frond portion of fresh Saccharina kelp (BS) or the sporophylls of fresh Undaria (SU) during May-July are of high-quality. The present study investigated the flavor and taste of BS and SU gonads in comparison with those from non-fed M. nudus (NF) using gas chromatography-mass spectrometry (GC-MS) and gas chromatography (GC)-sniffing techniques, and a taste-sensing system. Data of the estimated intensity of taste (EIT) were compared with assessment of gonads from M. nudus collected from an Eisenia bed (fishing ground) and a barren in July. Gonads from both BS and SU released pleasant green, sour, and fruity aromas characteristic of butyl acetate, which are here recognized essential flavor components of high-quality gonads. The gonads of BS and SU had a strong umami taste compared to those of NF, and the Eisenia bed and the barren. The most marketable M. nudus gonads were assessed to be those with green and fruity aromas from butyl acetate, sweet aroma from benzaldehyde, umami EIT > 13.8, bitterness EIT < 3.1, and without any unpleasant sulfurous odor from sulfur-containing compounds.

Landscape of electrophilic and inflammatory stress-mediated gene regulation in human lymphoblastoid cell lines.

Human lymphoblastoid cell lines (LCLs) are valuable for the functional analyses of diseases. We have established more than 4200 LCLs as one of the resources of an integrated biobank. While oxidative and inflammatory stresses play critical roles in the onset and progression of various diseases, the responsiveness of LCLs, especially that of biobank-made LCLs, to these stresses has not been established. To address how LCLs respond to these stresses, in this study, we performed RNA sequencing of eleven human LCLs that were treated with an electrophile, diethyl maleate (DEM) and/or an inflammatory mediator, lipopolysaccharide (LPS). We found that over two thousand genes, including those regulated by a master regulator of the electrophilic/oxidative stress response, NRF2, were upregulated in LCLs treated with DEM, while approximately three hundred genes, including inflammation-related genes, were upregulated in LPS-treated LCLs. Of the LPS-induced genes, a subset of proinflammatory genes was repressed by DEM, supporting the notion that DEM suppresses the expression of proinflammatory genes through NRF2 activation. Conversely, a part of DEM-induced gene was repressed by LPS, suggesting reciprocal interference between electrophilic and inflammatory stress-mediated pathways. These data clearly demonstrate that LCLs maintain, by and large, responsive pathways against oxidative and inflammatory stresses and further endorse the usefulness of the LCL supply from the biobank.

A multi-ethnic meta-analysis identifies novel genes, including ACSL5, associated with amyotrophic lateral sclerosis.

Amyotrophic lateral sclerosis (ALS) is a devastating progressive motor neuron disease that affects people of all ethnicities. Approximately 90% of ALS cases are sporadic and thought to have multifactorial pathogenesis. To understand the genetics of sporadic ALS, we conducted a genome-wide association study using 1,173 sporadic ALS cases and 8,925 controls in a Japanese population. A combined meta-analysis of our Japanese cohort with individuals of European ancestry revealed a significant association at the ACSL5 locus (top SNP p = 2.97 × 10-8). We validated the association with ACSL5 in a replication study with a Chinese population and an independent Japanese population (1941 ALS cases, 3821 controls; top SNP p = 1.82 × 10-4). In the combined meta-analysis, the intronic ACSL5 SNP rs3736947 showed the strongest association (p = 7.81 × 10-11). Using a gene-based analysis of the full multi-ethnic dataset, we uncovered additional genes significantly associated with ALS: ERGIC1, RAPGEF5, FNBP1, and ATXN3. These results advance our understanding of the genetic basis of sporadic ALS.

Induction of a 5-lipoxygenase product by daidzein is involved in the regulation of influenza virus replication.

This study was conducted to evaluate the regulation mechanism of influenza virus replication following treatment of Madin-Darby canine kidney cells with the soy isoflavone daidzein. We performed comparative qualitative and quantitative analyses of lipid peroxide between mock-infected and virus-infected cells treated with or without daidzein, as it had been reported that daidzein was an antioxidant and lipid peroxide levels increased upon virus infection. Contrary to our belief, lipid peroxides were not elevated in virus-infected cells and no decrease in lipid peroxides was observed in daidzein-treated cells. In daidzein-treated cells, 5-hydroxyeicosatetraenoic acid, the 5-lipoxygenase product derived from arachidonate, was significantly elevated compared to other lipid peroxides. Zileuton (5-lipoxygenase inhibitor) and 5-lipoxygenase knockdown reduced the daidzein-induced antiviral effect. Moreover, virus replication was regulated by treatment with 5-hydroperoxyeicosatetraenoic acid, a precursor of 5-hydroxyeicosatetraenoic acid and 5-lipoxygenase primary product. These results suggest that daidzein regulates virus replication via signal transduction through 5-lipoxygenase products.

