We investigated the effects of S-777469 (1-[[6-Ethyl-1-[4-fluorobenzyl]-5-methyl-2-oxo-1, 2-dihydropyridine-3-carbonyl]amino]-cyclohexanecarboxylic acid), a novel cannabinoid type 2 receptor (CB2) agonist, on 1-fluoro-2,4-dinitrobenzene (DNFB)-induced ear inflammation and mite antigen-induced dermatitis in mice. The oral administration of S-777469 significantly suppressed DNFB-induced ear swelling in a dose-dependent manner. In addition, S-777469 significantly alleviated mite antigen-induced atopic dermatitis-like skin lesions in NC/Nga mice. A histological analysis revealed that S-777469 significantly reduced the epidermal thickness and the number of mast cells infiltrating skin lesions. We demonstrated that S-777469 inhibited mite antigen-induced eosinophil accumulation in skin lesions and an endogenous CB2 ligand, 2-arachidonoylglycerol (2-AG)-induced eosinophil migration in vitro. Moreover, we confirmed that 2-AG levels significantly increased in skin lesions of mite antigen-induced dermatitis model. Together, these results suggest that S-777469 inhibits skin inflammation in mice by blocking the activities of 2-AG.

We have previously reported that S-777469 [1-([6-ethyl-1-(4-fluorobenzyl)-5-methyl-2-oxo-1,2-dihydropyridine-3-carbonyl]amino)-cyclohexanecarboxylic acid], a novel cannabinoid type 2 receptor (CB2) agonist, significantly suppressed compound 48/80-induced scratching behavior in mice in a dose-dependent manner when it was administered orally. Here, we demonstrated that the inhibitory effects of S-777469 on compound 48/80-induced scratching behavior are reversed by pretreatment with SR144528, a CB2-selective antagonist. In addition, we investigated the effects of S-777469 on itch-associated scratching behavior induced by several pruritogenic agents in mice and rats. S-777469 significantly suppressed scratching behavior induced by histamine or substance P in mice or by serotonin in rats. In contrast, the H1-antihistamine fexofenadine clearly inhibited histamine-induced scratching behavior but did not affect scratching behavior induced by substance P or serotonin. Moreover, S-777469 significantly inhibited histamine-induced peripheral nerve firing in mice. In conclusion, these results suggest that S-777469 produces its antipruritic effects by inhibiting itch signal transmission through CB2 agonism.

Summary Background The Kv1.3 voltage-gated potassium channel is selectively upregulated upon activation in effector memory T (TEM) cells in inflamed tissue, and plays an important role in maintenance of T-cell activation. Although Kv1.3 blockers have been shown to ameliorate allergic contact dermatitis (ACD) in a rat model, it remains unknown whether the effect of Kv1.3 blockers on ACD is mediated by suppressing TEM cell function and/or whether naive T-cells or central memory T (TCM) cells are influenced. Aim To analyse the detailed mechanism of Kv1.3 blockers in a rat model of ACD. Methods We examined the effects of a Kv1.3 blocker on inflammation and production of the effector cytokine interferon (IFN)-γ in inflamed tissue in rat ACD. Single-cell suspensions were isolated from inflamed rat ears (TEM cells), and regional lymph nodes (naive T/TCM cells), and the effect of Kv1.3 blockers on anti-CD3-stimulated IFN-γ production in vitro was measured. Results The Kv1.3 blocker significantly suppressed ear inflammation and IFN-γ production at the protein level in vivo. It also suppressed in vitro IFN-γ production from TEM cells from inflamed tissues, but did not suppress the function of naive T/TCM cells from lymph nodes. Conclusions We found that the Kv1.3 blocker ameliorated ACD by inhibiting TEM cell functions only, thus Kv1.3 blockers could be a potentially selective therapeutic agent for TEM cell-mediated inflammatory skin diseases without producing harmful side-effects.

