Improvement of LXR-mediated lipid metabolism in nephrotic model kidney accompanied by suppression of inflammation and fibrosis.

Kidney disease affects millions of people worldwide. Chronic kidney diseases, such as diabetic nephropathy, are often accompanied by nephrotic syndrome, which causes a large amount of protein and lipid to leak out into the urine. Leaked lipids are well known to accumulate in the proximal tubules as lipid droplets. However, the role of lipid metabolism in the kidney has not been thoroughly studied, and the relationship between accumulated lipid and pathological progression is often unknown. In this study, we showed that reducing accumulated lipids by exerting an agonistic effect on Liver X receptor, one of the nuclear receptors known to play an important role in lipid metabolism, suppressed the development of pathological conditions, such as inflammation and fibrosis, in a nephrosis model. Until now, many renal disease treatments have focused on suppressing the inflammatory response. However, it is now clear that even if the direct anti-inflammatory response is weak, the spread of inflammation and fibrosis can be suppressed by reducing accumulated lipids. Our results suggest that reducing abnormal lipid accumulation in the kidney could lead to disease treatment.

VEGF-C/VEGFR-3 signalling in macrophages ameliorates acute lung injury.

BACKGROUND: Successful recovery from acute lung injury requires inhibition of neutrophil influx and clearance of apoptotic neutrophils. However, the mechanisms underlying recovery remain unclear. We investigated the ameliorative effects of vascular endothelial growth factor (VEGF)-C/VEGF receptor 3 (VEGFR-3) signalling in macrophages in lipopolysaccharide (LPS)-induced lung injury. METHODS: LPS was intranasally injected into wild-type and transgenic mice. Gain and loss of VEGF-C/VEGFR-3 signalling function experiments employed adenovirus-mediated intranasal delivery of VEGF-C (Ad-VEGF-C vector) and soluble VEGFR-3 (sVEGFR-3) or anti-VEGFR-3 blocking antibodies and mice with a deletion of VEGFR-3 in myeloid cells. RESULTS: The early phase of lung injury was significantly alleviated by the overexpression of VEGF-C with increased levels of bronchoalveolar lavage (BAL) fluid interleukin-10 (IL-10), but worsened in the later phase by VEGFR-3 inhibition upon administration of Ad-sVEGFR-3 vector. Injection of anti-VEGFR-3 antibodies to mice in the resolution phase inhibited recovery from lung injury. The VEGFR-3-deleted mice had a shorter survival time than littermates and more severe lung injury in the resolution phase. Alveolar macrophages in the resolution phase digested most of the extrinsic apoptotic neutrophils and VEGF-C/VEGFR-3 signalling increased efferocytosis via upregulation of integrin αv in the macrophages. We also found that incubation with BAL fluid from acute respiratory distress syndrome (ARDS) patients, but not from controls, decreased VEGFR-3 expression and the efficiency of IL-10 expression and efferocytosis in human monocyte-derived macrophages. CONCLUSIONS: VEGF-C/VEGFR-3 signalling in macrophages ameliorates experimental lung injury. This mechanism may also provide an explanation for ARDS resolution.

An Automated, Clip-Type, Small Internet of Things Camera-Based Tomato Flower and Fruit Monitoring and Harvest Prediction System.

Automated crop monitoring using image analysis is commonly used in horticulture. Image-processing technologies have been used in several studies to monitor growth, determine harvest time, and estimate yield. However, accurate monitoring of flowers and fruits in addition to tracking their movements is difficult because of their location on an individual plant among a cluster of plants. In this study, an automated clip-type Internet of Things (IoT) camera-based growth monitoring and harvest date prediction system was proposed and designed for tomato cultivation. Multiple clip-type IoT cameras were installed on trusses inside a greenhouse, and the growth of tomato flowers and fruits was monitored using deep learning-based blooming flower and immature fruit detection. In addition, the harvest date was calculated using these data and temperatures inside the greenhouse. Our system was tested over three months. Harvest dates measured using our system were comparable with the data manually recorded. These results suggest that the system could accurately detect anthesis, number of immature fruits, and predict the harvest date within an error range of ±2.03 days in tomato plants. This system can be used to support crop growth management in greenhouses.

