Mast cells are major players in allergic responses. IgE-dependent activation through Fc epsilon RI leads to degranulation and cytokine production, both of which require Gab2. To clarify how the signals diverge at Gab2, we established Gab2 knock-in mice that express Gab2 mutated at either the PI-3K- or SHP-2-binding sites. Examination of these mutants showed that both binding sites were required for the degranulation and anaphylaxis response, but not for cytokine production or contact hypersensitivity. Furthermore, the PI-3K- but not the SHP-2-binding site was important for granule translocation during degranulation. We also identified a small GTPase, ARF1, as the downstream target of PI-3K that regulates granule translocation. Fc epsilon RI-stimulation induced ARF1 activation, and this response was dependent on Fyn and the PI-3K-binding site of Gab2. ARF1 activity was required for the Fc epsilon RI-mediated granule translocation. These results indicate that Fyn/Gab2/PI-3K/ARF1-mediated signaling is specifically involved in granule translocation and the anaphylaxis response. In this review, I discussed how Gab2 controls biological events especially for mast cell degranulation and allergy response.
B cells positively regulate immune responses through antibody production and effector T cell differentiation. In addition to such protective roles against pathogenesis, B cells also serve as negative regulators of autoimmunity by secreting an anti-inflammatory cytokine, interleukin-10 (IL-10). These B cell functions are caused by encountering their cognate antigens through their B cell receptors (BCR). A central response of BCR stimulation is intracellular Ca2+ elevation, which is derived mainly from two pathways, Ca2+ release from endoplasmic reticulum (ER) stores and Ca2+ influx from the extracellular space across the plasma membrane. Although a chief Ca2+ entry pathway in immune cells is store-operated Ca2+ (SOC) influx, which is triggered by depletion of Ca2+ from ER, its physiological role in B cells remains elusive. Stromal interaction molecules (STIM), which consist of STIM1 and its homolog, STIM2, serve as ER calcium sensors and are essential for SOC influx after antigen stimulation. We have recently found that STIM1- and STIM2-induced SOC influx is critical for regulatory B cell function required to limit experimental autoimmune encephalomyelitis (EAE), a mouse model of multiple sclerosis. Even through several B cell populations have been reported to suppress inflammation of autoimmune diseases through production of IL-10, which subset of them exerts their regulatory function during EAE is not fully understood. This review focuses on our recent progress in the role of STIM-dependent SOC influx as a key signal for B cell regulatory function and the latest findings for understanding how regulatory B cells suppress the development of EAE.
Immune system is high-dimensional integrated system distributed in the whole body. Many kinds of, total 1011 of immune cells are regulated by receiving appropriate signals in appropriate places. We have been attempting to understand immune system by revealing spatiotemporal regulation of immune cells at the whole body level by “Visualization of immune response in vivo”. Photoconvertible protein, “Kaede”-Tg mice allowed us to monitor cell-replacement and cell-movement in the whole body by marking cells with color of Kaede from green to red with exposure to violet light. It is applicable to small cell number populations in both lymphoid organs and also peripheral tissues under both normal and pathophysiological conditions. By using this system, we have demonstrated novel findings that “Naive CD4+ T cell recirculation is an active process that they recirculate through lymphoid organs to seek limited niche for interacting with endogenous antigens and upregulate their function.” and “Activated regulatory T cells emigrating from cutaneous immune response is responsible for termination of immune reponse.” I will introduce these new tools of us and would like to discuss what is needed to understand immune system in the entire body.
Dysregulation of the production of reactive oxygen species (ROS) determines cellular function. Cytochrome P450s (CYPs) regulates ROS production and contributes to the process of cell death. This review summarizes our recent findings, focusing on the involvement of CYPs in pathophysiology induced by ROS. 1. Quinone toxicity in hepatocytes: CYPs require electrons supplied from NADPH-cytochrome P450 reductase (NPR) during the process of metabolism. NPR also provides electrons to quinone compounds, which compete with CYPs over electrons. Inhibition of CYPs shifts NPR's electron flow more to quinones, which accelerates the redox cycle to enhance ROS production and quinone toxicity. 2. Myocardial ischemia-reperfusion injury: Reperfusion of blood flow after coronary artery occlusion induces cell damage, as evident by the extension of myocardial infarct size and caspase-independent cell apoptosis. CYP2C6 appears to be a source for ROS production, since sulfaphenazole, a selective inhibitor of CYP2C6, reduces this damage. ROS produced by CYP2C6 during the reperfusion causes translational activation of Noxa and BimEL, as well as the suppression of caspase activation, resulting in caspase-independent apoptosis. 3. Primary hepatocyte apoptosis: Inhibition of catalase and glutathione peroxidase increases intracellular ROS and elicits caspase-independent hepatocyte apoptosis. SKF-525A, a pan-CYP inhibitor, suppresses these ROS increases and hepatocyte apoptosis. Increased ROS activates ERK and AP-1 by inhibition of tyrosine phosphatase, and inhibits BimEL degradation by proteasome. These results in the accumulation of mitochondrial BimEL, which then induces the release of cytochrome c and endonuclease G (EndoG). Increased ROS also keeps caspases inactivated. As a result, EndoG executes nucleosomal DNA fragmentation.
