No abstract

Histamine provokes itching and is a major skin disease complaint. Histamine is known to excite a subset of sensory neurons, predominantly C-fibers. Although histamine is pruritogenic, its signaling pathways that excite sensory neurons have not been identified. Because the metabolic products of lipoxygenases (LOs) activate transient receptor potential vanilloid receptor-1 (TRPV1) in sensory neurons, we hypothesized that histamine excites sensory neurons by activating TRPV1 via phospholipase A 2 (PLA 2 ) and LO stimulation. In cultured sensory neurons, histamine evoked inward currents that were reduced by capsazepine, a TRPV1 blocker. Moreover, histamine provoked inward currents when histamine receptor subtype 1 (H1R) and TRPV1 were expressed heterologously, but not when H1R or TRPV1 was expressed alone. In addition, histamine caused Ca 2ϩ influxes in sensory neurons in wild-type mice but not in TRPV1 Ϫ/Ϫ mice. Furthermore, histamine caused a 2.5-fold increase in the production of 12-hydroxyeicosatetraenoic acid, a metabolite of LO, in cultured sensory neurons. When injected subcutaneously into the necks of mice, histamine caused bouts of scratching, which were greatly reduced by pretreatment with capsazepine, a TRPV1 blocker, and by inhibitors of PLA 2 , LO, and H1R. Furthermore, mice lacking TRPV1 markedly reduced histamine-induced scratching compared with wild type. Together, these results indicate that TRPV1 plays a key role in mediating the pruritogenic action of histamine via the PLA 2 /LO pathway.

Mutations in the BRCA1 (ref. 1) tumour suppressor gene are found in almost all of the families with inherited breast and ovarian cancers and about half of the families with only breast cancer. Although the biochemical function of BRCA1 is not well understood, it is important for DNA damage repair and cell-cycle checkpoint. BRCA1 exists in nuclear foci but is hyperphosphorylated and disperses after DNA damage. It is not known whether BRCA1 phosphorylation and dispersion and its function in DNA damage response are related. In yeast the DNA damage response and the replication-block checkpoint are mediated partly through the Cds1 kinase family. Here we report that the human Cds1 kinase (hCds1/Chk2) regulates BRCA1 function after DNA damage by phosphorylating serine 988 of BRCA1. We show that hCds1 and BRCA1 interact and co-localize within discrete nuclear foci but separate after gamma irradiation. Phosphorylation of BRCA1 at serine 988 is required for the release of BRCA1 from hCds1. This phosphorylation is also important for the ability of BRCA1 to restore survival after DNA damage in the BRCA1-mutated cell line HCC1937.

Tooth infections or injuries involving dental pulp are treated routinely by root canal therapy. Endodontically treated teeth are devitalized, susceptible to re-infections, fractures, and subsequent tooth loss. Here, we report regeneration of dental-pulp-like tissue by cell homing and without cell transplantation. Upon in vivo implantation of endodontically treated real-size, native human teeth in mouse dorsum for the tested 3 weeks, delivery of basic fibroblast growth factor and/or vascular endothelial growth factor (bFGF and/or VEGF) yielded re-cellularized and revascularized connective tissue that integrated to native dentinal wall in root canals. Further, combined delivery of bFGF, VEGF, or platelet-derived growth factor (PDGF) with a basal set of nerve growth factor (NGF) and bone morphogenetic protein-7 (BMP7) generated cellularized and vascularized tissues positive of VEGF antibody staining and apparent neo-dentin formation over the surface of native dentinal wall in some, but not all, endodontically treated teeth. Newly formed dental pulp tissue appeared dense with disconnected cells surrounded by extracellular matrix. Erythrocyte-filled blood vessels were present with endothelial-like cell lining. Reconstructed, multiple microscopic images showed complete fill of dental-pulp-like tissue in the entire root canal from root apex to pulp chamber with tissue integration to dentinal wall upon delivery of bFGF, VEGF, or PDGF with a basal set of NGF and BMP7. Quantitative ELISA showed that combinatory delivery of bFGF, VEGF, or PDGF with basal NGF and BMP7 elaborated von Willerbrand factor, dentin sialoprotein, and NGF. These findings represent the first demonstration of regenerated dental-pulp-like tissue in endodontically treated root canals of real-size, native human teeth. The present chemotaxis-based approach has potent cell homing effects for re-cellularization and revascularization in endodontically treated root canals in vivo, although in an ectopic model. Regeneration of dental pulp by cell homing, rather than cell delivery, may accelerate clinical translation.