atopic dermatitis acetone ether water protein gene product 9.5 transient receptor potential vanilloid subfamily 3 TO THE EDITOR Itch is a common symptom in various forms of dermatitis characterized by dry skin, such as senile xerosis and atopic dermatitis (AD). It is defined as an unpleasant sensation that provokes a desire to scratch and, because itch-elicited scratching aggravates lesions of the skin, the itch is intensified (Ikoma et al., 2006Ikoma A. Steinhoff M. Ständer S. et al.The neurobiology of itch.Nat Rev Neurosci. 2006; 7: 535-547Crossref PubMed Scopus (748) Google Scholar). Therefore, reduction of itching and scratching is an effective strategy for preventing aggravation of skin lesions and improving quality of life. Histamine is the best-known pruritogen and has been regarded as a main target for antipruritic therapies, but H1 receptor (histamine H1R) antagonists are often ineffective against certain kinds of pruritus including dry skin pruritus (Wahlgren et al., 1990Wahlgren C.F. Hägermark O. Bergström R. et al.The antipruritic effect of a sedative and a non-sedative antihistamine in atopic dermatitis.Br J Dermatol. 1990; 122: 545-551Crossref PubMed Scopus (138) Google Scholar). It is suggested that mediators other than histamine also have a key role in itch; for example, physiological temperature, inflammatory mediators, and nitric oxide. These putative pruritogens are also recognized as activators of transient receptor potential (TRP) V3 (Xu et al., 2002Xu H. Ramsey I.S. Kotecha S.A. et al.TRPV3 is a calcium-permeable temperature-sensitive cation channel.Nature. 2002; 418: 181-186Crossref PubMed Scopus (703) Google Scholar; Hu et al., 2006Hu H.Z. Xiao R. Wang C. et al.Potentiation of TRPV3 channel function by unsaturated fatty acids.J Cell Physiol. 2006; 208: 201-212Crossref PubMed Scopus (127) Google Scholar; Yoshida et al., 2006Yoshida T. Inoue R. Morii T. et al.Nitric oxide activates TRP channels by cysteine S-nitrosylation.Nat Chem Biol. 2006; 2: 596-607Crossref PubMed Scopus (457) Google Scholar), which is a warm-sensitive Ca2+-permeable cation channel highly expressed in epidermal keratinocytes (Peier et al., 2002Peier A.M. Reeve A.J. Andersson D.A. et al.A heat-sensitive TRP channel expressed in keratinocytes.Science. 2002; 296: 2046-2049Crossref PubMed Scopus (726) Google Scholar). Interestingly, we indicated previously that a gain-of-function mutation in TRPV3 caused itchy dermatitis in rodents (Asakawa et al., 2006Asakawa M. Yoshioka T. Matsutani T. et al.Association of a mutation in TRPV3 with defective hair growth in rodents.J Invest Dermatol. 2006; 126: 2664-2672Crossref PubMed Scopus (159) Google Scholar; Yoshioka et al., 2009Yoshioka T. Imura K. Asakawa M. et al.Impact of the Gly573Ser substitution in TRPV3 on the development of allergic and pruritic dermatitis in mice.J Invest Dermatol. 2009; 129: 714-722Abstract Full Text Full Text PDF PubMed Scopus (142) Google Scholar). However, we could not sufficiently suggest a possibility of TRPV3 as a therapeutic target of pruritus. Hence, we focused on TRPV3 as a new therapeutic target for histamine H1R antagonist–resistant pruritus and carried out experiments using ICRTRPV3-/- mice to determine the maximum therapeutic impact of TRPV3 for a certain type of itch (Inagaki et al., 2001Inagaki N. Nagao M. Igeta K. et al.Scratching behavior in various strains of mice.Skin Pharmacol Appl Skin Physiol. 2001; 14: 87-96Crossref PubMed Scopus (95) Google Scholar). The distinguishing feature of ICRTRPV3-/- mice is the presence of wavy whiskers. Information regarding TRPV3-knockout mice is shown in Supplementary Figure S1 online. In contradiction to previous reports (Moqrich et al., 2005Moqrich A. Hwang S.W. Earley T.J. et al.Impaired thermosensation in mice lacking TRPV3, a heat and camphor sensor in the skin.Science. 2005; 307: 1468-1472Crossref PubMed Scopus (590) Google Scholar; Cheng et al., 2010Cheng X. Jin J. Hu L. et al.TRP channel regulates EGFR signaling in hair morphogenesis and skin barrier formation.Cell. 2010; 141: 331-343Abstract Full Text Full Text PDF PubMed Scopus (217) Google Scholar), we did not find that mice lacking the TRPV3 gene also exhibit wavy hair coat (data not shown). This discrepancy may be due, partially, to the differences in mice strains used in the different studies. Download .pdf (.06 MB) Help with pdf files Supplementary Figure S1 Recently, Miyamoto et al., 2002Miyamoto T. Nojima H. Shinkado T. et al.Itch-associated response induced by experimental dry skin in mice.Jpn J Pharmacol. 2002; 88: 285-292Crossref PubMed Scopus (151) Google Scholar developed a murine model of dry skin pruritus, which was constructed by daily treatment of an acetone/ether (1:1) mixture and water (AEW) applied to the rostral back, and the resulting spontaneous scratching of these models were thought to be histamine-independent. By using a modification of this method, ICRTRPV3-/- mice and their age-matched littermates (ICR TRPV3+/+) were treated with AEW for 4 days to develop skin dryness and barrier disruption on their backs. Daily treatment with AEW increased transepidermal water loss and decreased stratum cutaneous hydration in both ICRTRPV3+/+ and ICRTRPV3-/- mice (Figure 1a). Hematoxylin–eosin staining revealed remarkable epidermal hyperplasia without infiltration of inflammatory cells in the dermis in both ICRTRPV3+/+ and ICRTRPV3-/- mice (Figure 1b). It has been reported that TRPV3 is required for the formation of the stratum corneum layer, which is thought to be a key factor in maintaining skin barrier functions (Cheng et al., 2010Cheng X. Jin J. Hu L. et al.TRP channel regulates EGFR signaling in hair morphogenesis and skin barrier formation.Cell. 2010; 141: 331-343Abstract Full Text Full Text PDF PubMed Scopus (217) Google Scholar). Contrary to our expectations, there was no difference in the manner of the development of dry skin caused by AEW treatment between mice with and without TRPV3 in this study. This may be because the mouse strain used in each study was different or the effects of AEW treatment were too strong to detect the effects of TRPV3 on the development of dry skin. To examine the impact of TRPV3 deletion on the development of spontaneous scratching behavior, we conducted behavioral tests. Repeated treatment with AEW resulted in a significant increase in spontaneous scratching directed toward the AEW-treated area, which was suppressed by subcutaneous injections of naltrexone, a μ-opioid receptor antagonist (Figure 2b). Given that μ-opioid receptor antagonists reduce experimentally induced itch in humans (Heyer et al., 1997Heyer G. Dotzer M. Diepgen T.L. et al.Opiate and H1 antagonist effects on histamine induced pruritus and alloknesis.Pain. 1997; 73: 239-243Abstract Full Text Full Text PDF PubMed Scopus (95) Google Scholar), spontaneous scratching behavior observed in the AEW-treated mice might reflect similar itch sensation in humans. In the AEW-treated ICRTRPV3-/- mice, there was no increase in the types of scratching behaviors compared with those without AEW-treatment (Figure 2c). To rule out the possibility of a sedative effect, we also measured the spontaneous motor activity and could not find any locomotor effects evoked by TRPV3 deletion in these mice (Figure 2a). These results indicated that TRPV3 has a pivotal role in the development of itch in mice with dry skin. It is well known that increased nerve density is involved in producing pruritus. In AD patients, increased sprouting of epidermal C-fibers is seen, inducing hypersensitivity to itching, which aggravates the disease (Paus et al., 2006Paus R. Schmelz M. Bíró T. et al.Frontiers in pruritus research: scratching the brain for more effective itch therapy.J Clin Invest. 2006; 116: 1174-1186Crossref PubMed Scopus (317) Google Scholar). In the present study, we also found that the density of the invasive nerve fibers in the skin was increased in AEW-treated mice, as observed by immunohistochemical examination of the sensory neurons using anti-protein gene product 9.5 (PGP9.5) antibody (Figure 3). PGP9.5-positive neurites in the dermis were more prominent in the AEW-treated skin of wild-type mice compared with that of ICRTRPV3-/- mice, and some fibers expanded into the epidermal layer. These results suggested that TRPV3 affected nerve sprouting in dry skin. Previous studies indicate that TRPV3 affects the production of epidermal nerve growth factor (Gopinath et al., 2005Gopinath P. Wan E. Holdcroft A. et al.Increased capsaicin receptor TRPV1 in skin nerve fibres and related vanilloid receptors TRPV3 and TRPV4 in keratinocytes in human breast pain.BMC Womens Health. 2005; 5: 4-9Crossref PubMed Scopus (137) Google Scholar; Yoshioka et al., 2009Yoshioka T. Imura K. Asakawa M. et al.Impact of the Gly573Ser substitution in TRPV3 on the development of allergic and pruritic dermatitis in mice.J Invest Dermatol. 2009; 129: 714-722Abstract Full Text Full Text PDF PubMed Scopus (142) Google Scholar), which suggests that TRPV3 causes pruritus in lesional skin through nerve fiber expansion. In AD patients with pruritus, higher expressions of TRPV3 messenger RNA are observed compared with those without pruritus (data not shown). This suggests that TPPV3 is involved in human and murine pruritus in a similar manner. Although we could not carry out pharmacological studies using TRPV3 antagonists to elucidate the therapeutic role of TRPV3 for a certain type of pruritus, we believe that this is the first report referring to their role by genetic studies using ICRTRPV3-/- mice. TRPV3 may have an important role in dry skin itch, and TRPV3 antagonists could be a therapeutic option in managing AD and dry skin patients with histamine H1R antagonist–resistant pruritus. We thank Shunji Shinohara for comments on the manuscript. Supplementary material is linked to the online version of the paper at http://www.nature.com/jid

