Clinical application of targeted tumour sequencing tests for detecting ERBB2 amplification and optimizing anti-HER2 therapy in gastric cancer.

BACKGROUND: Evaluation of human epidermal growth factor receptor 2 (HER2) overexpression caused by erb-b2 receptor tyrosine kinase 2 (ERBB2) amplification (AMP) by immunohistochemistry (IHC) and fluorescence in situ hybridization (FISH) is essential for treating unresectable metastatic gastric cancer (GC). A targeted tumour sequencing test enables comprehensive assessment of alterations in cancer-related genes, including ERBB2. This study aimed to evaluate the concordance between the targeted tumour sequencing test and IHC/FISH for detecting HER2-positive GC and to clarify the significance of ERBB2 AMP and concomitant genetic alterations in HER2 downstream pathways (DPs) in anti-HER2 therapy for unresectable metastatic GC patients. METHODS: ERBB2 copy number alteration (CNA) was examined via a targeted tumour sequencing test in 152 formalin-fixed paraffin-embedded (FFPE) GC tissues. ERBB2 CNA was compared to HER2 status evaluated by IHC/FISH in FFPE block sections, which were identical to those subjected to the targeted tumour sequencing test. Treatment outcomes of anti-HER2 therapy in 11 patients with unresectable metastatic GC was evaluated. RESULTS: ERBB2 AMP (≥ 2.5-fold change) was detected by the targeted tumour sequencing test in 15 patients (9.9%), and HER2 positivity (IHC 3 + or IHC 2+/FISH positive) was detected in 21 patients (13.8%). The overall percent agreement, positive percent agreement, negative percent agreement and Cohen's kappa between ERBB2 CNA and HER2 status were 94.7%, 66.7%, 99.2% and 0.75, respectively. Progression-free survival for trastuzumab therapy in patients with ERBB2 AMP was significantly longer than that in patients with no ERBB2 AMP detected by the targeted tumour sequencing test (median 14 months vs. 4 months, P = 0.007). Treatment response to trastuzumab therapy was reduced in patients with ERBB2 AMP and concomitant CNAs of genes in HER2 DPs. One patient with ERBB2 AMP and concomitant CNAs of genes in HER2 DPs achieved a durable response to trastuzumab deruxtecan as fourth-line therapy. CONCLUSIONS: A targeted tumour sequencing test is a reliable modality for identifying HER2-positive GC. ERBB2 AMP and concomitant genetic alterations detected through the targeted tumour sequencing test are potential indicators of treatment response to trastuzumab therapy. The targeted tumour sequencing test has emerged as a plausible candidate for companion diagnostics to determine indications for anti-HER2 therapy in the era of precision medicine for GC.

A novel method to localize patency capsule by ileo-colonoscopy facilitates endoscopic assessment of the small and large intestine in patients with Crohn's disease.

INTRODUCTION: Patients with Crohn's disease (CD) require an assessment of small bowel lesions, while difficulties exist in performing small intestinal examinations especially in small-sized medical offices. Small bowel capsule endoscopy (SBCE) is handy and can be performed in most clinical settings. The only drawback of SBCE is a requirement of patency testing prior to the exam because it sometimes requires CT scanning to localize the ingested patency capsule (PC), which may be a substantial burden for the patient. We have developed a novel PC detection system named PICS (Patency capsule, Ileo-Colonoscopy and Small bowel capsule endoscopy) method by which we can avoid CT scanning. In the PICS method, Ileo-Colonoscopy (ICS) is performed after 30 to 33 hours of PC ingestion and the PC can be localized by ICS in patients who have not excreted the PC, and the entire intestine can be examined in combination with subsequent SBCE without additional bowel preparation. The aim of this study was to assess the usefulness and safety of the PICS method for CD patients. METHODS: CD patients who underwent PICS method from April 2021 to March 2023 were reviewed for clinical data, outcome of PICS method including the rates of PC detection by ICS, the number of patients underwent SBCE, and adverse events. Lewis score was used to assess SBCE results. RESULTS: The PICS method was performed in 54 patients. The median age of patients was 28.5 years old and 64.8% of them were ileo-colic type. The median disease duration was 10.5 months and 24.1% had history of small bowel resection. Five cases (9.3%) confirmed gastrointestinal patency by ICS and none of the cases required CT scanning. One patient who could not be confirmed patency by ICS, and the other patient who excreted PC but was found ileal stenosis by ICS did not undergo SBCE. Remaining 52 patients received SBCE and the median Lewis score of them was 0 (IQR 0, 450). There were no adverse events including small bowel obstruction by PC and SBCE retention in this series. CONCLUSION: The PICS method is not only feasible and safe but also convenient to assess disease extent in patients with CD. By localizing PC with ICS, additional CT scanning could be unnecessary for SBCE, which benefits both physicians and CD patients.

