Conditional knockout of transient receptor potential melastatin 7 in the enamel epithelium: Effects on enamel formation.

Transient receptor potential melastatin 7 (TRPM7) is a unique ion channel connected to a kinase domain. We previously demonstrated that Trpm7 expression is high in mouse ameloblasts and odontoblasts, and that amelogenesis is impaired in TRPM7 kinase-dead mice. Here, we analyzed TRPM7 function during amelogenesis in Keratin 14-Cre;Trpm7fl/fl conditional knockout (cKO) mice and Trpm7 knockdown cell lines. cKO mice showed lesser tooth pigmentation than control mice and broken incisor tips. Enamel calcification and microhardness were lower in cKO mice. Electron probe microanalysis (EPMA) showed that the calcium and phosphorus contents in the enamel were lower in cKO mouse than in control mice. The ameloblast layer in cKO mice showed ameloblast dysplasia at the maturation stage. The morphological defects were observed in rat SF2 cells with Trpm7 knockdown. Compared with mock transfectants, the Trpm7 knockdown cell lines showed lower levels of calcification with Alizarin Red-positive staining and an impaired intercellular adhesion structures. These findings suggest that TRPM7 is a critical ion channel in enamel calcification for the effective morphogenesis of ameloblasts during amelogenesis.

Development of immunohistochemistry for detecting fluvoxamine in rat tissues using newly prepared monoclonal antibody: its precise localization in small intestine, kidney, and liver of rats.

A monoclonal antibody (mAb) was produced against a fluvoxamine (FLV)-bovine serum albumin conjugate that was specific to both the conjugate and free form of FLV. The mAb enabled us to develop an immunohistochemistry (IHC) method for pharmacokinetic analysis of FLV at the cell and tissue levels. We demonstrated that IHC can be used to detect the localization of FLV in the small intestine, kidney, and liver 1 h after drug administration at the cell and tissue levels. Protease digestion is an important factor for obtaining appropriate IHC staining results for localization of drugs. In this study, precise FLV localization could be determined with only 1 h of protease digestion in the kidneys, but in the small intestine and liver, the staining results with two digestive conditions had to be merged. IHC provided new findings, such as (1) nerve cells are likely to uptake more FLV than other cells and tissues; (2) the ability of reabsorption and secretion in the kidney varies depending on the site, and the amount of FLV in the primary urine is regulated downstream of the proximal tubule S3 segment; and (3) some of the FLV is excreted in the bile.

An Indirect Competitive Enzyme-Linked Immunosorbent Assay for the Determination of Brigatinib and Gilteritinib Using a Specific Polyclonal Antibody.

Brigatinib and gilteritinib are oral tyrosine kinase inhibitors (TKIs). We aimed to develop a simple and sensitive indirect competitive enzyme-linked immunosorbent assay (ELISA) to quantify brigatinib and gilteritinib in various biological matrices. Antiserum against these TKIs was obtained from mice by using 3-methoxy-4-(-4-(4-methylpiperazin-1-yl) piperidin-1-yl) aniline as a hapten, which has a common substructure with these TKIs. The generated antibody was used to develop an indirect competitive ELISA for these TKIs in human serum. The lower limit of quantification of brigatinib and gilteritinib in human serum was 6.2 and 6.8 ng/mL, respectively. The developed ELISA was used to examine the pharmacokinetics of these TKIs after oral administration in mice and rats. This ELISA is expected to be a valuable tool in pharmacokinetic studies of these TKIs.

Bone morphogenetic protein induces bone invasion of melanoma by epithelial-mesenchymal transition via the Smad1/5 signaling pathway.

