Quantitative prediction of CYP3A-mediated drug-drug interactions by correctly estimating fraction metabolized using human liver chimeric mice.

BACKGROUND AND PURPOSE: Fraction metabolized (fm ) and fraction transported (ft ) are important for understanding drug-drug interactions (DDIs) in drug discovery and development. However, current in vitro systems cannot accurately estimate in vivo fm due to inability to reflect the ft by efflux transporters (ft,efflux ). This study demonstrates how CYP3A-mediated DDI for CYP3A/P-gp substrates can be predicted using Hu-PXB mice as human liver chimeric mice. EXPERIMENTAL APPROACH: For estimating human in vitro fm by CYP3A enzyme (fm,CYP3A,in vitro ), six drugs, including CYP3A/P-gp substrates (alprazolam, cyclosporine, docetaxel, midazolam, prednisolone, and theophylline) and human hepatocytes were incubated with or without ketoconazole as a CYP3A inhibitor. We calculated fm,CYP3A,in vitro based on hepatic intrinsic clearance. To estimate human in vivo fm,CYP3A (fm,CYP3A,in vivo ), we collected information on clinical DDI caused by ketoconazole for these six drugs. We calculated fm,CYP3A,in vivo using the change of total clearance (CLtotal ). For evaluating the human DDI predictability, the six drugs were administered intravenously to Hu-PXB and SCID mice with or without ketoconazole. We calculated the change of CLtotal caused by ketoconazole. We compared the CLtotal change in humans with that in Hu-PXB and SCID mice. KEY RESULTS: The fm,CYP3A,in vitro was overestimated compared to the fm,CYP3A,in vivo . Hu-PXB mice showed much better correlation in the change of CLtotal with humans (R2 = 0.95) compared to SCID mice (R2 = 0.0058). CONCLUSIONS AND IMPLICATIONS: CYP3A-mediated DDI can be predicted by correctly estimating human fm,CYP3A,in vivo using Hu-PXB mice. These mice could be useful predicting hepatic fm and ft,efflux .

A novel 1-bp deletion variant in DAG1 in Japanese familial asymptomatic hyper-CK-emia.

Asymptomatic hyper-CK-emia (ASCK) is characterized by persistent elevation of creatine kinase (CK) in serum without any neurological symptoms. We ascertained a two-generation family of ASCK patients without clear neurological abnormalities except for the high levels of serum CK (810.5 ± 522.4 U/L). We identified a novel 1-bp deletion variant in the DAG1 gene shared by the patients in the family (NM_001177639: exon 3: c.930delC:p.R311Gfs*70). The variant causes premature termination of translation at codon 477, resulting in a protein product completely devoid of the essential DAG1 domain. Since ASCK has been associated with DAG1 in only one case carrying compound heterozygous missense variants, our new finding of a novel 1-bp deletion revealed the previously unknown dominant effect of DAG1 on ASCK.

Familial paroxysmal kinesigenic dyskinesia with a novel missense variant (Arg2866Trp) in NBEA.

Paroxysmal kinesigenic dyskinesia (PKD) is a movement disorder characterized by episodic involuntary movement attacks triggered by sudden movements, acceleration, or intention to move. We ascertained two Japanese familial cases with PKD. The proband is a 22-year-old woman who had noted sudden brief (<30 s) of involuntary movements provoked by kinesigenic trigger such as starting to run, getting on a train, picking up a telephone receiver and so on at the age of 14. Interictal brain single photon emission computed tomography (SPECT) showed hyperperfusion in the left thalamus. A 46-year-old woman, the mother of the proband was also suffering from brief attacks triggered by starting to run in her high school days. On neurological examination, both showed no abnormality. Whole exome sequencing combined with rigorous filtering revealed two heterozygous nonsynonymous variants (NM_001447: c.8976G > C [p.Gln2992His] in FAT2 and NM_015678: c.8596C > T [p.Arg2866Trp] in NBEA). Real time quantitative PCR analysis of Nbea mRNA levels in the developing rat brain revealed peak at postnatal day 28 and decline at postnatal day 56. This result might match the most common clinical course of PKD from the point of view of the most common age at remission. NBEA has been reported to be responsible for neurodevelopmental disease accompanied by epilepsy. We concluded the variant in NBEA most likely to be responsible for our familial cases of PKD.

Ddhd1 knockout mouse as a model of locomotive and physiological abnormality in familial spastic paraplegia.

We have previously reported a novel homozygous 4-bp deletion in DDHD1 as the responsible variant for spastic paraplegia type 28 (SPG28; OMIM#609340). The variant causes a frameshift, resulting in a functionally null allele in the patient. DDHD1 encodes phospholipase A1 (PLA1) catalyzing phosphatidylinositol to lysophosphatidylinositol (LPI). To clarify the pathogenic mechanism of SPG28, we established Ddhd1 knockout mice (Ddhd1[-/-]) carrying a 5-bp deletion in Ddhd1, resulting in a premature termination of translation at a position similar to that of the patient. We observed a significant decrease in foot-base angle (FBA) in aged Ddhd1(-/-) (24 months of age) and a significant decrease in LPI 20:4 (sn-2) in Ddhd1(-/-) cerebra (26 months of age). These changes in FBA were not observed in 14 months of age. We also observed significant changes of expression levels of 22 genes in the Ddhd1(-/-) cerebra (26 months of age). Gene Ontology (GO) terms relating to the nervous system and cell-cell communications were significantly enriched. We conclude that the reduced signaling of LPI 20:4 (sn-2) by PLA1 dysfunction is responsible for the locomotive abnormality in SPG28, further suggesting that the reduction of downstream signaling such as GPR55 which is agonized by LPI is involved in the pathogenesis of SPG28.