While inhaled glucocorticoids are the best treatment for the majority of chronic asthmatics, there is a small group who do not respond to these drugs or whose disease can only be controlled by high doses of oral glucocorticoids with risks of severe side effects. Therefore, a safe novel anti-asthmatic agent which has a different mechanism from that of glucocorticoids is needed for the management of asthma. We have previously shown that an orally active prostanoid DP receptor antagonist, S-5751, had potent anti-inflammatory effects in guinea pig and sheep asthma models. In this study, using a rat asthma like model, we found that lung neutrophilia and proinflammatory cytokine secretion as well as bronchial hyperresponsiveness and lung eosinophilia were induced by repeated antigen-inhalations after antigen-sensitization. These symptoms are similar to the pathogenesis of symptomatic asthma. Orally-administered prostanoid DP receptor antagonists S-5751 and pinagladin significantly suppressed not only bronchial hyperresponsiveness and lung eosinophilia but also neutrophilia and mucus secretion in the lung, while oral prednisolone inhibited only bronchial hyperresponsiveness and eosinophil infiltration. In addition, prostanoid DP receptor antagonists significantly suppressed interleukin (IL)-1β, IL-6 and CXCL1 mRNA in contrast to suppression of IL-4 and CCL11 mRNA by prednisolone. The majority of prostanoid DP receptor-expressing cells in both rat and human asthmatic lungs are infiltrative macrophages and/or monocytes. These results suggest that prostanoid DP receptor antagonists utilize different mechanisms from glucocorticoids, and that they would be a novel alternative and/or combination drug for asthma therapy.

