Pharmacokinetics and pharmacodynamics of 9-cis-retinoic acid in healthy men

A systematic review of retinoic acid in the journey of spermatogonium to spermatozoa: From basic to clinical application

Background: Retinoic acid plays an essential role in testicular development and functions, especially spermatogenesis. We have reviewed the role of retinoic acid from basic (molecular) to clinical application.

Methods: A search was conducted in the online database including PubMed, Google Scholar, and Scopus for English studies published in the last eight years about this issue. We used the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines in assessing the studies we are going to investigate.

Results: Studies indicated that retinoic acid plays an essential role during pluripotent stem cell migration and lineage commitment, cell differentiation, apoptosis, stem cell number regulation, and maturation arrest in spermatogenic cells. Retinoic acid can also affect related protein expression and signaling pathways at different stages of spermatogenesis. Four studies have applied retinoic acid to humans, all of them in the single-arm observational study. The results look promising but need further research with more controlled study methods, randomization, and large samples.

Conclusions: This current systematic review emphasizes a novel retinoic acid mechanism that has not been well described in the literature previously on its functions during the first seven days of spermatogenesis, leading to new directions or explanations of male infertility cause and treatments as a part of reproductive health care.

Alitretinoin for the treatment of severe chronic eczema of the hands

INTRODUCTION

Chronic hand eczema (CHE) is a frequent skin disorder affecting up to 10% of the population and strongly reduces Quality of Life (QoL). The first-line therapeutic strategies for the management of CHE include a change of lifestyle, an education program for the skin and the application of specific emollients. Topical corticosteroids or calcineurin inhibitors are the most used anti-inflammatory drugs. However, up to 65% of patients require systemic options. Alitretinoin, a retinoid structurally related to vitamin A, is the first systemic treatment approved in the European Union (EU) for severe CHE refractory to potent topical corticosteroids.

AREAS COVERED

This review summarizes the available data on the pharmacokinetics, pharmacodynamics, efficacy, and safety profile of oral alitretinoin for the treatment of CHE.

EXPERT OPINION

Alitretinoin can be considered as a valid therapeutic option for the treatment of CHE in patients not responding to ordinary treatments. Clinical trials and real-life experiences showed that it acts effectively on both objective and subjective clinical signs, resulting in a significant improvement in QoL of patients. As for other retinoids, caution should be taken in patients with certain chronic diseases (hepatopathies, kidney failure, hyperlipidemia, thyroid dysfunction) or childbearing potential women.

Low levels of alitretinoin in seminal fluids after repeated oral doses in healthy men

BACKGROUND

Alitretinoin, like all retinoids, is teratogenic, and can only be given to women of childbearing potential if pregnancy is excluded and a strict contraceptive programme is followed.

AIM

This study was designed to determine whether alitretinoin in the semen of men treated with alitretinoin poses a teratogenic risk to their female partners.

METHODS

In total, 24 healthy men aged 18-45 years received alitretinoin 20 mg (n = 12) or 40 mg (n = 12), once daily for 14 days. Subjects in the 40 mg dose group provided ejaculate at baseline, on day 1, before and approximately 4 h after dosing on day 2, and at follow-up on study day 21 (± 2).

RESULTS

Alitretinoin and 4-oxo-alitretinoin were detected in 11 of the 12 semen samples. The highest level of alitretinoin in semen was 7.92 ng/mL. Assuming an ejaculate volume of 10 mL, the amount of drug transferred in semen would be about 80 ng, 1/375,000 of a single 30 mg capsule. Complete absorption of 80 ng of alitretinoin from semen, presuming a volume of distribution confined to 5 L of circulating blood in the partner, would lead to an increase in plasma alitretinoin concentration of 0.016 ng/mL, which appears to be negligible compared with measured endogenous plasma levels. Increases in plasma levels of related retinoids are also negligible.

CONCLUSIONS

Alitretinoin in the semen of men receiving up to 40 mg of oral alitretinoin per day is unlikely to be associated with teratogenic risk in their female partners. Barrier contraception is therefore not required for men taking alitretinoin.

Development and characteristics of a human cell assay for screening agents for melanoma prevention

