Prolonged remissions of cystic and conglobate acne with 13-cis-retinoic acid

Prevention of 3-methylcholanthrene-induced skin tumors in mice by simultaneous application of 13-cis-retinoic acid and retinyl palmitate (vitamin A palmitate)

Two retinoids (13-cis-retinoic acid and retinyl palmitate ) have been shown to exert a good preventive effect in chemically induced papillomas and carcinomas of the skin in female Swiss mice; this effect was investigated over a period of 23 weeks. The tumors were induced by repeated topical application of 3-methylcholanthrene (0.3% MCA, dissolved in acetone; 14 applications). Retinyl palmitate (RP; 6 mg in 0.1 ml acetone/mouse; 10 applications) and 13-cis-retinoic acid (RA; 3 mg in 0.1 ml acetone/mouse; 10 applications) were also administered topically for the 3rd to 9th week from the start of the experiment. This investigation gave evidence for the fact that both the retinoids did not only inhibit the development of skin papillomas but had also a marked effect on skin carcinomas.

Food increases the bioavailability of isotretinoin

Twenty healthy male subjects received 80 mg (2 X 40 mg SEG capsules) oral isotretinoin separated by two-week washout periods in an open randomized crossover design. Isotretinoin was administered during a complete fast, 1 hour after a standard breakfast, with a standard breakfast, or 1 hour before a standard breakfast. Blood samples were obtained at specific times over a 72-hour period. Isotretinoin blood concentrations were determined by a specific HPLC method. The relative bioavailability (AUC) of isotretinoin was found to be approximately 1.5 to 2 times greater when the dose was administered 1 hour before, concomitantly with, or 1 hour after a meal than when it was given during a complete fast. In addition, because the Cmax value is lower when the dose is administered with food rather than 1 hour after a meal, coadministration of isotretinoin with food may be the best method of administration.

Localization of de novo sterologenesis in mammalian skin

Previous studies have demonstrated that the skin is an important site of de novo sterol synthesis and that there is a sex difference in cutaneous sterologenesis with male animals synthesizing more sterols than females. The aim of the present study was to localize the major sites of sterol synthesis within the skin and to determine which of these sites accounted for the sex differences in sterologenesis. In male and female rats whose dermal and epidermal layers are separated by dithiothreitol treatment, the dermis is the major site of skin sterologenesis (males 86% of total, females 82% of total). Moreover, the sex difference in skin sterol synthesis is quantitatively localized primarily within the dermal layer (approximately 2.5-fold greater in the dermis of males). Sterol synthesis is also increased in the epidermis of males. To rule out the possibility that sebaceous gland production accounted for our observations, we treated animals with isotretinoin (13-cis-retinoic acid), a drug that suppresses sebaceous gland sebum production. Sterol synthesis in the skin of both male and female rats is not significantly altered by isotretinoin administration and the sex difference in skin sterologenesis is unaffected. To further localize the sites of sterol synthesis within the skin, studies of hairless mice whose skin was split by DTT were initiated. In hairless mice, DTT separates the epidermis into upper (stratum corneum and granulosum) and lower (basal and spinous cells) strata. The basal layer was separated from the dermis by gentle scraping. As in rats, the dermis is the chief site of sterol synthesis in the skin. In addition, the lower layer of the epidermis (basal and spinous cells) is also a very active site of sterologenesis, accounting for 20% of total skin nonsaponifiable lipid synthesis. The upper epidermis accounted for only a small portion of total skin synthesis. It is highly likely that the bulk of cutaneous sterol synthesis occurs in the pilosebaceous epithelium.

Isotretinoin treatment of acne and related disorders: an update

In the one year since isotretinoin has been available in the United States for the treatment of severe, recalcitrant, nodulocystic acne, there has been extensive clinical verification of the reports of its dramatic efficacy in the treatment of this troublesome disease. Proper selection of patients, as well as treatment with adequate doses of drug for 3 to 5 months, will most often result in significant clinical improvement or total clearing. Although dosages of less than 1 mg/kg/day may produce a nearly equivalent degree of improvement with somewhat fewer or less severe side effects, the recommended daily dose remains 1 mg/kg/day because lower dosages are associated with more frequent relapses. In severe cases, the daily dosage may be increased to 2 mg/kg/day. Teratogenicity, elevation of serum triglycerides, liver function abnormalities, pancreatitis, and pseudotumor cerebri may all be associated with isotretinoin therapy and require close monitoring of the patient.

