Takafumi Ohmura

Involvement of a rapamycin-sensitive pathway in CD40-mediated activation of murine B cells in vitro

Activation of resting B cells requires an initial triggering of the B cell antigen receptor (BCR) and secondary stimuli through various cytokine receptors and B cell activation molecules including CD40. We found that activation of B cells through CD40 is selectively inhibited by an immunosuppressant drug, rapamycin. This effect of rapamycin on anti-CD40-mediated activation of B cells was observed using three different in vitro assays. Rapamycin suppressed the anti-CD40-induced proliferation of splenic B cells, suppressed differentiation to surface IgMhigh/IgDlow B cells, and inhibited an anti-CD40-mediated prevention of apoptosis induced by BCR cross-linkage of WEHI-231 cells. We next examined several known CD40 signal transduction pathways to identify the target of rapamycin in stimulated B cells. Rapamycin did not inhibit the activation of c-Jun N-terminal kinases (JNKs) induced by anti-CD40 stimulation nor the activation of immediate nuclear transcription factors of NF-kappaB. Therefore, rapamycin affects a novel element of the CD40 signal transduction pathway which influences the proliferation, differentiation, and prevention of apoptosis of B cells.

Trial of intraventricular ribavirin therapy for subacute sclerosing panencephalitis in Japan

Ten patients with SSPE were surveyed during the last 4 years from the viewpoint of clinical safety for use of ribavirin therapy. Although effectiveness varied among cases, they were all treated safely with intraventricular ribavirin. This study suggests that treatment is safe and well-tolerated.

Bromocriptine Reverses P-Glycoprotein-mediated Multidrug Resistance in Tumor Cells

One of the most important causes of anticancer treatment failure is the development of multidrug resistance (MDR). The main characteristics of tumor cells displaying the MDR phenomena are cross‐resistance to structurally unrelated cytotoxic drugs having different mechanisms of action and the overexpression of the MDR1 gene, which encodes a transmembrane glycoprotein named P‐ glycoprotein (P‐gp). This study evaluated whether bromocriptine, a D2 dopaminergic receptor agonist, influenced anticancer drug cytotoxicity and P‐gp activity in a P‐gp‐expressing cell line compared to a non‐expressing subline. The Ki values for P‐gp of cyclosporine and verapamil were 1.09 and 540 μM, respectively, and that of bromocriptine was 6.52 μM in a calcein‐AM efflux assay using porcine kidney epithelial LLC‐PK1 and L‐MDR1 cells, overexpressing human P‐gp. Bromocriptine at 10 μM reduced the IC50 of doxorubicin (DXR) in K562‐DXR from 9000 to 270 ng/ml and that of vincristine (VCR) in K562‐VCR from 700 to 0.30 ng/ml, whereas the IC50 values of DXR and VCR in the K562 subline were only marginally affected by these drugs. Bromocriptine restored the anticancer effect of DXR, VCR, vinblastine, vinorelbine and etoposide on MDR‐tumor cells overexpressing P‐gp. These observations suggest that bromocriptine has the potential to reverse tumor MDR involving the efflux protein P‐gp in the clinical situation.

Case study : differences in human Per2 gene expression, body temperature, cortisol, and melatonin parameters in remission and hypersomnia in a patient with recurrent hypersomnia

Recurrent hypersomnia is characterized by recurring episodes of hypersomnia of 18 h or more per day lasting from several days to several weeks. We report the case of a 17‐year‐old male subject with recurrent hypersomnia who displayed change in the 24 h expression of the hPer2 gene in whole red and white blood cells as well as markers [deep body temperature (DBT) and cortisol] of the circadian time structure during an episode of hypersomnia compared to remission. The patient was studied for the temporal characteristics of hPer2 gene, DBT, cortisol, and melatonin expression during a single 24 h span during an episode of hypersomnia and again during a single 24 h span in the following remission. The approximation of a 24 h cosine curve to the time series data revealed circadian rhythmicity (P < 0.05) only in DBT in the two stages of the disease with differences in amplitude and acrophase. Cortisol circadian rhythmicity was detected during remission, but not during hypersomnia. Statistically significant differences were detected by ANOVA between the remission and active disease stages in the 24 h mean level of hPer2 gene expression (P < 0.05), cortisol (P < 0.05), and DBT (P < 0.05). The findings of this case study suggest the expression of hPer2 gene and alterations in circadian time structure might play an important role in the pathogenesis of recurrent hypersomnia, although additional study is required.