This paper describes the development and initial evaluation of a human cell assay to identify potentially efficacious agents for preventing melanoma. Four human cell lines were used: normal melanocytes, a radial growth-phase-like melanoma cell line (WM3211), a vertical growth-phase-like melanoma cell line (Lu1205), and 83-2c, a cell strain cloned from metastatic melanoma. Four endpoints were evaluated in ultraviolet B-treated cells: annexin V, human leukocyte antigen-DR; E-cadherin, and N-cadherin. Annexin V was induced by nimesulide, 4-hydroxyphenylretinamide, and difluoromethylornithine in ultraviolet-B-treated radial growth-phase-like melanoma cells. None of the agents inhibited human leukocyte antigen-DR expression in ultraviolet-B-treated radial growth-phase-like melanoma cells, the only cells that strongly expressed human leukocyte antigen-DR. E-cadherin was overexpressed only in radial growth-phase-like melanoma cells relative to melanocytes, and ultraviolet B exposure dramatically reduced this expression. E-cadherin was only induced by difluoromethylornithine in ultraviolet-B-treated radial growth-phase-like melanoma cells. N-cadherin was over- expressed in all melanoma cell lines relative to melanocytes. In this study, all candidate preventive agents inhibited N-cadherin in ultraviolet B-treated radial growth-phase-like melanoma cells. Four agents inhibited N-cadherin in ultraviolet B-treated vertical growth-phase-like melanoma cells. The mean ratios of N-cadherin to E-cadherin levels and specific endpoint responses for both the radial growth-phase-like melanoma and vertical growth-phase-like melanoma cells were used to rank the agents. Agents were evaluated at clinically relevant concentrations. The rankings were difluoromethylornithine>4-hydroxyphenylretinamide>nimesulide>9-cis-retinoic acid>polyphenon E. Diphenylhydramine, D-mannitol, and nordihydroguaiaretic acid were inactive. The results of these initial studies suggest that ultraviolet-B-treated radial growth-phase-like melanoma cells are the most responsive to chemopreventive agents, and may be the cell line of choice for screening melanoma prevention agents.

Medication-induced intracranial hypertension in dermatology

Pseudotumor cerebri (PTC) is a syndrome of intracranial hypertension that is idiopathic or from an identified secondary cause. It is characterized by headaches and visual manifestations. The hallmark of PTC is papilledema and the feared consequence is visual loss that may be severe and permanent. The idiopathic form generally occurs in obese women of childbearing age. Various medications may produce PTC in patients at any age, including children. Several medications used in dermatology, particularly those used in the treatment of acne vulgaris, are associated with PTC. There is a strong association with tetracycline usage. Minocycline and doxycycline have also been linked to PTC, although there are relatively few reported cases. PTC has also been described with retinoids, including vitamin A (retinol) and isotretinoin. Although corticosteroids are often used to lower intracranial pressure acutely, corticosteroid withdrawal after long-term administration may induce increased intracranial pressure. A high index of suspicion, early diagnosis and treatment generally yield a good prognosis.

Chondrocytes isolated from tibial dyschondroplasia lesions and articular cartilage revert to a growth plate-like phenotype when cultured in vitro

We report here a comparative study of the development and behavior of chondrocytes isolated from normal growth plate tissue, tibial dyschondroplasic lesions, and from articular cartilage. The objective of these studies was to determine whether the properties exhibited by chondrocytes in dysplasic lesions or in articular cartilage were due to their cellular phenotype, their environment, or both. We had previously analyzed the electrolytes and amino acid levels in the extracellular fluid of avian growth plate chondrocytes. Using these data, we constructed a culture medium (DATP5) in which growth plate cells essentially recapitulate their normal behavior in vivo. Here, we used DATP5 to examine the behavior of chondrocytes isolated from lesions of tibial dyschondroplasia (TD). We found that once isolated from lesion and grown in this supportive medium, dysplasic chondrocytes behaved essentially like normal growth plate cells. These findings suggest that the cause of TD is local factors operating in vivo to prevent these cells from developing normally. With respect to articular chondrocytes, our data indicate that they more closely retain normal protein and proteoglycan synthesis when grown in serum-free media. These cells readily induced mineral formation in vitro, both in the presence and absence of serum. However, in serum-containing media, mineralization was significantly enhanced when the cells were exposed to retinoic acid (RA) or osteogenic protein-1 (OP-1). Our studies support previous work indicating the presence of autocrine factors produced by articular chondrocytes in vivo that prevent mineralization and preserve matrix integrity. The lack of inhibitory factors and the presence of supporting factors are likely reasons for the induction of mineralization by articular chondrocytes in vitro.

Correlation of in vitro chemopreventive efficacy data from the human epidermal cell assay with animal efficacy data and clinical trial plasma levels

The human epidermal cell (HEC) assay, which uses carcinogen exposed normal skin keratinocytes to screen for cancer prevention efficacy, was used to screen possible preventive agents. The endpoints measured were inhibition of carcinogen-induced growth and induction of involucrin, an early marker of differentiation. Sixteen of twenty agents (apigenin, apomine, budesonide, N-(2-carboxyphenyl)retinamide, ellagic acid, ibuprofen, indomethacin, melatonin, (-)-2-oxo-4-thiazolidine carboxylic acid, polyphenon E, resveratrol, beta-sitosterol, sulfasalazine, vitamin E acetate, and zileuton) were positive in at least one of the two assay endpoints. Four agents (4-methoxyphenol, naringenin, palmitoylcarnitine chloride, and silymarin) were negative in the assay. Nine of the sixteen agents were positive for both endpoints. Agents that showed the greatest response included: ellagic acid > budesonide, ibuprofen > apigenin, and quinicrine dihydrochloride. Fifty-eight of sixty-five agents that have been evaluated in the HEC assay have also been evaluated in one or more rodent bioassays for cancer prevention and several are in clinical trials for cancer prevention. The assay has an overall predictive accuracy of approximately 91.4% for efficacy in rodent cancer prevention irrespective of the species used, the tissue model, or the carcinogen used. Comparison of the efficacious concentrations in vitro to plasma levels in clinical trials show that concentrations that produced efficacy in the HEC assay were achieved in clinical studies for 31 of 33 agents for which plasma levels and/or C(max) levels were available. For two agents, 9-cis-retinoic acid (RA) and dehydroepiandrosterone (DHEA), the plasma levels greatly exceeded the highest concentration (HC) found to have efficacy in vitro. Thus, the HEC assay has an excellent predictive potential for animal efficacy and is responsive at clinically achievable concentrations.