Research strategies at the interface of medicine and psychiatry

The rapid growth of the neurosciences in the past decade has served to blur the differences and enhance the similarities between research in medicine and in psychiatry. As the number of relevant biological variables and the questions asked in relation to them has expanded, so has the number of medical disorders of interest to the clinical researcher in psychiatry. In addition to these new areas of common interest, consultation-liaison psychiatry and clinical psychiatric research share a common conceptual foundation based upon model development and testing. It is proposed, therefore, that research at the interface between medicine and psychiatry represents a new frontier for both consultation-liaison psychiatry and clinical psychiatric research. Goals and strategies for research at the interface are discussed with specific reference to current research efforts at the National Institutes of Health.

Isotretinoin in severe, recalcitrant cystic acne: a review

Isotretinoin, an isomer of retinoic acid, recently has been approved by the Food and Drug Administration for treatment of severe, recalcitrant acne. The most impressive effects include inhibition of sebum production and a reversible decrease in sebaceous gland size. Isotretinoin has proved to be an effective drug; response to therapy has been seen in virtually 100 percent of patients treated. Almost all patients experience reversible cutaneous and mucous-membrane symptoms while on isotretinoin treatment. Other common side effects include conjunctivitis (38 percent) and eye irritation (50 percent). The recommended dosage is 1-2 mg/kg/d for no longer than 16 weeks. Isotretinoin is currently the treatment of choice for severe, recalcitrant acne; however, because of potential side effects associated with retinoids, isotretinoin should be reserved for those patients who are unresponsive to conventional therapy, including topical and systemic antibiotics.

Effect of oral 13-cis-retinoic acid at three dose levels on sustainable rates of sebum secretion and on acne

Changes in sustainable rates of sebum secretion were followed in twenty patients with severe acne who were receiving oral treatment with 13-cis-retinoic acid in dosages of 0.1, 0.5, or 1.0 mg/kg/day. Sebum secretion was measured by absorption of skin surface lipid into bentonite clay and estimation of the amount of absorbed sebum by measurement of its wax ester component. Pretreatment rates of sebum secretion in the patients were greatly elevated in comparison with previously measured values in young adult subjects without acne. After 4 weeks of treatment, mean rates of sebum secretion on all three dose levels fell to or below the range for normal subjects. On-treatment rates of sebum secretion were significantly lower in patients on the highest dose compared to patients on the lowest dose. When the drug was discontinued, rates of sebum secretion recovered slowly. Clinical response was excellent in most of the subjects. The five subjects with least favorable response clinically all had better than average suppression of sebum production.

Healing of experimental corneal wounds treated with topically applied retinoids

We treated experimental corneal epithelial wounds in rabbits with topical retinoids. Treatment with 0.1% all-trans-retinoic acid three times per day resulted in a 21% increase in the healing rate compared to the control eyes. Treatment five times a day resulted in a 35% increase in healing rate. Treatment with topical retinoic acid also promoted corneal deturgescence. Retinyl palmitate, retinyl acetate, retinol, and 13-cis-retinoic acid had no effect on corneal wound healing. These data suggested that topically applied all-trans-retinoic acid may be effective in promoting corneal healing after surgery and in the treatment of persistent and recurring corneal epithelial defects.

Recent advances in the treatment of psoriasis

Because psoriasis is a disease of unknown etiology, all treatments are based on empirical experience and diverse scientific theories. Although there is no present cure for psoriasis, many forms of therapy are effective in control of the disorder. These range from topical medications such as tar, anthralin, corticosteroids; phototherapy and photochemotherapy; systemic medication, including cytotoxic agents; and vitamin A analogues or retinoids. This report focuses on modifications of existing therapies based on advances in basic science knowledge and technology, combination therapies, as well as new therapeutic agents and new approaches to the treatment of psoriasis.

