γH2AX, a DNA Double-Strand Break Marker, Correlates with PD-L1 Expression in Smoking-Related Lung Adenocarcinoma.

In recent years, the choice of immune checkpoint inhibitors (ICIs) as a treatment based on high expression of programmed death-ligand 1 (PD-L1) in lung cancers has been increasing in prevalence. The high expression of PD-L1 could be a predictor of ICI efficacy as well as high tumor mutation burden (TMB), which is determined using next-generation sequencing (NGS). However, a great deal of effort is required to perform NGS to determine TMB. The present study focused on γH2AX, a double-strand DNA break marker, and the suspected positive relation between TMB and γH2AX was investigated. We assessed the possibility of γH2AX being an alternative marker of TMB or PD-L1. One hundred formalin-fixed, paraffin-embedded specimens of lung cancer were examined. All of the patients in the study received thoracic surgery, having been diagnosed with lung adenocarcinoma or squamous cell carcinoma. The expressions of γH2AX and PD-L1 (clone: SP142) were evaluated immunohistochemically. Other immunohistochemical indicators, p53 and Ki-67, were also used to estimate the relationships of γH2AX. Positive relationships between γH2AX and PD-L1 were proven, especially in lung adenocarcinoma. Tobacco consumption was associated with higher expression of γH2AX, PD-L1, Ki-67, and p53. In conclusion, the immunoexpression of γH2AX could be a predictor for the adaptation of ICIs as well of as PD-L1 and TMB.

Lung Pathology of Mutually Exclusive Co-infection with SARS-CoV-2 and Streptococcus pneumoniae.

Postmortem lung pathology of a patient in Japan with severe acute respiratory syndrome coronavirus 2 infection showed diffuse alveolar damage as well as bronchopneumonia caused by Streptococcus pneumoniae infection. The distribution of each pathogen and the accompanying histopathology suggested the infections progressed in a mutually exclusive manner within the lung, resulting in fatal respiratory failure.

Human estrogen sulfotransferase and its related fluorescently labeled decapeptides specifically interact with oxidized low-density lipoprotein.

Estrogen sulfotransferase (SULT1E) mainly catalyzes the sulfation of estrogens, which are known to prevent the pathogenesis of atherosclerosis. Recently, we found that peptides with a YKDG sequence specifically bind to oxidized low-density lipoprotein (Ox-LDL), which plays a major role in the pathogenesis of atherosclerosis. Here, we investigated the interaction between human SULT1E1 (hSULT1E1), which has a YKEG sequence (residues 61-64) unlike other human SULTs, and Ox-LDL. Results from polyacrylamide gel electrophoresis and western blotting demonstrated that hSULT1E1 specifically binds to Ox-LDL and its major lipid component (lysophosphatidylcholine; LPC), and platelet-activating factor (PAF), which bears a marked resemblance to LPC in terms of structure and activity. Moreover, an N-terminally fluorescein isothiocyanate (FITC)-labeled decapeptide (MIYKEGDVEK; FITC-hSULT1E1-P10) corresponding to residues 59-68 of hSULT1E1 specifically binds to Ox-LDL, LPC, and PAF. Unveiling the specific interaction between hSULT1E1 and Ox-LDL, LPC, and PAF provides important information regarding the mechanisms underlying various diseases caused by Ox-LDL, LPC, and PAF, such as atherosclerosis. In addition, FITC-hSULT1E1-P10 could be used as an efficient fluorescent probe for the detection of Ox-LDL, LPC, and PAF, which could facilitate the mechanistic study, identification, diagnosis, prevention, and treatment of atherosclerosis.

Early detection of genotoxic hepatocarcinogens in rats using γH2AX and Ki-67: prediction by machine learning.