Recent studies revealed the importance of transporters in the behaviors of small molecules in the body. In mammals, the presence of a lot of transporters has been suggested, such as ATP-binding cassette (ABC) transporters and solute ligand carrier (SLC) transporters, some of which are clarified to be causative genes for various kinds of genetic disorders. In addition, a lot of transporters are known to mediate cellular import or export of drugs, to contribute to the pharmacokinetics of substrate drugs and to be involved in the interindividual differences of drug responses. In this review, I introduce our recent work on the transporter-mediated regulation of pharmacokinetics of lifestyle-related substances, such as cholesterol and urate.
The present study has investigated the effect of tacrolimus on the pharmacokinetics of an active metabolite of irinotecan (CPT-11), 7-ethyl-10-hydroxy-camptothecin (SN-38) and SN-38 glucuronide (SN-38G) in rats. The effect of tacrolimus on SN-38 glucuronidation was also investigated in human and rat liver microsomes. When tacrolimus (0.5 mg/kg) was intravenously injected in rats 15 min before intravenous injection of CPT-11 (5 mg/kg), tacrolimus decreased the plasma concentration of SN-38G. Tacrolimus significantly decreased the area under plasma concentration-time curve (AUC) of SN-38G without change in the mean residence time. On the contrary, significant changes in the pharmacokinetic parameters of SN-38 were not observed. SN-38 glucuronidation in human and rat liver microsomes was inhibited dose-dependently by the presence of tacrolimus and the 50% inhibition concentration (IC50) values of tacrolimus in rat and human liver microsomes were 10.33 μM and 3.58 μM, respectively. When the inhibition type was determined by Lineweaver-Burk and Dixon plots, the inhibition was noncompetitive and the calculated inhibition constant (Ki) values for rat and human liver microsomes were 12.57 μM and 3.88 μM, respectively. These findings suggest that tacrolimus inhibits UGT1A1-mediated SN-38 glucuronidation. Considering the IC50 and Ki values for tacrolimus, it is likely that tacrolimus does not alter the pharmacokinetics of SN-38 and SN-38G at the clinically used dosages, suggesting the possibility that tacrolimus can use safely for cancer patients with irinotecan chemotherapy.
In recent years there has been a rise in the number of diabetic patients in Japan, with the increase in elderly diabetic patients becoming a serious problem. This study looked at 488 elderly type 2 diabetes patients who were admitted as emergency cases to the Department of Internal Medicine, JA Yoshida General Hospital, Akitakada City, Japan. All patients were classified by age into three groups: <70, 70-80 and >80. The most common cause of emergency hospitalization in each of the three age groups was infection. This was significantly higher in the >80 group in comparison with<70 (p<0.05). The most common infection among the three groups was respiratory infection, followed by urinary tract infection. The number of emergency hospitalization cases due to hypoglycemia was much higher in the over 80 group, particularly in comparison with<70-80 (p<0.05). The incidence of hypoglycemia in our patients could be explained mainly by reduced energy intake. Most cases were treated with oral administration of hypoglycemic drugs. As elderly diabetic patients have a number of underlying illnesses that are prone to aggravation and may lead to unfavorable prognosis, early medical examination and disease detection are considered to be important. Pharmacists are required to educate patients, home-visit nursing care personnel on sick-day rule, and provide diabetes care.
One of the major roles of a school pharmacist is to maintain adequate air conditioning in the school to prevent the spread of infectious diseases. Influenza, the most important infectious disease at school, can be a cause of temporary closure of classes. We ordinarily examine relative humidity (RH), a popular parameter in the pharmaceutical field. However, RH is the ratio of vapor pressure to saturation vapor pressure at the indicated temperature and does not indicate the actual amount of water in the atmosphere. RH is temperature-dependent and varies easily with temperature. The use of absolute humidity (AH) is not common among school pharmacists because calculating AH from the measured temperature is not straightforward. In addition, commercially available humidity meters are usually designed for RH. We surveyed the relationship between climate data and influenza epidemics in Kobe from 2007 to 2012. We found that AH is more closely correlated with the number of patients than RH and that there is an AH threshold at which an influenza outbreak can occur in Kobe: 10 g/m3. The 2009 epidemic pattern, when influenza A (H1N1) virus spread throughout the country, was irregular and AH did not correlate with the number of patients. Because AH can be easily measured using a computer without the need of any additional instruments, we suggest that school pharmacists utilize AH in combination with temperature as a better parameter for predicting the onset of influenza epidemics. When AH in Kobe decreases to 10 g/m3, schools should be immediately cautioned.