Efficacy and Safety of Esaxerenone in Hypertensive Patients with Diabetes Mellitus Undergoing Treatment with Sodium-Glucose Cotransporter 2 Inhibitors (EAGLE-DH).

INTRODUCTION: The EAGLE-DH study assessed the efficacy and safety of esaxerenone in hypertensive patients with diabetes mellitus receiving sodium-glucose cotransporter 2 (SGLT2) inhibitors. METHODS: In this multicenter, open-label, prospective, interventional study, esaxerenone was started at 1.25 or 2.5 mg/day and could be gradually increased to 5 mg/day on the basis of blood pressure (BP) and serum potassium levels. Oral hypoglycemic or antihypertensive medications prior to obtaining consent was continued. Data were evaluated in the total population and creatinine-based estimated glomerular filtration rate (eGFR) subcohorts (eGFR ≥ 60 mL/min/1.73 m2 [G1-G2 subcohort] and 30 to < 60 mL/min/1.73 m2 [G3 subcohort]). RESULTS: In total, 93 patients were evaluated (G1-G2, n = 49; G3, n = 44). Morning home systolic/diastolic BP values (SBP/DBP) were significantly reduced from baseline to week 12 (- 11.8 ± 10.8/- 5.1 ± 6.3 mmHg, both P < 0.001) and week 24 (- 12.9 ± 10.5/- 5.7 ± 6.3 mmHg, both P < 0.001). Similar results were observed in both eGFR subcohorts. The urinary albumin-to-creatinine ratio significantly decreased from baseline to week 24 in the total population (geometric percentage change, - 49.1%, P < 0.001) and in both eGFR subcohorts. The incidences of treatment-emergent adverse events (TEAEs) and drug-related TEAEs were 45.2% and 12.9%, respectively; most were mild or moderate. Serum potassium levels increased over the first 2 weeks of esaxerenone treatment, gradually decreased by week 12, and remained constant to week 24. One patient in the G1-G2 subcohort had serum potassium levels ≥ 5.5 mEq/L. No patients had serum potassium ≥ 6.0 mEq/L. CONCLUSION: Esaxerenone effectively lowered BP, was safe, and showed renoprotective effects in hypertensive patients with diabetes mellitus receiving treatment with SGLT2 inhibitors. Esaxerenone and SGLT2 inhibitors did not interfere with either drug's efficacy and may reduce the frequency of serum potassium elevations, suggesting they are a compatible combination. CLINICAL TRIAL REGISTRATION: jRCTs031200273.

Aberrant phosphorylation of human LRH1 at serine 510 is predictable of hepatocellular carcinoma recurrence.

We previously identified the AKT-phosphorylation sites in nuclear receptors and showed that phosphorylation of S379 in mouse retinoic acid γ and S518 in human estrogen receptor α regulate their activity independently of the ligands. Since this site is conserved at S510 in human liver receptor homolog 1 (hLRH1), we developed a monoclonal antibody (mAb) that recognized the phosphorylation form of hLRH1S510 (hLRH1pS510) and verified its clinicopathological significance in hepatocellular carcinoma (HCC). We generated the anti-hLRH1pS510 mAb and assessed its selectivity. We then evaluated the hLRH1pS510 signals in 157 cases of HCC tissues by immunohistochemistry because LRH1 contributes to the pathogenesis of diverse cancers. The developed mAb specifically recognized hLRH1pS510 and worked for immunohistochemistry of formalin-fixed paraffin-embedded tissues. hLRH1pS510 was exclusively localized in the nucleus of HCC cells, but the signal intensity and positive rates varied among the subjects. According to the semi-quantification, 45 cases (34.9%) showed hLRH1pS510-high, and the remaining 112 cases (65.1%) exhibited hLRH1pS510-low. There were significant differences in the recurrence-free survival (RFS) between the two groups, and the 5-year RFS rates in the hLRH1pS510-high and hLRH1pS510-low groups were 26.5% and 46.1%, respectively. In addition, high hLRH1pS510 was significantly correlated with portal vein invasion, hepatic vein invasion, and high levels of serum alpha-fetoprotein (AFP). Furthermore, multivariable analysis revealed that hLRH1pS510-high was an independent biomarker for HCC recurrence. We conclude that aberrant phosphorylation of hLRH1S510 is a predictor of poor prognosis for HCC. The anti-hLRH1pS510 mAb could provide a powerful tool to validate the relevance of hLRH1pS510 in pathological processes such as tumor development and progression.

