Effects of corticosteroids on connective tissue and fibroblasts

The Effects of Steroids on Survival of Mouse and Human Tympanic Membrane Fibroblasts

OBJECTIVE

Tympanic membrane (TM) fibroblast cytotoxicity of quinolone ear drops is enhanced by dexamethasone and fluocinolone. Hydrocortisone has not been evaluated. We aimed to assess the effects of these 3 steroids on mouse and human TM fibroblast survival.

STUDY DESIGN

In vitro.

SETTING

Academic laboratory.

SUBJECTS AND METHODS

Mouse and human TM fibroblasts were exposed to hydrocortisone, dexamethasone, or fluocinolone at concentrations in commercial ear drops (1%, 0.1%, or 0.025%, respectively) and at steroid potency equivalents (1%, 0.033%, or 0.0033%, respectively), or dilute ethanol (control), twice within 24 hours or 4 times within 48 hours for 2 hours each time. Cells were observed with phase-contrast microscopy until the cytotoxicity assay was performed.

RESULTS

Mouse and human TM fibroblasts treated with any of the steroids had lower survival after 24 and 48 hours compared to control (all P < .0001). After 24 hours, viability of mouse fibroblasts treated with the steroids was not different (P > .05), while treatment with hydrocortisone decreased human TM fibroblast viability (P < .0001). After 48 hours, at concentrations found in ear drops and at equivalent steroid potency, dexamethasone and fluocinolone had similar survival in mouse and human fibroblasts (all P > .05), but hydrocortisone had lower survival in both mouse (P = .02 and P < .0001) and human (P < .0001) fibroblasts. Phase-contrast images mirrored the cytotoxicity findings.

CONCLUSION

Steroids found in commercial ear drops reduce survival of mouse and human TM fibroblasts. Hydrocortisone appears to be more cytotoxic than the more potent steroids, dexamethasone and fluocinolone. These findings should be considered when assessing clinical outcomes of ototopical preparations.

Hydrocortisone delay of tissue repair of experimental tympanic membrane perforations

The effects of topically applied hydrocortisone on experimental tympanic membrane (TM) perforations in rats were evaluated by otomicroscopy and light microscopy. Standardized TM perforations, occupying the whole upper rear quadrant, were performed, and a 2% hydrocortisone suspension (CORT) was applied once daily for 10 consecutive days. Application of CORT caused a delayed healing pattern, and even at 1 month only 2 of 12 perforations had healed. The keratinizing squamous epithelial cells of the TM appeared hypertrophic, whereas hyperplasia, characterizing a nontreated healing TM perforation, was less prominent. The connective tissue layer of the CORT-treated TM was invaded by abundant inflammatory cells, mainly polymorphonuclear leukocytes. Also, when applied to an intact TM, CORT caused hypertrophy of the epidermal cells and an inflammatory reaction within the TM.

Effect of dexamethasone on herpes simplex virus replication in mouse neuroblastoma cells (NB41A3): receptor characteristics

Monolayers of NB41A3 (MNB) cells were exposed to pharmacologic doses of dexamethasone (DXM). After 24-h, the cells were infected with herpes simplex virus type 1 (HSV-1) at a multiplicity of infection (m.o.i.) = 0.1. After every 24-h period, extracellular and intracellular virus aliquots were collected and frozen. The aliquots were titered in a standard plaque-forming assay. It was shown that the hormone led to a statistically significant increase of extra- and intracellular virus titers above the titers exhibited by these cells without added hormone. The same experiment was repeated in Vero cells, but the hormone did not elevate the resultant HSV-1 titers. A binding assay was performed on these two cell lines by use of 3H-DXM to determine if a DXM receptor was present. Specific binding was seen, but only in the MNB cell line. The Bmax of this receptor was 480 fmol/mg protein and it had a Kd of 2.3 nM. The S value of the receptor ligand complex equalled 8.0. These results indicate that cells possessing hormone receptors allow for a more efficient replication of the virus and suggest that these hormones may play an important role in the exacerbation of herpes simplex virus infection in vivo.

Increased DNA replication in the arterial adventitia after aortic ligation

After microsurgical dissection of the thoracic aorta of normotensive rats, biochemical and morphological comparisons were performed between the intima-media and adventitia. The DNA content, wet weight, and dry defatted weight of the adventitia were half that of the intima-media. Collagen was the main component of the adventitia (collagen greater than nonfibrous protein greater than elastin) whereas elastin was the main protein in the intima-media (elastin greater than nonfibrous protein greater than collagen), and the results correlated with morphological observations. Hypertension induced by aortic ligation between the renal arteries resulted in rapid elevations in circulating humoral factors and blood pressure. A sixfold increase in DNA synthesis was observed in the adventitia (p less than 0.001), resulting in a significant increase in DNA content as early as 6 days after aortic ligation (75% increase; p less than 0.001). Increased DNA replication was accompanied by elevations in nonfibrous protein and elastin contents. Autoradiograms showed labeled adventitial fibroblasts throughout the thickness of the adventitia and along the entire length of the aorta and smaller vessels. DNA synthesis and content and labeled smooth muscle cells were increased in the intima-media. These studies indicate that the adventitia participates in the development of vascular hypertrophy and arterial disease produced by aortic ligation.