We reported that the Gly573Ser substitution in transient receptor potential vanilloid 3 (TRPV3) led to increased ion channel activity in keratinocytes and caused spontaneous hairlessness in DS-Nh mice. DS-Nh mice also develop allergic and pruritic dermatitis. As the hairless and dermatitis phenotypes were both inherited in an autosomal dominant fashion and could not be segregated from each other, we speculated that TRPV3(Gly573Ser) might be responsible for the dermatitis. Here, we constructed TRPV3(Gly573Ser) transgenic mice, with a putative promoter sequence in the 5' region of TRPV3, to investigate the involvement of TRPV3 in the development of specific types of dermatitis. These transgenic mice spontaneously developed dermatitis, whereas wild-type mice did not display this phenotype when maintained under the same conditions. Histological and serological analyses were carried out to better understand the clinical features of TRPV3(Gly573Ser) transgenic mice. A physiological study revealed that TRPV3(Gly573Ser) induced a higher nerve growth factor response to heat. Finally, C57BL-Nh mice were used to investigate the penetrance of the TRPV3(Gly573Ser) gene for dermatitis. Interestingly, C57BL-Nh mice developed spontaneous scratching behavior, separately from the development of dermatitis. We propose that TRPV3(Gly573Ser) is a cause of pruritus and/or dermatitis associated with scratching, and suggest that TRPV3 may represent a therapeutic target in pruritic dermatitis.

Background.  Although dry skin and T cell‐dependent disease exacerbation are characteristic features of atopic dermatitis (AD), the involvement of T cells in the development of dry skin remains unclear.