Structural Studies of a Complex of a CAG/CTG Repeat Sequence-Specific Binding Molecule and A-A-Mismatch-Containing DNA.

Triplet repeat diseases are caused by the abnormal elongation of repeated sequences comprising three bases. In particular, the elongation of CAG/CTG repeat sequences is thought to result in conditions such as Huntington's disease and myotonic dystrophy type 1. Although the causes of these diseases are known, fundamental treatments have not been established, and specific drugs are expected to be developed. Pyrrole imidazole polyamide (PIP) is a class of molecules that binds to the minor groove of the DNA duplex in a sequence-specific manner; because of this property, it shows promise in drug discovery applications. Earlier, it was reported that PIP designed to bind CAG/CTG repeat sequences suppresses the genes that cause triplet repeat diseases. In this study, we performed an X-ray crystal structure analysis of a complex of double-stranded DNA containing A-A mismatched base pairs and a cyclic-PIP that binds specifically to CAG/CTG sequences. Furthermore, the validity and characteristics of this structure were analyzed using in silico molecular modeling, ab initio energy calculations, gel electrophoresis, and surface plasmon resonance. With our direct observation using atomic force microscopy and DNA origami, we revealed that the PIP caused structural changes in the DNA strands carrying the expanded CAG/CTG repeat. Overall, our study provides new insight into PIP from a structural perspective.

Chb-M', an Inhibitor of the RUNX Family Binding to DNA, Induces Apoptosis in p53-Mutated Non-Small Cell Lung Cancer and Inhibits Tumor Growth and Repopulation In Vivo.

Runt-related transcription factor (RUNX) proteins are considered to play various roles in cancer. Here, we evaluated the anticancer activity of Chb-M', a compound that specifically and covalently binds to the consensus sequence for RUNX family proteins, in p53-mutated non-small cell lung cancer cells. Chb-M' killed the cancer cells by inducing apoptosis. The compound showed an anticancer effect comparable to that of the clinically used drugs alectinib and ceritinib in vivo. Notably, Chb-M' extended the cancer-free survival of mice after ending treatment more effectively than did the other two drugs. The results presented here suggest that Chb-M' is an attractive candidate as an anticancer drug applicable to the treatment of non-small cell lung cancer and various other types of cancers.

Adjuvant chemotherapy for adenocarcinoma arising from intraductal papillary mucinous neoplasia: multicentre ADENO-IPMN study.

BACKGROUND: The clinical impact of adjuvant chemotherapy after resection for adenocarcinoma arising from intraductal papillary mucinous neoplasia is unclear. The aim of this study was to identify factors related to receipt of adjuvant chemotherapy and its impact on recurrence and survival. METHODS: This was a multicentre retrospective study of patients undergoing pancreatic resection for adenocarcinoma arising from intraductal papillary mucinous neoplasia between January 2010 and December 2020 at 18 centres. Recurrence and survival outcomes for patients who did and did not receive adjuvant chemotherapy were compared using propensity score matching. RESULTS: Of 459 patients who underwent pancreatic resection, 275 (59.9%) received adjuvant chemotherapy (gemcitabine 51.3%, gemcitabine-capecitabine 21.8%, FOLFIRINOX 8.0%, other 18.9%). Median follow-up was 78 months. The overall recurrence rate was 45.5% and the median time to recurrence was 33 months. In univariable analysis in the matched cohort, adjuvant chemotherapy was not associated with reduced overall (P = 0.713), locoregional (P = 0.283) or systemic (P = 0.592) recurrence, disease-free survival (P = 0.284) or overall survival (P = 0.455). Adjuvant chemotherapy was not associated with reduced site-specific recurrence. In multivariable analysis, there was no association between adjuvant chemotherapy and overall recurrence (HR 0.89, 95% c.i. 0.57 to 1.40), disease-free survival (HR 0.86, 0.59 to 1.30) or overall survival (HR 0.77, 0.50 to 1.20). Adjuvant chemotherapy was not associated with reduced recurrence in any high-risk subgroup (for example, lymph node-positive, higher AJCC stage, poor differentiation). No particular chemotherapy regimen resulted in superior outcomes. CONCLUSION: Chemotherapy following resection of adenocarcinoma arising from intraductal papillary mucinous neoplasia does not appear to influence recurrence rates, recurrence patterns or survival.

