Association between endocrine-disrupting chemical mixtures and non-alcoholic fatty liver disease with metabolic syndrome as a mediator among adults: A population-based study in Korea.

Endocrine-disrupting chemicals (EDCs) may play a role in non-alcoholic fatty liver disease (NAFLD); however, studies on the combined effects of EDC mixtures on NAFLD development are limited. Here, we explored the association between exposure to EDC mixtures and NAFLD and investigated the potential mediating role of metabolic syndrome (MetS). We included participants from the Korean National Environmental Health Survey Cycle 4 (2018-2020) and quantified the urinary concentrations of various EDCs-eight phthalate metabolites, three phenols, one antibacterial compound, four parabens, four polycyclic aromatic hydrocarbons, and one pyrethroid pesticide metabolite-as well as serum concentrations of five perfluorinated compounds (PFCs). NAFLD was defined as a hepatic steatosis index (HSI) ≥36 or a fatty liver index (FLI) ≥60. Weighted quantile sum (WQS) regression was employed to evaluate the associations between EDC mixtures and the risk of MetS or NAFLD. Causal mediation analysis was conducted to explore the potential mediating effect of MetS on the association between mixtures of EDCs and NAFLD risk. All estimates were adjusted for age, sex, educational level, physical activity, smoking status, involuntary smoking, and drinking habits. A total of 2942 adults were included in the analysis. Moderate-to-high positive correlations were identified between phthalate metabolites and PFCs. Higher WQS scores were associated with an elevated risk of MetS and NAFLD. The sex-stratified WQS regression model showed that the interactions between the WQS index and sex were significant for MetS and NAFLD. According to the causal mediation analysis, both the direct and indirect effects of EDC mixtures on NAFLD, with MetS as a mediator, were significant in females. Collectively, these findings highlight the need for interventions that could address both EDC mixture exposure and metabolic status to effectively reduce the risks associated with NAFLD and its related complications.

Pulmonary Foreign Body Granulomatosis after Cosmetic Injection.

INTRODUCTION: We occasionally encounter irregular marginated masses discovered incidentally in young individuals. In most cases, further investigations are conducted to assess the presence of a primary malignancy, as these masses often raise suspicions of malignancy. However, rare exceptional cases leave us perplexed. Granulomas arising from common lung infections and those induced by foreign substances can often pose challenge in distinguishing them from lung cancer. Therefore, we aimed to present a case of multiple pulmonary granulomatosis following cosmetic procedure. CASE PRESENTATION: A 55-year-old woman visited the hospital after an incidental discovery of an abnormal chest radiograph during a routine health check-up. Subsequent computed tomography (CT) scans showed worrisome lung nodules, leading to biopsies and positron emission tomography CT scans. Histological examination of the biopsied specimens revealed a chronic inflammatory reaction surrounded by multinucleated foreign body giant cells. Upon sharing the biopsy results with the patient and conducting additional history-taking, she had undergone various cosmetic procedures (botox injection, dermal filler treatments, and thread lifts) around the face and neck, approximately 5-6 months ago. It was hypothesized that these cosmetic materials might have led to the observed pulmonary granulomatosis. After 3 months of conservative care, a follow-up CT showed no change in the lesions. CONCLUSION: We present this case to underscore the importance of considering pulmonary foreign body granulomatosis as a potential differential diagnosis, especially when it closely resembles lung cancer, particularly following cosmetic injections.

Association between endocrine-disrupting chemical mixture and metabolic indices among children, adolescents, and adults: A population-based study in Korea.

Exposure to endocrine-disrupting chemicals (EDCs) play a role in the etiology of obesity and dyslipidemia. However, few studies have analyzed the combined effects of EDC mixtures. This study explored the association between concurrent exposure to EDCs and obesity or dyslipidemia in children, adolescents, and adults. A total of 1454 children, 891 adolescents, and 3758 (for BMI) and 3424 (for TG/HDL) adults from the Korean National Environmental Health Survey 2015 to 2017 were included in this cross-sectional study. Urinary concentrations of eight phthalate metabolites, three phenols, three parabens, and one pyrethroid pesticides metabolite were quantified. Body mass index (BMI) was measured for all participants, and triglyceride (TG) and high-density lipoprotein cholesterol (HDL-c) levels were measured for adolescents and adults. Associations between combined EDC mixtures with the BMI and TG to HDL-c ratio were evaluated using Bayesian Kernel Machine Regression (BKMR). In all age groups, most of the chemical exposures, with the exception of BPF and BPS, were detected in more than 90% of participants. There were significant moderate to high correlations within phthalate metabolites and a high correlation within parabens. The BKMR showed that EDC mixtures were associated with higher BMI in both adolescents and adults, with greater significance in adults compared with adolescents, and a higher TG/HDL in male adolescents. In adolescents, MEP and MCPP drove the main effects on BMI and TG/HDL, respectively. In adults, 3PBA and BPA drove the main effects on BMI. The findings of this study suggest that exposure to EDC mixtures is associated with higher BMI and TG/HDL, and adolescence may be a critical period for EDC mixture in terms of both outcomes. Further studies are needed, but strategies to reduce EDC exposure from early life stages may be necessary to lower the risk of metabolic disease.