Differences in xylem development between Dutch and Japanese tomato (Solanum lycopersicum) correlate with cytokinin levels in hypocotyls.

BACKGROUND AND AIMS: Dutch tomato cultivars tend to have a greater yield than Japanese cultivars even if they are grown under the same conditions. Factors contributing to the increased yield of the Dutch cultivars were a greater light use efficiency and greater leaf photosynthetic rate. On the other hand, the relationship between tomato yields and anatomical traits is still unclear. The aim of this study is to identify the anatomical traits related to the difference in yield between Dutch and Japanese cultivars. METHODS: Anatomical properties were compared during different growth stages of Dutch and Japanese tomatoes. Hormone profiles and related gene expression in hypocotyls of Dutch and Japanese cultivars were compared in the hypocotyls of 3- and 4-week-old plants. KEY RESULTS: Dutch cultivars have a more developed secondary xylem than Japanese cultivars, which would allow for greater transport of water, mineral nutrients and phytohormones to the shoots. The areas and ratios of the xylem in the hypocotyls of 3- to 6-week-old plants were larger in the Dutch cultivars. In reciprocal grafts of the Japanese and Dutch cultivars, xylem development at the scion and rootstock depended on the scion cultivar, suggesting that some factors in the scion are responsible for the difference in xylem development. The cytokinin content, especially the level of N6-(Δ 2-isopentenyl) adenine (iP)-type cytokinin, was higher in the Dutch cultivars. This result was supported by the greater expression of Sl-IPT3 (a cytokinin biosynthesis gene) and Sl-RR16/17 (a cytokinin-responsive gene) in the Dutch cultivars. CONCLUSIONS: These results suggest that iP-type cytokinins, which are locally synthesized in the hypocotyl, contribute to xylem development. The greater xylem development in Dutch cultivars might contribute to the high yield of the tomato.

Each liver X receptor (LXR) type has a different purpose in different situations.

LXRs, which are nuclear receptors, have 2 isoforms-LXRα and LXRß. Generally, LXRα is expressed in the liver, kidney, and a limited number of other organs, whereas LXRß is thought to be expressed ubiquitously. Nevertheless, no clear consensus has been reached on the role of each in kidney lipid metabolism. Many researchers have reported that lipids accumulate in renal tubular epithelial cells during nephrosis. The nephrosis model we used showed the presence of urinary protein 4 days after the induction of illness. Additionally, the model maintained high levels of urinary protein from day 7-14. Lipid accumulation was clearly verified at day 4 and extreme accumulation was observed at day 7. We observed increased expression of LXRα from an early stage of nephrosis. To explore the role of increased LXRα in diseased kidney in vitro, NRK52E, normal kidney tubular epithelial cells, were forced to overexpress LXRα. These cells showed significantly lower lipid accumulation than mock cells did. In contrast, LXRß knockdown lead to increased lipid accumulation in mock cells, and constancy in overexpressing cells. In normal kidneys, LXRß is expressed stably to control mainly the intracellular lipids. However, with increasing intracellular lipid accumulation, expression of LXRα and its downstream gene, ABCA1, was upregulated, followed by lipid excretion in an LXRα-dependent manner. This phenomenon strongly suggests the importance of LXRα in lipid metabolism in the diseased kidney.

Ivabradine for the Treatment of Cardiovascular Diseases.

Higher heart rate (HR) is independently related to worse outcomes in various cardiac diseases, including hypertension, coronary artery disease, and heart failure (HF). HR is determined by the pacemaker activity of cells within the sinoatrial node. The hyperpolarization-activated cyclic nucleotide-gated (HCN) 4 channel, one of 4 HCN isoforms, generates the If current and plays an important role in the regulation of pacemaker activity in the sinoatrial node. Ivabradine is a novel and only available HCN inhibitor, which can reduce HR and has been approved for stable angina and chronic HF in many countries other than Japan. In this review, we summarize the current knowledge of the HCN4 channel and ivabradine, including the function of HCN4 in cardiac pacemaking, the mechanism of action of If inhibition by ivabradine, and the pharmacological and clinical effects of ivabradine in cardiac diseases as HF, coronary artery disease, and atrial fibrillation.