Pathogenic mutations in the ALS gene CCNF cause cytoplasmic mislocalization of Cyclin F and elevated VCP ATPase activity.

Amyotrophic lateral sclerosis (ALS) is an adult-onset motor neuron disease characterized by a progressive decline in motor function. Genetic analyses have identified several genes mutated in ALS patients, and one of them is Cyclin F gene (CCNF), the product of which (Cyclin F) serves as the substrate-binding module of a SKP1-CUL1-F-box protein (SCF) ubiquitin ligase complex. However, the role of Cyclin F in ALS pathogenesis has remained unclear. Here, we show that Cyclin F binds to valosin-containing protein (VCP), which is also reported to be mutated in ALS, and that the two proteins colocalize in the nucleus. VCP was found to bind to the NH2-terminal region of Cyclin F and was not ubiquitylated by SCFCyclin F in transfected cells. Instead, the ATPase activity of VCP was enhanced by Cyclin F in vitro. Furthermore, whereas ALS-associated mutations of CCNF did not affect the stability of Cyclin F or disrupt formation of the SCFCyclin F complex, amino acid substitutions in the VCP binding region increased the binding ability of Cyclin F to VCP and activity of VCP as well as mislocalization of the protein in the cytoplasm. We also provided evidence that the ATPase activity of VCP promotes cytoplasmic aggregation of transactivation responsive region (TAR) DNA-binding protein 43, which is commonly observed in degenerating neurons in ALS patients. Given that mutations of VCP identified in ALS patients also increase its ATPase activity, our results suggest that Cyclin F mutations may contribute to ALS pathogenesis by increasing the ATPase activity of VCP in the cytoplasm, which in turn increases TDP-43 aggregates.

A low-frequency IL4R locus variant in Japanese patients with intravenous immunoglobulin therapy-unresponsive Kawasaki disease.

BACKGROUND: Kawasaki disease (KD) is a systemic vasculitis which may be associated with coronary artery aneurysms. A notable risk factor for the development of coronary artery aneurysms is resistance to intravenous immunoglobulin (IVIG) therapy, which comprises standard treatment for the acute phase of KD. The cause of IVIG resistance in KD is largely unknown; however, the contribution of genetic factors, especially variants in immune-related genes, has been suspected. METHODS: To explore genetic variants related to IVIG-unresponsiveness, we designated KD patients who did not respond to both first and second courses of IVIG therapy as IVIG-unresponsive patients. Using genomic DNA from 30 IVIG-unresponsive KD patients, we performed pooled genome sequencing targeting 39 immune-related cytokine receptor genes. RESULTS: The single nucleotide variant (SNV), rs563535954 (located in the IL4R locus), was concentrated in IVIG-unresponsive KD patients. Individual genotyping showed that the minor allele of rs563535954 was present in 4/33 patients with IVIG-unresponsive KD, compared with 20/1063 individuals in the Japanese genome variation database (odds ratio = 7.19, 95% confidence interval 2.43-21.47). Furthermore, the minor allele of rs563535954 was absent in 42 KD patients who responded to IVIG treatment (P = 0.0337), indicating that a low-frequency variant, rs563535954, is associated with IVIG-unresponsiveness in KD patients. Although rs563535954 is located in the 3'-untranslated region of IL4R, there was no alternation in IL4R expression associated with the mior allele of rs563535954. However, IVIG-unresponsive patients that exhibited the minor allele of rs563535954 tended to be classified into the low-risk group (based on previously reported risk scores) for prediction of IVIG-resistance. Therefore, IVIG-unresponsiveness associated with the minor allele of rs563535954 might differ from IVIG-unresponsiveness associated with previous risk factors used to evaluate IVIG-unresponsiveness in KD. CONCLUSION: These findings suggest that the SNV rs563535954 could serve as a predictive indicator of IVIG-unresponsiveness, thereby improving the sensitivity of risk scoring systems, and may aid in prevention of coronary artery lesions in KD patients.

Biobank Establishment and Sample Management in the Tohoku Medical Megabank Project.