Did air pollution continue to affect bike share usage in Seoul during the COVID-19 pandemic?

INTRODUCTION: The role of cycling has become more important in the urban transport system during the Covid-19 pandemic. As public transport passengers have tried to avoid crowded vehicles due to safety concerns, a rapid surge of cycling activities has been noted in many countries. This implies that more cyclists might be exposed to air pollution, potentially leading to health problems in cities like Seoul where the level of air pollution is high. METHODS: We utilised three years of bike sharing programme (Ddareungi) data in Seoul and time series models to examine the changes in the relationship between particulate concentration (PM2.5) and total daily cycling duration before and during the pandemic. RESULTS: We find that cyclists reacted less to the PM2.5 level during the pandemic, potentially due to the lack of covid-secure travel modes. Specifically, our results show significant negative associations between concentrations of PM2.5 and total daily cycling duration before the pandemic (year 2018 and 2019). However, this association became insignificant in 2020. CONCLUSIONS: Building comprehensive cycling infrastructure that can reduce air pollution exposure of cyclists and improving air quality alert systems could help build a more resilient city for the future.

The Effect of Daily Low Dose Tadalafil on Cerebral Perfusion and Cognition in Patients with Erectile Dysfunction and Mild Cognitive Impairment.

OBJECTIVE: The aims of this study were to investigate the effects of daily low-dose tadalafil on cognitive function and to examine whether there was a change in cerebral blood flow (CBF) in patients with erectile dysfunction (ED) and mild cognitive impairment. METHODS: Male patients aged 50 to 75 years with at least three months of ED (International Index of Erectile Function [IIEF]-5 score ≤ 21) and mild cognitive impairment (Montreal Cognitive Assessment [MoCA] score ≤ 22) were included in the study. The subjects were prescribed a low-dose PDE5 inhibitor (tadalafil 5 mg) to be taken once daily for eight weeks. Changes in MoCA score and single-photon emission computed tomography (SPECT) study between the two time-points were assessed by paired t tests. RESULTS: Overall, 30 male patients were assigned to the treatment group in this study and 25 patients completed the eight-week treatment course. Five patients were withdrawn due to adverse events such as myalgia and dizziness. Mean baseline IIEF and MoCA scores were 7.52 ± 4.84 and 18.92 ± 1.78. After the eight-week treatment, mean IIEF and MoCA scores were increased to 12.92 ± 7.27 (p < 0.05) and 21.8 ± 1.71 (p < 0.05), respectively. Patients showed increased relative regional CBF in the postcentral gyrus, precuneus, and brainstem after tadalafil administration versus at baseline (p < 0.001). CONCLUSION: The results of this prospective clinical study suggest that daily use of tadalafil 5 mg increases some regional CBF and improves cognitive function in patients with ED and mild cognitive impairment.

Prediction of vesicoureteral reflux in children with febrile urinary tract infection using relative uptake and cortical defect in DMSA scan.

BACKGROUND: Vesicoureteral reflux (VUR) is an important urologic anomaly that causes renal injury in children with febrile urinary tract infection (UTI). The present study aimed to evaluate the associations of abnormalities detected on technetium-99m-labeled dimercaptosuccinic acid (DMSA) scans, focusing on the association with VUR of the levels of relative decrease in kidney function and cortical defects after a first febrile UTI in children. METHODS: All 171 children underwent ultrasonography, DMSA scan and voiding cystourethrography (VCUG). The features of ultrasound and DMSA scans were compared between patients with (n = 48) and without VUR (n = 123). The relative uptake (RU) by each kidney was derived from the absolute value of the differences between the value for RU of radionuclide in the right kidney and that in the left kidney. The extent of cortical defects (ECD) was graded according to the number of compartments that contained cortical defect in both kidneys (right upper/right lower, left upper/left lower). Receiver operating characteristic curves were constructed to examine the diagnostic value of these parameters of ultrasound and DMSA scans for predicting VUR. RESULTS: The ratio of patients having hydronephrosis on ultrasound or cortical defects on DMSA scan did not differ significantly between VUR and non-VUR groups. However, the absolute values of the RU and the scores for ECD were significantly higher in the VUR group than in the non-VUR group. The area under the curves for these two parameters were higher than those for the presence of hydronephrosis or the presence of cortical defects or both. CONCLUSION: Decreased relative function and increased extents of cortical defects on DMSA scan may be associated with the presence of VUR. These findings may assist pediatricians to decide whether febrile UTI children need to undergo VCUG.