Efficacy and Safety of Ivabradine in Japanese Patients With Chronic Heart Failure　- J-SHIFT Study.

BACKGROUND: Increased heart rate (HR) is an independent risk factor for cardiovascular outcomes in chronic heart failure (HF). Ivabradine, anIfinhibitor, improved outcomes in patients with HF and reduced ejection fraction (HFrEF) in the SHIFT study. We evaluated its efficacy and safety in Japanese HFrEF patients in a randomized, double-blind, placebo-controlled phase III study: the J-SHIFT study. The main objective was to confirm a hazard ratio of <1 in the primary composite endpoint of cardiovascular death or hospital admission for worsening HF.Methods and Results:Patients with NYHA functional class II-IV, left ventricular EF ≤35%, and resting HR ≥75 beats/min in sinus rhythm under optimal medical therapy received ivabradine (n=127) or placebo (n=127). Mean reduction in resting HR was significantly greater in the ivabradine group (15.2 vs. 6.1 beats/min, P<0.0001). However, symptomatic bradycardia did not occur. A total of 26 (20.5%) patients in the ivabradine group and 37 (29.1%) patients in the placebo group had the primary endpoint event (hazard ratio 0.67, 95% CI 0.40-1.11, P=0.1179) during median follow-up of 589 days. Mild phosphenes were reported in 8 (6.3%) patients in the ivabradine group and 4 (3.1%) patients in the placebo group (P=0.3760). CONCLUSIONS: The J-SHIFT study supported the efficacy and safety of ivabradine for Japanese HFrEF patients, in accord with the SHIFT study.

Reduction of Membrane Protein CRIM1 Decreases E-Cadherin and Increases Claudin-1 and MMPs, Enhancing the Migration and Invasion of Renal Carcinoma Cells.

CRIM1 is a membrane protein that has been reported to be related to cell proliferation. CRIM1 is expressed in renal carcinoma cells, but its involvement in proliferation and malignant transformation remains unclear. We analyzed whether alterations in the characteristics of cancer cells are observed following knockdown of CRIM1. Decreased expression of CRIM1 did not affect proliferation or anchorage-independent growth. The results of wound healing and invasion assays showed that reduced expression of CRIM1 increased cells' migratory and invasive abilities. Expression analysis of factors involved in migration and invasion in CRIM1-knockdown cells revealed that expression of the cell adhesion factor E-cadherin declined and expression of claudin-1, which is upregulated in metastatic cancer cells, increased. In addition, increased expression of matrix metalloproteinase (MMP) 2 and MMP9, protease essential for cancer cell invasiveness, was observed. Furthermore, an increase in phosphorylated focal adhesion kinase (FAK), which increases cell migration, was observed. Increased expression of the E-cadherin transcription repressors Snail, Slug, and ZEB-1 were observed, and mRNA levels of E-cadherin were decreased. Therefore, expression of E-cadherin is thought to be decreased by both suppression of E-cadherin mRNA expression and promotion of degradation of the E-cadherin protein. In addition, expression of CRIM1 was decreased in renal cancer cells undergoing epithelial-mesenchymal transition (EMT) stimulated by tumor necrosis factor alpha (TNF-α). Thus, CRIM1 regulates the expression of several EMT-related factors and appears to play a role in suppressing migration and invasion through control of EMT.

Heart Rate Control With If Inhibitor, Ivabradine, in Japanese Patients With Chronic Heart Failure　- A Randomized, Double-Blind, Placebo-Controlled Phase II Study.