Direct DNA double-strand breaks result in phosphorylation of H2AX, a variant of the histone H2 protein. Phosphorylated H2AX (γH2AX) may be a potential indicator in the evaluation of genotoxicity and hepatocarcinogenicity. In this study, γH2AX and Ki-67 were detected in the short-term responses (24 h after chemical administration) to classify genotoxic hepatocarcinogens (GHs) from non-GH chemicals. One hundred and thirty-five 6-week-old Crl: CD(SD) (SPF) male rats were treated with 22 chemicals including 11 GH and 11 non-GH, sacrificed 24 h later, and immunostained with γH2AX and Ki-67. Positivity rates of these markers were measured in the 3 liver ZONEs 1-3; portal, lobular, and central venous regions. These values were input into 3 machine learning models-Naïve Bayes, Random Forest, and k-Nearest Neighbor to classify GH and non-GH using a 10-fold cross-validation method. All 11 and 10 out of 11 GH caused significant increase in γH2AX and Ki-67 levels, respectively (P < .05). Of the 3 machine learning models, Random Forest performed the best. GH were identified with 95.0% sensitivity (76/80 GH-treated rats), 90.9% specificity (50/55 non-GH-treated rats), and 90.0% overall correct response rate using γH2AX staining, and 96.2% sensitivity (77/80), 81.8% specificity (45/55), and 90.4% overall correct response rate using Ki-67 labeling. Random Forest model using γH2AX and Ki-67 could independently predict GH in the early stage with high accuracy.

A case of chronic gastric anisakiasis coexisting with early gastric cancer.

Background: Anisakiasis is a parasitic disease caused by the consumption of raw or undercooked fish that is infected with Anisakis third-stage larvae. In countries, such as Japan, Italy, and Spain, where people have a custom of eating raw or marinated fish, anisakiasis is a common infection. Although anisakiasis has been reported in the gastrointestinal tract in several countries, reports of anisakiasis accompanied by cancer are rare. Case presentation: We present the rare case of a 40-year-old male patient with anisakiasis coexisting with mucosal gastric cancer. Submucosal gastric cancer was suspected on gastric endoscopy and endoscopic ultrasonography. After laparoscopic distal gastrectomy, granulomatous inflammation with Anisakis larvae in the submucosa was pathologically revealed beneath mucosal tubular adenocarcinoma. Histological and immunohistochemical investigation showed cancer cells as intestinal absorptive-type cells that did not produce mucin. Conclusion: Anisakis larvae could have invaded the cancer cells selectively because of the lack of mucin in the cancerous epithelium. Anisakiasis coexisting with cancer is considered reasonable rather than coincidental. In cancer with anisakiasis, preoperative diagnosis may be difficult because anisakiasis leads to morphological changes in the cancer.

Honeycomb lung is a major risk factor for preoperative radiological tumor size underestimation in patients with primary lung cancer.

Background: Lung cancer frequently occurs in lungs with background idiopathic interstitial pneumonias (IIPs). Limited resection is often selected to treat lung cancer in patients with IIPs in whom respiratory function is already compromised. However, accurate surgical margins are essential for curative resection; underestimating these margins is a risk for residual lung cancer after surgery. We aimed to investigate the findings of lung fields adjacent to cancer segments affect the estimation of tumor size on computed tomography compared with the pathological specimen. Methods: This analytical observational study retrospectively investigated 896 patients with lung cancer operated on at Fujita Health University from January 2015 to June 2020. The definition of underestimation was a ≥10 mm difference between the radiological and pathological maximum sizes of the tumor. Results: The lung tumors were in 15 honeycomb, 30 reticulated, 207 emphysematous, and 628 normal lungs. The ratio of underestimation in honeycomb lungs was 33.3% compared to 7.4% without honeycombing (P=0.004). Multivariate analysis showed that honeycombing was a significant risk factor for tumor size underestimation. A Bland-Altman plot represented wide 95% limits of agreement, -40.8 to 70.2 mm, between the pathological and radiological maximum tumor sizes in honeycomb lungs.

Estrogen Sulfotransferase is Highly Expressed in Vascular Endothelial Cells Overlying Atherosclerotic Plaques.

