The influence of insulin-like growth factor (IGF) on C19 steroid conversions by human gingiva and in cultured gingival fibroblasts

Effects of laser irradiation on the release of basic fibroblast growth factor (bFGF), insulin like growth factor-1 (IGF-1), and receptor of IGF-1 (IGFBP3) from gingival fibroblasts

Various studies have shown biostimulation effects of laser irradiation by producing metabolic changes within the cells. Little is known about the biological effect of laser irradiation on the oral tissues. Among the many physiological effects, it is important to recognize that low-level laser therapy (LLLT) may affect release of growth factors from fibroblasts. Therefore, the aim of the present study was to determine whether the laser irradiation can enhance the release of basic fibroblast growth factor (bFGF), insulin-like growth factor-1 (IGF-1), and receptor of IGF-1 (IGFBP3) from human gingival fibroblasts (HGF). The number of all samples in the study were 30, and the samples were randomly divided into three equal groups; In the first group (single dose group), HGF were irradiated with laser energy of 685 nm, for 140 s, 2 J/cm(2) for one time, and in the second group, energy at the same dose was applied for two consecutive days (double dose group). The third group served as nonirradiated control group. Proliferation, viability, and bFGF, IGF-1, IGFBP3 analysis of control and irradiated cultures were compared with each other. Both of the irradiated groups revealed higher proliferation and viability in comparison to the control group. Comparison of the single-dose group with the control group revealed statistically significant increases in bFGF (p < 0.01) and IGF-1 (p < 0.01), but IGFBP3 increased insignificantly (p > 0.05). When the double dose group was compared with the control group, significant increases were determined in all of the parameters (p < 0.01). In the comparison of the differences between the two irradiated groups (one dose and two doses), none of the parameters displayed any statistically significant difference (p > 0.05). In both of the laser groups, LLLT increased the cell proliferation and cell viability. The results of this study showed that LLLT increased the proliferation of HGF cells and release of bFGF, IGF-1, and IGFBP3 from these cells. LLLT may play an important role in periodontal wound healing and regeneration by enhancing the production of the growth factors.

Influence of sex hormones on the periodontium

OBJECTIVES

Sex hormones have long been considered to play an influential role on periodontal tissues, bone turnover rate, wound healing and periodontal disease progression. The objectives of this review article are to (1) address the link between sex hormones and the periodontium, (2) analyse how these hormones influence the periodontium at different life times and (3) discuss the effects of hormone supplements/replacement on the periodontium.

MATERIALS AND METHODS

Two autonomous searches were performed in English language utilizing Medline, Premedline and Pubmed as the online databases. Publications up to 2002 were selected and further reviewed. In addition, a manual search was also performed including specific related journals and books.

RESULTS

It is certain that sexual hormones play a key role in periodontal disease progression and wound healing. More specifically, these effects seem to differentiate by gender as well as lifetime period. In addition, the influence of sex hormones can be minimized with good plaque control and with hormone replacement.

CONCLUSION

Despite profound research linking periodontal condition with sex hormones kinetics, more definitive molecular mechanisms and therapy still remain to be determined.

Effects of the anti-androgen finasteride on the modulatory actions of oestradiol on androgen metabolism by human gingival fibroblasts

5 alpha-Reduction of androgen substrates results in the formation of the biologically active androgen 5 alpha-dihydrotestosterone (DHT), while 17 beta-hydroxysteroid dehydrogenase metabolises androgen substrates to 4-androstenedione or testosterone. The aim here was to study the effect of the anti-androgen finasteride on 5 alpha-reduction of androgens by human gingival fibroblasts (HGF) and its modulation by oestradiol-17 beta. Duplicate cultures of HGF were incubated with [14C]testosterone/[14C]4-androstenedione in Eagle minimum essential medium (n=6) in the presence or absence of oestradiol-17 beta (O) or finasteride (F; 0.1-3 microg/ml) for 24 h. The steroid metabolites were analysed and quantified using a radioisotope scanner. With [14C]testosterone as substrate, oestradiol stimulated the formation of DHT by 63% (n=6; P<0.01). In contrast, finasteride inhibited this activity by 61% (n=6; P<0.01). The combination of O+F produced 43% less inhibition than finasteride alone (n=6; P<0.01). There were 200-300% increases in the formation of 4-androstenedione in response to O and F, being less pronounced in combination. Oestradiol stimulated the formation of DHT from [14C]4-androstenedione by 300-600% and finasteride reduced the yield of DHT by 40-64%; there was less inhibition in combination with O. There were 300-700% increases in the formation of testosterone in response to F and O alone and in combination (n=6; P<0.01). Oestradiol-induced stimulation of 5 alpha-reductase activity on androgen substrates by HGF is suggestive of hormone modulatory mechanisms in the healing periodontium of both sexes. Its inhibition by finasteride is suggestive of type 2 isoenzyme activity, confirming target-tissue functions in the gingiva.