Oral malignant melanoma, which frequently invades the hard palate or maxillary bone, is extremely rare and has a poor prognosis. Bone morphogenetic protein (BMP) is abundantly expressed in bone matrix and is highly expressed in malignant melanoma, inducing an aggressive phenotype. We examined the role of BMP signaling in the acquisition of an aggressive phenotype in melanoma cells in vitro and in vivo. In five cases, immunohistochemistry indicated the phosphorylation of Smad1/5 (p-Smad1/5) in the nuclei of melanoma cells. In the B16 mouse and A2058 human melanoma cell lines, BMP2, BMP4, or BMP7 induces morphological changes accompanied by the downregulation of E-cadherin, and the upregulation of N-cadherin and Snail, markers of epithelial-mesenchymal transition (EMT). BMP2 also stimulates cell invasion by increasing matrix metalloproteinase activity in B16 cells. These effects were canceled by the addition of LDN193189, a specific inhibitor of Smad1/5 signaling. In vivo, the injection of B16 cells expressing constitutively activated ALK3 enhanced zygoma destruction in comparison to empty B16 cells by increasing osteoclast numbers. These results suggest that the activation of BMP signaling induces EMT, thus driving the acquisition of an aggressive phenotype in malignant melanoma.

Development of a Competitive Enzyme-Linked Immunosorbent Assay for the Determination of Sunitinib Unaffected by Light-Induced Isomerization.

Sunitinib is an oral multi-targeted tyrosine kinase inhibitor approved for treating metastatic renal cell carcinoma. This study reports a specific and sensitive competitive enzyme-linked immunosorbent assay (ELISA) for the pharmacokinetic evaluation of sunitinib. Anti-sunitinib serum was obtained from mice by using N-(2-(diethylamino)ethyl)-5-formyl-2,4-dimethyl-1H-pyrrole-3-carboxamide (DFPC) as a hapten, which has the same substructure as sunitinib, in order to avoid the effects of structural changes in the geometrical isomers of sunitinib. Enzyme labeling of sunitinib with horseradish peroxidase was similarly performed using DFPC. Serum sunitinib concentrations below the limit of quantification of 0.52 ng/mL were reproducibly measurable. This ELISA was specific for sunitinib (Z- and E-isomers) and showed very low cross-reactivity (0.094%) with its major metabolite, N-desethyl sunitinib. Its analytical applicability was demonstrated by a kinetic study with human liver microsomes. In addition, the levels of sunitinib measured by ELISA in a kinetic study with human liver microsomes were comparable with those measured by HPLC, and there was a strong correlation between the values determined by both methods (y = 1.065x - 51.2, R2 = 0.9804). The developed ELISA provides for the specific and sensitive quantification of sunitinib without the influence of its major metabolite or light-induced geometric isomers. This ELISA will be a valuable tool in pharmacokinetic studies of sunitinib.

Immunohistochemical localization and pharmacokinetics of the anti-MRSA drug teicoplanin in rat kidney using a newly developed specific antibody.

We prepared a polyclonal antibody against a teicoplanin (TEIC)-bovine serum albumin conjugate that was specific to both conjugated and free forms of TEIC. We demonstrated that this antibody could be used to detect the time-dependent localization of TEIC in rat kidneys. Immunohistochemistry revealed immunoreactivity specifically in the microvilli and apical cytoplasm of epithelial cells in proximal tubule segments S1 and S2, 1 h after intravenous TEIC injection, with higher staining intensity in the S2 segments. The epithelial cells of S3 segments showed moderate immunostaining with a few cells exhibiting nuclear staining. Furthermore, we found that the distal tubules and collecting ducts contained both TEIC-positive and -negative cells. TEIC immunoreactivity decreased rapidly over time; only weak staining remained in the S3 segments, distal tubules, and collecting ducts 24 h after administration. No staining was detected 7 days after injection. These results were significantly different from those of our previous study obtained using vancomycin, which showed moderate staining in the proximal tubule segments S1 and S2, distal tubules, and the collecting ducts 8 days after administration. The lower TEIC accumulation in tissues may account for a lower risk of adverse events compared to that using vancomycin.

Development of a sandwich enzyme-linked immunosorbent assay for the quantification of ponatinib in serum.

