After PMN addition, all samples were incubated for a further 6 or 12 h. TLR4-specific neutralizing antibodies and knockdown of using RNA interference, even in the presence of PMNs, demonstrating the direct role of epithelial TLR4 in the protective process. Furthermore, treatment with neutralizing antibodies specific for TNF- resulted in strongly reduced expression accompanied MAP2K2 by augmented epithelial cell damage and fungal invasion. To our knowledge, this is the first description of such a PMN-dependent, TLR4-mediated protective mechanism at epithelial surfaces, which may provide significant insights into how microbial infections are managed and controlled in the oral mucosa. Introduction The mucosal epithelium has immense importance in host defense and immune surveillance, because it is the primary cell layer that initially encounters the majority of microorganisms. This specialized interaction will result in either passive coexistence between microbe and host, as in the case of commensal microbes, or a breach of the mucosal barrier and subsequent NCGC00244536 cell injury, as in the case of microbial pathogens (1). Barrier function alone is NCGC00244536 usually adequate to restrain commensal microbes, but is often insufficient to NCGC00244536 protect against microbial pathogens. Accordingly, the oral epithelium is able to secrete a variety of defense effector molecules and to orchestrate an immune inflammatory response to activate myeloid cells in the submucosal layers to clear any invading pathogens (2, 3). Immune responsiveness to many microbial pathogens depends on a family of pattern recognition receptors known as TLRs, which are the major innate recognition system for microbial invaders in vertebrates (4). Ten TLR members exist in humans; these are triggered by conserved molecular structures (pathogen-associated NCGC00244536 molecular patterns) expressed by bacteria, viruses, and fungi. These include LPS, peptidoglycan, lipoprotein moieties, protein motifs, and nucleotide sequences (4, 5). However, in addition to their function in host defense, recent findings indicate that TLRs also appear to have a more general role in epithelial homeostasis and protection from cell injury (6). is a ubiquitous commensal organism and the most common fungal pathogen of humans and accounts for more than 50% of all fungal systemic infections (7, 8). Host defense mechanisms against mucosal candidiasis are not well understood, but include both innate and adaptive responses. Both TLR2 and TLR4 have been implicated in host defense against (5); however, NCGC00244536 the majority of these studies have been based on TLR recognition by myeloid cells and thus indicate a general role for the TLRs in systemic candidiasis (9, 10). A great deal less is known about interactions of TLRs with at mucosal surfaces. Several TLRs are expressed constitutively in the oral epithelium (11), and increased expression of TLR2 and TLR4 has previously been observed in inflamed gingival epithelial tissues (12). is able to activate NF-B in epidermal keratinocytes, the main transcriptional factor associated with TLR signaling, and can also stimulate the production of IL-8 (13), a powerful chemokine involved in recruitment of polymorphonuclear leukocytes (PMNs) to sites of microbial infection (1, 4, 14). PMNs represent a central component of the innate immune response (15). In many mucosal infections and inflammatory disorders, the combination of epithelial injury, disease activity, and symptoms parallel PMN infiltration of the mucosa (16, 17). Similarly, during oral infections, transepithelial migration of PMNs is believed to play a crucial role in the clearance of infection and in epithelial homeostasis (18). Previously, using a model of oral reconstituted human epithelium (RHE), we demonstrated that PMNs could protect the epithelium from infections (20). However, the mechanism by which PMNs and epithelial cells interact to protect the mucosal surfaces from microbial invasion is as yet unclear. Our study aimed to resolve this key issue by addressing 2 fundamental questions that would significantly enhance our understanding of this primary defense mechanism. Do PMNs protect the.
Neurokinin Receptors