Cytosolic estrogen sulfotransferase (SULT1E1) mainly catalyzes the sulfoconjugation and deactivation of estrogens that are known to exert potent anti-atherogenic effects. However, it remains unknown about the connection between SULT1E1 and atherosclerosis. Recently, we reported that SULT1E1 is highly expressed in the aorta with plaques of high fat-fed ApoE knockout (KO) mice (mouse model of atherosclerosis), and interacts with oxidized low-density lipoprotein (Ox-LDL) known as a major component of atherosclerotic lesions. In this study, immunohistochemical staining for SULT1E1 in the aorta of high fat-fed ApoE KO mice showed that SULT1E1 is detected in vascular endothelial cells overlying atherosclerotic plaques. Results from Western blotting showed that Ox-LDL induces the protein expression of both SULT1E1 and peroxisome proliferator-activated receptor (PPAR) γ in human umbilical vein endothelial cells (HUVECs), and then that a PPARγ antagonist GW9662, but not a PPARα antagonist GW6471, inhibited the protein expression of SULT1E1 induced by Ox-LDL. Moreover, GW9662 significantly increased the proliferation of HUVECs induced by Ox-LDL. Our results suggest that SULT1E1 and PPARγ, both of which are increased by Ox-LDL, may interact with each other, and then may reduce cooperatively Ox-LDL-induced proliferation of vascular endothelial cells overlying atherosclerotic plaques, leading to against atherosclerosis.

Automated Classification of Idiopathic Pulmonary Fibrosis in Pathological Images Using Convolutional Neural Network and Generative Adversarial Networks.

Interstitial pneumonia of uncertain cause is referred to as idiopathic interstitial pneumonia (IIP). Among the various types of IIPs, the prognosis of cases of idiopathic pulmonary fibrosis (IPF) is extremely poor, and accurate differentiation between IPF and non-IPF pneumonia is critical. In this study, we consider deep learning (DL) methods owing to their excellent image classification capabilities. Although DL models require large quantities of training data, collecting a large number of pathological specimens is difficult for rare diseases. In this study, we propose an end-to-end scheme to automatically classify IIPs using a convolutional neural network (CNN) model. To compensate for the lack of data on rare diseases, we introduce a two-step training method to generate pathological images of IIPs using a generative adversarial network (GAN). Tissue specimens from 24 patients with IIPs were scanned using a whole slide scanner, and the resulting images were divided into patch images with a size of 224 × 224 pixels. A progressive growth GAN (PGGAN) model was trained using 23,142 IPF images and 7817 non-IPF images to generate 10,000 images for each of the two categories. The images generated by the PGGAN were used along with real images to train the CNN model. An evaluation of the images generated by the PGGAN showed that cells and their locations were well-expressed. We also obtained the best classification performance with a detection sensitivity of 97.2% and a specificity of 69.4% for IPF using DenseNet. The classification performance was also improved by using PGGAN-generated images. These results indicate that the proposed method may be considered effective for the diagnosis of IPF.

Comparison of Fine-Tuned Deep Convolutional Neural Networks for the Automated Classification of Lung Cancer Cytology Images with Integration of Additional Classifiers.

OBJECTIVE: It is essential to accurately diagnose and classify histological subtypes into adenocarcinoma (ADC), squamous cell carcinoma (SCC), and small cell lung carcinoma (SCLC) for the appropriate treatment of lung cancer patients. However, improving the accuracy and stability of diagnosis is challenging, especially for non-small cell carcinomas. The purpose of this study was to compare multiple deep convolutional neural network (DCNN) technique with subsequent additional classifiers in terms of accuracy and characteristics in each histology. METHODS: Lung cancer cytological images were classified into ADC, SCC, and SCLC with four fine-tuned DCNN models consisting of AlexNet, GoogLeNet (Inception V3), VGG16 and ResNet50 pretrained by natural images in ImageNet database. For more precise classification, the figures of 3 histological probabilities were further applied to subsequent machine learning classifiers using Naïve Bayes (NB), Support vector machine (SVM), Random forest (RF), and Neural network (NN). RESULTS: The classification accuracies of the AlexNet, GoogLeNet, VGG16 and ResNet50 were 74.0%, 66.8%, 76.8% and 74.0%, respectively. Well differentiated typical morphologies were tended to be correctly judged by all four architectures. However, poorly differentiated non-small cell carcinomas lacking typical structures were inclined to be misrecognized in some DCNNs. Regarding the histological types, ADC were best judged by AlexNet and SCC by VGG16. Subsequent machine learning classifiers of NB, SVV, RF, and NN improved overall accuracies to 75.1%, 77.5%, 78.2%, and 78.9%, respectively. CONCLUSION: Fine-tuning DCNNs in combination with additional classifiers improved classification of cytological diagnosis of lung cancer, although classification bias could be indicated among DCNN architectures.