SPON1 is an independent prognostic biomarker for ovarian cancer.

BACKGROUND: Ovarian cancer has the worst outcome among gynecological malignancies; therefore, biomarkers that could contribute to the early diagnosis and/or prognosis prediction are urgently required. In the present study, we focused on the secreted protein spondin-1 (SPON1) and clarified the prognostic relevance in ovarian cancer. METHODS: We developed a monoclonal antibody (mAb) that selectively recognizes SPON1. Using this specific mAb, we determined the expression of SPON1 protein in the normal ovary, serous tubal intraepithelial carcinoma (STIC), and ovarian cancer tissues, as well as in various normal adult tissues by immunohistochemistry, and verified its clinicopathological significance in ovarian cancer. RESULTS: The normal ovarian tissue was barely positive for SPON1, and no immunoreactive signals were detected in other healthy tissues examined, which was in good agreement with data obtained from gene expression databases. By contrast, upon semi-quantification, 22 of 242 ovarian cancer cases (9.1%) exhibited high SPON1 expression, whereas 64 (26.4%), 87 (36.0%), and 69 (28.5%) cases, which were designated as SPON1-low, possessed the moderate, weak, and negative SPON1 expression, respectively. The STIC tissues also possessed SPON1-positive signals. The 5-year recurrence-free survival (RFS) rate in the SPON1-high group (13.6%) was significantly lower than that in the SPON1-low group (51.2%). In addition, high SPON1 expression was significantly associated with several clinicopathological variables. Multivariable analysis revealed that high SPON1 was an independent prognostic factor for RFS of ovarian cancer. CONCLUSIONS: SPON1 represents a prognostic biomarker for ovarian cancer, and the anti-SPON1 mAb could be valuable as an outcome predictor.

Claudin-4-adhesion signaling drives breast cancer metabolism and progression via liver X receptor ß.

BACKGROUND: Cell adhesion is indispensable for appropriate tissue architecture and function in multicellular organisms. Besides maintaining tissue integrity, cell adhesion molecules, including tight-junction proteins claudins (CLDNs), exhibit the signaling abilities to control a variety of physiological and pathological processes. However, it is still fragmentary how cell adhesion signaling accesses the nucleus and regulates gene expression. METHODS: By generating a number of knockout and rescued human breast cell lines and comparing their phenotypes, we determined whether and how CLDN4 affected breast cancer progression in vitro and in vivo. We also identified by RNA sequencing downstream genes whose expression was altered by CLDN4-adhesion signaling. Additionally, we analyzed by RT-qPCR the CLDN4-regulating genes by using a series of knockout and add-back cell lines. Moreover, by immunohistochemistry and semi-quantification, we verified the clinicopathological significance of CLDN4 and the nuclear receptor LXRß (liver X receptor ß) expression in breast cancer tissues from 187 patients. RESULTS: We uncovered that the CLDN4-adhesion signaling accelerated breast cancer metabolism and progression via LXRß. The second extracellular domain and the carboxy-terminal Y197 of CLDN4 were required to activate Src-family kinases (SFKs) and the downstream AKT in breast cancer cells to promote their proliferation. Knockout and rescue experiments revealed that the CLDN4 signaling targets the AKT phosphorylation site S432 in LXRß, leading to enhanced cell proliferation, migration, and tumor growth, as well as cholesterol homeostasis and fatty acid metabolism, in breast cancer cells. In addition, RT-qPCR analysis showed the CLDN4-regulated genes are classified into at least six groups according to distinct LXRß- and LXRßS432-dependence. Furthermore, among triple-negative breast cancer subjects, the "CLDN4-high/LXRß-high" and "CLDN4-low and/or LXRß-low" groups appeared to exhibit poor outcomes and relatively favorable prognoses, respectively. CONCLUSIONS: The identification of this machinery highlights a link between cell adhesion and transcription factor signalings to promote metabolic and progressive processes of malignant tumors and possibly to coordinate diverse physiological and pathological events.

Factors Associated with the Antihypertensive Effect of Esaxerenone and Serum Potassium Elevation: A Pooled Analysis of Seven Phase III Studies.