The tyrosine kinase inhibitor ponatinib is extensively metabolized in the body, and consequently the development of specific immunoassays for pharmacokinetic studies and therapeutic drug monitoring of ponatinib is challenging. If two antibodies simultaneously recognize the entire structure of ponatinib, they could be utilized to establish an ultra-specific sandwich immunoassay for ponatinib, free of any interference from ponatinib metabolites. In this study, we created two types of anti-ponatinib polyclonal antibodies that recognize two different ponatinib epitopes, and sandwiched almost all structural components of ponatinib in these two antibodies in order to develop an enzyme-linked immunosorbent assay (ELISA) technique not affected by any ponatinib metabolites. After optimization, this sandwich ELISA showed a linear detection range of 640 pg/mL to 2000 ng/mL and a limit of quantification of 640 pg/mL. This sandwich ELISA was specific to ponatinib and showed no cross-reactivity with the major metabolite M14. Comparison between the sandwich ELISA and HPLC, using serum samples from 15 rats orally administered a single dose of 15 mg/kg ponatinib, showed a linear regression (y = 0.9662x + 3.5354, r = 0.9683). Thus, in this study, we successfully developed the first ultra-specific sandwich ELISA for ponatinib in serum.

Expression and distribution patterns of spermine, spermidine, and putrescine in rat hair follicle.

No expression and distribution patterns of polyamines (PAs), spermine, spermidine, and their precursor putrescine in mammalian hair follicle are available, although polyamines are known to correlate well with hair growth and epidermal tumor genesis. Immunohistochemistry (IHC) using our original two monoclonal antibodies (mAbs) ASPM-29 specific for spermine or spermidine, and APUT-32 specific for putrescine allowed us to detect immunoreactivity for polyamines in hair follicles from normal adult rats. A wide range of immunoreactivity for the total spermine and spermidine was observed in the compartments of hair follicle: The highest degree of immunoreactivity for polyamines was observed in the matrix, in the Huxley's layer, in the deeper Henle's layer, and in the cuticle of the inner root sheath/the hair cuticle, while moderate immunoreactivity existed in the lower-to-mid cortex and the companion layer, followed by lower immunoreactivity in the outer root sheath, including the bulge region and in the deeper medulla, in which the immunoreactivity was also evident in their nuclei. In addition, somewhat surprisingly, with IHC by APUT-32 mAb, we detected significant levels of putrescine in the compartments, in which the immunostaining pattern was the closely similar to that of the total spermine and spermidine. Thus, among these compartments, the cell types of the matrix, the Huxley's layer, the deeper Henle's layer, and the cuticle of the inner root sheath/the hair cuticle seem to have the biologically higher potential in compartments of anagen hair follicle, maybe suggesting that they are involved more critically in the biological event of hair growth. In addition, we noted sharp differences of immunostaining by IHCs between ASPM-29 mAb and APUT-32 mAb in the epidermis cells and fibroblast. ASPM-29 mAb resulted in strong staining in both the cell types, but APUT-32 mAb showed only very light staining in both types. Consequently, the use of the two IHCs could be extremely useful in further studies on hair cycle and epidermal tumor genesis experimentally or clinically.

Preparation of Antibodies and Development of an Enzyme-Linked Immunosorbent Assay for the Tyrosine Kinase Inhibitors Lapatinib and Nilotinib.

In this paper, we describe the production of the first specific antibodies against the tyrosine kinase inhibitors lapatinib and nilotinib. Anti-lapatinib antibody was obtained by immunizing rabbits with an antigen conjugated with bovine serum albumin using 3-chloro-4-((3-fluorobenzyl)oxy)aniline. Anti-nilotinib antibody was produced by immunizing mice with an antigen conjugated with bovine serum albumin using 2-(5-amino-2-methylanilino)-4-(3-pyridyl)pyrimidine. The generated antibodies were used to develop highly sensitive and specific enzyme-linked immunosorbent assays (ELISAs) for lapatinib and nilotinib in human serum. The assays were capable of detecting lapatinib and nilotinib at serum concentrations as low as 40 and 8 ng/mL, respectively. Using the two ELISAs, drugs levels were easily measured in the serum of rats after a single dose oral administration of lapatinib or nilotinib. The assays are therefore expected be valuable tools for therapeutic drug monitoring in the clinical setting and pharmacokinetic studies of lapatinib and nilotinib.