Prognostic Significance of NQO1 Expression in Non-neoplastic Esophageal Squamous Epithelium for Patients With Esophageal Cancer.

BACKGROUND/AIM: NAD(P)H dehydrogenase [quinone] 1 (NQO1), an antioxidant enzyme, confers resistance to anticancer agents. NQO1 C609T is a single-nucleotide polymorphism associated with reduced protein expression in the non-neoplastic esophageal squamous epithelium (ESE). This study aimed to investigate immunohistochemical NQO1 expression in non-neoplastic ESE and to elucidate its prognostic significance in patients with esophageal squamous cell carcinoma (ESCC) undergoing neoadjuvant therapy followed by esophagectomy. MATERIALS AND METHODS: NQO1 expression in non-neoplastic ESE was determined in surgical specimens from 83 patients with ESCC using immunohistochemistry. The association between NQO1 expression and clinicopathological factors, and the prognostic significance of NQO1 expression for relapse-free survival (RFS) were statistically evaluated. RESULTS: Patients with complete loss or weak NQO1 expression and patients with moderate or strong NQO1 expression were classified into the NQO1-negative (n=29) and NQO1-positive (n=54) groups, respectively. The downstaging of T classification status after neoadjuvant therapy was significantly more frequent in the NQO1-negative group than in the NQO1-positive group (59% vs. 33%; p=0.036). The NQO1-negative group had significantly more favorable RFS than the NQO1-positive group (p=0.035). Multivariate survival analysis demonstrated that NQO1 negative expression had a favorable prognostic impact on RFS (HR=0.332; 95%CI=0.136-0.812; p=0.016). CONCLUSION: Immunohistochemical evaluation of NQO1 expression in non-neoplastic ESE has clinical utility for predicting patient prognosis after neoadjuvant therapy followed by esophagectomy and might be helpful for selecting candidates for adjuvant therapy to treat ESCC.

Prognostic Role of Preoperative Chemotherapy in Liver-Limited Metastasis from Gastric Cancer.

BACKGROUND: We investigated the prognostic role of preoperative chemotherapy in patients who underwent hepatectomy for liver-limited metastasis (LLM) from gastric cancer (GC). METHODS: A retrospective analysis was conducted for 52 consecutive patients who underwent macroscopically complete (R0 or R1) resection for synchronous or metachronous LLM from GC. RESULTS: Of the 52 patients, 18 (35%) received preoperative chemotherapy (PC group), while 34 (65%) underwent upfront surgery (US group). The PC group had a significantly longer overall survival than the US group (cumulative 5-year OS rate: 47.6% vs. 24.8%, p = 0.041). Multivariate analysis of OS revealed that preoperative chemotherapy was an independent favorable prognostic factor (hazard ratio: 0.445, p = 0.036). Patients showing a partial response to preoperative chemotherapy on RECIST had an improved OS compared with those exhibiting stable or progressive disease after preoperative chemotherapy and with US (p = 0.025), even among those with solitary LLM (p = 0.062) and multiple LLM (p = 0.026). At recurrence after hepatectomy for LLM, the PC group had a significantly higher incidence of solitary tumors than the US group (p = 0.043) and had a higher chance to undergo surgical resection for recurrent sites (p = 0.006). CONCLUSIONS: Preoperative chemotherapy can be recommended for patients with LLM from GC. The evaluation of the efficacy of preoperative chemotherapy offers additional information to determine the surgical indication for LLM.

Visual Field Improvement and Electrode Extrusion Prevention by Extended Endaural Incision With Cavity Obliteration for Cochlear Implantation in Ears After Canal Wall-Down Mastoidectomy: Experience of Four Cases.

There is no global consensus on the surgical technique of cochlear implantation (CI) in ears with an open cavity after canal wall-down (CWD) mastoidectomy. Here, we report CI surgery with an endaural incision for the ears after CWD mastoidectomy. The endaural incision was extended upward to obliterate the open cavity of the temporal fascial flap. The endaural incision was extended downward to close the open cavity inlet. After inserting the implanted electrode, the open cavity was obliterated using a temporal fascial flap, and the cavity was closed at the inlet. We performed this type of CI surgery in four ears in three patients. This extended endaural incision provided an excellent view for pedicling the temporal fascial flap with the superficial temporal artery and for open cavity closure without any serious complications. This technique allowed us to opt for CI surgery of the ears after CWD mastoidectomy.