Abstract Background Recently, it has been reported that the Gly573Ser substitution of transient receptor potential V3 (TRPV3) leads to increased ion-channel activity in keratinocytes. Our previous studies have indicated that the spontaneous hairless and dermatitis phenotypes of DS-Nh mice, which were newly established as an animal model of atopic dermatitis (AD), are caused by TRPV3Gly573Ser. Although this substitution causes hairlessness in several kinds of rodents, in our investigations, dermatitis developed in only a few animals. Here, we generated NC/Nga-Nh mice to elucidate the role of TRPV3Gly573Ser in NC/Nga mice, which is one of the most studied animal models of AD. Methods To establish and validate the new AD animal model, NC/Nga-Nh mice were generated using NC/Nga and DS-Nh mice, and their clinical features were compared. Next, T-cell receptor (TCR) Vβ usage in splenocytes, evaluation of bacterial colonization, and serological and histological analyses were carried out. Finally, repeated-hapten-application dermatitis was induced in these mice. Results NC/Nga-Nh mice did not develop spontaneous dermatitis, whereas DS-Nh mice displayed this phenotype when maintained under the same conditions. Serological analysis indicated that there really was a phenotypic difference between these mice, and TCR repertoire analysis indicated that TCRVβ haplotypes played an important role in the development of dermatitis. Artificial dermatitis developed in DS and NC/Nga-Nh mice, but not in DS-Nh and NC/Nga mice. Histological and serological analyses indicated that mouse strains were listed in descending order of number of skin mast cells: DS-Nh > DS ≈ NC/Nga-Nh > NC/Nga, and serum IgE levels were increased after 2,4,6 trinitrochlorobenzene application in these mice. Serum IgE level in DS-Nh mice was lower than that mesured in other strains. Conclusion Our results confirm the contribution of the TRPV3Gly573Ser gene to the development of repeated hapten dermatitis, but not spontaneous dermatitis in NC/Nga mice.

Cytosolic phospholipase A2α (cPLA2α) preferentially hydrolyzes membrane phospholipids containing arachidonic acid, resulting in the biosynthesis of eicosanoids such as prostaglandins and leukotrienes. To examine the contribution of cPLA2α to skin inflammation, we evaluated the effect of (E)-N-[(2S,4R)-4-[N-(biphenyl-2-ylmethyl)-N-2-methylpropylamino]-1-[2-(2,4-difluorobenzoyl)benzoyl]pyrrolidin- 2-yl]methyl-3-[4-(2,4-dioxothiazolidin-5-ylidenemethyl) phenyl]acrylamide (RSC-3388), a potent and selective cPLA2α inhibitor, on 2,4,6-trinitro-1-chlorobenzene (TNCB)-induced ear inflammation and mite antigen-induced dermatitis in mice. Topical application of RSC-3388 showed a significant inhibitory activity against TNCB-induced ear swelling and eicosanoid production in mice. Comprehensive expression analysis using Gene-Chip technology and subsequent experiments concerning mRNA and protein expression demonstrated that RSC-3388 clearly reduced the levels of interleukin-1β, macrophage inflammatory protein-1α (MIP-1α) and MIP-1β in a TNCB-induced mouse model. In addition, RSC-3388 ointment significantly alleviated atopic dermatitis-like skin lesions induced by repeated application of mite antigen. Furthermore, increased expression of cPLA2α, assessed by anti-phospho-cPLA2α antibody, was observed in the skin lesions of mite-antigen-induced dermatitis. These results indicate that cPLA2α is involved in the development of skin inflammation in mice, and RSC-3388 is expected to be useful for the treatment of inflammatory skin disorders such as atopic dermatitis.

We recently reported that Gly573Ser substitution of the transient receptor potential cation channel, subfamily V member 3 (TRPV3) caused hair loss in DS-Nh mice. To further elucidate the effects of this mutation on the development of the spontaneous hairless phenotype, we examined the temperature–response to epidermal sheets from DS-Nh and DS mice. It was indicated that the mutation was gain-of-function. We also performed genetic and histological analyses with both strain skins. DNA microarray data revealed that the levels of keratin-associated protein 16-1, 16-3, and 16-9 genes related to the anagen phase were decreased in the skins of DS-Nh mice compared with those of three days old DS mice. Histological analysis revealed that the anagen phase persisted in DS-Nh mice, and that the telogen phase was seen in DS but not DS-Nh mice at 21 days of age. Regulation of TRPV3 appears to be important for appropriate hair development in rodents.