The Tohoku Medical Megabank biobank (TMM biobank) is the first major population-based biobank established in Japan. The TMM biobank was established based on two population cohorts and is a reconstruction program from the Great East Japan Earthquake and Tsunami of 2011. The biobank stores more than 3.4 million tubes of biospecimens and associated health and analytic data obtained from approximately 150,000 TMM cohort participants between May 2013 and December 2018, and the TMM biobank currently shares high-quality specimens and data. Various biospecimens, including peripheral and cord blood mononuclear cells, buffy coat, plasma, serum, urine, breast milk and saliva have been collected in the TMM biobank. To minimize human error and maintain the quality of data and specimens, we have been utilizing laboratory information management system into various biobank procedures from registration to storage with various automation systems, such as liquid dispensing, DNA extraction and their storage. The biobank procedures for the quality management system (ISO 9001:2015) and information security management system (ISO 27001:2013) are certified by the International Organization for Standardization. The quality of our biobank samples fulfills the pre-analytical requirements for researchers conducting next-generation whole genome sequencing, DNA array analyses, proteomics, metabolomics, etc. We established analytical centers to conduct standard genomic and multiomic analyses in-house and share the generated data. Additionally, we generate thousands of Epstein-Barr virus (EBV)-transformed lymphoblastoid cell lines and proliferating T cells for functional studies. The TMM biobank serves as an indispensable infrastructure for academic, clinical and industrial research to actualize next-generation medicine in Japan.

Probucol induces the generation of lipid peroxidation products in erythrocytes and plasma of male cynomolgus macaques.

We previously reported that probucol, a lipid lowering agent, protected mice from malaria infection via depletion in plasma α-tocopherol. The antioxidant α-tocopherol in host circulation is necessary for the malaria parasites to protect themselves from oxidative stress in erythrocytes where high amounts of reactive oxygen species are generated. To assess the potential for the clinical application of probucol as an anti-malarial therapy, it was necessary to determine the effects of probucol by using primate experiments. Here we verified that probucol induces an α-tocopherol decrement in cynomolgus macaque erythrocytes and plasma. After 2 weeks of probucol administration at doses of 200 or 400 mg/kg/day, the α-tocopherol contents in erythrocytes tended to decrease. The contents of hydroxyoctadecadienoic acids and 7ß-hydroxycholesterol, peroxidation products derived from linoleic acid and cholesterol, respectively, increased in erythrocytes. On the other hand, plasma α-tocopherol concentration showed a marginal decrement. Plasma lipid peroxidation products were transiently increased in the early stages of probucol administration. No adverse effects were observed throughout the experiment, although the dosage of probucol was higher than the clinical maximum dosage. Considering that malaria proliferates in erythrocytes, probucol-induced disruption of redox homeostasis in erythrocytes could be effective in the inhibition of parasite proliferation.

Yuzu (Citrus junos Tanaka) Peel Attenuates Dextran Sulfate Sodium-induced Murine Experimental Colitis.

Ulcerative colitis is a well-known inflammatory bowel disease. Although there are drugs that are effective against this disease, the prevention and attenuation of ulcerative colitis by food rich in functional ingredients without side effects is desired because some drugs have side effects. In this study, we investigated the effects of yuzu (Citrus junos Tanaka), a citrus fruit native to northeast Asia, on a mouse dextran sulfate sodium (DSS)-induced colitis model. Mice given drinking water containing DSS showed significant weight loss, colon shortening, diarrhea, and visible fecal blood. In contrast, mice fed a diet containing 5% yuzu peel for 14 d before receiving DSS showed significant attenuation of these phenotypes. To clarify the mechanism underlying the attenuation, we investigated the anti-inflammatory and antioxidant effects of yuzu peel. We found that yuzu peel extract suppressed tumor necrosis factor-α (TNF-α) production in lipopolysaccharide (LPS)-stimulated mice and murine macrophage cell line through suppression of nuclear factor-κB (NF-κB) activation. In addition, we confirmed that yuzu peel extract had a moderate antioxidant effect. These results suggest that yuzu peel attenuates the pathologies of DSS-induced colitis by coordinately suppressing inflammation and oxidative stress against lipids in vivo.

Ubiquitylation of Ku80 by RNF126 Promotes Completion of Nonhomologous End Joining-Mediated DNA Repair.

Repair of damaged DNA is critical for maintenance of genetic information. In eukaryotes, DNA double-strand breaks (DSBs) are recognized by the Ku70-Ku80 heterodimer, which then recruits proteins that mediate repair by nonhomologous end joining (NHEJ). Prolonged retention of Ku70/80 at DSBs prevents completion of repair, however, with ubiquitylation of Ku80 having been implicated in Ku70/80 dissociation from DNA. Here, we identify RNF126 as a ubiquitin ligase that is recruited to DSBs and ubiquitylates Ku80, with UBE2D3 serving as an E2 enzyme. Knockdown of RNF126 prevented Ku70/80 dissociation from DSBs and inhibited break repair. Attenuation of Ku80 ubiquitylation by replacement of ubiquitylation site lysines with arginine residues delayed Ku70/80 release from chromatin after DSB induction by genotoxic insults. Together, our data indicate that RNF126 is a novel regulator of NHEJ that promotes completion of DNA repair by ubiquitylating Ku80 and releasing Ku70/80 from damaged DNA.

