Biomedical subjects

Chris R Irwin

Publications and source records attributed to Chris R Irwin.

5 recordsLinked to original sources

PubMed2006

The cytotoxic effects of human neutrophil peptide-1 (HNP1) and lactoferrin on oral squamous cell carcinoma (OSCC) in vitro.

Alpha-defensin or human neutrophil peptide-1 (HNP1) is a neutrophil-derived antimicrobial peptide with cytotoxic effects towards cancer cells. Lactoferrin is also stored in human neutrophils and is a glycoprotein involved in mediating cytotoxicity towards tumour cells. This study investigated the sensitivity of normal oral keratinocyte and oral squamous cell carcinoma (OSCC) cells to HNP1 and lactoferrin in various combinations. A concentration of 100 microg/ml HNP1 induced the most significant cytotoxic effect on both normal and OSCC cells. Lactoferrin (12.5, 25 and 250 microg/ml) also significantly induced cell death in OSCC cells after 72 h. Of note, a combination of 10 microg/ml HNP1 and 50 microg/ml lactoferrin induced a differential effect, not observed with either concentration alone, which stimulated proliferation in normal cells, but induced cell death in OSCC cells throughout the study. These results indicate a potentially important co-operative role for HNP1 and lactoferrin in facilitating a selective cytotoxic effect on tumour cells.

Carcinoma, Squamous Cell↗

PubMed2003

Chlorhexidine-containing mucoadhesive polymeric compacts designed for use in the oral cavity: an examination of their physical properties, in vitro/in vivo drug release properties and clinical acceptability.

This study describes the formulation, physicochemical and mucoadhesive properties and in in vitro/in vivo release of chlorhexidine from mucoadhesive, polymeric compacts, designed for application within the oral cavity. Compacts were prepared by direct compression of mixtures containing 100 mg sodium carboxymethylcellulose (NaCMC), 25 mg hydroxyethylcellulose (HEC)/75 mg polyacrylic acid (PAA) and 75 mg HEC/25 mg PAA. The mechanical and mucoadhesive properties of the drug-loaded compacts were examined using a texture analyzer in compression and tension modes, respectively. Evaluation of mucoadhesion was performed using a mucin-coated gauze substrate. In vitro release of chlorhexidine was performed under sink conditions (phosphate buffered saline, pH 7.0, 37 degrees C) using a Caleva 7ST dissolution apparatus. Salivary chlorhexidine levels were determined following intra-oral placement of drug-containing formulations. Quantification of the mass of chlorhexidine released both in vitro and in vivo was performed using HPLC with ultraviolet detection. Furthermore, the in vivo acceptability of the various polymeric compacts was assessed in volunteers using standard questionnaires. Compacts composed of HEC/PAA exhibited greater in vivo retention than those composed of NaCMC. Compacts composed of 25 mg PAA and 75 mg HEC displayed greatest patient acceptability. Introduction of chlorhexidine into these compacts did not significantly compromise either the work required for compact fracture or the in vitro mucoadhesion. Controlled release of chlorhexidine from these compacts was observed both in vitro and in vivo, the concentration of chlorhexidine in saliva exceeding the minimum inhibitory concentration of the common oral pathogens over the study period. In light of the patient acceptability and in vivo performance, it is suggested that the compact composed of 25 mg PAA/75 mg HEC containing 10 mg chlorhexidine offers considerable promise for use as an antimicrobial agent in the oral cavity.

Journal Article↗

PubMed2003

The effects of cyclosporin on the collagenolytic activity of gingival fibroblasts.