Fatal disseminated mucormycosis associated with COVID-19.

Secondary fungal infections are a critical problem that accompany immunosuppressive therapy for severe coronavirus disease 2019 (COVID-19). We report a fatal case of COVID-19 with disseminated mucormycosis diagnosed during autopsy. A 58-year-old man with diabetes was hospitalized for severe COVID-19 and treated with remdesivir, systemic steroids and tocilizumab. Following treatment, he was provided extracorporeal membrane oxygenation support. However, he died of multiple organ failure accompanied by pulmonary and kidney infarction, as revealed by computed tomography. Autopsy revealed that the infarction was caused by thromboangiitis due to mucormycosis in the brain, lungs, heart, liver and kidneys. Therefore, the diagnosis of disseminated mucormycosis was established. Disseminated mucormycosis is a rare complication of COVID-19. Although its early diagnosis is difficult, the disease progresses rapidly. Hence, we propose that immunosuppressive treatment for COVID-19 should be administered with caution considering the risk of developing severe opportunistic infections, such as mucormycosis.

Interaction of Native- and Oxidized-Low-Density Lipoprotein with Human Estrogen Sulfotransferase.

Cytosolic estrogen sulfotransferase (SULT1E) mainly catalyzes the sulfate conjugation of estrogens, which decrease atherosclerosis progression. Recently we reported that a YKEG sequence in human SULT1E1 (hSULT1E1) corresponding to residues 61-64 can bind specifically to oxidized low-density lipoprotein (Ox-LDL), which plays a major role in the pathogenesis of atherosclerosis; its major oxidative lipid component lysophosphatidylcholine (LPC), and its structurally similar lipid, platelet-activating factor (PAF). In this study, we investigated the effect of Ox-LDL on the sulfating activity of hSULT1E1. In vivo experiments using a mouse model of atherosclerosis showed that the protein expression of SULT1E1 was higher in the aorta of mice with atherosclerosis compared with that in control animals. Results from a sulfating activity assay of hSULT1E1 using 1-hydroxypyrene as the substrate demonstrated that Ox-LDL, LPC, and PAF markedly decreased the sulfating activity of hSULT1E1, whereas native LDL and 1-palmitoyl-2-(5'-oxo-valeroyl)-sn-glycero-3-phosphocholine (POVPC) as one of the oxidized phosphatidylcholines showed the opposite effect. The sulfating activity greatly changed in the presence of LPC, PAF, and POVPC in their concentration-dependen manner (especially above their critical micelle concentrations). Moreover, Ox-LDL specifically recognized dimeric hSULT1E1. These results suggest that the effects of Ox-LDL and native LDL on the sulfating activity of hSULT1E1 might be helpful in elucidating the novel mechanism underlying the pathogenesis of atherosclerosis, involving the relationship between estrogen metabolism, LDL, and Ox-LDL.

Weakly supervised learning for classification of lung cytological images using attention-based multiple instance learning.

