Identification of N-acyl-N-indanyl-α-phenylglycinamides as selective TRPM8 antagonists designed to mitigate the risk of adverse effects.

Transient receptor potential melastatin 8 (TRPM8), a temperature-sensitive ion channel responsible for detecting cold, is an attractive molecular target for the treatment of pain and other disorders. We have previously discovered a selective TRPM8 antagonist, KPR-2579, which inhibited bladder afferent hyperactivity induced by acetic acid instillation into the bladder. However, additional studies have revealed potential adverse effects with KPR-2579, such as the formation of a reactive metabolite, CYP3A4 induction, and convulsions. In this report, we describe the optimization of α-phenylglycinamide derivatives to mitigate the risk of these adverse effects. The optimal compound 13x exhibited potent inhibition against icilin-induced wet-dog shakes and cold-induced frequent voiding in rats, with a wide safety margin against the potential side effects.

KPR-5714, a Novel Transient Receptor Potential Melastatin 8 Antagonist, Improves Overactive Bladder via Inhibition of Bladder Afferent Hyperactivity in Rats.

Transient receptor potential (TRP) melastatin 8 (TRPM8) is a temperature-sensing ion channel mainly expressed in primary sensory neurons (Aδ-fibers and C-fibers in the dorsal root ganglion). In this report, we characterized KPR-5714 (N-[(R)-3,3-difluoro-4-hydroxy-1-(2H-1,2,3-triazol-2-yl)butan-2-yl]-3-fluoro-2-[5-(4-fluorophenyl)-1H-pyrazol-3-yl]benzamide), a novel and selective TRPM8 antagonist, to assess its therapeutic potential against frequent urination in rat models with overactive bladder (OAB). In calcium influx assays with HEK293T cells transiently expressing various TRP channels, KPR-5714 showed a potent TRPM8 antagonistic effect and high selectivity against other TRP channels. Intravenously administered KPR-5714 inhibited the hyperactivity of mechanosensitive C-fibers of bladder afferents and dose-dependently increased the intercontraction interval shortened by intravesical instillation of acetic acid in anesthetized rats. Furthermore, we examined the effects of KPR-5714 on voiding behavior in conscious rats with cerebral infarction and in those exposed to cold in metabolic cage experiments. Cerebral infarction and cold exposure induced a significant decrease in the mean voided volume and increase in voiding frequency in rats. Orally administered KPR-5714 dose-dependently increased the mean voided volume and decreased voiding frequency without affecting total voided volume in these models. This study demonstrates that KPR-5714 improves OAB in three different models by inhibiting exaggerated activity of mechanosensitive bladder C-fibers and suggests that KPR-5714 may provide a new and useful approach to the treatment of OAB. SIGNIFICANCE STATEMENT: TRPM8 is involved in bladder sensory transduction and plays a role in the abnormal activation in hypersensitive bladder disorders. KPR-5714, as a novel and selective TRPM8 antagonist, may provide a useful treatment for the disorders related to the hyperactivity of bladder afferent nerves, particularly in overactive bladder.

KPR-2579, a novel TRPM8 antagonist, inhibits acetic acid-induced bladder afferent hyperactivity in rats.

AIMS: Transient receptor potential melastatin 8 (TRPM8) is proposed to be a promising therapeutic target for hypersensitive bladder disorders. We examined the effects of KPR-2579, a novel selective TRPM8 antagonist, on body temperature and on mechanosensitive bladder single-unit afferent activities (SAAs) provoked by intravesical acetic acid (AA) instillation in rats. METHODS: Female Sprague-Dawley rats were used. Effects of cumulative intravenous (i.v.) administrations of KPR-2579 (0.03-1 mg/kg) on deep body temperature were investigated (N = 18). In separate animals, effects of bolus administration of KPR-2579 (0.03 or 0.3 mg/kg, i.v.) on bladder hyperactivity induced by intravesical instillation of 0.1% AA were investigated using cystometry (N = 57) in a conscious free-moving condition or urethane-anesthetized condition, and SAA measurements (N = 41) were performed in a urethane-anesthetized condition. RESULTS: KPR-2579 at any doses tested did not affect body temperature. In cystometry measurements, a high dose (0.3 mg/kg) of KPR-2579 counteracted the shortened intercontraction interval provoked by AA instillation. In SAA measurements, 48 single afferent fibers (n = 24 in each fiber) were isolated. AA instillations significantly increased the SAAs of C fibers, but not of Aδ fibers, in the presence of KPR-2579's vehicle and a low dose (0.03 mg/kg) of KPR-2579. Pretreatment with a high dose (0.3 mg/kg) of KPR-2579 significantly inhibited the AA-induced activation of C-fiber SAAs. CONCLUSION: The present results suggest that TRPM8 channels play a role in the AA-induced pathological activation of mechanosensitive bladder C fibers in rats. KRP-2579 may be a promising drug for hypersensitive bladder disorders.