The structure and expression of the guinea pig Fc receptor for IgG1 and IgG2 (Fcγ1/γ2R)

Abstract A cDNA clone encoding the receptor for guinea pig immunoglobulin G was isolated from a guinea pig peritoneal macrophage cDNA library. The cloned cDNA encoded 271 amino acids containing an N-terminal signal sequence. The deduced amino acid sequence is most homologous to murine FcγRIIs 2 . The receptor protein could be expressed in COS-7 and L cells transfected with the cDNA, suggesting that the expression of this receptor does not require the co-expression of a second chain such as γ chain of FceRI or CD3ζ chain. The transformant L cells showed the binding to both the guinea pig IgG1 and IgG2 antibodies complexed with antigen, indicating that the cDNA we cloned was the one for guinea pig Fcγ 1 /γ 2 R.

Carbamazepine-imatinib interaction in a child with chronic myeloid leukemia

Imatinib mesylate, a selective tyrosine kinase inhibitor, is the frontline therapeutic agent used for the treatment of chronic myeloid leukemia (CML), and its therapeutic efficacy is associated with trough concentrations. Therefore, monitoring imatinib trough concentrations is strongly recommended for successful treatment of CML patients. It has been recently shown that some drugs altered imatinib plasma levels in adult patients. However, drug interactions with imatinib in children are still unknown. Here, we report a case of a 12‐year‐old child with epilepsy who was also diagnosed with CML and given imatinib in addition to an enzyme‐inducing antiepileptic drug, carbamazepine. Compared to population kinetics data, the data obtained for the patient showed a significant decrease of imatinib plasma concentrations. Our findings suggest that monitoring imatinib plasma concentrations in children receiving enzyme‐inducing antiepileptic drugs is needed to optimize the therapeutic efficacy of imatinib.

Dissection of the Role of Macrophages in Triggering T Lymphocytes for Interleukin 2 Production by Monoclonal Antibody OKT3

Unfractionated human peripheral blood mononuclear cells produce a small amount of interleukin 2 (IL 2) by stimulation with a monoclonal anti‐T3 antibody (OKT3) in vitro. The IL 2 production could be greatly augmented by the addition of a phorbol ester, 12‐O‐tetradecanoyl‐phorbol‐13‐acetate (TPA).

False tacrolimus concentrations measured by antibody-conjugated magnetic immunoassay in liver transplant patient: 2 case reports and literature review.

Safe use of tacrolimus relies on regular whole-blood drug monitoring. Of the methods used to assess whole-blood tacrolimus concentration, antibody-conjugated magnetic immunoassay is mostly used for therapeutic drug monitoring because it requires only a minimal sample preparation and no pretreatment procedure. However, several cases recently have been reported in which abnormally false elevated tacrolimus concentrations were measured by antibody-conjugated magnetic immunoassay (>15 ng/mL), despite the absence of clinical symptoms. We present 2 cases of falsely detected tacrolimus concentrations that did not show abnormally high values within the therapeutic range. Whole-blood tacrolimus concentrations obtained by antibody-conjugated magnetic immunoassay showed well-controlled concentrations (approximately 2-8 ng/mL), whereas those obtained by another immunoassay and in washed erythrocytes were below the assay range (< 1.2 ng/mL). Thus, antibody-conjugated magnetic immunoassay can elicit falsely positive results of tacrolimus concentrations, even though they are within the therapeutic range.

A reduced linezolid dosage maintains favorable efficacy with minimal hematologic toxicity in a methicillin-resistant Staphylococcus aureus-infected patient with renal insufficiency

Abstract The optimal dosage of linezolid to avoid hematologic toxicity is unknown. We report the case of an 87-y-old woman with renal insufficiency who developed a surgical site infection with refractory methicillin-resistant Staphylococcus aureus. The standard dosage of linezolid (1200 mg daily) was not initially tolerated by the patient due to severe thrombocytopenia, but she was successfully treated when the dose was reduced by half (600 mg daily) based on a population pharmacokinetic–pharmacodynamic model. Appropriate dose adjustments can be made to optimize linezolid therapy especially in cases with preexisting renal dysfunction.

Structural differences among guinea pig Fcγ1γ2 receptors on macrophages, polymorphonuclear cells, and lymphocytes

Using the cDNA, D-3, coding for Fc gamma 1/gamma 2 receptor of guinea pig macrophages that binds IgG1 and IgG2 (Fc gamma 1/gamma 2R), we examined the cell distribution of this receptor by RNA blot analysis. The Fc gamma 1/gamma 2R mRNA was expressed in polymorphonuclear cells and B cells as well as in macrophages, but not at the detectable level in T cells. The cDNA amplified from RNA of polymorphonuclear cells in the polymerase chain reaction was the same as D-3. The cDNA of B cells was found to have about 140 bp cDNA segment inserted to the cytoplasmic tail of D-3. We found that the cDNA amplified from T cell RNA differed in signal peptide and extracellular domain sequence from cDNAs of other cell types. This cDNA does not seem to be amplified from the mRNAs of contaminating other cell types.