Antitumor activity of oral 9-cis-retinoic acid in HIV-associated Kaposi's sarcoma

OBJECTIVE

To assess the efficacy, safety and tolerance of oral 9-cis-retinoic acid in HIV-infected patients with Kaposi's sarcoma.

METHODS

Sixty-six patients with AIDS-related Kaposi's sarcoma were enrolled at 14 centers; 60 received the study medication and were analyzed and, of these, 45 (75%) had received prior therapy for Kaposi's sarcoma. Once daily oral 9-cis-retinoic acid (alitretinoin, Panretin) was administered at doses up to 140 mg/m2. Most patients (72%) received a maximum dose of 100 mg/m2. Response was assessed using AIDS Clinical Trials Group (ACTG) criteria.

RESULTS

The median age was 38 years and the median absolute CD4 cell count was 194 x 10(6) cells/l (range 6-784 x 10(6)). Despite the use of three- and four-drug antiviral regimens (83%), the median HIV RNA at baseline was 8701 copies/ml [range < 500 (lower limit of detection) to 4.24 x 10(6)]. The tumor response rate was 37% (95% confidence interval 25-49). Tumor response was associated with improved quality-of-life measures. There was a significant increase in interleukin 6 (IL-6) levels from baseline to week 4. Responders had significantly lower baseline soluble IL-6 receptor levels (P = 0.029) than non-responders. The median time to response was 9 weeks (mean, 13 weeks; range, 4-36). HIV RNA levels did not change significantly during therapy nor did they correlate with tumor responses. Study drug was discontinued by 28 patients for adverse events, which included headache (13) and skin toxicity (10).

CONCLUSION

Oral 9-cis-retinoic acid is an active antitumor drug for AIDS-related Kaposi's sarcoma. Treatment is associated with skin and constitutional toxicity and further studies are needed to improve its long-term tolerance.

Pharmacokinetics of chronically administered all-trans-retinoyl-beta-glucuronide in mice

After the subcutaneous injection of retinoyl beta-glucuronide (RAG), both RAG and retinoic acid (RA), formed by the hydrolysis of RAG in vivo, achieved peak plasma concentrations within 1-2 h. Thereafter, RA was rapidly cleared from the plasma whereas RAG was eliminated much more slowly. No significant changes were noted in the peak (2 h) plasma levels of RAG for treatment periods up to 56 days (one injection of RAG/day), in the clearance rate of RAG from plasma, or in plasma retinol concentrations. Similarly, no consistent decrease in plasma levels of the RA hydrolysis product was observed. Mice undergoing these long-term chronic treatments with RAG did not show any clinical manifestations of retinoid toxicity. Taken together, our findings that chronic dosing with RAG produces sustained levels of both the parent compound and the RA hydrolysis product, combined with the apparent low toxicity of RAG, suggest that RAG could be a safe and useful alternative to some retinoids which are presently being utilized in the clinic.

The effect of 9-cis-retinoic acid on proliferation and differentiation of a spermatogonia and retinoid receptor gene expression in the vitamin A-deficient mouse testis

Retinoid X receptors (RXRs) are key regulators in retinoid signaling. Knowledge about the effects of 9-cis-retinoic acid (9-cis-RA), the natural ligand for the RXRs, may also provide insight in the functions of RXRs. In this study, the effect of 9-cis-RA on spermatogenesis in vitamin A-deficient (VAD) mice was examined. Administration of 9-cis-RA stimulated the differentiation and subsequent proliferation of the growth-arrested A spermatogonia in the testis of VAD mice. However, compared with all-trans-retinoic acid (ATRA), relatively higher doses of 9-cis-RA were necessary. This could not simply be due to a lower or delayed activity of 9-cis-RA, as simultaneous administration of ATRA and 9-cis-RA did not cause a synergistic effect. Instead, the presence of 9-cis-RA diminished the effect of ATRA by approximately one third. Studies of in vivo transport and metabolism showed that ATRA and 9-cis-RA, after administration to VAD mice, penetrated the testis equally well. However, 9-cis-RA was metabolized much faster than ATRA, and other metabolites were formed. This may account for the above-described differential effects of ATRA and 9-cis-RA on spermatogenesis. Similar to ATRA, 9-cis-RA transiently induced the messenger RNA expression of the nuclear RA receptor RAR beta, suggesting a role for this receptor in the effects of retinoids on the differentiation and proliferation of A spermatogonia. In contrast, the messenger RNA expression of the nuclear retinoid receptors RXR alpha, -beta, and -gamma was not changed significantly by administration of their ligand, 9-cis-RA. Hence, 9-cis-RA does not seem to exert its effect on spermatogenesis through altered expression of the RXRs.