Synthesis and optimization of novel α-phenylglycinamides as selective TRPM8 antagonists.

Transient receptor potential melastatin 8 (TRPM8) is activated by innocuous cold and chemical substances, and antagonists of this channel have been considered to be effective for pain and urinary diseases. N-(3-aminopropyl)-2-{[(3-methylphenyl)methyl]oxy}-N-(2-thienylmethyl)benzamide hydrochloride (AMTB), a TRPM8 antagonist, was proposed to be effective for overactive bladder and painful bladder syndrome; however, there is a potential risk of low blood pressure. We report herein the synthesis and structure-activity relationships of novel phenylglycine derivatives that led to the identification of KPR-2579 (20l), a TRPM8 selective antagonist. KPR-2579 reduced the number of icilin-induced wet-dog shakes and rhythmic bladder contraction in rats, with no negative cardiovascular effects at the effective dose.

Synthesis and structure-activity relationships of 1-benzylindane derivatives as selective agonists for estrogen receptor beta.

The estrogen receptor beta (ERß) selective agonist is considered a promising candidate for the treatment of estrogen deficiency symptoms in ERß-expressing tissues, without the risk of breast cancer, and multiple classes of compounds have been reported as ERß selective agonists. Among them, 6-6 bicyclic ring-containing structures (e.g., isoflavone phytoestrogens) are regarded as one of the cyclized analogues of isobutestrol 5b, and suggest that other cyclized scaffolds comprising 5-6 bicyclic rings could also act as selective ERß ligands. In this study, we evaluated the selective ERß agonistic activity of 1-(4-hydroxybenzyl)indan-5-ol 7a and studied structure-activity relationship (SAR) of its derivatives. Some functional groups improved the properties of 7a; introduction of a nitrile group on the indane-1-position resulted in higher selectivity for ERß (12a), and further substitution with a fluoro or a methyl group to the pendant phenyl ring was also preferable (12b, d, and e). Subsequent chiral resolution of 12a identified that R-12a has a superior profile over S-12a. This is comparable to diarylpropionitrile (DPN) 5c, one of the promising selective ERß agonists and indicates that this indane-based scaffold has the potential to provide better ERß agonistic probes.

TAK-441, a novel investigational smoothened antagonist, delays castration-resistant progression in prostate cancer by disrupting paracrine hedgehog signaling.

Hedgehog (Hh) signaling is a highly conserved intercellular and intracellular communication mechanism that governs organogenesis and is dysregulated in cancers of numerous tissues, including prostate. Up-regulated expression of the Hh ligands, Sonic (Shh) and Desert (Dhh), has been reported in androgen-deprived and castration-resistant prostate cancer (CRPC). In a cohort of therapy naive, short- and long-term neoadjuvant hormone therapy-treated (NHT), and CRPC specimens, we observed elevated Dhh expression predominantly in long-term NHT specimens and elevated Shh expression predominantly in CRPC specimens. Together with previously demonstrated reciprocal signaling between Shh-producing prostate cancer (PCa) cells and urogenital mesenchymal fibroblasts, these results suggest that castration-induced Hh expression promotes CRPC progression through reciprocal paracrine signaling within the tumor microenvironment. We tested whether the orally available Smoothened (Smo) antagonist, TAK-441, could impair castration-resistant progression of LNCaP PCa xenografts by disrupting paracrine Hh signaling. Although TAK-441 or cyclopamine did not affect androgen withdrawal-induced Shh up-regulation or viability of LNCaP cells, castration-resistant progression of LNCaP xenografts was significantly delayed in animals treated with TAK-441. In TAK-441-treated xenografts, expression of murine orthologs of the Hh-activated genes, Gli1, Gli2 and Ptch1, was substantially suppressed, while expression of the corresponding human orthologs was unaffected. As androgen-deprived LNCaP cells up-regulate Shh expression, but are not sensitive to Smo antagonists, these studies indicate that TAK-441 leads to delayed castration-resistant progression of LNCaP xenografts by disrupting paracrine Hh signaling with the tumor stroma. Thus, paracrine Hh signaling may offer unique opportunities for prognostic biomarker development, drug targeting and therapeutic response monitoring of PCa progression.