Quantification of Sorafenib in Human Serum by Competitive Enzyme-Linked Immunosorbent Assay.

The multikinase inhibitor sorafenib has been used in the treatment of hepatocellular carcinoma, renal cell carcinoma, and differentiated thyroid carcinoma. Here we have demonstrated the production of the first specific antibody against sorafenib. Anti-sorafenib serum was obtained by immunizing mice with an antigen conjugated with bovine serum albumin and carboxylic modified 4-(4-aminophenoxy)-N-methyl-2-pyridinecarboxamide (AMPC) using the N-succinimidyl ester method. Enzyme labeling of sorafenib with horseradish peroxidase was similarly performed using carboxylic modified AMPC. A simple competitive enzyme-linked immunosorbent assay (ELISA) for sorafenib was developed using the principle of direct competition between sorafenib and the enzyme marker for anti-sorafenib antibody, which had been adsorbed by the plastic surface of a microtiter plate. Serum sorafenib concentrations lower than 0.04 µg/mL were reproducibly measurable using the ELISA. This ELISA was specific to sorafenib and showed very slight cross-reactivity (2.5%) with a major metabolite, sorafenib N-oxide. The values of serum sorafenib levels from 32 patients measured by this ELISA were comparable with those measured by HPLC, and there was a strong correlation between the values determined by the two methods (Y=1.016X-0.137, r=0.979). The specificity and sensitivity of the ELISA for sorafenib should provide a valuable new tool for use in therapeutic drug monitoring and pharmacokinetic studies of sorafenib.

Establishment of a novel model of chondrogenesis using murine embryonic stem cells carrying fibrodysplasia ossificans progressiva-associated mutant ALK2.

Fibrodysplasia ossificans progressiva (FOP) is a genetic disorder characterized by heterotopic endochondral ossification in soft tissue. A mutation in the bone morphogenetic protein (BMP) receptor ALK2, R206H, has been identified in patients with typical FOP. In the present study, we established murine embryonic stem (ES) cells that express wild-type human ALK2 or typical mutant human ALK2 [ALK2(R206H)] under the control of the Tet-Off system. Although wild-type ALK2 and mutant ALK2(R206H) were expressed in response to a withdrawal of doxycycline (Dox), BMP signaling was activated only in the mutant ALK2(R206H)-expressing cells without the addition of exogenous BMPs. The Dox-dependent induction of BMP signaling was blocked by a specific kinase inhibitor of the BMP receptor. The mutant ALK2(R206H)-carrying cells showed Dox-regulated chondrogenesis in vitro, which occurred in co-operation with transforming growth factor-ß1 (TGF-ß1). Overall, our ES cells are useful for studying the molecular mechanisms of heterotopic ossification in FOP in vitro and for developing novel inhibitors of chondrogenesis induced by mutant ALK2(R206H) associated with FOP.

Identification of a novel bone morphogenetic protein (BMP)-inducible transcript, BMP-inducible transcript-1, by utilizing the conserved BMP-responsive elements in the Id genes.

Bone morphogenetic proteins (BMPs) inhibit myogenesis and induce osteoblastic differentiation in myoblasts. They also induce the transcription of several common genes, such as Id1, Id2 and Id3, in various cell types. We have reported that a GC-rich element in the Id1 gene functions as a BMP-responsive element (BRE) that is regulated by Smads. In this study, we analyzed and identified BREs in the 5'-flanking regions of the mouse Id2 and Id3 genes. The core GGCGCC sequence was conserved among the BREs in the Id1, Id2 and Id3 genes and was essential for the response to BMP signaling via Smads. We found a novel BRE on mouse chromosome 13 at position 47,723,740-47,723,768 by searching for conserved sequences containing the Id1 BRE. This potential BRE was found in the 5'-flanking region of a novel gene that produces a non-coding transcript, termed BMP-inducible transcript-1 (BIT-1), and this element regulated the expression of this gene in response to BMP signaling. We found that BIT-1 is expressed in BMP target tissues such as the testis, brain, kidney and cartilage. These findings suggest that the transcriptional induction of the Ids, BIT-1 and additional novel genes containing the conserved BRE sequence may play an important role in the regulation of the differentiation and/or function of target cells in response to BMPs.