The influence of prostaglandins on steroid conversions by human gingival fibroblasts

The aim of this investigation was to study the effects of prostaglandins E1 and E2 (PGE1 and PGE2) on the accumulation, release and metabolism of C19 steroids by human gingival fibroblasts (HGF) and gingivae, due to their anabolic potential in inflammatory repair. For the accumulation studies, HGF were incubated with 14C-testosterone at timed intervals and the cell-digests analysed for label uptake. The release of 5 alpha-dihydrotestosterone (DHT) by HGF was studied by preincubating the cells with 14C-DHT and reincubating with cold steroid to quantify its release at timed intervals. For the metabolic studies, HGF/gingival tissue were incubated with 14C-testosterone and serial concentrations of PGE1 and PGE2 to study their effects on the synthesis of DHT. The incubations were terminated at 24 h and extracted metabolites were analysed and quantified. The accumulation of 14C-testosterone by human gingival fibroblasts was elevated 3-fold at 24 h by PGE1 (n = 3, p < 0.001; 1-way ANOVA). The release of 14C-DHT was enhanced nearly 2-fold by PGE1 (n = 3, p < 0.001), compared with controls. Both PGE1 and PGE2 caused 2-fold increases in DHT synthesis by HGF and 3-fold increases in 4-androstenedione formation (n = 4, p < 0.001). With the tissue incubations PGE1/PGE2 caused 3-4 fold increases in DHT synthesis (n = 5, p < 0.005; Wilcoxon signed rank statistic for paired observations). Direct stimulation of the accumulation/release and metabolism of these steroids by prostaglandins in gingivae may contribute to the anabolic potential of androgens in inflammatory periodontal disease.

The effect of PDGF, TGF-beta and IGF in combination on androgen metabolism by fibroblasts

The aim of this investigation is to study growth factor combinations (PDGF/IGF PDGF/TGF-beta and TGF-beta/IGF) on the metabolism of 2 androgen substrates 14C-testosterone/14C-4-androstenedione to the matrix stimulatory androgen 5alpha-dihydrotestosterone (DHT). Human gingival fibroblasts in culture were incubated in Eagle's MEM with the radiolabelled substrates and growth factors for 24 h, when the medium was extracted and analysed for radioactive metabolites. When 14C-testosterone was used as substrate, there was an 80% increase in DHT synthesis over controls with the PDGF/IGF combination (n=7; p<0.01), which was less than the effects of each of the growth factors alone. Similarly, PDGF/TGF-beta resulted in a 2-fold increase in DHT synthesis over controls (n=5; p<0.01) which compared with individual PDGF incubations, and the TGF-beta/IGF combination resulted in a 30% increase in DHT synthesis over controls (n=3; p<0.01); this was less than the 2.8/2.5-fold increases produced individually. Similarly, when 14C-4-androstenedione was used as the substrate, there were 2-fold increases in DHT synthesis in response to combinations of PDGF/IGF and PDGF/TGF-beta (n=5; p<0.01). These results demonstrate feedback inhibition when individually active growth factors function in combination; this may be indicative of mechanisms for physiological homeostasis seen in vivo.

Effects of the anti-androgen finasteride on 5alpha-reductase activity in human gingival fibroblasts in response to minocycline

In addition to their antimicrobial properties, tetracyclines have antiinflammatory and pro-anabolic effects on the reparatory potential of connective tissue and bone. The physiologically active androgen 5alpha-dihydrotestosterone (DHT) implicated in matrix synthesis is formed in gingivae from androgen substrates. The aim of this investigation is to study the androgen metabolic response of gingivae to minocycline, in the presence or absence of the anti-androgen finasteride. Chronically inflamed gingival tissue derived from 12 subjects aged 30-50 years and passaged fibroblasts derived from this source, were used for the experiments. Duplicate incubations were performed in Eagle's MEM with 14C-testosterone/14C-4-androstenedione in the presence or absence of minocycline (5-60 microg/ml) or finasteride for 24 h. The androgen substrate 14C-testosterone was metabolised mainly to DHT and 4-androstenedione, while 14C-4-androstenedione was converted mainly to DHT and testosterone. Minocycline at 20-30 microg/ml stimulated the formation of these metabolites from both substrates by 13-25%. In the tissue incubations there were 3- and 2-fold increases in DHT and 4-androstenedione formation (n=12; p<0.01). The anti-androgen finasteride caused significant inhibition of 5alpha-reductase activity on both substrates at 0.1 & 1.0 microg/ml with total inhibition at 10 & 50 microg/ml (n=3; p<0.01). Minocycline-induced stimulation of 5alpha-reductase activity was also inhibited by finasteride (n=4; p<0.02). Since finasteride inhibition of 5alpha-reductase activity is specific for the type 2 isoenzyme associated with anabolic functions of target tissue, this enzyme activity may contribute to some of the cited anabolic tissue responses to minocycline.