Phospholipid composition of liver in rats fed high levels of 13-cis retinoic acid

The composition of liver phospholipids was studied in rats fed for 4 weeks diets containing 0, 100 or 300 mg 13-cis retinoic acid per kg diet. There was a significant decrease in phosphatidylcholine content, whereas the levels of phosphatidylethanolamine were slightly increased in liver phospholipids of rats fed 13-cis retinoic acid. The fatty acid composition of total phospholipids, PC, PE, and P1 + PS fractions revealed a general increase in the levels of 18:2 and 20:3 omega 6, whereas the levels of 20:4 omega 6 and C22 fatty acids were reduced in most of the hepatic phospholipids isolated from rats fed 13-cis retinoic acid containing diets. A decrease in the double-bond index of fatty acids was also observed in phospholipids of rats fed 13-cis retinoic acid. The data suggest that high levels of 13-cis retinoic acid may possibly be influencing the activities of microsomal desaturating and chain-elongating enzymes in the liver.

Effect of 13-cis retinoic acid on fatty acid composition and membrane-associated enzymes in rat submandibular salivary glands

Weanling rats were fed for 4 weeks semipurified diets containing 0, 100 or 300 mg 13-cis retinoic acid per kg diet. The activities of (Na+ + K+)-ATPase, Mg2+-ATPase and gamma-glutamyltranspeptide were measured in submandibular salivary gland (SMSG) homogenates. The activity of (Na+ + K+)-ATPase in the SMSG was reduced in rats fed 13-cis retinoic acid. There was no effect on the activities of the other two enzymes. Fatty acid composition of total lipids in SMSG suggest that decrease in (Na+ + K+)-ATPase activity may be associated with changes in fatty acid composition of total lipids.

Pharmacokinetics of isotretinoin during repetitive dosing to patients

The multiple dose pharmacokinetics of isotretinoin and its major blood metabolite, 4-oxo-isotretinoin, were studied in 10 patients with cystic acne and 11 patients with various keratinization disorders. Blood samples were obtained at predetermined times following the first dose, interim doses and the final dose. Blood concentrations of isotretinoin and 4-oxo-isotretinoin were measured by a specific and sensitive HPLC method. A lag time was usually observed prior to the onset of absorption following oral administration of the drug in a soft elastic gelatin capsule. Absorption then proceeded rapidly and maximum blood concentrations usually occurred within 4 h of drug administration. The harmonic mean half-life for the elimination of isotretinoin by the cystic acne patients was approximately 10 h after the initial dose and did not change significantly following 25 days of 40 mg b.i.d. dosing. Steady-state blood concentrations remained relatively constant after the fifth day of dosing. The harmonic mean elimination half-life in the patients with various disorders of keratinization was about 16 h. The results of the 2 studies suggest that no significant changes in the pharmacokinetics of isotretinoin occur during multiple dosing and that the multiple dose pharmacokinetic profile is predictable and can be described using a linear pharmacokinetic model. This suggests that the steady-state concentrations of isotretinoin can be predicted from single dose data.

Use of a human tumor cloning system to screen retinoids for antineoplastic activity

Retinoid analogs are being actively evaluated as antitumor agents in man. A human tumor cloning system was used to assess the antineoplastic activity of all-trans-retinoic acid, all-trans-retinol and 13-cis-retinoic acid. The effect of retinoids on the formation of tumor colony forming units (T-CFU) was surveyed for 67 different human tumors. These analogs showed minor activity in a variety of neoplasms. The decrease in T-CFU varied between histologic tumor types and between tumor of the same type. No significant difference between retinoid analogs was noted.

In vitro retinoid binding and release from a collagen sponge material in a simulated intravaginal environment

Four in vitro preparations were constructed to simulate the intravaginal release of two retinoids, all-trans-retinoic acid (t-RA) and 13-cis-retinoic acid (c-RA), from a 0.7% collagen sponge diaphragm insert. Four t-RA concentrations, 0.019, 0.05, 0.1, and 0.15% in methanol were added to the sponge. The release into an artificial vaginal fluid was monitored serially over 72 h by serial analysis for t-RA and c-RA using high-pressure liquid chromatography. In each preparation, retinoid release was immediate and noncontinuous. At 37 degrees C, the retinoids were stable for at least 48 h. Trans-retinoic acid was the predominant retinoid recovered. Only trace amounts of the cis-isomer were released. Peak t-RA levels were 20 microM after 0.01%, 60-80 microM after 0.05%, 100-200 microM after 0.1%, and 320 microM after 0.15%. When the vaginal fluid bath was changed after 5 h, no further significant retinoid release occurred. There was significant loss of up to 70% of the applied t-RA into the collagen sponge. The retinoid binding was concentration dependent (higher binding with higher concentrations) and was maximal only after 24 h of co-incubation. The discontinuous release of t-RA and the high degree of binding to collagen would seem to preclude use of the diaphragm insert as a vaginal drug delivery system, at least for retinoids.

