Synephrine and Its Derivative Compound A: Common and Specific Biological Effects.

This review is focused on synephrine, the principal phytochemical found in bitter orange and other medicinal plants and widely used as a dietary supplement for weight loss/body fat reduction. We examine different aspects of synephrine biology, delving into its established and potential molecular targets, as well as its mechanisms of action. We present an overview of the origin, chemical composition, receptors, and pharmacological properties of synephrine, including its anti-inflammatory and anti-cancer activity in various in vitro and animal models. Additionally, we conduct a comparative analysis of the molecular targets and effects of synephrine with those of its metabolite, selective glucocorticoid receptor agonist (SEGRA) Compound A (CpdA), which shares a similar chemical structure with synephrine. SEGRAs, including CpdA, have been extensively studied as glucocorticoid receptor activators that have a better benefit/risk profile than glucocorticoids due to their reduced adverse effects. We discuss the potential of synephrine usage as a template for the synthesis of new generation of non-steroidal SEGRAs. The review also provides insights into the safe pharmacological profile of synephrine.

Roles Played by Stress-Induced Pathways in Driving Ethnic Heterogeneity for Inflammatory Skin Diseases.

Immune-mediated skin conditions (IMSCs) are a diverse group of autoimmune diseases associated with significant disease burden. Atopic dermatitis and psoriasis are among the most common IMSCs in the United States and have disproportionate impact on racial and ethnic minorities. African American patients are more likely to develop atopic dermatitis compared to their European American counterparts; and despite lower prevalence of psoriasis among this group, African American patients can suffer from more extensive disease involvement, significant post-inflammatory changes, and a decreased quality of life. While recent studies have been focused on understanding the heterogeneity underlying disease mechanisms and genetic factors at play, little emphasis has been put on the effect of psychosocial or psychological stress on immune pathways, and how these factors contribute to differences in clinical severity, prevalence, and treatment response across ethnic groups. In this review, we explore the heterogeneity of atopic dermatitis and psoriasis between African American and European American patients by summarizing epidemiological studies, addressing potential molecular and environmental factors, with a focus on the intersection between stress and inflammatory pathways.

The long winding road to the safer glucocorticoid receptor (GR) targeting therapies.

Glucocorticoids (Gcs) are widely used to treat inflammatory diseases and hematological malignancies, and despite the introduction of novel anti-inflammatory and anti-cancer biologics, the use of inexpensive and effective Gcs is expected to grow. Unfortunately, chronic treatment with Gcs results in multiple atrophic and metabolic side effects. Thus, the search for safer glucocorticoid receptor (GR)-targeted therapies that preserve therapeutic potential of Gcs but result in fewer adverse effects remains highly relevant. Development of selective GR agonists/modulators (SEGRAM) with reduced side effects, based on the concept of dissociation of GR transactivation and transrepression functions, resulted in limited success, and currently focus has shifted towards partial GR agonists. Additional approach is the identification and inhibition of genes associated with Gcs specific side effects. Others and we recently identified GR target genes REDD1 and FKBP51 as key mediators of Gcs-induced atrophy, and selected and validated candidate molecules for REDD1 blockage including PI3K/Akt/mTOR inhibitors. In this review, we summarized classic and contemporary approaches to safer GR-mediated therapies including unique concept of Gcs combination with REDD1 inhibitors. We discussed protective effects of REDD1 inhibitors against Gcs-induced atrophy in skin and bone and underlined the translational potential of this combination for further development of safer and effective Gcs-based therapies.

Targeting transcription factor NFkappaB: comparative analysis of proteasome and IKK inhibitors.

