Influence of prostaglandins on connective tissue cell growth and function

Phospholipase A2 activity in vitro cultured cells--influence of ascorbate supplementation

Non-malignant LLCMK cells and malignant B16 cells were supplemented with ascorbate, over the concentration range 0-100 micrograms/ml ascorbate. The effects of ascorbate supplementation on cell growth and phospholipase A2 activity of the membrane fractions of the respective cell lines were determined. Increasing ascorbate supplementation had a significant inhibitory effect on the growth of the B16 cells. Phospholipase A2 activity in the control B16 cells was lower than that detected in the control LLCMK cells. Phospholipase A2 activity decreased significantly in the B16 cells upon increasing ascorbate supplementation, while the supplementation of ascorbate to the LLCMK cells did not have any significant effect on phospholipase A2 activity in these cells.

Prostaglandins influence myofibroblast contractility in Dupuytren's disease

This study investigated if the vasoactive prostaglandins, PGE2, and PGF2 alpha, were identifiable in association with nodular myofibroblasts of patients with Dupuytren's disease. Immunocytochemic studies, using antibodies specific for these prostaglandins, have confirmed their association with myofibroblasts. Radioimmunoassay was used to quantitate the prostaglandins. Our results indicate a significant increase of both prostaglandins, especially PGF2 alpha, in Dupuytren's palmar fascia when compared with control fascia. These endogenous prostaglandins may influence the contractile behavior of myofibroblasts in Dupuytren's disease to contribute to the pathobiology of this disorder.

[Angiotensin-converting enzyme (ACE). Increased serum activities in patients with dermatological diseases (author's transl)]

Serum activities of ACE were investigated in 40 patients with dermatological disease and in nine patients with sarcoidosis. The method of Cushman and Cheung, modified according to Lieberman, was used. Both sarcoidosis patients and patients with dermatological diseases showed marked elevations of ACE-activity. The increase in ACE-activity might result from inflammation and immunological events.

The regulation of prostaglandin E1 formation: a candidate for one of the fundamental mechanisms involved in the actions of vitamin C

Vitamin C stimulates the formation of PGE1 in human platelets. The effect occurs over the physiologically relevant range of concentrations. PGE1 is required for T lymphocyte function and plays a major part in the regulation of immune responses. PGE1 is also important in the regulation of collagen and ground substance metabolism, in cholesterol metabolism and in regulation of responsiveness to insulin. It is proposed that defective formation of PGE1 could account for many of the features of scurvy and for many of the reported therapeutic effects of vitamin C. If correct, vitamin C will be of value only in conjunction with an adequate supply of dihomogammalinolenic acid, the precursor of PGE1. Essential fatty acids, pyridoxine and zinc are all required to achieve this.

Time-dependent stimulatory and inhibitory effects of prostaglandin E1 on exudative and tissue components of granulomatous inflammation in rats

1 The effects of prostaglandin (PGE(1)), following local administration during different phases of developing sponge-induced granulomata, were studied in normal and essential fatty acid deficient (EFAD) rats.2 In normal rats, a single dose of 1 mug PGE(1) on implantation (day 1) increased exudate production without altering total leucocyte counts after 6 h and stimulated granulomatous tissue formation after 8 days.3 Repeated daily administration of the same dose of PGE(1) on days 1 to 3 had no effect, while administration on days 4 to 7 (i.e. when tissue growth is already in progress) inhibited granuloma formation.4 In EFAD rats, which are known to produce only very small amounts of endogenous prostaglandins, acute (6 h) exudate formation was unaffected by 0.05 mug PGE(1). However, early stimulatory and later inhibitory effects of 0.05 mug PGE(1) per day were obtained on the granulomatous tissue, similar to those obtained with the 20 fold higher dose in normal rats.5 The early stimulatory action of PGE(1) on granulomatous tissue formation was enhanced, in normal rats, by concomitant administration of 10 mug theophylline. This latter compound did not influence the later inhibitory effect of PGE(1).6 These results indicate that PGE(1) exerts either pro- or anti-inflammatory actions on the proliferative (tissue) component of the inflammatory process, depending on the time of administration. While the stimulatory effect following early administration may have been secondary to an initial cyclic adenosine 3',5'-monophosphate-mediated, vascular response, such a mechanism is unlikely to have been responsible for the later anti-inflammatory action of PGE(1).7 The implications of these results are discussed in relation to the postulated negative-feedback role of endogenous PGE in chronic inflammation.

Effect of prostaglandins on cyclic nucleotide levels in cultured keratinocytes

Ginea pig ear epidermal cells (keratinocytes) were established in primary cultures using trypsin, and treated in their proliferative phase of growth with prostaglandins E1, D1, F1 alpha, E2, D2, or F2 alpha. This phase is induced by the addition of retinoic acid during cell plating. Intracellular content of cAMP and cGMP was measured by radioimmunoassay at various times after treatment. Maximum stimulation of cAMP levels was observed with PGD2, smaller increases with PGE2 and relatively transient rises with PGF2 alpha which were of low significance, but confirm earlier data. Similar results were observed with PGD1, PGE1, and PGF1 alpha with smaller increases. The effects of D and E PGs were biphasic. Significant increases in cGMP were immediately observed with PGD2 and PGE2. With PGF2 alpha, maximum cGMP levels were noted after some delay. All PGs tested showed some effect in elevating cyclic nucleotides in keratinocytes. The most striking result was the increase in cAMP on PGD2 treatment.

Distribution and further studies on the activity of prostaglandin E in chronic granulomatous inflammation

Pre-formed granulomata, induced by cannulated, carrageenin-soaked, subdermal sponge implants, were used to further analyse the effects of exogenous PGE and the involvement of endogenous PGE in this model of chronic inflammatory tissue changes in rats. Experiments with 14C-PGE2 indicated that administration of PGE into the sponge creates a kinetic situation likely to imitate, but superimposed upon, the continuous discharge of endogenous PGE in the granuloma. The granuloma-reducing, anti-flammatory effect of PGE can be mimicked by dibutyryl cyclic-AMP, phosphodiesterase inhibitors and indomethacin. Most probably these compounds, in common with PGE, exert their anti-granuloma action through elevation of intracellular cyclic-AMP (in macrophages and/or fibroblasts). The anti-granuloma action is not necessarily associated with a reduction in the endogenous PGE-level and vice versa. The involvement of endogenous PGE in the tissue events of granulomatous inflammation is conjectural as yet.