Development of a specific and sensitive enzyme-linked immunosorbent assay for the quantification of imatinib.

Imatinib is an oral tyrosine kinase inhibitor used for first-line treatment of chronic myeloid leukemia. Therapeutic drug monitoring targeting trough plasma levels of about 1000 ng/mL may help to optimize imantinib's therapeutic effect. This paper reports a specific and sensitive enzyme-linked immunosorbent assay (ELISA) for a pharmacokinetic evaluation of imatinib. Anti-imatinib antibody was obtained by immunizing rabbits with an antigen conjugated with bovine serum albumin and succinimidyl 4-{(4-methyl-1-piperazinyl)methyl}-benzoate. Enzyme labeling of imatinib with horseradish peroxidase was similarly performed using succinimidyl 4-{(4-methyl-1-piperazinyl)methyl}-benzoate. A simple ELISA for imatinib was developed using the principle of direct competition between imatinib and the enzyme marker for anti-imatinib antibody which had been adsorbed by the plastic surface of a microtiter plate. Serum imatinib concentrations lower than 40 pg/mL were reproducibly measurable using the ELISA. This ELISA was specific to imatinib and showed very slight cross-reactivity (1.2%) with a major metabolite, N-desmethyl imatinib. Using this assay, drug levels were easily measured in the blood of mice after their oral administration of imatinib at a single dose of 50 mg/kg. The specificity and sensitivity of the ELISA for imatinib should provide a valuable new tool for use in therapeutic drug monitoring and pharmacokinetic studies of imatinib.

Mobility gene expression differences among wild-type, Mmp20 null and Mmp20 over-expresser mice plus visualization of 3D mouse ameloblast directional movement.

Enamel forming ameloblasts move away from the dentino-enamel junction and also move relative to each other to establish enamel shape during the secretory stage of enamel development. Matrix metalloproteinase-20 (MMP20) is a tooth specific proteinase essential for proper enamel formation. We previously reported that MMP20 cleaves cadherins and may regulate ameloblast movement. Here, we used an Amelx promoter driven tdTomato reporter to label mouse ameloblasts. With these transgenic mice, we assessed ameloblast mobility group dynamics and gene expression. Three-dimensional imaging of mouse ameloblasts were observed in hemi-mandibles by using a tissue clearing technique. The three-dimensional ameloblast layer in Tg(Amelx-Mmp20) mice that overexpress MMP20 was uneven and the ameloblasts migrated away from this layer. Mouse ameloblast movement toward incisal tips was monitored by ex vivo time-lapse imaging. Gene expression related to cell migration and adhesion was analyzed in ameloblasts from wild-type mice, Mmp20-/- mice with no functional MMP20 and from Tg(Amelx-Mmp20) overexpressing mice. Gene expression was altered in Mmp20-/- and Tg(Amelx-Mmp20) mice compared to wild type. Among the genes assessed, those encoding laminins and a gap junction protein were upregulated in Mmp20-/- mice. New techniques and findings described in this study may lead to an improved understanding of ameloblast movement during enamel formation.

Localization of Sites of Osimertinib Action in Rat Intestine, Skin, and Lung by Immunohistochemistry.

Osimertinib is a third-generation, irreversible tyrosine kinase inhibitor (TKI) of epidermal growth factor receptor (EGFR) that selectively inhibits both EGFR-TKI-sensitizing and EGFR T790M resistance mutations and has shown efficacy in patients with non-small-cell lung cancer. In this study, we created osimertinib-specific antibodies and developed an immunohistochemistry (IHC) for locating the sites of osimertinib action. Moreover, we located osimertinib-protein conjugates in intestinal, dermal, and lung tissues of rats, thereby using our IHC to visualize the sites of the adverse effects of osimertinib, including diarrhea, skin disorder, and interstitial pneumonia. This report is the first to elucidate the localization of the sites of action of osimertinib in the rat intestine, skin, and lung and is expected to help clarify the mechanism of osimertinib-induced adverse effects.