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.

Cutaneous magnetic stimulation reduces rat chronic pain via activation of the supra-spinal descending pathway.

Recent studies have demonstrated that magnetic stimulation (MS) can induce cellular responses such as Ca(2+) influx into the cultured neurons and glia, leading to increased intracellular phosphorylation. We have demonstrated previously that MS reduces rat neuropathic pain associated with the prevention of neuronal degeneration. Thus, we aimed to elucidate the actions of MS in relation to modulation of spinal neuron-glia and the descending inhibitory system in chronic pain. The male SD rats intrathecally implanted with catheters were subjected to sciatic nerve ligation (CCI). MS is a low power apparatus characterized by two different frequencies, 2 KHz and 83 MHz. Rats were given MS to the skin (injured sciatic nerve) for 10 min from the seventh day after CCI. The paw withdrawal latency (PWL) evoked by thermal stimuli was measured for 14 days after CCI. Immunohistochemistry for Iba-1 or GFAP was performed after 4% paraformaldehyde fixation (microscopic analysis). We employed microdialysis for measuring CSF 5-HIAA as a reflection of 5-HT release by MS stimulation. Following CCI, rats showed a decrease in PWL after CCI, and the decrease continued until the 14th day. With MS treatment, the decrease in PWL was reduced during the 10-14 day after CCI. Injection of JNK-1 inhibitors on the 14th day antagonized the analgesic effect of MS. MS also eliminated the CCI-induced decrease in GFAP immunoreactivity. Moreover, MS evoked spinal 5-HT release reflected by increase in spinal 5-HIAA level. Thus, we demonstrate that a novel magnetic stimulator used cutaneously can ameliorate chronic pain by not only preventing abnormal spinal neuron-glia interaction, but also through the activation of the supra-spinal descending inhibitory system.

Efficacy of the combination of KPR-5714, a novel transient receptor potential melastatin 8 (TRPM8) antagonist, and ß3-adrenoceptor agonist or anticholinergic agent on bladder dysfunction in rats with bladder overactivity.

Transient receptor potential melastatin 8 (TRPM8) channels may contribute to the pathophysiological bladder afferent hyperactivity, thus a TRPM8 antagonist would be a promising therapeutic target for the bladder hypersensitive disorders including urinary urgency in overactive bladder (OAB). We aimed to investigate a pharmacological effect of KPR-5714, a novel selective TRPM8 antagonist, on TRPM8 channels, M3 receptors and ß3-adrenoceptors using the transfected cells of each gene at first. Then, combination effects of KPR-5714 and mirabegron, a ß3-adrenoceptor agonist, or tolterodine tartrate, an anticholinergic agent, were studied on rhythmic bladder contractions (RBCs) in normal rats and bladder function in frequent-voiding rats. In vitro measurements showed that KPR-5714 acts on neither ß3-adrenoceptor nor M3 receptor. In normal rats, KPR-5714 and mirabegron significantly reduced the frequency of RBCs, and a combined administration showed an additive effect. In rats with cerebral infarction, KPR-5714 and mirabegron significantly reduced the voiding frequency, and a combined administration showed an additive effect. In rats exposed to cold temperature, KPR-5714 and tolterodine tartrate significantly reduced the voiding frequency accompanied by the increased mean voided volume, and a combined administration showed additive effects. The present study demonstrated that the combined administration of KPR-5714 and mirabegron or tolterodine tartrate showed the additive effects on bladder dysfunction in different animal models, suggesting that the combination therapy of TRPM8 antagonist and ß3-adrenoceptor agonist or anticholinergic agent can be the potential treatment option for obtaining additive effects in comparison with monotherapy for OAB.