Comparative analysis of chemical compositions between non-transgenic soybean seeds and those from plants over-expressing AtJMT, the gene for jasmonic acid carboxyl methyltransferase.

Transgenic overexpression of the Arabidopsis gene for jasmonic acid carboxyl methyltransferase (AtJMT) is involved in regulating jasmonate-related plant responses. To examine its role in the compositional profile of soybean (Glycine max), we compared the seeds from field-grown plants that over-express AtJMT with those of the non-transgenic, wild-type (WT) counterpart. Our analysis of chemical compositions included proximates, amino acids, fatty acids, isoflavones, and antinutrients. Overexpression of AtJMT in the seeds resulted in decreased amounts of tryptophan, palmitic acid, linolenic acid, and stachyose, but increased levels of gadoleic acid and genistein. In particular, seeds from the transgenic soybeans contained 120.0-130.5% more genistein and 60.5-82.1% less stachyose than the WT. A separate evaluation of ingredient values showed that all were within the reference ranges reported for commercially available soybeans, thereby demonstrating the substantial equivalence of these transgenic and non-transgenic seeds.

Over-expression of BvMTSH, a fusion gene for maltooligosyltrehalose synthase and maltooligosyltrehalose trehalohydrolase, enhances drought tolerance in transgenic rice.

Plant abiotic stress tolerance has been modulated by engineering the trehalose synthesis pathway. However, many stress-tolerant plants that have been genetically engineered for the trehalose synthesis pathway also show abnormal development. The metabolic intermediate trehalose 6-phosphate has the potential to cause aberrations in growth. To avoid growth inhibition by trehalose 6-phosphate, we used a gene that encodes a bifunctional in-frame fusion (BvMTSH) of maltooligosyltrehalose synthase (BvMTS) and maltooligosyltrehalose trehalohydrolase (BvMTH) from the nonpathogenic bacterium Brevibacterium helvolum. BvMTS converts maltooligosaccharides into maltooligosyltrehalose and BvMTH releases trehalose. Transgenic rice plants that over-express BvMTSH under the control of the constitutive rice cytochrome c promoter (101MTSH) or the ABA-inducible Ai promoter (105MTSH) show enhanced drought tolerance without growth inhibition. Moreover, 101MTSH and 105MTSH showed an ABA-hyposensitive phenotype in the roots. Our results suggest that over-expression of BvMTSH enhances drought-stress tolerance without any abnormal growth and showes ABA hyposensitive phenotype in the roots.

Fanconi's Syndrome Associated with Prolonged Adefovir Dipivoxil Therapy in a Hepatitis B Virus Patient.

Adefovir dipivoxil (ADV) is commonly used as an antiviral agent in the treatment of chronic hepatitis B or human immunodeficiency virus infection. Nephrotoxicity has been shown to occur at daily dosages of 60-120 mg. Fanconi's syndrome is a generalized dysfunction of the renal proximal tubular cells, which is usually accompanied by complications. Here we report a case of Fanconi's syndrome in a chronic hepatitis B patient who had been treated with a prolonged regimen of ADV at 10 mg/day. A 47-year-old man complained of severe back and chest-wall pain. He had chronic hepatitis B and had been treated with ADV at a daily dose of 10 mg for 38 months. He was hospitalized because of severe bone pain, and laboratory and radiologic findings suggested a diagnosis of Fanconi's syndrome with osteomalacia. After discontinuation of the ADV, he recovered and was discharged from hospital. His laboratory findings had normalized within 2 weeks. This case indicates that Fanconi's syndrome can be acquired by a chronic hepatitis B patient taking ADV at a conventional dosage of 10 mg/day. Therefore, patients treated with long-term ADV should be checked regularly for the occurrence of ADV-induced Fanconi's syndrome.