Long-term Outcomes following Resection of Adenocarcinoma Arising from Intraductal Papillary Mucinous Neoplasm (A-IPMN) versus Pancreatic Ductal Adenocarcinoma (PDAC): A Propensity-score Matched Analysis.

OBJECTIVE: The aim of the present study was to compare long-term post-resection oncological outcomes between A-IPMN and PDAC. SUMMARY BACKGROUND DATA: Knowledge of long term oncological outcomes (e.g recurrence and survival data) comparing between adenocarcinoma arising from intraductal papillary mucinous neoplasms (A-IPMN) and pancreatic ductal adenocarcinoma (PDAC) is scarce. METHODS: Patients undergoing pancreatic resection (2010-2020) for A-IPMN were identified retrospectively from 18 academic pancreatic centres and compared with PDAC patients from the same time-period. Propensity-score matching (PSM) was performed and survival and recurrence were compared between A-IPMN and PDAC. RESULTS: 459 A-IPMN patients (median age,70; M:F,250:209) were compared with 476 PDAC patients (median age,69; M:F,262:214). A-IPMN patients had lower T-stage, lymphovascular invasion (51.4%vs. 75.6%), perineural invasion (55.8%vs. 71.2%), lymph node positivity (47.3vs. 72.3%) and R1 resection (38.6%vs. 56.3%) compared to PDAC(P<0.001). The median survival and time-to-recurrence for A-IPMN versus PDAC were 39.0 versus19.5months (P<0.001) and 33.1 versus 14.8months (P<0.001), respectively (median follow-up,78 vs.73 months). Ten-year overall survival for A-IPMN was 34.6%(27/78) and PDAC was 9%(6/67). A-IPMN had higher rates of peritoneal (23.0 vs. 9.1%, P<0.001) and lung recurrence (27.8% vs. 15.6%, P<0.001) but lower rates of locoregional recurrence (39.7% vs. 57.8%; P<0.001). Matched analysis demonstrated inferior overall survival (P=0.005), inferior disease-free survival (P=0.003) and higher locoregional recurrence (P<0.001) in PDAC compared to A-IPMN but no significant difference in systemic recurrence rates (P=0.695). CONCLUSIONS: PDACs have inferior survival and higher recurrence rates compared to A-IPMN in matched cohorts. Locoregional recurrence is higher in PDAC but systemic recurrence rates are comparable and constituted by their own distinctive site-specific recurrence patterns.

Malignancy After Living Donor Liver Transplantation.

OBJECTIVES: De novo malignancy (DNM) is a major cause of death in long-term recipients of liver transplantation (LT). We herein report our experience with DNM after living-donor LT (LDLT). PATIENTS AND METHODS: A total of 111 LDLT procedures were performed in our institute from 1999 to 2022. Among them, 70 adult (>13 years old) LDLT recipients who survived for more than 1 year were included in this study. RESULTS: During a median follow-up of 146 (range, 12-285) months, 7 out of 70 recipients developed 8 DNMs, including lung cancer in 4, post-transplant lymphoproliferative disease in 3, and skin cancer in 1. One patient developed metachronal skin cancer and post-transplant lymphoproliferative disease. The pre-LT smoking history rate in patients with DNM was higher than in patients without DNM (P = .004). The survival time after DNM was 6 (1-166) months. Only 2 patients underwent R0 resection. DNM did not recur during follow-up. Other patients who underwent R1 resection and/or chemotherapy and/or radiotherapy all died due to DNMs during the follow-up. The cumulative DNM incidence was 3.5% at 10 years and 18.4% at 20 years after LDLT. The cumulative survival rate in patients with DNM was significantly worse than that in patients without DNM after LDLT (P = .049). CONCLUSION: The survival rate of patients with DNM was lower than that of those without DNM. A pre-LT smoking history is a risk factor for DNM. R0 resection is effective for improving the prognosis of patients with DNM. Regular cancer screening is important for detecting DNM early after LDLT.

Design, synthesis, and biological evaluation of novel benzo[6,7]indolo[3,4-c]isoquinolines as anticancer agents with topoisomerase I inhibition.