INTRODUCTION: This study investigated factors associated with the antihypertensive effects of esaxerenone and the incidence of serum potassium elevation in patients with hypertension. METHODS: Using pooled data from seven phase III studies, the study analyzed factors associated with changes in office systolic (SBP) and diastolic (DBP) blood pressure from baseline to 12 weeks, and factors associated with incidence of serum potassium levels ≥ 5.5 mEq/L in esaxerenone-treated patients. RESULTS: Overall, 1466 and 1472 patients were included in the full analysis and safety analysis sets, respectively. Male sex (4.02/2.40 mmHg), weight ≥ 78.4 kg (4.62/2.09 mmHg), hypertension duration ≥ 10 years (2.66/1.71 mmHg), prior antihypertensive treatment (2.38/1.40 mmHg), plasma aldosterone concentration ≥ 120 pg/mL (1.66/1.17 mmHg), urinary albumin-to-creatinine ratio (UACR) ≥ 300 mg/gCr (8.94/4.85 mmHg) or 30-299 mg/gCr (5.17/4.15 mmHg), and smoking (2.62/1.27 mmHg) were associated with mean changes in SBP and DBP. Fasting blood glucose ≥ 126 mg/dL (- 2.73 mmHg) was associated with the mean change in SBP only, and older age (65-74 years, - 2.12 mmHg; and ≥ 75 years, - 3.06 mmHg) with mean change in DBP only. Factors significantly associated with incidence of serum potassium levels ≥ 5.5 mEq/L were higher baseline serum potassium (≥ 4.5 mEq/L, odds ratio [OR] 6.702); lower estimated glomerular filtration rate (≥ 90 mL/min/1.73 m2, OR 0.148; 60-89 mL/min/1.73 m2, OR 0.331 vs 30-59 mL/min/1.73 m2, respectively); higher UACR (30-299 mg/gCr, OR 7.317); higher DBP (≥ 100 mmHg, OR 3.248); and grade I hypertension (OR 2.168). CONCLUSION: Esaxerenone is effective in patients with a broad range of backgrounds, though some factors may predict increased benefit. Regarding elevated serum potassium, careful therapeutic management is recommended for patients with higher baseline serum potassium and reduced renal function. CLINICAL TRIAL REGISTRATION: UMIN000047026.

Claudin­9 is a novel prognostic biomarker for endometrial cancer.

The tight­junction protein claudin­9 (CLDN9) is barely distributed in normal adult tissues but is ectopically expressed in various cancer types. Although multiple databases indicated upregulation of CLDN9 in endometrial cancers at the mRNA level, its protein expression and biological roles remain obscure. In the present study, the prognostic significance of CLDN9 expression in endometrial cancer was evaluated by immunohistochemical staining and semi­quantification using formalin­fixed paraffin­embedded specimens obtained from 248 endometrial carcinoma cases. A total of 43 cases (17.3%) had high CLDN9 expression, whereas 205 cases (82.7%) exhibited low CLDN9 expression. The 5­year disease­specific survival rates in the high and low CLDN9 expression groups were 62.8 and 87.8% (P<0.001), respectively. In addition, multivariate analysis revealed that high CLDN9 expression was an independent prognostic factor (hazard ratio, 4.99; 95% CI, 1.96­12.70; P<0.001). Furthermore, CLDN9 expression was significantly correlated with the expression of CLDN6 (P<0.001), which is the closest CLDN member to CLDN9 and a poor prognostic factor for endometrial carcinoma. The 5­year disease­specific survival rate of cases with CLDN6­high/CLDN9­high, CLDN6­high/CLDN9­low and CLDN6­low/CLDN9­high status was 30.0, 37.5 and 72.7%, respectively, whereas that of CLDN6­low/CLDN9­low was 89.8% (P=0.004). In conclusion, aberrant CLDN9 expression is a predictor of poor prognosis for endometrial cancer and may be utilized in combination with CLDN6 to achieve higher sensitivity.

Efficacy and Safety of Esaxerenone in Hypertensive Patients with Diabetic Kidney Disease: A Multicenter, Open-Label, Prospective Study.