Non-specific phytohormonal induction of AtMYB44 and suppression of jasmonate-responsive gene activation in Arabidopsis thaliana.

The Arabidopsis thaliana transcription factor gene AtMYB44 was induced within 10 min by treatment with methyl jasmonate (MeJA). Wound-induced expression of the gene was observed in local leaves, but not in distal leaves, illustrating jasmonate-independent induction at wound sites. AtMYB44 expression was not abolished in Arabidopsis mutants insensitive to jasmonate (coi1), ethylene (etr1), or abscisic acid (abi3-1) when treated with the corresponding hormones. Moreover, various growth hormones and sugars also induced rapid AtMYB44 transcript accumulation. Thus, AtMYB44 gene activation appears to not be induced by any specific hormone. MeJA-induced activation of jasmonate-responsive genes such as JR2, VSP, LOXII, and AOS was attenuated in transgenic Arabidopsis plants overexpressing the gene (35S:AtMYB44), but significantly enhanced in atmyb44 knockout mutants. The 35S:MYB44 and atmyb44 plants did not show defectiveness in MeJA-induced primary root growth inhibition, indicating that the differences in jasmonate-responsive gene expression observed was not due to alterations in the jasmonate signaling pathway. 35S:AtMYB44 seedlings exhibited slightly elevated chlorophyll levels and less jasmonate- induced anthocyanin accumulation, demonstrating suppression of jasmonate-mediated responses and enhancement of ABA-mediated responses. These observations support the hypothesis of mutual antagonistic actions between jasmonate- and abscisic acid-mediated signaling pathways.

[A case of liver abscess with subcapsular hematoma mimicking ruptured hepatic cholangiocarcinoma].

Subcapsular hematoma is a very rare complication of liver abscess. We report a case of liver abscess with subcapsular hematoma mimicking ruptured hepatic cholangiocarcinoma. A 59-year-old man presented with right upper quadrant pain and febrile sense. Computed tomography showed a low attenuated mass with extensive subcapsular hematoma on the right hepatic lobe. The initial impression was a hematoma caused by the rupture of cholangiocarcinoma. Hepatic arteriography was performed, but no active bleeding focus was found. After drainage of the subcapsular hematoma, a hematoma wall biopsy through the drainage catheter and a liver biopsy of the low attenuated mass were performed. The biopsies showed many neutrophils, macrophages, and granulation tissues consistent with an abscess, but no malignant cells were detected. After antibiotics therapy for 6 weeks, computed tomography was performed 4 months later, and revealed complete resolution of the hematoma and the low attenuated hepatic lesion.

[A case of metastatic hepatocellular carcinoma of the rib, treated by transcatheter arterial chemoembolization].

Bone is a common site of metastasis in patients with hepatocellular carcinoma (HCC). We report a rare case of rib metastasis from HCC treated by transcatheter arterial chemoembolization (TACE). A 55-year-old man with liver cirrhosis presented with right lower chest pain. The diagnosis was an HCC with a bone metastasis in the right eighth rib. Intra-arterial injections of doxorubicin mixed with Lipiodol and Gelfoam particles were instituted through the right eighth intercostal artery. Computed tomography and a Tc(99)-labeled scan performed 2 months after the third TACE revealed no viable HCC in the right eighth rib.

The Arabidopsis AtLEC gene encoding a lectin-like protein is up-regulated by multiple stimuli including developmental signal, wounding, jasmonate, ethylene, and chitin elicitor.

The Arabidopsis gene AtLEC (At3g15356) gene encodes a putative 30-kDa protein with a legume lectin-like domain. Likely to classic legume lectin family of genes, AtLEC is expressed in rosette leaves, primary inflorescences, and roots, as observed in Northern blot analysis. The accumulation of AtLEC transcript is induced very rapidly, within 30 min, by chitin, a fungal wall-derived oligosaccharide elictor of the plant defense response. Transgenic Arabidopsis carrying an AtLEC promoter-driven beta-glucuronidase (GUS) construct exhibited GUS activity in the leaf veins, secondary inflorescences, carpel heads, and silique receptacles, in which no expression could be seen in Northern blot analysis. This observation suggests that AtLEC expression is induced transiently and locally during developmental processes in the absence of an external signal such as chitin. In addition, mechanically wounded sites showed strong GUS activity, indicating that the AtLEC promoter responds to jasmonate. Indeed, methyl jasmonate and ethylene exposure induced AtLEC expression within 3-6 h. Thus, the gene appears to play a role in the jasmonate-/ethylene-responsive, in addition to the chitin-elicited, defense responses. However, chitin-induced AtLEC expression was also observed in jasmonate-insensitive (coi1) and ethylene-insensitive (etr1-1) Arabidopsis mutants. Thus, it appears that chitin promotes AtLEC expression via a jasmonate- and/or ethylene-independent pathway.