Nuclear factorkappaB (NFkappaB) plays a critical role in cancer development and progression. Thus, the NFkappaB signaling pathway provides important targets for cancer chemoprevention and anticancer chemotherapy. The central steps in NFkappaB activation are phosphorylation and proteasome-dependent degradation of its inhibitory proteins termed IkappaBs. Consequently, the major pharmacological approaches to target NFkappaB include (1) repression of IkappaB kinases (IKKs) and (2) blocking the degradation of IkappaBs by proteasome inhibitors. We quantitatively compared the efficacy of various proteasome inhibitors (MG132, lactacystin and epoxomicin) and IKK inhibitors (BAY 11-7082 and PS1145) to block NFkappaB activity induced by TNFalpha or TPA and to sensitize LNCaP prostate carcinoma cells to apoptosis. Our studies revealed significant differences between these two classes of NFkappaB inhibitors. We found that proteasome inhibitors epoxomicin and MG132 attenuated NFkappaB induction much more effectively than the IKK inhibitors. Furthermore, in contrast to IKK inhibitors, all studied proteasome inhibitors specifically blocked TPA-induced generation de novo of NFkappaB p50 homodimers--(p50/p50). These results suggest that the proteasome plays a dominant role in TPA-induced formation of functional p50 homodimers, while IKK activity is less important for this process. Interestingly, profound attenuation of p50/p50 DNA-binding does not reduce the high potency of proteasome inhibitors to suppress NFkappaB-dependent transcription. Finally, proteasome inhibitors were much more effective in sensitizing LNCaP cells to TNFalpha-induced apoptosis compared to IKK inhibitors at the concentrations when both types of agents similarly attenuated NFkappaB activity. We conclude that this remarkable pro-apoptotic potential of proteasome inhibitors is partially mediated through NFkappaB-independent mechanism.

Epithelial cells in the hair follicle bulge do not contribute to epidermal regeneration after glucocorticoid-induced cutaneous atrophy.

One of the major adverse effects of glucocorticoid therapy is cutaneous atrophy, often followed by the development of resistance to steroids. It is accepted that epithelial stem cells (SCs) located in the hair follicle bulge divide during times of epidermal proliferative need. We determined whether follicular epithelial SCs and their transit amplifying progeny were stimulated to proliferate in response to the chronic application of glucocorticoid fluocinolone acetonide (FA). After first two applications of FA, keratinocyte proliferation in the interfollicular epidermis (IFE) and hair follicles was minimal and resulted in significant epidermal hypoplasia. We observed that a 50% depletion of the interfollicular keratinocyte population triggered a proliferative response. Unexpectedly, less than 2% of the proliferating keratinocytes were located in the bulge region of the hair follicle, whereas 82% were in IFE. It is known that cell desensitization to glucocorticoids is mediated via temporary decrease of glucocorticoid receptor (GR) expression. We found that GR expression was significantly decreased in IFE keratinocytes after each FA treatment. In contrast, many bulge keratinocytes retained GR in the nucleus. Our results indicate that bulge keratinocytes, including follicular SCs, are more sensitive to the antiproliferative effect of glucocorticoids than basal keratinocytes, possibly due to the incomplete process of desensitization.

Glucocorticoid receptor functions as a potent suppressor of mouse skin carcinogenesis.

Glucocorticoids are effective inhibitors of epidermal proliferation and skin tumorigenesis. Glucocorticoids affect cellular functions via glucocorticoid receptor (GR), a well-known transcription factor. Recently, we generated skin-targeted transgenic mice overexpressing GR under control of the keratin5 promoter (K5-GR mice). To test the hypothesis that GR plays a role as a tumor suppressor in skin, we bred K5-GR transgenic mice with Tg.AC transgenic mice, which express v-Ha-ras oncogene in the skin, and compared the susceptibility of F1 offspring to TPA-induced skin carcinogenesis. GR overexpression in the epidermis dramatically inhibited skin tumor development. In K5-GR/ras+ double transgenic mice papillomas developed later and the average number of tumors per animal was 15% (in males) and 40% (in females) of the number seen in wild type (w.t./ras+) littermates. In addition, the papillomas in w.t./ras+ animals were eight to nine times larger. GR overexpression resulted in a decrease in keratinocyte proliferation combined with a modest increase in apoptosis and differentiation of keratinocytes in K5-GR/ras+ papillomas. Our data clearly indicate that interference of GR transgenic protein with nuclear factor kappa B (NF-kappaB) transcription factor had resulted in NF-kappaB blockage in K5-GR/ras+ tumors. We discuss the role of NF-kappaB blockage in tumor-suppressor effect of GR.

Selenium compounds inhibit I kappa B kinase (IKK) and nuclear factor-kappa B (NF-kappa B) in prostate cancer cells.