Intronic variant in IQGAP3 associated with hereditary neuropathy with proximal lower dominancy, urinary disturbance, and paroxysmal dry cough.

In 2008, we reported a clinically and genetically new type of autosomal dominant disorder of motor and sensory neuropathy with proximal dominancy in the lower extremities, urinary disturbance, and paroxysmal dry cough. To identify the nucleotide variant causative of this disease, we reanalyzed the linkage of the original Japanese pedigree including seven newly ascertained subjects with updated information. We assigned the locus of the disease to 1p13.3-q23 (maximum logarithm-of-odds score = 2.71). Exome sequencing for five patients and one healthy relative from the pedigree revealed 2526 patient-specific single-nucleotide variants (SNVs). By rigorous filtering processes using public databases, our linkage results, and functional prediction, followed by Sanger sequencing of the pedigree and 520 healthy Japanese individuals, we identified an intronic SNV in IQGAP3, a gene known to be associated with neurite outgrowth. Upon pathological examination of the sural nerve, moderate, chronic, mainly axonal neuropathy was observed. By histochemical analyses, we observed a patient-specific increase of IQGAP3 expression in the sural nerve. We concluded that the variant of IQGAP3 is associated with the disease in our pedigree.

Spinocerebellar ataxia 27 with a novel nonsense variant (Lys177X) in FGF14.

Spinocerebellar ataxia 27 (SCA27) is an autosomal dominant SCA caused by variants in the fibroblast growth factor 14 (FGF14) gene. We examined a Japanese SCA patient whose deceased father also suffered from SCA. The patient was a 63-year-old male. He graduated from junior high school but received no further education. The predominant complaint was slowly progressive dysarthria and gait disturbance, which appeared at age 47. He showed pathological saccadic dysmetria, saccadic intrusions into smooth pursuit eye movements, dysarthria, and limb and truncal ataxia. His gait was wide-based but he did not require a walking stick. Limb muscle strength was intact. Deep tendon reflexes were normal or slightly reduced. Pathological reflexes were absent. He demonstrated mildly impaired vibration sense in the lower limbs. There was no urinary dysfunction. Brain MRI showed cerebellar atrophy without brainstem involvement. We first confirmed the absence of repeat expansion in genes known to be responsible for SCAs 1-3, 6-8, 10, 12, 17, 36 and dentatorubral-pallidoluysian atrophy. By exome analysis, we identified a novel heterozygous variant (NM_004115, c.529A>T; Lys177X) in exon 4 of the FGF14 gene. This variant is expected to generate a truncated FGF14 protein lacking the heparin binding sites, those are likely to modify the activity of FGF14. We confirmed the absence of the variant in 502 healthy Japanese individuals by Sanger sequencing. There is no record of the variant in public databases. We conclude that the novel variation in FGF14 is causative for SCA27 in this patient.

TDRKH is a candidate gene for an autosomal dominant distal hereditary motor neuropathy.

Distal hereditary motor neuropathies (dHMNs) comprise a group of clinically and genetically heterogeneous inherited lower motor neuron syndromes mainly characterized by a distal-predominant pattern of progressive muscle atrophy, weakness and hyporeflexia, without sensory dysfunction. Although at least 21 causative genes for dHMN have been reported, mutational scanning of these genes often fails to identify the causative variants in dHMN cohorts, suggesting that additional causative genes remain to be identified. We studied a four-generation pedigree of a Japanese family with autosomal dominant dHMN to provide insight into the pathogenetic basis of the disease. Neurological examinations were performed on all six family members enrolled in this study. Whole-exome sequencing (WES) was used to identify the causative gene for dHMN. The clinical features of the patients included muscle weakness with distal extensor dominancy in the lower extremities, accompanied by facial and neck flexor muscle impairment, no sensory involvement, and areflexia. Nerve conduction studies demonstrated axonal changes mainly in the peroneal nerve. WES combined with rigorous filtering revealed three missense variants (NM_001083964: c.851G > A [p.Arg284His] in TDRKH, NM_002858: c.1654G > T [p.Gly552Cys] in ABCD3, NM_001005164: c.898A > T [p.Ile300Phe], in OR52E2). The variant in TDRKH is located in a conserved region of the tudor domain which is also present in the survival of motor neuron (SMN) protein, encoded by the SMN1 gene. Therefore, we concluded the variant in TDRKH is likely to be responsible for dHMN in our pedigree.

Effect of kumquat (Fortunella crassifolia) pericarp on natural killer cell activity in vitro and in vivo.

Natural killer (NK) cells play a key role in innate immune defense against infectious disease and cancer. A reduction of NK activity is likely to be associated with increased risk of these types of disease. In this study, we investigate the activation potential of kumquat pericarp acetone fraction (KP-AF) on NK cells. It is shown to significantly increase IFN-γ production and NK cytotoxic activity in human KHYG-1 NK cells. Moreover, oral administration of KP-AF significantly improves both suppressed plasma IFN-γ levels and NK cytotoxic activity per splenocyte in restraint-stressed mice. These results indicate that raw kumquat pericarp activates NK cells in vitro and in vivo. To identify the active constituents, we also examined IFN-γ production on KHYG-1 cells by the predicted active components. Only ß-cryptoxanthin increased IFN-γ production, suggesting that NK cell activation effects of KP-AF may be caused by carotenoids such as ß-cryptoxanthin.