Influence of thyroid-stimulating hormone on 18F-fluorodeoxyglucose and 99mTc-methoxyisobutylisonitrile uptake in human poorly differentiated thyroid cancer cells in vitro.

OBJECTIVE: In poorly differentiated thyroid cancer originating from thyroid follicular cells, the ability to concentrate iodine is lost. This makes recurrence undetectable by (131)I whole-body scan. In this situation, other radiopharmaceuticals, such as (18)F-fluorodeoxyglucose ((18)F-FDG) and technetium-99m-methoxyisobutylisonitrile ((99m)Tc-MIBI), are used to evaluate recurrence or metastasis. Some reports suggest that (18)F-FDG uptake is increased by thyroid-stimulating hormone (TSH) stimulation. This study aimed to determine the influence of TSH on (18)F-FDG and (99m)Tc-MIBI uptake in human poorly differentiated thyroid cancer cells in vitro. MATERIALS AND METHODS: The cells were stimulated with 1000 muU/ml of recombinant human thyroid-stimulating hormone (rhTSH) for 1 day, 3 days, and 5 days. Each cell was incubated with 0.5 MBq/ml-1 MBq/ml of (18)F-FDG or 0.5 MBq/ml-1 MBq/ml of (99m)Tc-MIBI for 1 h at 37 degrees C. The uptake of each radiopharmaceutical in the cells was quantified as a percent of whole radioactivity per total viable cell number. The quantification of glucose transporter 1, 2, 3 and 4 mRNA expression was measured using RT-PCR. RESULTS: TSH stimulation increased (18)F-FDG uptake in a time-dependent manner. Following 5 days of rhTSH stimulation, (18)F-FDG uptake was approximately 2.2 times that of the control. The increase in (18)F-FDG uptake following rhTSH stimulation was correlated to the increase in GLUT4 mRNA level. The GLUT1 mRNA level was unchanged. An increased uptake of (99m)Tc-MIBI was observed with a pattern similar to that of (18)F-FDG. The (99m)Tc-MIBI uptake was approximately 1.5 times that of the control 5 days later. CONCLUSIONS: These results suggest that TSH stimulates (18)F-FDG and (99m)Tc-MIBI uptake in poorly differentiated papillary thyroid cancer, and therefore (18)F-FDG-PET or (99m)Tc-MIBI scans under TSH stimulation may be more accurate than under suppression.

Value of the model for end-stage liver disease for predicting survival in hepatocellular carcinoma patients treated with transarterial chemoembolization.

OBJECTIVE: The aim of this study was to evaluate the prognostic value of the model for end-stage liver disease (MELD) and its modified forms, and to compare these scoring systems with other staging systems for hepatocellular carcinoma (HCC) patients treated with transarterial chemoembolization (TACE). MATERIAL AND METHODS: A total of 325 patients who underwent TACE for the initial treatment of HCC between January 2000 and May 2007 were enrolled in the study. Before TACE was carried out, MELD, MELD-Na, Child-Pugh score, Okuda stage, CLIP score, JIS score, BCLC stage, and UICC stage were checked. After one month, delta MELD and delta MELD-Na were calculated. RESULTS: Mean MELD/MELD-Na/delta MELD/delta MELD-Na scores were 7.5+/-3.7, 8.0+/-4.7, -0.2+/-3.5 and 0.04+/-4.5, respectively. MELD (p=0.009) and MELD-Na (p=0.017) significantly correlated with survival, but delta MELD and delta MELD-Na did not (p >0.05). The Child-Pugh score and other staging systems correlated significantly with survival (p <0.05). The AUROC values for 3, 12, and 36 months' survival were 0.633, 0.545, and 0.615 for MELD; 0.655, 0.555, and 0.612 for MELD-Na; 0.639, 0.616, and 0.691 for Child-Pugh score; 0.714, 0.662, and 0.717 for the Okuda score; 0.837, 0.86, and 0.792 for the CLIP score; 0.859, 0.814, and 0.808 for the JIS score; 0.846, 0.833, and 0.749 for BCLC stage; and 0.878, 0.812, and 0.735 for UICC stage, respectively. CONCLUSIONS: MELD and MELD-Na showed good correlations with survival, especially for patients with early-stage disease. However, these were not superior to those of other staging systems or Child-Pugh score. These parameters should only be used as supportive data.