BACKGROUND: Elevated heart rate (HR) is an independent risk factor for cardiovascular outcomes in various cardiac diseases, including heart failure (HF). METHODS AND RESULTS: Randomized placebo-controlled study was conducted to evaluate the effects of ivabradine, an Ifinhibitor, on the resting HR in 126 Japanese symptomatic HF patients with left ventricular ejection fraction ≤35%, resting HR ≥75 beats/min in sinus rhythm, and stable, optimal background treatment. Patients were randomly allocated into 3 groups: placebo; starting dose of ivabradine 2.5 mg twice daily (BID; 2.5 mg group); 5 mg BID group. The dose was increased up to 7.5 mg BID according to dose-adjustment criteria. After the 6-week treatment, the reductions in resting HR were significant in both the 2.5-mg (16.6±8.1 beats/min) and 5-mg (16.4±9.6 beats/min) groups (P<0.0001 for both groups) compared with placebo (1.7±8.7 beats/min). The most frequent side effect of ivabradine was phosphenes, but all were mild. Treatment was discontinued in 1 patient due to HF in the 5 mg group. CONCLUSIONS: Ivabradine starting at 2.5 or 5 mg BID effectively reduced resting HR in Japanese HF patients. Ivabradine at the starting dose of 2.5 mg BID could be safer than 5 mg BID. (Circ J 2016; 80: 668-676).

Angiostatin prevents IL-1ß-induced down-regulation of eNOS expression by inhibiting the NF-κB cascade.

This study aimed to elucidate the protective potential of angiostatin in inflamed endothelial cells in culture. We assessed the effect of angiostatin on the expression of ICAM-1 and eNOS. Angiostatin prevented IL-1ß-induced down-regulation of eNOS expression, but produced no significant changes on IL-1ß-induced up-regulation of ICAM-1. We then explored the effect of angiostatin on IL-1ß-mediated inflammatory signaling and found that angiostatin inhibited IL-1ß-mediated nuclear translocation of NF-κB. Thus, our results suggest that angiostatin prevents IL-1ß-induced down-regulation of eNOS expression via inhibition of the NF-κB cascade; this may be the anti-inflammatory mechanism of angiostatin.

Aralin, a type II ribosome-inactivating protein from Aralia elata, exhibits selective anticancer activity through the processed form of a 110-kDa high-density lipoprotein-binding protein: a promising anticancer drug.

Aralin from Aralia elata is a newly identified type II ribosome- inactivating protein, which preferentially induces apoptosis in cancer cells. In this study, we identified that the aralin receptor is a 110-kDa high-density lipoprotein-binding protein (HDLBP), which functions as a HDL receptor. The sensitivities of tumor cell lines to aralin were dependent on the expression levels of the 110-kDa HDLBP and its forced expression in aralin-resistant Huh7 cells conferred aralin sensitivity. HDLBP-knockdown HeLa cells showed a significant aralin resistance in vitro and in vivo. Conversely, ectopic expression of the 150-kDa HDLBP resulted in increased aralin sensitivity in vivo, accompanying enhanced expression of the 110-kDa HDLBP. Thus, these results showed that the 110-kDa HDLBP in lipid rafts acted as an aralin receptor and that its expression levels determined aralin sensitivity, suggesting that aralin could be a promising anticancer drug for HDLBP-overexpressing tumors.

Reevaluation of the efficacy and safety of the neutrophil elastase inhibitor, Sivelestat, for the treatment of acute lung injury associated with systemic inflammatory response syndrome; a phase IV study.