INTRODUCTION: Clinical data of esaxerenone in hypertensive patients with diabetic kidney disease (DKD) are lacking. We evaluated the efficacy and safety of esaxerenone in patients with DKD and an inadequate response to blood pressure (BP)-lowering treatment. METHODS: In this multicenter, open-label, prospective study, patients were divided into urinary albumin-to-creatinine ratio subcohorts (UACR < 30, 30 to < 300, and 300 to < 1000 mg/gCr). Esaxerenone was initiated at 1.25 mg/day and followed by incremental dose escalation based on BP and serum potassium level monitoring. The treatment period was 12 weeks. The primary endpoint was change in morning home systolic BP/diastolic BP (SBP/DBP) from baseline to end of treatment (EOT). Secondary endpoints included achievement rate of target BP, change in UACR from baseline, and safety. RESULTS: In total, 113 patients were enrolled. Morning home SBP/DBP significantly decreased from baseline to EOT in the total population (- 11.6/- 5.2 mmHg, both p < 0.001) and in all UACR subcohorts (all p < 0.001). The target BP achievement rate was 38.5%. Significant reductions in bedtime home and office BPs were also shown in the total population and all UACR subcohorts. UACR significantly improved from baseline to EOT in the total (- 50.9%, p < 0.001) and all UACR subcohorts (all p < 0.001). Incidence of serum potassium elevation as drug-related treatment emergent adverse events was 2.7%. The change from baseline in estimated glomerular filtration rate (eGFR) was - 4.8 mL/min/1.73 m2. CONCLUSION: Esaxerenone demonstrated a BP-lowering effect and improved albuminuria. The effects were consistent regardless of the severity of albuminuria without clinically relevant serum potassium elevation and eGFR reduction. CLINICAL TRIAL REGISTRATION: jRCTs06119002.

Paraneoplastic anti-N-methyl-D-aspartate receptor encephalitis associated with small cell lung cancer and cytotoxic T-cell-mediated pathology: Case report.

Anti-N-methyl-D-aspartate receptor (NMDAR) antibody encephalitis is caused by a reversible inhibition of ion channel actions by autoantibodies and is associated with a relatively good prognosis. Pathological findings of NMDAR encephalitis usually do not show neurophagorous nodules, but rare or mild inflammatory infiltration. We report a patient of small cell lung cancer (SCLC)-related paraneoplastic encephalitis with NMDAR antibodies, a cytotoxic T-cell-mediated pathology of the brain, and a rapid clinical course. This case highlights that the neuropathological diversity of NMDAR encephalitis may be even broader than previously thought and that NMDAR antibodies may also be found in various pathological conditions with a vigorous immune response.

Aberrant expression of claudin-6 contributes to malignant potentials and drug resistance of cervical adenocarcinoma.

Recent studies have revealed that aberrant expression of tight junction (TJ) proteins is a hallmark of various solid tumors and it is recognized as a useful therapeutic target. Claudin-6 (CLDN6), a member of the family of TJ transmembrane proteins, is an ideal therapeutic target because it is not expressed in human adult normal tissues. In this study, we found that CLDN6 is highly expressed in uterine cervical adenocarcinoma (ADC) and that high CLDN6 expression was correlated with lymph node metastasis and lymphovascular infiltration and was an independent prognostic factor. Shotgun proteome analysis revealed that cell-cell adhesion-related proteins and drug metabolism-associated proteins (aldo-keto reductase [AKR] family proteins) were significantly increased in CLDN6-overexpressing cells. Furthermore, overexpression of CLDN6 enhanced cell-cell adhesion properties and attenuated sensitivity to anticancer drugs including doxorubicin, daunorubicin, and cisplatin. Taken together, the results indicate that aberrant expression of CLDN6 enhances malignant potentials and drug resistance of cervical ADC, possibly due to increased cell-cell adhesion properties and drug metabolism. Our findings provide an insight into a new therapeutic strategy, a CLDN6-targeting therapy, against cervical ADC.

Alloantigen-activated (AAA) CD4+ T cells reinvigorate host endogenous T cell immunity to eliminate pre-established tumors in mice.