Mesenchymal cell TRPM7 expression is required for bone formation via the regulation of chondrogenesis.

Transient receptor potential melastatin-subfamily member 7 (TRPM7) is a bifunctional protein containing a kinase fused to an ion channel permeated with cations, including Ca2+ and Mg2+. Trpm7-null mice show embryonic lethality. Paired related homeobox 1 (Prx1) is expressed in undifferentiated mesenchymal cells such as the progenitor cells of both chondrocytes and osteoblasts involved in limb skeleton formation. Prx1-Cre-dependent Trpm7 mesenchymal-deleted mice were generated to examine the role of TRPM7 in bone development. We found that Prx1-Cre;Trpm7fl/fl mice had shortened bones and impaired trabecular bone formation. Trabecular bone parameters, such as the bone volume (BV/TV), and trabecular number (Tb.N), were decreased in Prx1-Cre;Trpm7fl/fl mice. The cortical bone parameters of cortical bone area (Ct.Ar) and cortical bone thickness (Ct.Th) were also down-regulated in these mice. The bone formation rate in Prx1-Cre;Trpm7fl/fl mice was unchanged, but the hypertrophic area and cell size of the zone were smaller, and the expression of Col2a1, Col10a1 and Mmp13 was downregulated compared with control mice. These findings suggest impaired chondrogenesis in Prx1-Cre;Trpm7fl/fl mice compared to control mice. The receptor activator of nuclear factor-kappa B ligand (RANKL) expression was increased, and RANKL-positive cells and osteoclasts were markedly accumulated in the boundary region between the growth plate and trabecular bone. In contrast, TRPM7 KR mice, which are kinase-dead mutants in which the TRPM7 ion channel function has not been altered, showed no marked differences in trabecular or cortical bone parameters compared to wild-type mice. These findings suggest that TRPM7 is critical as a cation channel rather than as a kinase in bone development via the regulation of chondrogenesis.

Identification and functional analysis of Zranb2 as a novel Smad-binding protein that suppresses BMP signaling.

Smads 1/5/8 transduce the major intracellular signaling of bone morphogenetic proteins (BMPs). In the present study, we analyzed Smad1-binding proteins in HEK293T cells using a proteomic technique and identified the protein, zinc-finger, RAN-binding domain-containing protein 2 (ZRANB2). Zranb2 interacted strongly with Smad1, Smad5, and Smad8 and weakly with Smad4. The overexpression of Zranb2 inhibited BMP activities in C2C12 myoblasts in vitro, and the injection of Zranb2 mRNA into zebrafish embryos induced weak dorsalization. Deletion analyses of Zranb2 indicated that the serine/arginine-rich (SR) domain and the glutamine-rich domain were required for the inhibition of BMP activity and the interaction with Smad1, respectively. Zranb2 was found to be localized in the nucleus; however, the SR domain-deleted mutant localized to the cytoplasm. The knockdown of endogenous Zranb2 in C2C12 cells enhanced BMP activity. Zranb2 suppressed Smad transcriptional activity without affecting Smad phosphorylation, nuclear localization, or DNA binding. Taken together, these findings suggested that Zranb2 is a novel BMP suppressor that forms a complex with Smads in the nucleus.

Selective inhibition of NF-κB suppresses bone invasion by oral squamous cell carcinoma in vivo.