Although the pathogenic role of interleukin-13 (IL-13) is a key for atopic dermatitis (AD), the mechanism of IL-13 production in AD remains unclear. To investigate the role of the T-cell receptor V beta (TCR V beta) haplotype in the development of dermatitis and the production of IL-13 in the naturally occurring dermatitis model by staphylococcal enterotoxin C (SEC)-producing Staphylococcus aureus, we raised DS-Nh mice harbouring the TCR V beta(a) haplotype with a central deletion in the TCRBV gene segments, including TCR V beta 8S2. Observation and histopathological analysis of the two mouse substrains with spontaneous dermatitis indicated that later onset and weaker severity of AD-like dermatitis were identified in mice with TCR V beta(a) compared to those with TCR V beta(b). Immunohistochemical examination revealed the infiltration of a large number of CD4-bearing T cells in the skin lesions in mice with TCR V beta(b) but not in those with TCR V beta(a). Interestingly, much lower levels of serum IL-13 were detected in mice with the TCR V beta(a) than in those with the TCR V beta(b) haplotype. In vitro, synthetic ligands (Pam(2)CSK4) of toll-like receptor 2 (TLR2) synergistically produced IL-13 with SEC in splenocytes of mice with TCR V beta(b) but not of those with TCR V beta(a), and natural killer T cells were essential for this synergism. Our findings suggested that this TCR V beta-haplotype-dependent synergism with TLR2 plays an important role in the development of AD-like dermatitis in DS-Nh mice.

ABSTRACT Cortactin and the translocated intimin receptor, Tir, interacted with each other in pedestal formation in HeLa cells infected with enteropathogenic Escherichia coli (EPEC). Cortactin is shown to be necessary for organizing actin pedestals in response to EPEC, based on the expression of green fluorescent protein-fused cortactin derivatives in HeLa cells.

Enterohaemorrhagic Escherichia coli (EHEC) belongs to a family of pathogens that cause attaching and effacing (A/E) lesion on target cells. The EspB protein of EHEC is translocated both to the host cell cytoplasm and to the membrane, and is essential for the signalling events leading to A/E lesion. To determine the actual role of EspB in this process, we tried to identify the EspB binding partner of the host cell protein, using a yeast two-hybrid assay, and obtained a cytoskeletal-associated protein, alpha-catenin. The alpha-catenin bound directly to the N-terminal region of EspB, both in solid (overlay assay) and solution (pull-down assay) phases, and it was recruited to the EHEC adherence site, dependent on EspB. Expression of the N-terminal region of EspB, as well as the whole EspB in host cells, inhibited F-actin accumulation on the adherence site. We conclude that EspB recruits a-catenin at the EHEC adherence site by direct interaction, and that the recruitment of alpha-catenin is essential for EHEC-induced A/E lesion formation.

Enteropathogenic Escherichia coli (EPEC) is able to inject its own receptor, a transmembrane protein called translocated intimin receptor, Tir, into the host epithelial cell. The bacterium then uses an outer membrane protein, intimin, to bind to Tir and remains firmly attached to the host cell surface for the duration of the infection. The bacterium is also able to trigger the rearrangement of several host cell proteins, culminating with the formation of an actin-rich, pedestal-like structure beneath the EPEC adherence site. Although several cytoskeletal proteins are rearranged following EPEC infection, the exact role played by these proteins during pedestal formation remains unknown. We report here that talin, an integrin-binding protein, is recruited by EPEC and associates directly with Tir. By surface plasmon resonance (SPR), the predicted value for the dissociation constant (KD) for Tir-talin binding was 1.86 x 10(-7) M. We also demonstrate that microinjection of anti-talin antibodies into HeLa cells resulted in the complete inability to focus actin filaments beneath the attached bacterium. These findings demonstrate that talin is essential for EPEC-induced pedestal formation in infected cells.

Vibrio parahaemolyticus produces a thermostable direct hemolysin (TDH) that has been implicated in the pathogenesis of diarrheal diseases in human. Isc increase was observed with TDH addition to the serosal side rather than to the mucosal side. Ise increase caused by TDH was inhibited by the depletion of extra-cellular Cl-. TDH increases Cl- secretion in Caco-2 cells. The TDH exhibits higher sensitivity to the mucosal side than to the serosal side.

ABSTRACT A hemolytic toxin related to thermostable direct hemolysin (TDH), TDH-related hemolysin (TRH), produced by Kanagawa-phenomenon-negative Vibrio parahaemolyticus is suspected of playing an important, but yet-to-be-elucidated role in diarrhea caused by this organism. In cultured human colonic epithelial cells, TRH increases Cl − secretion, followed by elevation of intracellular calcium.