BACKGROUND: Cancer vaccines that induce endogenous antitumor immunity represent an ideal strategy to overcome intractable cancers. However, doing this against a pre-established cancer using autologous immune cells has proven to be challenging. "Allogeneic effects" refers to the induction of an endogenous immune response upon adoptive transfer of allogeneic lymphocytes without utilizing hematopoietic stem cell transplantation. While allogeneic lymphocytes have a potent ability to activate host immunity as a cell adjuvant, novel strategies that can activate endogenous antitumor activity in cancer patients remain an unmet need. In this study, we established a new method to destroy pre-developed tumors and confer potent antitumor immunity in mice using alloantigen-activated CD4+ (named AAA-CD4+) T cells. METHODS: AAA-CD4+ T cells were generated from CD4+ T cells isolated from BALB/c mice in cultures with dendritic cells (DCs) induced from C57BL/6 (B6) mice. In this culture, allogeneic CD4+ T cells that recognize and react to B6 mouse-derived alloantigens are preferentially activated. These AAA-CD4+ T cells were directly injected into the pre-established melanoma in B6 mice to assess their ability to elicit antitumor immunity in vivo. RESULTS: Upon intratumoral injection, these AAA-CD4+ T cells underwent a dramatic expansion in the tumor and secreted high levels of IFN-γ and IL-2. This was accompanied by markedly increased infiltration of host-derived CD8+ T cells, CD4+ T cells, natural killer (NK) cells, DCs, and type-1 like macrophages. Selective depletion of host CD8+ T cells, rather than NK cells, abrogated this therapeutic effect. Thus, intratumoral administration of AAA-CD4+ T cells results in a robust endogenous CD8+ T cell response that destroys pre-established melanoma. This locally induced antitumor immunity elicited systemic protection to eliminate tumors at distal sites, persisted over 6 months in vivo, and protected the animals from tumor re-challenge. Notably, the injected AAA-CD4+ T cells disappeared within 7 days and caused no adverse reactions. CONCLUSIONS: Our findings indicate that AAA-CD4+ T cells reinvigorate endogenous cytotoxic T cells to eradicate pre-established melanoma and induce long-term protective antitumor immunity. This approach can be immediately applied to patients with advanced melanoma and may have broad implications in the treatment of other types of solid tumors.

CLDN15 is a novel diagnostic marker for malignant pleural mesothelioma.

Malignant mesothelioma is a cancer with a poor survival rate. It is difficult to diagnose mesotheliomas because they show a variety of histological patterns similar to those of various other cancers. However, since currently used positive markers for mesotheliomas may show false positives or false negatives, a novel mesothelial positive marker is required. In the present study, we screened 25 claudins and found that claudin-15 is expressed in the mesothelial cells. We made new rat anti-human claudin-15 (CLDN15) monoclonal antibodies that selectively recognize CLDN15, and investigated whether CLDN15 is a good positive marker for malignant pleural mesotheliomas (MPMs) using MPM tissue samples by immunohistochemistry and semi-quantification of the expression level using an immunoreactive score (IRS) method. Of 42 MPM samples, 83% were positive for CLDN15. The positive ratio was equal to or greater than other positive markers for MPMs including calretinin (81%), WT-1 (50%), and D2-40 (81%). In 50 lung adenocarcinoma sections, four cases were positive for CLDN15 and the specificity (92%) was comparable with other markers (90-100%). Notably, CLDN15 was rarely detected in 24 non-mesothelial tumors in the tissue microarray (12/327 cases). In conclusion, CLDN15 can be used in the clinical setting as a positive marker for MPM diagnosis.

The claudin-transcription factor signaling pathway.

Claudins (CLDNs) represent major transmembrane proteins of tight junctions and contribute to the barrier function. They also serve as anchors for several signaling proteins, but the underlying molecular basis has yet to be established. The present review covers the recent progress in our understanding of the CLDN signaling pathway in health and disease. We discuss the functional relevance of phosphotyrosine motifs in the C-terminal cytoplasmic domain of CLDNs and define mutual regulation between CLDNs and Src-family kinases (SFKs). In addition, we focus on the crosstalk between CLDN and transcription factor signaling. We also describe how aberrant CLDN-transcription factor signaling promotes or inhibits cancer progression. We propose that a link between various cell adhesion molecules and transcription factors coordinates a range of physiological and pathological events via activation or suppression of target genes.

Reduced Claudin-12 Expression Predicts Poor Prognosis in Cervical Cancer.