INTRODUCTION: Sivelestat, a neutrophil elastase inhibitor, has been approved in Japan for the treatment of patients with acute lung injury (ALI) associated with systemic inflammatory response syndrome (SIRS). The Pharmaceuticals and Medical Devices Agency (PMDA) has ordered to conduct a postmarket clinical study in order to reevaluate the efficacy and safety of Sivelestat in actual clinical settings in Japan. METHODS: According to the PMDA's order, we evaluated the efficacy and safety of Sivelestat in Japanese patients with ALI associated with SIRS using ventilator-free days (VFD) as the primary endpoint. The surrogate endpoints are ventilator-weaning rate, ICU discharge rate, and 180-day survival rate. Study design was an open-label, non-randomized, multi-center clinical trial. Sivelestat was intravenously administered at 0.2 mg/kg/h continuously for a maximum of 14 days. Sivelestat group and control group were compared by adjusting the outcome values using an inverse probability of treatment weighted method based on the propensity scores. RESULTS: Four hundred and four Sivelestat group patients and 177 control group patients were enrolled. The adjusted mean number of VFD was 15.7 and 12.1 in the Sivelestat group and control group, respectively (P = 0.0022). Both the adjusted ventilator-weaning rate and ICU discharge rate were significantly higher in the Sivelestat group than in the control group (P = 0.0028 and P = 0.019, respectively). The adjusted 180-day survival rate was significantly higher in the Sivelestat group than in the control group (71.8 percent vs. 56.3 percent). CONCLUSIONS: Sivelestat contributed to early weaning from the mechanical ventilation, while showing no negative effect on the long-term outcomes of ALI associated with SIRS. The results of this study suggest the clinical usefulness of Sivelestat in this patient population.

Implication of Akt-dependent Prp19 alpha/14-3-3beta/Cdc5L complex formation in neuronal differentiation.

PRP19alpha and CDC5L are major components of the active spliceosome. However, their association process is still unknown. Here, we demonstrated that PRP19 alpha/14-3-3beta/CDC5L complex formation is regulated by Akt during nerve growth factor (NGF)-induced neuronal differentiation of PC12 cells. Analysis of PRP19 alpha mutants revealed that the phosphorylation of PRP19 alpha at Thr 193 by Akt was critical for its binding with 14-3-3beta to translocate into the nuclei and for PRP19 alpha/14-3-3beta/CDC5L complex formation in neuronal differentiation. Forced expression of either sense PRP19 alpha or sense 14-3-3beta RNAs promoted NGF-induced neuronal differentiation, whereas down-regulation of these mRNAs showed a suppressive effect. The nonphosphorylation mutant PRP19 alpha T193A lost its binding ability with 14-3-3beta and acted as a dominant-negative mutant in neuronal differentiation. These results imply that Akt-dependent phosphorylation of PRP19 alpha at Thr193 triggers PRP19 alpha/14-3-3beta/CDC5L complex formation in the nuclei, likely to assemble the active spliceosome against neurogenic pre-mRNAs.

Deficiency of protein-L-isoaspartate (D-aspartate) O-methyl-transferase expression under endoplasmic reticulum stress promotes epithelial mesenchymal transition in lung adenocarcinoma.

A prognostic association between the novel chaperone protein-L-isoaspartate (D-aspartate) O-methyltransferase (PIMT) and lung adenocarcinoma has recently been reported. Here, we evaluated the functional roles of PIMT in the progression of lung adenocarcinoma. PIMT expression was detectable in 6 lung adenocarcinoma cell lines: A549, H441, H460, H1650, Calu 1, and Calu 6 cell lines. In A549 and H441 cells, knockdown by PIMT using silencing RNA of PIMT (si-PIMT) and/or small hairpin-RNA (sh-PIMT) induced a decrease in the expression of E-cadherin with an increase in vimentin expression, indicating that the epithelial to mesenchymal transition (EMT) was induced. Cell mobility, including migration and invasion capability, was increased in sh-PIMT A549 stable and si-PIMT H441 cells compared to in control cells. Endoplasmic reticulum (ER) stress, such as Thapsigargin (Tg) stress and hypoxia, induced EMT in A549 cells but not in other cell types, with an increase in GRP78 expression, whereas overexpression of PIMT reduced the EMT and cell invasion under stress conditions. The expression of hypoxia inducible factor-1 alpha (HIF1α) and Twist increased in sh-PIMT A549 and si-PIMT H441 cells, and Tg stress increased HIF1α expression levels in A549 cells in a dose-dependent manner. Moreover, LW6, an HIF1α inhibitor, reduced EMT, cancer invasion, and the levels of Twist in sh-PIMT A549 cells. Our results indicate that deficiency of supplemental PIMT expression under ER stress facilitates EMT and cell invasion in some cell types of lung adenocarcinoma.