Characterization of fermented seaweed sauce prepared from nori (Pyropia yezoensis).

High-salt content seaweed sauces were prepared for the first time using nori (Pyropia yezoensis) by fermentation and characterized. Components and taste of the two nori sauces (NSs) prepared separately were compared with those of soy and fish sauces. The NSs were rich in total nitrogen compounds (1.5 g N/100 ml on average) and potassium (880 mg/100 g), and had a unique free amino acid composition (e.g., taurine 617 mg/100 g), explaining their unique taste as evaluated by a taste sensing system. As for their food function, inhibitory activity of angiotensin-converting enzyme was observed. As for their food safety, arsenic was detected at a 0.8 mg/100 g level in total, but inorganic arsenic was not detected (<0.05 mg/100 g) and not regarded as a problem. Allergy-causing substances contained in wheat, soy beans, and crustaceans were not detected (<0.1 mg/100 g) with NSs. These results suggest that the nori sauce has a high potential as a novel nutritional source for humans.

Probucol dramatically enhances dihydroartemisinin effect in murine malaria.

BACKGROUND: Artemisinin-based combination therapy (ACT) has been adopted as national policy for the first-line treatment in large number of malaria-endemic regions. However, artemisinin-resistant parasites have emerged and are spreading, with slow-cleaning parasites being reported in patients treated with ACT. It means that more parasites are exposed to the partner drug alone and the risk of developing resistant parasites against the partner drug is increasing. Therefore, the development of a new method to enhance the effect of artemisinin is required. In this study, the potential effect of probucol as a combination drug of dihydroartemisinin (DHA), an artemisinin derivative, was examined. METHODS: C57BL/6 J mice infected with Plasmodium yoelii XL-17 were treated with probucol and/or DHA. The mice were fed with a probucol mixed diet from 2 weeks before infection and through infection period. DHA was injected to mice three to 5 days post infection once a day. In addition, 0.5 % (w/w) probucol was mixed with vitamin E supplemented diet (800 mg/kg) and fed to mice infected with P. yoelii XL-17 to examine the mechanisms of probucol on murine malaria. Furthermore, 8-OHdG, a biomarker of oxidized DNA, was detected in infected red blood cells (iRBC) taken from infected mice by immunofluorescent staining. RESULTS: With dose-dependent manner, both probucol and DHA decreased parasitaemia and increased survival rate of mice infected with P. yoelii XL-17. A significantly larger amount of 8-OHdG was detected in iRBC taking from probucol-treated mice than control mice. In addition, a large amount of vitamin E supplementation eliminated the effect of probucol against P. yoelii XL-17 infection and lowered the effect of probucol on host plasma vitamin E concentration. The effective doses for probucol and DHA were 0.5 % and 30 mg/kg, respectively, in each single treatment. While the combination treatment of 0.25 % probucol and 7.5 mg/kg DHA was effective in all mice from P. yoelii XL-17 infection. CONCLUSION: This study demonstrated that probucol has some impact on malaria by oxidative stress through the induction of host plasma vitamin E deficiency. Moreover, the effective dose of DHA on malaria was decreased by prophylactic treatment of probucol. This finding indicates that probucol might be a candidate for a prophylactic treatment drug to enhance the effect of DHA.

The induction of lipid peroxidation during the acute oxidative stress response induced by intratracheal instillation of fine crystalline silica particles in rats.

Crystalline silica (SiO2) is an important material for industry but is considered potentially carcinogenic. Inhalation of a crystalline SiO2 aerosol may contribute to serious lung diseases. Crystalline SiO2 particles are commonly used as a positive control in toxicity assays of particulate materials (e.g. nanoparticles). Crystalline SiO2 induces oxidative stress resulting in lipid peroxidation, but the acute oxidative stress response in the lung is not well understood. Lipid peroxidation during the acute stage of oxidative stress after instillation of crystalline SiO2 into rats was examined by bronchoalveolar lavage fluid (BALF) analysis. The levels of 8-iso-prostaglandin F2α and hydroxyoctadecadienoic acid (HODE) in the BALF were measured using liquid chromatography coupled to quadrupole mass spectrometry. The concentration of the antioxidant protein heme oxygenase-1 (HO-1) in the BALF was determined using enzyme-linked immunosorbent assay. Intratracheal instillation of crystalline SiO2 increased the level of HODE and HO-1 in BALF at 24 h after administration. The levels of HODE and HO-1 returned to baseline at 72 h after instillation. Lactate dehydrogenase leakage was observed only after 1 h instillation. These results suggest that the contribution of oxidative stress to the pulmonary toxicity of crystalline SiO2 is minimal in the early acute stage after exposure.