Effect of WAVE2 phosphorylation on activation of the Arp2/3 complex.

Members of the family of WASP-family Verprolin homologous proteins (WAVEs) activate the Arp2/3 complex to induce actin polymerization. The WAVE family comprises three proteins, namely, WAVE1, WAVE2 and WAVE3. Among them, WAVE2 is crucial for activation of the Arp2/3 complex for the formation of branched actin filaments in lamellipodia. Activation of mitogen-activated protein (MAP) kinase signalling results in the phosphorylation of the WAVE family proteins; however, which of the three WAVE proteins is phosphorylated is unclear. We found that in vitro WAVE2 is directly phosphorylated by a MAP kinase, i.e. extracellular signal-regulated kinase (ERK) 2. The proline-rich region and the verprolin, cofilin and acidic (VCA) region of WAVE2 were phosphorylated. Interestingly, the phosphorylated VCA region had a higher affinity for the Arp2/3 complex. However, the phosphorylation of the VCA region resulted in reduced induction of Arp2/3-mediated actin polymerization in vitro. The role of the phosphorylation of the proline-rich region was not determined.

CLK-dependent exon recognition and conjoined gene formation revealed with a novel small molecule inhibitor.

CDC-like kinase phosphorylation of serine/arginine-rich proteins is central to RNA splicing reactions. Yet, the genomic network of CDC-like kinase-dependent RNA processing events remains poorly defined. Here, we explore the connectivity of genomic CDC-like kinase splicing functions by applying graduated, short-exposure, pharmacological CDC-like kinase inhibition using a novel small molecule (T3) with very high potency, selectivity, and cell-based stability. Using RNA-Seq, we define CDC-like kinase-responsive alternative splicing events, the large majority of which monotonically increase or decrease with increasing CDC-like kinase inhibition. We show that distinct RNA-binding motifs are associated with T3 response in skipped exons. Unexpectedly, we observe dose-dependent conjoined gene transcription, which is associated with motif enrichment in the last and second exons of upstream and downstream partners, respectively. siRNA knockdown of CLK2-associated genes significantly increases conjoined gene formation. Collectively, our results reveal an unexpected role for CDC-like kinase in conjoined gene formation, via regulation of 3'-end processing and associated splicing factors.The phosphorylation of serine/arginine-rich proteins by CDC-like kinase is a central regulatory mechanism for RNA splicing reactions. Here, the authors synthesize a novel small molecule CLK inhibitor and map CLK-responsive alternative splicing events and discover an effect on conjoined gene transcription.

Epigenetic modulation of retinoic acid receptor beta2 by the histone deacetylase inhibitor MS-275 in human renal cell carcinoma.

PURPOSE: Histone deacetylase (HDAC) inhibitors have been shown to reverse epigenetic repression of certain genes, including retinoic acid receptor beta2 (RARbeta2). In this study, we examined whether RARbeta2 expression is repressed in human renal cell carcinoma (RCC) and whether the HDAC inhibitor MS-275 may revert its epigenetic repression. EXPERIMENTAL DESIGN: Six human tumor RCC cell lines were analyzed for RARbeta2 gene expression and for methylation and acetylation status at the promoter level. Modulation of RARbeta2 expression and correlation with antitumor activity by combination of MS-275 with 13-cis-retinoic acid (CRA) was assessed in a RARbeta2-negative RCC cell line. RESULTS: RARbeta2 expression was either strongly present, weakly expressed, or absent in the RCC cell lines analyzed. Methylation-specific PCR indicated that the RARbeta2 promoter was partially methylated in three of the cell lines. CRA treatment did not inhibit clonogenic growth in the RARbeta2-negative cell line RCC1.18, whereas MS-275 induced a dose-dependent inhibitory effect. A greater inhibitory effect was observed with combination treatment (MS-275 + CRA). Treatment with MS-275 was associated with histone acetylation at the promoter level and synergistic gene reexpression of RARbeta2 in combination with CRA. RARbeta2 reexpression was associated with synergistic induction of the retinoid-responsive gene HOXA5. In vivo, single-agent CRA treatment showed no significant effect, whereas MS-275 and the combination induced a regression of RCC1.18 tumor xenografts. Discontinuation of treatment produced tumor recurrence in MS-275-treated mice, whereas animals treated with the combination remained tumor free. CONCLUSION: The HDAC inhibitor MS-275 seems to revert retinoid resistance due to epigenetic silencing of RARbeta2 in a human RCC model and has greater antitumor activity in combination with CRA compared with single agents. Thus, the combination of HDAC inhibitors and retinoids may represent a novel therapeutic approach in patients with RCC.