The effects of epidermal growth factor, interleukin-1, and phenytoin, alone and in combination, on C19 steroid conversions in fibroblasts

The formation of the biologically active metabolite 5 alpha-dihydrotestosterone (DHT) from testosterone in response to phenytoin (Ph), interleukin-1 (IL-1), and epidermal growth factor (EGF) was investigated. The androgen DHT stimulates matrix synthesis in connective tissue and bone. Duplicate incubations were performed with confluent human gingival fibroblasts, 14C-testosterone, and optimal stimulatory concentrations of IL-1 (5 IU/ml), EGF (10 ng/ml), Ph (5 micrograms/ml), Ph + EGF, and Ph + IL-1 respectively for 24 hours in Eagle's MEM at 37 degrees C. The medium was then analyzed for radioactive metabolites. Similar incubations were performed with human gingival tissue using 14C-4-androstenedione as substrate in the presence or absence of EGF, Ph, and EGF + Ph. In the cell lines studied, EGF stimulated DHT and 4-androstenedione synthesis by 20% (n = 5; P < 0.01; Wilcoxon signed rank statistic for paired observations). IL-1 stimulated DHT and 4-androstenedione synthesis by 2-fold (n = 6; P < 0.01). Ph stimulated DHT and 4-androstenedione synthesis by 2-fold increases (n = 3; P < 0.01). Combinations of phenytoin and EGF stimulated DHT and 4-androstenedione synthesis by 33% and 37% greater than the effect of phenytoin alone (n = 3; P < 0.01). Combinations of Ph and IL-1 caused a 45% increase in the amount of DHT formed and a 66% increase in 4-androstenedione when compared to the effect of phenytoin alone (n = 3; P < 0.01). 14C-4-androstenedione was converted to DHT and testosterone by human gingival tissue. There were 2-fold, 4-fold, and 2.5-fold increases in DHT synthesis and 5-fold, 2-fold, and 6-fold increases in the formation of testosterone in response to EGF, Ph, and EGF + Ph respectively (n = 3; P < 0.01). EGF and IL-1 present in inflammatory exudate may have implications on phenytoin-induced overgrowth via the steroid metabolic pathway.

5 alpha reductase activity in human gingiva and gingival fibroblasts in response to bacterial culture supernatants, using [14C]4-androstenedione as substrate

5 alpha-Reduction of androgen substrates is increased in inflamed gingiva. It was therefore relevant to study the effect of bacterial culture supernatants derived from Prevotella intermedius (P.i), Porphyromonas gingivalis (P.g) and Actinobacillus actinomycetemcomitans (A.a) on the metabolism of [14C]4-androstenedione to 5 alpha-dihydrotestosterone (DHT) in gingival tissue and cultured fibroblasts. Chronically inflamed human gingival tissue and cultured gingival fibroblasts from the same source were incubated in duplicate with [14C]4-androstenedione and optimal concentrations of P.i, P.g. and A.a culture supernatants in Eagle's minimal essential medium in a CO2 incubator for 24 h at 37 degrees C. The metabolites were then extracted, separated and quantified using a radioisotope scanner. There were 87, 50 and 6% increases in DHT synthesis by human gingival tissue in response to the culture supernatants of P.i, P.g and A.a, respectively, over control incubations (n = 3; p < 0.01: Wilcoxon signed-ranked statistic for paired observations). With the cells in culture, all four fibroblast cell lines produced DHT and testosterone from [14C]4-androstenedione in varying amounts. The production of DHT was enhanced in the presence of each the bacterial culture supernatants to varying degrees (P.i 40%, P.g 35% and A.a 40%; p < 0.01). Combinations of the bacterial extracts: (P.i + P.g), (P.i + A.a), (P.g + A.a) and (P.i + P.g + A.a) showed intermediate or suppressor effects on DHT formed compared with individual incubations. Culture supernatants of these pathogens can influence DHT synthesis in fibroblasts, and effect that is modulated by baseline androgen metabolism and the proportion of virulent pathogens present. This may have some bearing on host susceptibility on host and the progression of the periodontal lesion.