In cytological examination, suspicious cells are evaluated regarding malignancy and cancer type. To assist this, we previously proposed an automated method based on supervised learning that classifies cells in lung cytological images as benign or malignant. However, it is often difficult to label all cells. In this study, we developed a weakly supervised method for the classification of benign and malignant lung cells in cytological images using attention-based deep multiple instance learning (AD MIL). Images of lung cytological specimens were divided into small patch images and stored in bags. Each bag was then labeled as benign or malignant, and classification was conducted using AD MIL. The distribution of attention weights was also calculated as a color map to confirm the presence of malignant cells in the image. AD MIL using the AlexNet-like convolutional neural network model showed the best classification performance, with an accuracy of 0.916, which was better than that of supervised learning. In addition, an attention map of the entire image based on the attention weight allowed AD MIL to focus on most malignant cells. Our weakly supervised method automatically classifies cytological images with acceptable accuracy based on supervised learning without complex annotations.

Mutual stain conversion between Giemsa and Papanicolaou in cytological images using cycle generative adversarial network.

OBJECTIVE: Papanicolaou and Giemsa stains used in cytology have different characteristics and complementary roles. In this study, we focused on cycle-consistent generative adversarial network (CycleGAN), which is an image translation technique using deep learning, and we conducted mutual stain conversion between Giemsa and Papanicolaou in cytological images using CycleGAN. METHODS: A total of 191 Giemsa-stained images and 209 Papanicolaou-stained images were collected from 63 patients with lung cancer. From those images, 67 images from nine cases were used for testing and the remaining images were used for training. For data augmentation, the number of training images was increased by rotation and inversion, and the images were pipelined to CycleGAN to train the mutual conversion process involving Giemsa- and Papanicolaou-stained images. Three pathologists and three cytotechnologists performed visual evaluations of the authenticity of cell nuclei, cytoplasm, and cell layouts of the test images translated using CycleGAN. RESULTS: As a result of converting Giemsa-stained images into Papanicolaou-stained images, the background red blood cell patterns present in Giemsa-stained images disappeared, and cell patterns that reproduced the shape and staining of the cell nuclei and cytoplasm peculiar to Papanicolaou staining were obtained. Regarding the reverse-translated results, nuclei became larger, and red blood cells that were not evident in Papanicolaou-stained images appeared. After visual evaluation, although actual images exhibited better results than converted images, the results were promising for various applications. DISCUSSION: The stain translation technique investigated in this paper can complement specimens under conditions where only single stained specimens are available; it also has potential applications in the massive training of artificial intelligence systems for cell classification, and can also be used for training cytotechnologist and pathologists.

Roles of hypothalamic subgroup histamine and orexin neurons on behavioral responses to sleep deprivation induced by the treadmill method in adolescent rats.

Sleep deprivation induces several negative effects on behavior, emotion, attention, and learning ability. Sleep appears to be particularly important during adolescent brain development. In the present study, we examined the effects of sleep deprivation on behavior and hypothalamic neurotransmission including histamine and orexin neurons in adolescent rats using the treadmill method. Adolescent male rats were divided into three groups: treadmill sleep-deprived, treadmill control, and cage control groups. Energy expenditure, anxiety-like behavior, and locomotor activity were examined among the three groups. Histamine concentration in the cortex and diencephalon and the number of c-Fos-positive neurons in the hypothalamus were also examined. In addition, histamine and orexin neurons in the hypothalamus were simultaneously identified using rat histidine decarboxylase and orexin-A immunohistochemistry, respectively. Both energy expenditure and anxiety-related behavior significantly increased by the experimental 3-day sleep deprivation, while exploratory locomotor activity significantly decreased. Histamine contents did not change in the cortex, but significantly decreased in the diencephalon of sleep-deprived rats. Increased expression of c-Fos-positive neurons, including subgroup histamine and orexin neurons, was observed in the hypothalamus. These findings indicate that sleep deprivation increases energy expenditure and anxiety in adolescent rats and provide evidence for the pivotal role of hypothalamus subgroup histamine and orexin neurons in the behavioral response to sleep deprivation.

Effects of a chicken extract on food-deprived activity stress in rats.