Suppression of hyaluronic acid synthesis in synovial organ cultures by corticosteroid suspensions

The effects of sparingly soluble corticosteroid suspensions prepared for intraarticular therapy, of their vehicles, and of hydrocortisone on synovial hyaluronic acid (HA) synthesis were compared in organ cultures of normal canine villous synovium. Both hydrocortisone and the corticosteroid suspensions suppressed HA synthesis, as did 2 vehicle components, polysorbate 80 and myristyl-gamma-picrolinium chloride. Cultures of synovium from joints of dogs which, 1 day previously, had been injected with methylprednisolone acetate suspension synthesized less HA than did control cultures from noninjected joints of the same animals. The results indicate that suppression of HA synthesis is a mechanism by which these drugs can act to reduce joint HA content and promote resolution of synovial effusions.

Effect of glucocorticoids on glycosaminoglycan metabolism in cultured human skin fibroblasts

Human skin fibroblasts were exposed to 3 anti-inflammatory steroids in order to study their effects on the glycosaminoglycan metabolism. The potent glucocorticoids, fluocinolone acetonide and budesonide, even at low concentrations strongly reduced the accumulation of hyaluronic acid and sulfated glycosaminoglycans in the medium, at the cell surface, and in the cells. Hydrocortisone had considerably less effect. The 3 compartments were not influenced to the same extent and the least inhibition was noted in the cell surface pool. Dermatan sulfate was decreased to the same relative extent in all 3 compartments, while hyaluronic acid and heparan sulfate were specifically retained at the cell surface, explaining why this compartment was less affected than the others. Dermatan sulfate was studied in more detail regarding effects on its copolymeric structure. Glucocorticoid treatment changed the uronosyl composition of the polysaccharides so that a relative decrease of glucuronic acid residues and a relative increase of iduronic acid residues were noted. This change was most evident in dermatan sulfate of the medium and of the cell surface. Thus, glucocorticoid treatment not only reduces the quantity of various glycosaminoglycans but also changes the distribution, the relative proportion, and the structure of connective tissue proteoglycans. These effects probably contribute to the development of skin atrophy, which often is observed after long-term treatment with potent glucocorticoids.

Glutamine synthetase activity in the developing secondary palate and induction by dexamethasone

Glutamine synthetase (EC 6.3.1.2) (GS) and glutamyltransferase (EC 2.3.2.1) (GT) specific activity were examined in developing A/Jax and C57BL/6J (C57) mouse fetal secondary palates. In addition, the induction of palatal GS was also examined after maternal injection of dexamethasone. Palatal GT activity was uniformly higher in A/J than C57 palates with both strains showing highest activity late on day 13 of gestation and a drop in activity by early day 14. In contrast, A/J palatal GS activity peaked transiently late on day 13, dropped by early day 14 and remained lower throughout the remaining period of palatal development. Palatal GS activity in C57 mouse fetuses, although failing to show a discrete transient peak of activity, remained at a constant elevated level from early day 13 to late day 14 and did not decrease until day 15 of gestation. These elevated levels of palatal GS and GT activity correspond to the gestation period of maximal palatal glycoconjugate biosynthesis. Thus, palatal GS activity may play an important regulatory role in the synthesis of these macromolecules. A/J and C57BL/6J mice exhibit different susceptibilities to glucocorticoid-induced cleft palate. However, maternal administration of a non-teratogenic dose of dexamethasone on either late day 12 or late day 13 resulted in a dramatic stimulation of both A/J and C57 fetal palatal GS but not GT activity when assay 18 h later. A/J palatal tissue responded to dexamethasone with greater induction of palatal GS activity than enzyme activity in C57 palates. Palatal GS, sensitive to glucocorticoid stimulation, may thus be an important link in expressing hormonal control of normal palatal differentiation.

Effect of five anti-inflammatory steroids on collagen and glycoaminoglycan synthessis in vitro

The effect of five anti-inflammatory corticosteroids, i.e. hydrocortisone, hydrocortisone 17-butyrate, betamethasone 17-valerate, nicocortonide acetate and nicocortonide, on the synthesis of hyaluronic acid, sulphated glycosaminoglycans and collagen by cultured skin fibroblasts was studied. As inhibitors of all these parameters the steroids could be arranged in order hydrocortisone < hydrocortisone 17-butyrate < betamethasone 17-valerate, nicocortonide acetate and nicocortonide. The corticosteroid concentrations required for inhibition of hyaluronic acid were very low as compared to those required for inhibition of sulphated glycosaminoglycan and collagen synthesis.