Inhibitors of CLK protein kinases suppress cell growth and induce apoptosis by modulating pre-mRNA splicing.

Accumulating evidence has demonstrated the importance of alternative splicing in various physiological processes, including the development of different diseases. CDC-like kinases (CLKs) and serine-arginine protein kinases (SRPKs) are components of the splicing machinery that are crucial for exon selection. The discovery of small molecule inhibitors against these kinases is of significant value, not only to delineate the molecular mechanisms of splicing, but also to identify potential therapeutic opportunities. Here we describe a series of small molecules that inhibit CLKs and SRPKs and thereby modulate pre-mRNA splicing. Treatment with these small molecules (Cpd-1, Cpd-2, or Cpd-3) significantly reduced the levels of endogenous phosphorylated SR proteins and caused enlargement of nuclear speckles in MDA-MB-468 cells. Additionally, the compounds resulted in splicing alterations of RPS6KB1 (S6K), and subsequent depletion of S6K protein. Interestingly, the activity of compounds selective for CLKs was well correlated with the activity for modulating S6K splicing as well as growth inhibition of cancer cells. A comprehensive mRNA sequencing approach revealed that the inhibitors induced splicing alterations and protein depletion for multiple genes, including those involved in growth and survival pathways such as S6K, EGFR, EIF3D, and PARP. Fluorescence pulse-chase labeling analyses demonstrated that isoforms with premature termination codons generated after treatment with the CLK inhibitors were degraded much faster than canonical mRNAs. Taken together, these results suggest that CLK inhibitors exhibit growth suppression and apoptosis induction through splicing alterations in genes involved in growth and survival. These small molecule inhibitors may be valuable tools for elucidating the molecular machinery of splicing and for the potential development of a novel class of antitumor agents.

P-glycoprotein inhibition by the multidrug resistance-reversing agent MS-209 enhances bioavailability and antitumor efficacy of orally administered paclitaxel.

PURPOSE: Recent studies in humans and mice have demonstrated that intestinal P-glycoprotein plays a causative role in the limited absorption of orally administered paclitaxel. Multidrug resistance (MDR)-reversing agents, such as cyclosporin A and PSC 833, are known to increase the systemic exposure to orally administered paclitaxel by enhancing absorption in the intestinal tract and decreasing elimination via the biliary tract. In this study, we demonstrated that coadministration of the MDR-reversing agent MS-209, which is known to inhibit P-glycoprotein function by direct interaction, improved the bioavailability of orally administered paclitaxel and consequently enhanced its antitumor activity. METHODS: The pharmacokinetics of paclitaxel were examined by measuring [(3)H]paclitaxel in plasma drawn from rats and mice given the drug with or without MS-209. The influence of MS-209 on the intestinal transport of [(3)H]paclitaxel was studied using a human colorectal cancer cell line, Caco-2. The in vivo efficacy of orally administered paclitaxel in combination with MS-209 was further evaluated in B16 melanoma-bearing mice. RESULTS: The plasma concentration of [(3)H]paclitaxel following oral administration was significantly increased by coadministration of MS-209 at 100 mg/kg in both rats and mice. In rats, the AUC of [(3)H]paclitaxel following oral administration was strikingly increased (1.9-fold) by coadministration of MS-209, whereas the AUC of [(3)H]paclitaxel following i.v. injection was slightly increased (1.3-fold) by MS-209. The increase in apparent bioavailability of oral paclitaxel due to MS-209 was 1.4-fold. To demonstrate this enhancing action in vitro, we studied the influence of MS-209 on the transport of [(3)H]paclitaxel using Caco-2 cells, which is a well-known model of intestinal efflux. The transport of [(3)H]paclitaxel across the Caco-2 monolayer was markedly inhibited in the presence of MS-209, and the apparent K(i)of MS-209 for the active transport of [(3)H]paclitaxel was 0.4 microM. Moreover, paclitaxel administered orally at 100 mg/kg per day with MS-209 at 100 mg/kg per day showed significant antitumor activity in B16 melanoma-bearing mice, whereas paclitaxel administered orally alone at the same dose showed no antitumor activity. These results suggest that the coadministration of MS-209 improved low systemic exposure to paclitaxel through inhibition of P-glycoprotein, which is involved in drug excretion via the intestinal tract, resulting in a clear antitumor activity of paclitaxel administered orally. CONCLUSION: The present study suggests that coadministration of MS-209 may be a useful way to improve the bioavailability of drugs not suitable for oral administration due to elimination via the intestinal tract.