BACKGROUND: The immunosuppressive agent cyclosporin is associated with a number of major side-effects including the development of gingival overgrowth. Although the pathogenesis of cyclosporin-induced gingival overgrowth remains unclear, it has been suggested that the finely regulated balance between extracellular matrix synthesis and degradation may be disturbed, resulting in an accumulation of excess connective tissue components within the gingival tissue. The aim of this study was to investigate the effect of cyclosporin on matrix metalloproteinases (MMP)-1 and tissue inhibitors of MMP (TIMP)-1 expression at the mRNA, protein, and enzyme activity levels. METHODS: Gingival fibroblasts were grown to confluence and then cultured in serum-free medium supplemented with cyclosporin over the concentration range of 0 to 2000 ng/ml. MMP-1 and TIMP-1 mRNA levels in cultures were determined by reverse transcription polymerase chain reaction (RT-PCR), protein levels in whole conditioned medium were assessed by enzyme-linked immunosorbent assay (ELISA), and collagenolytic activity determined using a 3H-acetylated type I collagen degradation assay. Tissue mRNA levels in normal and overgrown gingiva were also determined by RT-PCR. RESULTS: Results indicated that cyclosporin inhibited MMP-1 expression at both the mRNA and protein level in a dose- and time-dependent fashion. The effects on TIMP-1 expression were less clear, cyclosporin inhibiting mRNA expression, but having no effect on TIMP-1 protein levels at any concentration studied. Addition of the drug resulted in reduced levels of collagenolytic activity in the culture medium. MMP-1 mRNA expression was significantly reduced in overgrown compared to normal tissue. CONCLUSIONS: These results add support to the hypothesis that the accumulation of collagen seen in gingival overgrowth can be explained by a cyclosporin-induced inhibition of collagenolytic activity within the gingival tissues.

Analysis of Variance↗

PubMed2002

The role of soluble interleukin (IL)-6 receptor in mediating the effects of IL-6 on matrix metalloproteinase-1 and tissue inhibitor of metalloproteinase-1 expression by gingival fibroblasts.

BACKGROUND: Interleukin-6 (IL-6) is a multifunctional cytokine thought to play a role in the tissue destruction that characterizes periodontal disease. IL-6 exerts its cellular effects through a cell-surface receptor which also exists in a soluble form (sIL-6r). This study investigated the effects of IL-6 on matrix metalloproteinase (MMP)-1 activity in gingival fibroblast cultures, specifically determining the role of the sIL-6r in mediating these actions. METHODS: Fibroblasts were grown to confluence, washed in Hank's balanced saline solution (HBSS), and then cultured for 72 hours in serum-free medium supplemented with 0.2% bovine serum albumin, 1 microgram/ml Escherichia coli LPS and containing various combinations of IL-6 and its soluble receptor over the concentration range 0 to 1,000 ng/ml. MMP-1 and tissue inhibitor of MMP (TIMP)-1 protein levels in the conditioned medium were assessed by enzyme-linked immunosorbent assay (ELISA) and collagenolytic activity determined using a 3H-acetylated type I collagen degradation assay. RESULTS: Results indicated that the addition of IL-6 alone to cultures, over the concentration range 0 to 1,000 ng/ml, had no significant effect on MMP-1 protein expression. However, addition of IL-6 in combination with its soluble receptor resulted in a statistically significant, dose-dependent upregulation in MMP-1 expression. The IL-6/sIL-6r combination also induced a significant increase in collagenolytic activity in cultures. IL-6 and sIL-6r, either alone or in combination, had no marked effect on TIMP expression or cell growth. CONCLUSIONS: These data strongly suggest that future clinical studies investigating the role of IL-6 in periodontal disease must also determine the levels of sIL-6r within the periodontal tissues.

Adult↗

PubMedDate not supplied

Phenotypic differences between oral and skin fibroblasts in wound contraction and growth factor expression.

Wounds of the oral mucosa heal in an accelerated fashion with reduced scarring compared with cutaneous wounds. The differences in healing outcome between oral mucosa and skin could be because of phenotypic differences between the respective fibroblast populations. This study compared paired mucosal and dermal fibroblasts in terms of collagen gel contraction, alpha-smooth muscle actin expression (alpha-SMA), and production of the epithelial growth factors: keratinocyte growth factor (KGF) and hepatocyte growth factor/scatter factor (HGF). The effects of transforming growth factor -beta1 and -beta3 on each parameter were also determined. Gel contraction in floating collagen lattices was determined over a 7-day period. alpha-SMA expression by fibroblasts was determined by Western blotting. KGF and HGF expression were determined by an enzyme-linked immunosorbent assay. Oral fibroblasts induced accelerated collagen gel contraction, yet surprisingly expressed lower levels of alpha-SMA. Oral cells also produced significantly greater levels of both KGF and HGF than their dermal counterparts. Transforming growth factor-beta1 and -beta3, over the concentration range of 0.1-10 ng/mL, had similar effects on cell function, stimulating both gel contraction and alpha-SMA production, but inhibiting KGF and HGF production by both cell types. These data indicate phenotypic differences between oral and dermal fibroblasts that may well contribute to the differences in healing outcome between these two tissues.

Actins↗