BACKGROUND: Within the claudin (CLDN) family, CLDN12 mRNA expression is altered in various types of cancer, but its clinicopathological relevance has yet to be established due to the absence of specific antibodies (Abs) with broad applications. METHODS: We generated a monoclonal Ab (mAb) against human/mouse CLDN12 and verified its specificity. By performing immunohistochemical staining and semiquantification, we evaluated the relationship between CLDN12 expression and clinicopathological parameters in tissues from 138 cases of cervical cancer. RESULTS: Western blot and immunohistochemical analyses revealed that the established mAb selectively recognized the CLDN12 protein. Twenty six of the 138 cases (18.8%) showed low CLDN12 expression, and the disease-specific survival (DSS) and recurrence-free survival rates were significantly decreased compared with those in the high CLDN12 expression group. We also demonstrated, via univariable and multivariable analyses, that the low CLDN12 expression represents a significant prognostic factor for the DSS of cervical cancer patients (HR 3.412, p = 0.002 and HR 2.615, p = 0.029, respectively). CONCLUSIONS: It can be concluded that a reduced CLDN12 expression predicts a poor outcome for cervical cancer. The novel anti-CLDN12 mAb could be a valuable tool to evaluate the biological relevance of the CLDN12 expression in diverse cancer types and other diseases.

Aberrant Claudin-6-Adhesion Signaling Promotes Endometrial Cancer Progression via Estrogen Receptor α.

Cell adhesion proteins not only maintain tissue integrity, but also possess signaling abilities to organize diverse cellular events in a variety of physiologic and pathologic processes; however, the underlying mechanism remains obscure. Among cell adhesion molecules, the claudin (CLDN) family is often aberrantly expressed in various cancers, but the biological relevance and molecular basis for this observation have not yet been established. Here, we show that high CLDN6 expression accelerates cellular proliferation and migration in two distinct human endometrial cancer cell lines in vitro. Using a xenograft model, we also revealed that aberrant CLDN6 expression promotes tumor growth and invasion in endometrial cancer tissues. The second extracellular domain and Y196/200 of CLDN6 were required to recruit and activate Src-family kinases (SFK) and to stimulate malignant phenotypes. Knockout and overexpression of ESR1 in endometrial carcinoma cells showed that the CLDN6-adhesion signal links to estrogen receptor α (ERα) to advance tumor progression. In particular, aberrant CLDN6-ERα signaling contributed to collective cell behaviors in the leading front of endometrial cancer cells. Importantly, we demonstrate that CLDN6/SFK/PI3K-dependent AKT and SGK (serum- and glucocorticoid-regulated kinase) signaling in endometrial cancer cells targets Ser518 in the human ERα to activate ERα transcriptional activity in a ligand-independent manner, thereby promoting tumor progression. Furthermore, CLDN6, at least in part, also regulated gene expression in an ERα-independent manner. IMPLICATIONS: The identification of this machinery highlights regulation of the transcription factors by cell adhesion to advance tumor progression.

Prognostic Significance of Aberrant Claudin-6 Expression in Endometrial Cancer.

BACKGROUND: Among the claudin (CLDN) family, CLDN6 exhibits aberrant expression in various cancers, but its biological relevance has not yet been established. We generated a monoclonal antibody (mAb) against human CLDN6 and verified its specificity. By immunohistochemical staining and semi-quantification, we evaluated the relationship between CLDN6 expression and clinicopathological parameters in tissues from 173 cases of endometrial cancer. RESULTS: The established mAb selectively recognized CLDN6 protein. Ten of the 173 cases (5.8%) showed high CLDN6 expression (score 3+), whereas 19 (11.0%), 18 (10.4%) and 126 (72.4%) cases revealed low CLDN6 expression (score 2+, 1+ and 0, respectively). In addition, intratumor heterogeneity of CLDN6 expression was observed even in the cases with high CLDN6 expression. The 5-year survival rates in the high and low CLDN6 groups was approximately 30% and 90%, respectively. Among the clinicopathological factors, the high CLDN6 expression was significantly associated with surgical stage III/IV, histological grade 3, lymphovascular space involvement, lymph node metastasis and distant metastasis. Furthermore, the high CLDN6 expression was an independent prognostic marker for overall survival of endometrial cancer patients (hazard ratio 3.50, p = 0.014). CONCLUSIONS: It can be concluded that aberrant CLDN6 expression is useful to predict poor outcome for endometrial cancer and might be a promising therapeutic target.