Can the neurovascular compression volume of the trigeminal nerve on magnetic resonance cisternography predict the success of local anesthetic block after initial treatment by the carbamazepine?

OBJECTIVES: Whether NVC volume on magnetic resonance (MR) cisternography might be related to the success of local anesthetic block by tetracaine (TNB) as an additional treatment after carbamazepine (CBZ) treatments in patients with trigeminal neuralgia (TN) was evaluated. STUDY DESIGN: Detectable NVC volumes were measured from MR cisternography in 65 patients with TN treated by TNB after CBZ treatments. The correlation between the success of TNB and the NVC volume or the improvement in pain by CBZ was evaluated retrospectively. RESULTS: A significant difference was found between the improvement in pain by CBZ and the success of TNB, but not between NVC volume on MR cisternography and the success of TNB. CONCLUSIONS: The present results suggest that the success of CBZ as initial treatment, but not NVC volume on MR cisternography, may be a significant predictor of the success of TNB as additional therapy in patients with TN.

A rat pain model of facial cancer.

Cancer pain is a very severe problem for patients with advanced or terminal cancer. However, the induction mechanism remains unknown. Orofacial cancer patients often report difficulties in eating and swallowing, different from patients with cancer in other regions. Although several cancer pain animal models have been reported, these models have focused on the sciatic nerve areas. To understand the mechanisms of pain associated with orofacial cancer, we recently created a rat facial cancer model by inoculation of cancer cells into the vibrissal pad. This model provides mechanical allodynia, thermal hyperalgesia, and feeding disorder characteristics, similar to orofacial cancer patients. Hence, this model is useful for the evaluation of cancer pain of the trigeminal nerve area. In this chapter, we describe in detail the generation of a facial cancer pain model of rats by inoculation of Walker carcinosarcoma 256B cells.

Distinct time courses of microglial and astrocytic hyperactivation and the glial contribution to pain hypersensitivity in a facial cancer model.

Although recent evidence suggests that central glial hyperactivation is involved in cancer-induced persistent pain, the time course of this hyperactivation and the glial contribution to pain hypersensitivity remain unclear. The present study investigated the time-dependent spatial changes of microglial and astrocytic hyperactivation in the trigeminocervical complex, which consists of the medullary (MDH) and upper cervical (UCDH) dorsal horns, and pain-related behaviors in a rat facial cancer model in which Walker 256B-cells are inoculated into the vibrissal pad. In this model, the tumors grew within the vibrissal pad, from which sensory nerve fibers project into the MDH, but did not expand into the infraorbital region, from which fibers project into the UCDH. Nevertheless, mechanical allodynia and thermal hyperalgesia were observed not only in the vibrissal pad but also in the infraorbital region. Western blotting and immunofluorescence studies indicated that microglia were widely activated in the trigeminocervical complex on day 4 and gradually inactivated by day 11. In contrast, astrocytes were only activated in the MDH on day 4; the hyperactivation later expanded into the UCDH. Daily administration of the glial hyperactivation inhibitor propentofylline beginning on day 4 suppressed the glial hyperactivation on later days. Propentofylline treatment largely prevented allodynia/hyperalgesia in the infraorbital region beginning on day 5, although established allodynia/hyperalgesia in the vibrissal pad was less sensitive to the treatment. These results suggest that central glial hyperactivation, transient microglial hyperactivation and persistent astrocytic hyperactivation, contributes to the development of pain hypersensitivity but not to the maintenance of pain in this model.