Effect of oral 13-cis-retinoic acid on serum lipids

Serum lipid concentrations were measured in eighteen patients with severe acne before, during and after treatment with 0.8 mg/kg 13-cis-retinoic acid for 3 months. Cholesterol and triglyceride concentrations increased and HDL-cholesterol concentrations fell significantly during therapy. There were significant abnormalities of liver function and small decreases in indices of thyroid function. These changes had reverted to normal by 1 month after treatment. The data suggest that use of the drug in acne is likely to be limited by its toxicity.

Premature epiphyseal closure in a child receiving oral 13-cis-retinoic acid

A boy with epidermolytic hyperkeratosis was treated systemically for 4 1/2 years with 13-cis-retinoic acid. At the age of 10 1/2 years, he developed pain in his right knee and radiographic evidence of partial closure of the proximal epiphysis of the right tibia. Similar radiographic changes have been described in individuals ingesting excessive amounts of vitamin A.

A double-blind study of the effects of 13-cis-retinoic acid on acne, sebum excretion rate and microbial population

Forty-eight acne patients were treated orally with 13-cis-retinoic acid in a double-blind dose response study. There was a marked clinical improvement with a concomitant reduction in sebum excretion rate (SER) and production rate of free fatty acids (FFA). Microbial numbers decreased significantly; the decrease in propionibacteria was greater than that of aerobic bacteria. The decline in micro-organisms occurred after the reduction in sebum and FFA production. This suggests that the effect of the drug upon micro-organisms is secondary to the change in sebum excretion but it is nevertheless an important factor in the resolution of the acne.

Phase II trial of 13-cis-retinoic acid in metastatic breast cancer

Studies have suggested that both natural and synthetic retinoids have extensive chemopreventive activity against a variety of carcinogens in vivo and in vitro. We have previously shown that growth of human breast cancer cells can be inhibited by retinoids, and retinoic acid-binding proteins have been demonstrated in these cell lines and tumor biopsies. We studied the activity of 13-cis-retinoic acid in the treatment of 18 patients with advanced breast cancer refractory to standard cytotoxic and/or endocrine therapy. Patients began on 0.5 mg/kg and escalated to 8 mg/kg over a one-month period unless toxicity (dry skin, dry mucosa, cheilitis, conjunctivitis) forced dose reduction. All these toxicities responded promptly to dose reduction. Four patients exhibited drug related hypercalcemia, 2 complained of severe earache and several had nausea, vomiting and abdominal cramping. There were no objective responses as defined by standard criteria. One patient with thrombocytopenia secondary to documented marrow involvement demonstrated a recovery of platelet count from 9000 to 110,000. 13-cis-Retinoic acid is not of apparent value in women with heavily pretreated breast cancer.

Pharmacokinetics of isotretinoin following a single oral dose

A pharmacokinetic profile was developed following oral administration of a single 100-mg oral dose of isotretinoin to 12 normal male volunteers. Concentrations of isotretinoin and its isomer, tretinoin, were measured in blood samples from 12 subjects and in urine and fecal samples from three of the 12 subjects. Blood concentration-time data during a 72-hour sampling interval were variable and, in five of the 12 cases, showed pronounced secondary and tertiary concentration maxima which were consistent with the theory of enterohepatic circulation (EHC) of isotretinoin in man. In five of the 12 subjects, adequate fits of the data could not be obtained using classical bi- or triexponential equations but were successfully fitted using a recently developed recycling model. Maximum blood concentrations of isotretinoin ranged from 74 to 511 ng/ml and occurred between 1 and 4 hours after dosing. Secondary maxima generally occurred between 6 and 24 hours after dosing. The harmonic mean elimination half-life was approximately 20 hours. These findings suggest that steady-state blood concentrations should be observed within one week. Negligible amounts of unchanged isotretinoin were excreted in urine, whereas 53 to 74 per cent of the dose was recovered as intact isotretinoin in the feces. The amount of intact drug in the feces could reflect biliary excretion of the conjugate of isotretinoin that is deconjugated beyond the site where absorption may occur, as well as unabsorbed drug.