Nuclear factor-κB (NF-κB) is constitutively activated in many cancers, including oral squamous cell carcinoma (OSCC), and is involved in the invasive characteristics of OSCC, such as growth, antiapoptotic activity and protease production. However, the cellular mechanism underlying NF-κB's promotion of bone invasion by OSCC is unclear. Therefore, we investigated the role of NF-κB in bone invasion by OSCC in vivo. Immunohistochemical staining of OSCC invading bone in 10 patients indicated that the expression and nuclear translocation of p65, a main subunit of NF-κB, was increased in OSCC compared with normal squamous epithelial cells. An active form of p65 phosphorylated at serine 536 was present mainly in the nucleus in not only differentiated tumor cells but also tumor-associated stromal cells and bone-resorbing osteoclasts. We next injected mouse OSCC SCCVII cells into the masseter region of C(3) H/HeN mice. Mice were treated for 3 weeks with a selective NF-κB inhibitor, NBD peptide, which disrupts the association of NF-κB essential modulator (NEMO) with IκB kinases. NBD peptide treatment inhibited TNFα-induced and constitutive NF-κB activation in SCCVII cells in vitro and in vivo, respectively. Treatment with NBD peptide decreased zygoma and mandible destruction by SCCVII cells, reduced number of osteoclasts by inhibiting RANKL expression in osteoblastic cells and SCCVII cells, increased apoptosis and suppressed the proliferation of SCCVII cells. Taken together, our data clearly indicate that inhibition of NF-κB is useful for inhibiting bone invasion by OSCC.

Immunocytochemistry for vancomycin using a monoclonal antibody that reveals accumulation of the drug in rat kidney and liver.

We prepared monoclonal antibodies against N-(γ-maleimidobutyryloxy)succinimide-conjugated vancomycin (VM). The monoclonal antibody was specific for conjugated or free VM. The monoclonal antibody enabled us to develop an immunocytochemical method for detecting the uptake of VM in the rat kidney and liver. Three hours after a single intravenous (i.v.) injection of VM at the therapeutic dose, the immunocytochemistry revealed that VM accumulated in large amounts in both the S1 and S2 segments and in much smaller amounts in the S3 segment of the proximal tubules as well as in the distal tubules and collecting ducts. The drug was detected in the cytoplasm, cytoplasmic irregular granules, nuclei, and microvilli of the proximal tubule cells. The distal tubules and collecting ducts contained scattered swollen cells in which both the nuclei and cytoplasm were heavily immunostained. Twenty-four hours after injection, most of the swollen cells returned back to normal size and had somewhat decreased immunostaining. Also, significant amounts of VM remained accumulated for as long as 8 days postadministration. In the liver, similar drug accumulation was observed in the Kupffer cells and the endothelial cells of the hepatic sinusoids but not in the hepatocytes, suggesting that vancomycin cannot be eliminated via the liver. Immunoelectron microscopic studies demonstrated that in the collecting ducts, uptake of VM occurred exclusively in the lysosomes and cytoplasm of the principal cells and scarcely in the intercalated cells. Furthermore, double fluorescence staining using rats simultaneously administered with VM and gentamicin strongly suggests that both drugs colocalized in lysosomes in the proximal tubule cells of kidneys.

Immunohistochemical Localization of Alogliptin, a DPP-4 Inhibitor, in Tissues of Normal and Type 2 Diabetes Model Rat.

We investigated the pharmacokinetics of alogliptin (AG) at the cell and tissue level in healthy Wistar rats and a type 2 diabetic Goto-Kakizaki (GK) rat model. Immunohistochemistry of the renal tissue in these rats, post 1 hr of AG administration, showed that the signal was observed in the glomeruli, proximal tubule S3 segments, distal tubules, collecting ducts, and only in the brush border of the epithelial cells of the proximal tubule S1, S2 segments. After 6 hr of AG administration, the staining intensity of the regions other than the S3 segments was considerably reduced in Wistar rats, with no change observed in GK rats. At 24 hr, the staining intensity was considerably reduced, even in GK rats; however, the staining of the S3 segment remained unaltered in both. Hepatocytes in zone III of the hepatic lobule were more intensely stained than those in zone I in Wistar rats at 1 hr. However, almost no staining was observed in the hepatocytes of GK rats at 1 hr. Complete loss of signal was observed in the hepatocytes of the Wistar rats after 6 hr. This study revealed that the pharmacokinetics of AG in GK rats are different from those in Wistar rats.