Crystallization and preliminary X-ray diffraction data of the rat histone H1(0) globular domain.

The linker histones H1 are a family of lysine-rich proteins that associate with the stretch of DNA that enters and exits the nucleosome. The linker histones facilitate the compaction and condensation of chromatin. The globular domain of histone H1(0), a specific subtype of histone H1, was crystallized at 288 K using the microbatch under silicone oil method with potassium phosphate as a precipitating agent. Diffraction data were collected to a resolution of 1.98 A. The crystal belongs to the trigonal space group P3(1)21, with unit-cell parameters a = 54.13, b = 54.13, c = 71.99 A, and contains one molecule per asymmetric unit. The V(M) value and solvent content were calculated to be 3.04 A3 Da(-1) and 59.6%, respectively.

Thioredoxin overexpression in mice, model of attenuation of oxidative stress, prevents benzene-induced hemato-lymphoid toxicity and thymic lymphoma.

OBJECTIVE: Reactive oxygen species (ROS), generated following benzene exposure, are considered to trigger the development of hematopoietic neoplasms, although little supporting evidence has been found. In this study, we examined whether the experimental elimination of ROS generated following benzene exposure prevents the development of benzene-induced hematopoietic disorders to clarify the mechanism underlying the development of benzene-induced hematopoietic disorders. METHODS: C57BL/6 mice, overexpressing human thioredoxin (h-Trx-Tg), were used to examine the possible nullification of ROS induction following benzene exposure. The experimental group was exposed to 300 ppm benzene 6 hours/day, 5 days/week, for 26 weeks, and lifetime observation followed by molecular and histopathological examinations were carried out. RESULTS: The present study using h-Trx-Tg mice showed a complete suppression of the development of thymic lymphoma induced by benzene inhalation (0% in h-Trx-Tg vs 30% in wild-type (Wt) mice). This was associated with a 48% decrease in the incidence of clastogenic micronucleated reticulocyte induction in the h-Trx-Tg mice compared with the Wt control after 2 weeks of inhalation. As underlying mechanisms, the attenuation of oxidative stress was accompanied by a complete abrogation of hemato-lymphoid toxicity, as shown by the upregulation of the activity of superoxide-dismutase, and a consequently stable ROS level, as determined by cell sorting using 2', 7'-dichlorodihydrofluorescein diacetate, along with a significant attenuation of the overexpression of a cell cycle-dependent kinase inhibitor, p21. CONCLUSION: The attenuation of benzene-induced oxidative stress and that of the consequent lymphomagenesis were observed for the first time, and these indicate a role of oxidative stress in benzene-induced clastogenesis and lymphomagenesis. (These attenuations were not seen in nonthymic lymphomas, and no leukemias developed in C57BL/6 used in this study.) During the constitutive overexpression of h-Trx, the expression of aryl-hydrocarbon receptor in h-Trx-Tg mice was downregulated, which may also contribute to the attenuation.

Mechanisms of benzene-induced hematotoxicity and leukemogenicity: cDNA microarray analyses using mouse bone marrow tissue.

Although the mechanisms underlying benzene-induced toxicity and leukemogenicity are not yet fully understood, they are likely to be complicated by various pathways, including those of metabolism, growth factor regulation, oxidative stress, DNA damage, cell cycle regulation, and programmed cell death. With this as a background, we performed cDNA microarray analyses on mouse bone marrow tissue during and after a 2-week benzene exposure by inhalation. Our goal was to clarify the mechanisms underlying the hematotoxicity and leukemogenicity induced by benzene at the level of altered multigene expression. Because a few researchers have postulated that the cell cycle regulation mediated by p53 is a critical event for benzene-induced hematotoxicity, the present study was carried out using p53-knockout (KO) mice and C57BL/6 mice. On the basis of the results of large-scale gene expression studies, we conclude the following: (a) Benzene induces DNA damage in cells at any phase of the cell cycle through myeloperoxidase and in the redox cycle, resulting in p53 expression through Raf-1 and cyclin D-interacting myb-like protein 1. (b) For G1/S cell cycle arrest, the p53-mediated pathway through p21 is involved, as well as the pRb gene-mediated pathway. (c) Alteration of cyclin G1 and Wee-1 kinase genes may be related to the G2/M arrest induced by benzene exposure. (d) DNA repair genes such as Rad50 and Rad51 are markedly downregulated in p53-KO mice. (e) p53-mediated caspase 11 activation, aside from p53-mediated Bax gene induction, may be an important pathway for cellular apoptosis after benzene exposure. Our results strongly suggest that the dysfunction of the p53 gene, possibly caused by strong and repeated genetic and epigenetic effects of benzene on candidate leukemia cells, may induce fatal problems such as those of cell cycle checkpoint, apoptosis, and the DNA repair system, finally resulting in hemopoietic malignancies. Our cDNA microarray data provide valuable information for future investigations of the mechanisms underlying the toxicity and leukemogenicity of benzene.