Therapy of acne

Today acne vulgaris is a disease which can be well controlled using a combination of topical, systemic, and physical therapeutic modalities. However, successful acne management depends to a large extent on physician interest and the ability of the physician to apply therapy to the evolutionary stage of the disease and to the disturbed pathogenetic mechanisms. It is this author's opinion that grades I and II comedonal and papulopustular acne can be effectively treated solely with topical preparations, particularly the concurrent use of tretinoin with benzoyl peroxide or topical antibiotics. The majority of patients with grades III and IV inflammatory disease require oral antibiotics in addition to aggressive topical treatments. Intralesional steroids can be effective in all grades of acne when lesions develop an inflammatory nodulocystic quality. The physician should consider the use of estrogen (in females) or oral vitamin A in the small group of patients with grades III and IV inflammatory-cystic acne that has been unresponsive to conventional therapy. Combined systemic therapies of high-dose antibiotics, systemic corticosteroids, and sulfones clearly take precedence over topical preparations in conglobate acne and acne fulminans. Finally, oral isotretinoin, alone and perhaps in combination with more conventional modalities, should play an important role in the future management of severe inflammatory-cystic acne.

Changes in long-term sebum production from isotretinoin therapy

Sebum production has been measured in twenty patients in whom 13-cis-retinoic acid therapy had been discontinued for at least 20 weeks. While sebum production had returned to pretreatment levels by 30 weeks in seven subjects, 30% to 80% reduction in sebaceous gland activity was still present for as long as 80 weeks in eight subjects. Four of these eight patients, who were followed for more than a year, still had marked sebaceous inhibition when last tested. The prolonged remission seen in patients with nodulocystic acne may be related in part to continued sebaceous gland inhibition in some patients, but it obviously is not the only actor responsible for the long-term improvement that is seen.

Actions of isotretinoin and etretinate on the pilosebaceous unit

Isotretinoin administered subcutaneously to male hamsters results in marked involution of the sebaceous glands of the flank organ without discernible effort on the other androgen-dependent structures, pigmented hair follicles, and dermal melanocytes. Treatment of androgen-stimulated female hamsters with isotretinoin prevented the androgen-induced growth of the sebaceous glands but not the formation of large pigmented hairs and dermal pigment cells. Etretinate, in comparable dosage, did not show the inhibitor effect on sebaceous gland growth. The hamster flank organ seems a promising system for assessment of the sebaceous gland inhibitory activity of retinoids and may be predictive for therapeutic activity in acne.

Comparative effect of isotretinoin and etretinate on acne and sebaceous gland secretion

Isotretinoin (13-cis-retinoic acid) was compared with the aromatic retinoid, etretinate, in patients with severe nodulocystic acne. Evaluation of fifty-six such men receiving 1 mg/kg of one or the other of these two drugs was performed with regard to clinical improvement and change in sebum production. Lesion counting demonstrated a significant improvement in patients receiving isotretinoin, particularly in facial lesions. There was significantly less improvement with etretinate. Similarly, isotretinoin produced a marked suppression of sebum production. There was little effect of etretinate on sebum production. Side effects were limited primarily to the skin and mucous membranes.

General clinical toxicology of oral retinoids

Four retinoids - retinol (vitamin A), tretinoin (retinoic acid), etretinate (the ethyl ester of trimethoxymethylphenyl retinoic acid), and isotretinoin (13-cis-retinoic acid, Accutane) - have been administered orally in humans for therapeutic purposes. A review of the available information on the clinical toxic effects of these substances indicated that, while they express similar spectra of toxicity, they also differ in the extent to which they affect various body systems. This suggests that differential efficacy of the retinoids may be related, in part, to the cutaneous sites of maximum activity.

Changes in lipid metabolism during retinoid administration

Administration of oral vitamin A and the synthetic retinoids to humans and experimental animals has been accompanied by changes in lipid metabolism. these changes include alterations in serum, liver, and skin surface lipids. While the immediate cause(s) of the serum and liver changes remain(s) obscure, the skin surface lipid alterations appear to be secondary to changes in sebum production. The most marked effect of retinoid feeding seen in clinical or animal studies is that of hypertriglyceridemia. The increased serum triglycerides are found primarily in the very low-density lipoprotein (VLDL) fraction of the blood and occur during both the fasted and fed state. In rats, oral all-trans-retinoic acid, 13-cis-retinoic acid, and natural vitamin A have resulted in hypertriglyceridemia, while in man, 13-cis-retinoic acid, etretinate, and natural vitamin A have been reported to elicit this response. Current studies using the rat indicate that elevated serum triglycerides may be secondary to both increased liver secretion and decreased extrahepatic breakdown. Ongoing work from our laboratory and the possible primary causes of the systemic lipid changes are discussed.