A water-soluble chicken extract is popularly consumed as a traditional health food. The studies made revealed that it could increase the survival time and inhibit the increase of locomotor activity in rats loaded with food-deprived activity stress. The mechanism for this might be related to an elevation of the brain histamine level, and the active ingredient, carnosine, might contribute to this effect.

Decreased CSF histamine in narcolepsy with and without low CSF hypocretin-1 in comparison to healthy controls.

STUDY OBJECTIVE: To examine whether cerebrospinal fluid (CSF) histamine contents are altered in human narcolepsy and whether these alterations are specific to hypocretin deficiency, as defined by low CSF hypocretin-1. METHODS: Patients meeting the ICSD-2 criteria for narcolepsy with and without cataplexy and who had CSF hypocretin-1 results available were selected from the Stanford Narcolepsy Database on the basis of CSF availability and adequate age and sex matching across 3 groups: narcolepsy with low CSF hypocretin-1 (n=34, 100% with cataplexy), narcolepsy without low CSF hypocretin-1 (n=24, 75% with cataplexy), and normal controls (n=23). Low CSF hypocretin-1 was defined as CSF < or =110 pg/mL (1/3 of mean control values). Six of 34 patients with low CSF hypocretin-1, six of 24 subjects with normal CSF hypocretin-1, and all controls were unmedicated at the time of CSF collection. CSF histamine was measured in all samples using a fluorometric HPLC system. RESULTS: Mean CSF histamine levels were: 133.2 +/- 20.1 pg/mL in narcoleptic subjects with low CSF hypocretin-1, 233.3 +/- 46.5 pg/mL in patients with normal CSF hypocretin-1 (204.9 +/- 89.7 pg/mL if only patients without cataplexy are included), and 300.5 +/- 49.7 pg/mL in controls, reaching statistically significant differences between the 3 groups. CONCLUSION: CSF histamine levels are reduced in human narcolepsy. The reduction of CSF histamine levels was more evident in the cases with low CSF hypocretin-1, and levels were intermediate in other narcolepsy cases. As histamine is a wake-promoting amine known to decrease during sleep, decreased histamine could either passively reflect or partially mediate daytime sleepiness in these pathologies.

Methamphetamine- and 3,4-methylenedioxymethamphetamine-induced behavioral changes in histamine H3-receptor knockout mice.

Histamine H(3) receptors inhibit the release of not only histamine itself, but also other neurotransmitters including dopamine. Previous papers have reported that histaminergic neurons inhibit psychostimulant-induced behavioral changes. To examine whether deficiency in histamine H(3) receptors influences psychostimulant-induced behavioral sensitization and reward, we examined locomotor activity, conditioned place preference (CPP), and c-Fos expression in histamine H(3) receptor-gene knockout mice (H3KO) and their wild-type (WT) counterparts before and after treatment with methamphetamine (METH) and 3,4-methylenedioxymethamphetamine (MDMA). The increase in locomotion induced by treatment with METH or MDMA was lower in histamine H3KO mice than in WT mice, while the locomotor sensitization was developed by METH or MDMA in both strains. However, no significant difference in METH- and MDMA-induced preference scores of CPP between histamine H3KO mice and WT mice was observed. Following treatment with METH, the number of c-Fos-positive neurons in the the caudate-putamen of histamine H3KO mice was lower than that in the caudate-putamen of WT mice. In contrast, there was no significant difference in the number of the psychostimulant-induced c-Fos-positive cells in the nucleus accumbens between the two strains of mice. These findings suggest that deficiency in histamine H(3) receptors may have inhibitory effects on psychostimulant-induced increase in locomotion, but insignificant effects on the reward.

Selective cognitive dysfunction in mice lacking histamine H1 and H2 receptors.