Aryl hydrocarbon receptor mediates benzene-induced hematotoxicity.

Benzene can induce hematotoxicity and leukemia in humans and mice. Since a review of the literature shows that the CYP2E1 knockout mouse is not known to possess any benzene toxicity, the metabolism of benzene by CYP2E1 in the liver is regarded to be prerequisite for its cytotoxicity and genotoxicity, although the mechanism is not fully understood yet. Because it was found some years ago that benzene was also a substrate for CYP1A1, we investigated the involvement of the aryl hydrocarbon receptor (AhR) in benzene hematotoxicity using AhR wild-type (AhR(+/+)), heterozygous (AhR(+/-)), and homozygous (AhR(-/-)) male mice. Interestingly, following a 2-week inhalation of 300 ppm benzene (a potent dose for leukemogenicity), no hematotoxicity was induced in AhR(-/-) mice. Further, there were no changes in cellularity of peripheral blood and bone marrow (BM), nor in levels of granulocyte-macrophage colony-forming units in BM. This lack of hematotoxicity was associated with the lack of p21 overexpression, which was regularly seen in the wild-type mice following benzene inhalation. Combined treatment with two major benzene metabolites, phenol and hydroquinone, induced hemopoietic toxicity, although it was not known whether this happened due to a surprising lack of expression of CYP2E1 by AhR knockout, or due to a lack of other AhR-mediated CYP enzymes, including 1A1 (i.e., a possible alternative pathway of benzene metabolism). The former possibility, evaluated in the present study, failed to show a significant relationship between AhR and the expression of CYP2E1. Furthermore, a subsequent evaluation of AhR expression after benzene inhalation tended to show higher but less significant expression in the liver, and none in the BM, compared with sham control. Although this study failed to identify the more likely of the above-mentioned two possibilities, the study using AhR knockout mice on benzene inhalation presents the unique possibility that the benzene toxicity may be regulated by AhR signaling.

Exacerbation of benzene pneumotoxicity in connexin 32 knockout mice: enhanced proliferation of CYP2E1-immunoreactive alveolar epithelial cells.

The pulmonary pathogenesis triggered by benzene exposure was studied. Since the role of the connexin 32 (Cx32) gap junction protein in mouse pulmonary pathogenesis has been suggested, in the present study, we explored a possible role of Cx32 in benzene-induced pulmonary pathogenesis using the wild-type (WT) and Cx32 knockout (KO) mice. The mice were exposed to 300 ppm benzene by inhalation for 6 h per day, 5 days per week for a total of 26 weeks, and then sacrificed to evaluate the pneumotoxicity or allowed to live out their life span to evaluate the reversibility of the lesions and tumor incidence. Our results clearly revealed exacerbated pneumotoxicity in the benzene-exposed Cx32 KO mice, characterized by diffuse granulomatous interstitial pneumonia, markedly increased mucin secretion of bronchial/bronchiolar and alveolar epithelial cells, and hyperplastic alveolar epithelial cells positive for CYP2E1. But the results did not indicate any enhancement of pulmonary tumorigenesis in the Cx32 KO mice though the number of animals was small.