Action of isotretinoin in acne rosacea and gram-negative folliculitis

Good to excellent clinical results have been obtained in the treatment of severe inflammatory acne (acne conglobata, acne fulminans, and acne conglobata with hidradenitis and dissecting cellulitis of the scalp) with orally administered isotretinoin (13-cis-retinoic acid). Similar promising results have been obtained in patients with severe rosacea and gram-negative folliculitis. Isotretinoin probably has multiple modes of action, including (1) inhibition of sebaceous gland activity, (2) inhibition of the growth of Propionibacterium acnes within the follicle, although the retinoid is not antibacterial, (3) inhibition of inflammation, and (4) alteration of the pattern of keratinization within the follicle, as demonstrated by light and ultrastructural studies.

Isotretinoin versus placebo in the treatment of cystic acne. A randomized double-blind study

Thirty-three patients with treatment-resistant cystic and conglobate acne entered a randomized, double-blind protocol testing the efficacy of isotretinoin versus placebo. There was an overall 57% increase in the number of cystic lesions in seventeen patients who initially received placebo. Sixteen of these seventeen patients then received isotretinoin, with a resultant 98% improvement. The sixteen patients who had been randomly assigned to receive initial therapy with isotretinoin had a 95% improvement. Twenty-seven of the thirty-two patients treated with isotretinoin cleared completely. The average maximum dosage of isotretinoin received by these patients was 1.2 mg/kg/day. Eighteen patients received only one 4-month course of isotretinoin. Fifteen patients received two courses. These included twelve patients with predominantly truncal acne who responded partially to the first course, and three patients who had cleared completely after one course of therapy but had mild relapses after an average of six months off of treatment. All patients are now in remission averaging 38 months in duration. Skin biopsies and quantitative measurement of sebum production during therapy indicated a profound inhibition of sebaceous gland size and function, which may be central to the mechanism of action of isotretinoin in acne.

The effects of retinoids on neutrophil functions in vitro

Vitamin A (retinol) and its analogues (retinoids) are clinically effective in cystic acne and psoriasis, diseases in which neutrophils may constitute major components of inflammatory cell infiltrates. We found that the earliest histopathologic alteration in psoriasis is the disappearance of neutrophils at 2 to 4 weeks after the initiation of therapy with etretinate. Since retinoids may exert anti-inflammatory effects by virtue of an action upon neutrophils, we studied the effects of the following retinoids on discrete neutrophil functions in vitro: retinol, retinyl acetate, retinal, tretinoin, isotretinoin, etretinate, and Ro 10-1670. Although they had no significant effects upon aggregation, chemokinesis, or chemotaxis, all of the retinoids, with the exception of etretinate and Ro 10-1670, profoundly inhibited superoxide anion production and lysosomal enzyme release. Tretinoin and isotretinoin were the most effective inhibitors. We propose that these drugs exert their pharmacologic effects (resolution of inflammatory lesions) by inhibiting the release of mediators of inflammation and by preventing the accumulation of neutrophils in acne lesions when applied topically or systemically, respectively.

Effects of all-trans-retinoic acid (retinoic acid) and 4-hydroxyphenylretinamide on synovial cells and articular cartilage

We studied the effects of two retinoids, naturally occurring all-trans-retinoic acid (retinoic acid) and the synthetic 4-hydroxyphenylretinamide (4-OH-PRT) on monolayer cultures of rabbit synovial fibroblasts and on explants of rabbit articular cartilage. Treatment of fibroblasts with phorbol myristate acetate (PMA; 10(-8) M) induced the synthesis and secretion of large amounts of collagenase: this was inhibited if the cells were treated with retinoic acid (10(-6) M) or dexamethasone (10(-7 M). Combined treatment with retinoic acid and the steroid prednisolone, at concentrations as low as 19(-10) M, gave an additive inhibition of collagenase production. Both retinoids inhibited collagenase production, but only 4-OH-PRT prevented the increase in prostaglandin E2 (PGE2) induced by PMA. Levels of plasminogen activator were also increased by treatment with PMA, and concomitant addition of either retinoid further enhanced this stimulation. Possible toxicity was assessed by measuring release of glycosaminoglycans (GAG) from explants of articular cartilage. Treatment with retinoic acid induced release of 80% of the total GAG, whereas treatment with 4-OH-PRT resulted in release of 40% of the total, a finding similar to that seen with untreated samples. 4-OH-PRT inhibited production of collagenase and PGE2 by rabbit synovial fibroblasts but was not toxic to articular cartilage.