A novel series of benzo[6,7]indolo[3,4-c]isoquinolines 3a-3f was designed by scaffold hopping of topoisomerase I inhibitor benzo[g][1]benzopyrano[4,3-b]indol-6(13H)-ones (BBPIs), which were developed by structural modification of the natural marine product lamellarin. The unconventional pentacycle was constructed by Bischler-Napieralski-type condensation of amide 11 and subsequent intramolecular Heck reaction. In vitro anticancer activity of the synthesized benzo[6,7]indolo[3,4-c]isoquinolines was evaluated on a panel of 39 human cancer cell lines (JFCR39). Among the compounds tested, N-(3-morpholinopropyl) derivative 3e showed the most potent antiproliferative activity, with a mean GI50 value of 39 nM. This compound inhibited topoisomerase I activity by stabilizing the enzyme-DNA complex.

Cerebellar and Occipital Alterations in Brain Perfusion in a Patient With Post-acute COVID-19 Encephalopathy Misdiagnosed As Primary Psychotic Disorder.

We describe the case of an unvaccinated 21-year-old Japanese male who experienced psychotic symptoms attributed to encephalopathy, known as post-acute COVID-19 syndrome (PACS). One week after his discharge following the remission of a SARS-CoV-2 infection, he experienced hyperactive delirium and unexpected movements of his limbs. As COVID-19-associated encephalopathy was suspected as a cause of the psychotic symptoms, he was admitted to the Department of Neurology. He received antiviral and steroid pulse therapy, but his psychiatric symptoms did not improve completely. Consequently, he was admitted to our psychiatric ward with a diagnosis of a primary psychotic disorder. Although he did not take psychopharmacotherapy, he gradually achieved a remission of psychiatric symptoms. At three months post-SARS-CoV-2 infection, single-photon emission computed tomography (SPECT) revealed hypoperfusion in the bilateral cerebellar dentate nuclei and occipital lobes. However, no abnormal findings were observed on fluorine-18 fluoro-deoxy-glucose positron emission tomography (18F-FDG PET) at six months after the infection. This case indicates that (1) brain perfusion SPECT can be effective for detecting functional alterations in post-acute COVID-19-associated encephalopathy, and (2) it is necessary to carefully monitor patients' progress instead of quickly diagnosing a primary psychotic disorder.

Successful Challenge With Brexpiprazole for Idiopathic Hypersomnia in a Patient With Bipolar Disorder: A Case Report.

We describe a 32-year-old Japanese female with hypersomnia and bipolar disorder. She had developed hypersomnia and sleep attacks in her teens. She was misdiagnosed with narcolepsy at a neurology department and then received methylphenidate (MPH) for many years. After giving birth, she developed postpartum depression and suffered from mood swings and irritability. Following 10-year treatment with methylphenidate, she experienced MPH-induced psychosis when she was in a manic state. Her psychosis improved rapidly with the cessation of methylphenidate. Furthermore, brexpiprazole treatment ameliorated her manic symptoms and hypersomnolence. Post-discharge, she was diagnosed with idiopathic hypersomnia based on nocturnal polysomnography and a multiple sleep latency test. This case indicates that brexpiprazole as a serotonin dopamine activity modulator might provide therapeutic effects against not only the patient's manic symptoms but also idiopathic hypersomnia.

EXPRESS: Sandhi-based predictability of pitch accent facilitates word recognition in Kansai Japanese speakers.

We investigated the predictability effects of pitch accent on word recognition using the sandhi rule in Kansai Japanese (KJ). Native KJ speakers and native Tokyo Japanese (TJ) speakers (control group) saw four objects while hearing modifier + noun phrases in a speeded image-selection task. The register tone of the noun's initial mora was predictable or unpredictable based on the tone of the modifier's final mora in KJ but not in TJ. Experiment 1 found faster reaction times in the predictable vs. unpredictable condition in KJ speakers but only when the modifier had an all-low tone. This suggests that the modifier ending that changes following the sandhi rule functions as a reliable cue to constrain an upcoming tone, whereas the modifier ending that remains the same does not (although the next tone is predictable). Unexpectedly, we found the same but weaker effect in TJ speakers. Experiment 2 replicated this effect and additionally showed that the facilitation effect was not because TJ speakers were exposed to KJ well enough to become familiar with the KJ sandhi rule. We speculate that the effect in TJ speakers is related to a language-universal constraint against a sequence of low tones without a high tone within a phonological word, which may urge listeners to listen for a high tone in the upcoming input.

[Long-Term Survival after Liver and Pulmonary Metastasectomy Following Chemotherapy for Metastatic Pancreatic Ductal Adenocarcinoma-A Case Report].