The suppression of cellular proliferation in SV40-transformed 3T3 cells by glucocorticoids

Glucocorticosteroids, when added two hours after cell plating to SV40-transformed, 3T3 mouse fibroblasts in low serum (0.3% v/v), biotin-supplemented medium, suppress cellular proliferation by 24 hours. While some cell death probably occurs, the growth inhibition is not primarily due to cytotoxicity and cytolysis. This conclusion is supported by the following: 1) both dead and viable cell numbers are suppressed, 2) little cell debris is evident in the medium, and 3) very high concentrations of glucocorticoids do not cause an increase in the dead cell count. Furthermore, this growth suppression, which is specific for glucocorticoids since several non-glucocorticoid steroids have no inhibitory effect, is not permanent nor irreversible. Removal of the glucocorticoid and replacement with 10% serum restore rapid proliferation. Although higher concentrations (1% and 10%) of serum afford some protection against glucocorticoid inhibition, this protection is not simply a consequence of faster growth rates. SV3T3 cells can be grown in serum-free medium supplemented with biotin, transferrin, insulin, and epidermal growth factor (EGF). Under these conditions growth rates are comparable to high serum media, yet glucocorticoids are still powerful inhibitors. However, the omission of insulin from serum-free, glucocorticoid cultures does result in observable cell death and lysis. Flow microfluorometry and autoradiographic studies have determined that glucocorticoid-inhibited cells are partially blocked in G1. The proportions of S phase and G2 + M cells are greatly reduced with an accompanying accumulation of G1 cells. These results suggest that glucocorticoids regulate a biochemical step(s) in G1 which is critical for DNA initiation.

Involvement of glucocorticoids in the development of the secondary palate

Genetic differences between various inbred strains of mice in the levels of glucocorticoid receptors embryonic in maxillary mesenchyme cells appear to be reflected in the magnitude of the responses to steroids in these cells. High levels of glucocorticoids cause significant growth inhibition in maxillary mesenchyme cells with subsequent alterations in the production of extracellular matrix components. The presence of higher levels of cytoplasmic glucocorticoid receptor proteins may be one factor which could predispose those strains such as A/J to a greater inhibition of craniofacial growth in vivo by glucocorticoids and therefore increase the frequency of cleft palate production. Furthermore, women with infertility treated with glucocorticoids to support pregnancy give birth to infants with a marked decrease in birth weight [98]. Pharmacologic doses of glucocorticoids can also cause a dramatic reduction in the growth of a number of fetal tissues in mice and humans. In fact, there is evidence that glucocorticoids may be a causative factor in the production of cleft palate in primates [52]. The nature of the molecular elements which determine the biochemical and physiologic responses to glucocorticoids in the palate still remains largely unknown. Although in the mouse there is some evidence to suggest that the major histocompatibility locus (H-2) might be involved, the level(s) at which this control is exerted is unknown. It is possible that this locus may regulate in some manner the level of glucocorticoid receptors and the response to glucocorticoids in the secondary palate. Moreover, there is evidence to suggest that other genes distinct from, but closely linked to the H-2 locus may be important in determining both the strain-dependent differences in susceptibility to glucocorticoid-induced cleft palate and the intracellular levels of cyclic AMP in the secondary palate. It is also apparent that glucocorticoids in conjunction with other hormones or growth factors such as epidermal growth factor and agents which regulate cyclic nucleotide metabolism are essential for the normal development of the secondary palate. Excesses or deficiencies in either the level of these growth regulators and/or in their receptors in specific fetal tissues at defined periods in development are likely to lead to certain fetal malformations. Definition and integration of the genetic, biochemical, and endocrine factors which are involved in the control of cellular growth as influenced by alterations in the composition of cell surface and extracellular matrix components should provide some insights into the events associated with normal palatogenesis.

The decrease of hyaluronate synthesis by anti-inflammatory steroids in vitro

The effect of anti-inflammatory steroids (prednisolone and derivatives of hydrocortisone, dexamethasone and betamethasone) on the synthesis of hyaluronic acid and sulphated glycosaminoglycans in human skin fibroblast culture was studied. The concentrations of steroids varied between 1 x 10(-10)M and 1 x 10(-6)M. All tested steroids decreased the synthesis of hyaluronic acid to the same final level which was about 40--50% of the controls, but the concentrations required varied between different steroids. The relative inhibitory potencies of the steroids were calculated based on concentrations needed to decrease the synthesis of hyaluronate. When the inhibitory potency of hydrocortisone was calculated as one, the values of the other steroids were: prednisolone 5, hydrocortisone 17- butyrate 20, betamethasone alcohol 30, dexamethasone alcohol 38, betamethasone 17-valerate 350--400, dexamethasone monosodium phosphate and betamethasone disodium phosphate over 400. Hydrocortisone sodium succinate was as potent an inhibitor of hyaluronate synthesis as hydrocortisone alcohol. None of the tested steroids affected the synthesis of sulphated glycosaminoglycans at these concentrations. The changes ovbserved in glycosaminoglycans in the medium were in accordance with the changes in the cell layer. The possible significance of hyaluronate synthesis inhibition by anti-inflammatory steroids is discussed.

A comparison of the effects of prednisolone and methylprednisolone on human lymphoblastoid cells

Methylprednisolone is more effective than prednisolone in mediating long-term cytolysis and immediate inhibition of nucleoside uptake in human lymphoblastoid cells. This suggests that methylation of prednisolone makes it more potent by aiding interaction with a cellular target rather than increasing its stability.