Selenium compounds are potential chemopreventive agents for prostate cancer. There are several proposed mechanisms for their anticancer effect, including enhanced apoptosis of transformed cells. Because the transcription factor nuclear factor-kappa B (NF-kappa B) is often constitutively activated in tumors and is a key antiapoptotic factor in mammalian cells, we tested whether selenium inhibited NF-kappa B activity in prostate cancer cells. In our work, we used sodium selenite and a novel synthetic compound, methylseleninic acid (MSeA), that served as a precursor of the putative active monomethyl metabolite methylselenol. We found that both selenium forms inhibited cell growth and induced apoptosis in DU145 and JCA1 prostate carcinoma cells. Sodium selenite and MeSeA, at the concentrations that induced apoptosis, inhibited NF-kappa B DNA binding induced by tumor necrosis factor-alpha and lipopolysaccharide in DU145 and JCA1 prostate cells. Both compounds also inhibited kappa B. Luciferase reporter activity in prostate cells. A key to NF-kappa B regulation is the inhibitory kappa B (I kappa B) proteins that in response to diverse stimuli are rapidly phosphorylated by I kappa B kinase complex, ubiquitinated, and undergo degradation, releasing NF-kappa B factor. We showed that sodium selenite and MSeA inhibited I kappa B kinase activation and I kappa B-alpha phosphorylation and degradation induced by TNF-alpha and lipopolysaccharide in prostate cells. NF-kappa B blockage by I kappa B-alpha d.n. mutant resulted in the sensitization of prostate carcinoma cells to apoptosis induced by selenium compounds. These results suggest that selenium may target the NF-kappa B activation pathway to exert, at least in part, its cancer chemopreventive effect in prostate.

Functional roles of Akt signaling in mouse skin tumorigenesis.

The mouse skin carcinogenesis protocol is a unique model for understanding the molecular events leading to oncogenic transformation. Mutations in the Ha-ras gene, and the presence of functional cyclin D1 and the EGF receptor, have proven to be important in this system. However, the signal transduction pathways connecting these elements during mouse skin carcinogenesis are poorly understood. This paper studies the relevance of the Akt and ERK pathways in the different stages of chemically induced mouse skin tumors. Akt activity increases throughout the entire process, and its early activation is detected prior to increased cyclin D1 expression. ERK activity rises only during the later stages of malignant conversion. The observed early increase in Akt activity appears to be due to raised PI-3K activity. Other factors acting on Akt such as ILK activation and decreased PTEN phosphatase activity appear to be involved at the conversion stage. To further confirm the involvement of Akt in this process, PB keratinocytes were transfected with Akt and subsequently injected into nude mice. The expression of Akt accelerates tumorigenesis and contributes to increased malignancy of these keratinocytes as demonstrated by the rate of appearance, the growth and the histological characteristics of the tumors. Collectively, these data provide evidence that Akt activation is one of the key elements during the different steps of mouse skin tumorigenesis.

The role of IKK in constitutive activation of NF-kappaB transcription factor in prostate carcinoma cells.

Rel/NF-kappaB transcription factors are implicated in the control of cell proliferation, apoptosis and transformation. The key to NF-kappaB regulation is the inhibitory IkappaB proteins. During response to diverse stimuli, IkappaBs are rapidly phosphorylated by IkappaB kinases (IKKs), ubiquitinated and undergo degradation. We have investigated the expression and function of NF-kappaB, IkappaB inhibitors and IKKs in normal prostate epithelial cells and prostate carcinoma (PC) cell lines LNCaP, MDA PCa 2b, DU145, PC3, and JCA1. We found that NF-kappaB was constitutively activated in human androgen-independent PC cell lines DU145, PC3, JCA1 as well as androgen-independent CL2 cells derived from LNCaP. In spite of a strong difference in constitutive kappaB binding, Western blot analysis did not reveal any significant variance in the expression of p50, p65, IkappaBs, IKKalpha, and IKKbeta between primary prostate cells, androgen-dependent and androgen-independent PC cells. However, we found that in androgen-independent PC cells IkappaBalpha was heavily phosphorylated and displayed a faster turnover. Using an in vitro kinase assay we demonstrated constitutive activation of IKK in androgen-independent PC cell lines. Blockage of NF-kappaB activity in PC cells by dominant-negative IkappaBalpha resulted in increased constitutive and TNF-alpha-induced apoptosis. Our data suggest that increased IKK activation leads to the constitutive activation of NF-kappaB 'survival signaling' pathway in androgen-independent PC cells. This may be important for the support of their androgen-independent status and growth advantage.