The patient was a 61-year-old man with a diagnosis of carcinoma of the pancreatic head. Abdominal computed tomography( CT)showed no distant metastasis, and he underwent subtotal stomach-preserving pancreatoduodenectomy. Immediately after surgery, he received liver perfusion chemotherapy with 5-fluorouracil followed by systemic gemcitabine. Eighteen months after surgery, CT revealed liver metastasis in the S6 segment, and partial hepatectomy was performed. The pathological diagnosis was liver metastasis of pancreatic cancer. Postoperatively, the patient was treated with gemcitabine and S-1 therapy for 1 year and then switched to S-1 monotherapy for about 6 months. Four years after the initial surgery, CT showed 2 metastases in the right lung. After 2 months of S-1 monotherapy, wedge resection of the upper and lower lobes of the right lung was performed. Gemcitabine and nab-paclitaxel therapy were administered, after the metastasectomy, but pleural dissemination appeared on CT 5 years after the initial surgery. Modified FOLFIRINOX therapy was started and continued for 8 months, but CT revealed further disseminated lesions in the diaphragm. Palliative irradiation was provided, but the disease gradually progressed. After multidisciplinary treatment, the patient survived for 6 years and 3 months after the initial surgery.

Risk factors for death from other diseases after curative gastrectomy and lymph node dissection for gastric cancer.

BACKGROUND: Recent advances in treatment are expected to bring a cure to more patients with gastric cancer (GC). Focusing on the risk of death from other diseases (DOD) has become a crucial issue in patients cured of GC. The aim of this study was to elucidate the risk factors for DOD in patients who underwent curative gastrectomy with lymph node dissection for GC. METHODS: We enrolled 810 patients who underwent curative gastrectomy with lymph node dissection for GC from January 1990 to December 2014 and had no recurrence or death of GC until December 2019. We investigated the risk factors for DOD defined as death excluding death from a malignant neoplasm, accident, or suicide after gastrectomy, focusing on the perioperative characteristics at gastrectomy. RESULTS: Among 315 deaths from any cause, 210 died from diseases other than malignancy, accidents and suicide. The leading cause of DOD was pneumonia in 54 patients (25.7%). The actual survival period in 167 patients (79.5%) with DOD was shorter than their estimated life expectancy at gastrectomy. Multivariate analysis revealed that a high Charlson Comorbidity Index score (score 1-2: hazard ratio [HR] 2.192, 95% confidence interval [CI] 1.713-2.804, P < 0.001 and score ≥ 3: HR 4.813, 95% CI 3.022-7.668, P < 0.001), total gastrectomy (HR 1.620, 95% CI 1.195-2.197, P = 0.002) and the presence of postoperative complications (HR 1.402, 95% CI 1.024-1.919, P = 0.035) were significant independent risk factors for DOD after gastrectomy for GC, in addition to age of 70 years or higher, performance status of one or higher and body mass index less than 22.0 at gastrectomy. CONCLUSIONS: Pneumonia is a leading cause of DOD after curative gastrectomy and lymph node dissection for GC. Paying attention to comorbidities, minimizing the choice of total gastrectomy and avoiding postoperative complications are essential to maintain the long-term prognosis after gastrectomy.

Reduction of claudin-5 and aquaporin-4 in the rat hippocampal CA-1 and CA-3 regions of a learned helplessness model of depression.

BACKGROUND: Although findings from both animal and clinical research indicate that the blood-brain barrier (BBB) contributes to the pathogenesis of various psychiatric disorders (including depression), the underlying mechanisms are unknown. We investigated the levels of the tight-junction proteins claudin-5 and aquaporin-4 (AQP-4) in astrocytes of learned helplessness (LH) rats (an animal model of depression) and non-LH rats (a model of resilience). METHODS: We administered inescapable mild electric shock to rats and then identified the LH and non-LH rats by a post-shock test. The expressions of claudin-5 and AQP-4 in several brain regions of the LH and non-LH rats were then evaluated by a western blot analysis. RESULTS: The levels of both claudin-5 and AQP-4 in the CA-1 and CA-3 hippocampal areas of the LH group were significantly lower than those of the control group, whereas those of the non-LH rats were not significantly different from those of the control and LH rats. CONCLUSIONS: These results suggest that LH rats but not non-LH rats experienced down-regulations of claudin-5 and AQP-4 in the CA-1 and CA-3. It is possible that a region-specific modulation of claudin-5 and AQP-4 is involved in the mechanisms of vulnerability but not resilience in depression.