Distinct mechanisms underlie the regulation of body fluid balance by neurokinin B and angiotensin II in the rat brain.

Although central injections of either neurokinin B (NKB) or angiotensin II (ANGII) induce a pressor response, they show different involvements in fluid intake behaviors. The aim of the present study was to elucidate the mechanisms by which these two peptides regulate body fluid balance in rats. We demonstrate that intracerebroventricular injections of NKB (1nmol) and ANGII (0.1nmol) both induce pressor responses. However, only ANGII induced significant water intake and increased sodium preference. Co-injection of NKB suppressed the ANGII-induced sodium preference but did not affect the ANGII-induced water intake. Immunohistochemistry for c-Fos, a marker of neuronal activation, revealed that both NKB and ANGII increased neuronal activation in the circumventricular organs and the hypothalamic paraventricular and supraoptic nuclei. In contrast, only ANGII significantly increased c-Fos immunoreactivity in the paraventricular thalamic nucleus, the central amygdala (CeA) and the ventrolateral bed nucleus of the stria terminalis (BSTvl). Co-injection of NKB suppressed the ANGII-induced c-Fos expression in the CeA and BSTvl. These results suggest that centrally injected NKB and ANGII lead to common cardiovascular responses by neuronal pathways through the circumventricular organs and hypothalamus but that they regulate fluid intake behaviors through different pathways. It is likely that the opposing effects of these two peptides on sodium preference can be explained by their differential actions in the CeA and BSTvl, both of which are inhibited by NKB and activated by ANGII.

Neuronal effects of neurokinin B on the rat subfornical organ.

The subfornical organ is an essential central nucleus for angiotensin II-induced body fluid regulation. Similar to angiotensin II, centrally injected neurokinin B (NKB) may induce cardiovascular responses by the subfornical organ; however, it does not induce water intake. To clarify this inconsistency, we investigated the neuronal effects of NKB on subfornical organ neurons in slice preparations along with its behavioral effects in vivo. In electrophysiological extracellular recordings, NKB excited angiotensin II-insensitive and inhibited angiotensin II-sensitive neurons. Centrally injected NKB inhibited peripherally injected angiotensin II-induced water intake. These results suggest that NKB-mediated neuronal effects on the subfornical organ are likely to be involved in antidipsogenic responses in addition to the previously reported cardiovascular responses.

Behavioral characteristics and c-Fos expression in the medullary dorsal horn in a rat model for orofacial cancer pain.

It is well known that patients with orofacial cancer suffer from cancer-induced pain which produces feeding difficulties. To understand the mechanisms of pain associated with orofacial cancer, we have recently created a model for rat orofacial cancer by inoculation with Walker carcinosarcoma 256B-cells into the vibrissal pads. The present study used both behavioral and immunohistochemical techniques to investigate changes in pain-related and ingestive behavior, along with c-Fos expression in the medullary dorsal horn which is a site for processing orofacial pain. The tumor mass grew gradually and contacted the nerve trunks within days after the inoculation of tumor cells. Physical difficulties in ingestion were observed after day 10 post-inoculation and facial grooming periods were prolonged. Sensitivities of the inoculated vibrissal pads to mechanical and thermal stimuli were increased on days 4 and 7, suggesting the development of mechanical allodynia and thermal hyperalgesia. Although hyposensitivity to mechanical and thermal stimulation was observed in the inoculated region after day 10, hyperalgesia developed on the margin of the tumor, suggesting that the hypersensitive region spread with growth of tumor mass. In the medullary dorsal horn, the levels of c-Fos immunoreactivity of the ipsilateral side increased significantly on days 4, 7 and 10, supporting the behavioral observations. These results indicate that the rat model shows symptoms similar to those in patients with orofacial cancer, for example, induction of feeding disorder and neuropathic pain.