Previous pharmacological experiments provide conflicting findings that describe both facilitatory and inhibitory effects of neuronal histamine on learning and memory. Here, we examined learning and memory and synaptic plasticity in mice with a null mutation of gene coding histamine H1 or H2 receptor in order to clarify the role of these receptors in learning and memory processes. Learning and memory were evaluated by several behavioral tasks including object recognition, Barnes maze and fear conditioning. These behavioral tasks are highly dependent on the function of prefrontal cortex, hippocampus or amygdala. Object recognition and Barnes maze performance were significantly impaired in both H1 receptor gene knockout (H1KO) and H2 receptor gene knockout (H2KO) mice when compared to the respective wild-type (WT) mice. Conversely, both H1KO and H2KO mice showed better auditory and contextual freezing acquisition than their respective WT mice. Furthermore, we also examined long-term potentiation (LTP) in the CA1 area of hippocampus in H1KO and H2KO mice and their respective WT mice. LTP in the CA1 area of hippocampus was significantly reduced in both H1KO and H2KO mice when compared with their respective WT mice. In conclusion, our results demonstrate that both H1 and H2 receptors are involved in learning and memory processes for which the frontal cortex, amygdala and hippocampus interact.

Effects of histamine H(3) antagonists and donepezil on learning and mnemonic deficits induced by pentylenetetrazol kindling in weanling mice.

Childhood epilepsy is one of the main risk factors for a variety of problems involving cognition and behavior. Pentylenetetrazol (PTZ) kindling is currently an acceptable model for epilepsy research. The objectives of this study are to clarify the learning and mnemonic characteristics of PTZ kindling in developing mice, and to examine the effects of thioperamide and JNJ-5207852, two histamine H(3) receptor antagonists and donepezil, an acetylcholinesterase (AChE) inhibitor, on learning and memory deficits induced by PTZ kindling in the brains of developing mice. PTZ kindling led to learning and mnemonic deficits as assessed by social discrimination, acoustic fear conditioning, water maze and passive avoidance tests. Thioperamide and JNJ-5207852, ameliorated PTZ kindling-induced learning and mnemonic deficits in all tests except for the water maze test. In addition, the learning and mnemonic impairments induced by PTZ kindling were significantly improved by donepezil in all tests. These findings suggest that histamine and acetylcholine are involved in the different processes of learning and memory in the brain and that histamine H(3) receptor antagonists might be useful in the treatment of cognitive impairment in epilepsy.

Blockage of histamine H1 receptor attenuates social isolation-induced disruption of prepulse inhibition: a study in H1 receptor gene knockout mice.

RATIONALE: Histaminergic neurotransmission has been implicated in the pathophysiology of stress-related psychiatric diseases. Although several atypical antipsychotics are potent H1 antagonists, the clinical significance of interaction between atypical antipsychotics and H1 receptors is still unknown. OBJECTIVE: In this study, we investigated the effects of H1 receptors blockage on social isolation-induced behavioral changes in H1 receptor gene knockout (H1KO) mice and their wild-type (WT) mice. METHODS: Both H1KO and their WT mice were subjected to 4-week social isolation rearing after weaning (21 postnatal days). After the 4-week isolation period, mice behavioral changes were evaluated using behavioral tests. RESULTS: Locomotor activity in home cages was significantly lower in isolation-reared WT mice than in socially reared WT mice. However, no change in locomotor activity was observed between socially and isolation-reared H1KO mice. Social isolation significantly impaired prepulse inhibition (PPI) of startle response in WT mice but not in H1KO mice. In addition, social isolation significantly impaired spatial learning and memory in WT mice but not in H1KO mice. Furthermore, H1KO mice treated with methamphetamine (METH) showed no enhancement in isolation-induced disruption of PPI. A neurochemical study revealed that isolation-reared WT mice had significantly lower dopamine (DA) levels and slightly increased DA turnover in the cortex than socially reared WT mice. Conversely, isolation-reared H1KO mice showed significantly higher DA contents as compared with socially reared H1KO mice. CONCLUSION: The results of our study indicate that blockage of H1 receptor-mediated neurotransmission attenuates social isolation-induced behavioral changes and that the therapeutic effects of atypical antipsychotics are mediated, at least in part, by interaction with H1 receptors in the brain.