Serotonin/5-HT1A Signaling in the Neurovascular Unit Regulates Endothelial CLDN5 Expression.

We previously reported that site-selective claudin-5 (CLDN5) breakdown and protein kinase A (PKA) activation are observed in brain microvessels of schizophrenia, but the underlying molecular basis remains unknown. The 5-HT1 receptors decline the intracellular cAMP levels and inactivate the major downstream PKA, and the 5-HT1A receptor is a promising target for schizophrenia. Therefore, we elucidated the involvement of serotonin/5-HT1A signaling in the endothelial CLDN5 expression. We demonstrate, by immunohistochemistry using post-mortem human brain tissue, that the 5-HT1A receptor is expressed in brain microvascular endothelial cells (BMVECs) and mural cells of the normal prefrontal cortex (PFC) gray matter. We also show that PKA is aberrantly activated not only in BMVECs but also in mural cells of the schizophrenic PFC. We subsequently revealed that the endothelial cell-pericyte tube-like structure was formed in a novel two-dimensional co-culture of human primary BMVECs and a human brain-derived pericyte cell line, in both of which the 5-HT1A receptor was expressed. Furthermore, we disclose that the serotonin/5-HT1A signaling enhances endothelial CLDN5 expression in BMVECs under two-dimensional co-culture conditions. Our findings provide novel insights into the physiological and pathological significance of serotonin/5-HT1A signaling in the region-specific regulation of the blood-brain barrier.

Cell adhesion signals regulate the nuclear receptor activity.

Cell adhesion is essential for proper tissue architecture and function in multicellular organisms. Cell adhesion molecules not only maintain tissue integrity but also possess signaling properties that contribute to diverse cellular events such as cell growth, survival, differentiation, polarity, and migration; however, the underlying molecular basis remains poorly defined. Here we identify that the cell adhesion signal initiated by the tight-junction protein claudin-6 (CLDN6) regulates nuclear receptor activity. We show that CLDN6 recruits and activates Src-family kinases (SFKs) in second extracellular domain-dependent and Y196/200-dependent manners, and SFKs in turn phosphorylate CLDN6 at Y196/200. We demonstrate that the CLDN6/SFK/PI3K/AKT axis targets the AKT phosphorylation sites in the retinoic acid receptor γ (RARγ) and the estrogen receptor α (ERα) and stimulates their activities. Interestingly, these phosphorylation motifs are conserved in 14 of 48 members of human nuclear receptors. We propose that a similar link between diverse cell adhesion and nuclear receptor signalings coordinates a wide variety of physiological and pathological processes.

Attenuation of pulmonary fibrosis in type I collagen-targeted reporter mice with ALK-5 inhibitors.

Idiopathic pulmonary fibrosis (IPF) is a progressive and fatal disease, and consequently, effective antifibrotic drugs are strongly desired. Although we have previously reported a validated Col1a1-Luc Tg rat model for fibrosis, there are only a few mouse models that enable the evaluation of fibrosis in a short time period and with high sensitivity. Therefore, we generated a Col1a1-internal ribosome entry site (IRES)-Luc knock-in (KI) mouse in which the IRES-luciferase gene construct was inserted into the 3'-UTR of the type I collagen alpha 1 gene (Col1a1). There was a high correlation between luciferase activity and hydroxyproline content in the KI mice, which is similar to the result that we have previously reported for the Col1a1-Luc Tg rat model. In a bleomycin (BLM)-induced lung fibrosis model, luciferase activity in the lung showed a significant increase 3 days after BLM treatment, while only a slight increase was observed in the hydroxyproline content. An ALK-5 inhibitor-R-268712-was effective in inhibiting the luciferase activity in both the in vivo BLM-induced lung fibrosis model and in vitro primary mouse lung fibroblasts. This suggests that fibroblasts are the major collagen-producing cells in lung fibrosis. In human lung fibroblasts, TGF-ß stimulation induced α-smooth muscle actin as observed by immunostaining, suggesting that myofibroblast transdifferentiation (MTD) plays an important role in lung fibrosis. Together, these results indicated that ALK-5 inhibitors might affect lung fibrosis mainly via the inhibition of MTD. Thus, the Col1a1-IRES-Luc KI mouse might be useful for the evaluation of antifibrotic effects and their underlying mechanisms.