Durability of antiviral response in HBeAg-positive chronic hepatitis B patients who maintained virologic response for one year after lamivudine discontinuation.

The purpose of this study is to determine the long-term relapse rate and associated risk factors in HBeAg-positive chronic hepatitis B (CHB) patients who had maintained virologic response (VR) for 1 year after lamivudine (LMV) discontinuation. We enrolled 55 treatment-naive HBeAg-positive CHB patients who achieved and maintained VR until 1 year after LMV discontinuation. Delayed relapse was defined as an elevation of HBV DNA after sustained VR for 1 year. During follow-up, 16 of 55 patients (29%) showed delayed relapse. Beginning 1 year after LMV discontinuation, the cumulative rates of relapse after 2 and 4 years were 29 and 44%, respectively. In multivariate analysis, age (P = 0.029) and >2,000 copies/ml HBV DNA 3 months after LMV discontinuation (P = 0.047) were significant predictors of delayed relapse. Delayed relapse is not infrequent, even in patients who maintain VR for 1 year after LMV discontinuation. Therefore, LMV maintenance therapy might be considered in HBeAg-positive CHB patients who achieve VR.

Bifunctional recombinant fusion enzyme between maltooligosyltrehalose synthase and maltooligosyltrehalose trehalohydrolase of thermophilic microorganism Metallosphaera hakonensis.

MhMTS and MhMTH are trehalose (alpha-D-glucopyranosyl- [1,1]-alpha-D-glucopyranose) biosynthesis genes of the thermophilic microorganism Metallosphaera hakonensis, and encode a maltooligosyltrehalose synthase (MhMTS) and a maltooligosyltrehalose trehalohydrolase (MhMTH), respectively. In this study, the two genes were fused inframe in a recombinant DNA, and expressed in Escherichia coli to produce a bifunctional fusion enzyme, MhMTSH. Similar to the two-step reactions with MhMTS and MhMTH, the fusion enzyme catalyzed the sequential reactions on maltopentaose, maltotriosyltrehalose formation, and following hydrolysis, producing trehalose and maltotriose. Optimum conditions for the fusion enzyme-catalyzed trehalose synthesis were around 70 degrees and pH 5.0-6.0. The MhMTSH fusion enzyme exhibited a high degree of thermostability, retaining 80% of the activity when pre-incubated at 70 degrees for 48 h. The stability was gradually abolished by incubating the fusion enzyme at above 80 degrees . The MhMTSH fusion enzyme was active on various sizes of maltooligosaccharides, extending its substrate specificity to soluble starch, the most abundant natural source of trehalose production.

Overexpression of AtMYB44 enhances stomatal closure to confer abiotic stress tolerance in transgenic Arabidopsis.

AtMYB44 belongs to the R2R3 MYB subgroup 22 transcription factor family in Arabidopsis (Arabidopsis thaliana). Treatment with abscisic acid (ABA) induced AtMYB44 transcript accumulation within 30 min. The gene was also activated under various abiotic stresses, such as dehydration, low temperature, and salinity. In transgenic Arabidopsis carrying an AtMYB44 promoter-driven beta-glucuronidase (GUS) construct, strong GUS activity was observed in the vasculature and leaf epidermal guard cells. Transgenic Arabidopsis overexpressing AtMYB44 is more sensitive to ABA and has a more rapid ABA-induced stomatal closure response than wild-type and atmyb44 knockout plants. Transgenic plants exhibited a reduced rate of water loss, as measured by the fresh-weight loss of detached shoots, and remarkably enhanced tolerance to drought and salt stress compared to wild-type plants. Microarray analysis and northern blots revealed that salt-induced activation of the genes that encode a group of serine/threonine protein phosphatases 2C (PP2Cs), such as ABI1, ABI2, AtPP2CA, HAB1, and HAB2, was diminished in transgenic plants overexpressing AtMYB44. By contrast, the atmyb44 knockout mutant line exhibited enhanced salt-induced expression of PP2C-encoding genes and reduced drought/salt stress tolerance compared to wild-type plants. Therefore, enhanced abiotic stress tolerance of transgenic Arabidopsis overexpressing AtMYB44 was conferred by reduced expression of genes encoding PP2Cs, which have been described as negative regulators of ABA signaling.