Determination of 13-cis-retinoic acid and its major metabolite, 4-oxo-13-cis-retinoic acid, in human blood by reversed-phase high-performance liquid chromatography

A high-performance liquid chromatography (HPLC) method for the quantitation of 13-cis-retinoic acid (13-cis-RA) and its major metabolite, 4-oxo-13-cis-RA, in human blood has been developed. The method includes extraction of 1 ml of blood with diethyl ether at pH 6 and the analysis of the extract by reversed-phase HPLC with solvent programming and detection at 365 nm. The quantitation ranges for 13-cis-RA and 4-oxo-13-cis-RA are 10--2000 and 50--2000 ng/ml of blood, respectively. The method also provides estimates of the concentrations of all-trans-RA and 4-oxo-all-trans-RA. The mean intra- and inter-assay variabilities for all four compounds were 6% or less. The method separates 13-cis-RA and 4-oxo-13-cis-RA from 9-cis-RA, all-trans-RA, 4-oxo-all-trans-RA, and some other possible metabolites, such as hydroxy and epoxy retinoic acids. The method has been successfully applied to the analyses of over 1200 blood samples from four 13-cis-RA clinical studies.

Retinoic acid. Inhibition of the clonal growth of human myeloid leukemia cells

Vitamin A and its analogues (retinoids) affect normal and malignant hematopoietic cells. We examined the effect of retinoids on the clonal growth in vitro of myeloid leukemia cells. Retinoic acid inhibited the clonal growth of the KG-1, acute myeloblastic leukemia, and the HL-60, acute promyelocytic leukemia, human cell lines. The KG-1 cells were extremely sensitive to retinoic acid, with 50% of the colonies inhibited by 2.4-nM concentrations of the drug. A 50% growth inhibition of HL-60 was achieved by 25 nM retinoic acid. Complete inhibition of growth of both leukemia cell lines was seen with 1 microM retinoic acid. Exposure of KG-1 cells to retinoic acid for only 3-5 d was sufficient to inhibit all clonal growth. The all-trans and 13-cis forms of retinoic acid were equally effective in inhibiting proliferation. Retinal, retinyl acetate, and retinol (vitamin A) were less potent inhibitors. Clonal growth of the human K562 and mouse M-1 myeloid leukemic cell lines was not affected by 10 microM retinoic acid. Retinoic acid also inhibited the clonal growth of leukemia cells from five of seven patients with acute myeloid leukemia. Retinoic acid at concentrations of 5 nM to 0.3 microM inhibited 50% clonal growth, and 1 microM retinoic acid inhibited 64-98% of the leukemic colonies. The inhibition of clonal growth of KG-1 and HL-60 cell lines and of leukemic cells from two patients was not associated with the presence of a specific cytoplasmic retinoic acid-binding protein. Our study suggests that retinoic acid may prove to be effective in the treatment of human myeloid leukemia.

Effect of 13-cis-retinoic acid on sebum production and Propionibacterium acnes in severe nodulocystic acne

Ten patients treated with 13-cis-retinoic acid demonstrated a 70% reduction in sebum excretion on the forehead and cheek. An average reduction of 66% occurred in the 1st month, slowly increased to 70% by the 3rd month, and then remained constant for the final 2 months of therapy. Concomitant with this sebum excretion reduction was a fall in the number of Propionibacterium acnes recovered from both sites. Pretreatment values of 10(4) P. acnes per square centimeter (cm2) fell to 10(3) per cm2 after 1 month and 10(2) after 9 months of therapy. P. acnes was not recovered from six of the ten subjects in the following 3 months and only at levels of 10(2) per cm2 in three subjects. One subject's P. acnes level was reduced to only 10(4) per cm2. Following discontinuation of therapy, sebum levels and P. acnes counts showed a trend to recover to pretreatment levels within 2 months.