A previous study in the hairless mouse, in which the photoimmune protective properties of a topical phytoestrogen or 17-beta-estradiol were abrogated by the estrogen receptor antagonist ICI 182,780, revealed that estrogen receptor (Er) signaling is involved in the regulation of the suppression of immune function by UVB (290-320 nm) radiation. Here we identify the expression of Er-beta but not Er-alpha mRNA in hairless mouse skin, whereas Er-alpha and Er-beta mRNA were present in normal haired mouse skin. This suggests that the non-classical estrogen target Er-beta is involved in the photoimmune modulation, and is consistent with Er-alpha being more closely associated with hair growth control, as indicated by other studies. In mice with a null mutation for Er-beta, there was a significant exacerbation of the solar simulated UV (290-400 nm)-induced suppression of contact hypersensitivity. Immunohistochemical analysis revealed that the Er-beta deficiency inhibited the normally immunoprotective upregulation by the UVA (320-400 nm) waveband of the epidermal expression of the cytokines IFN-gamma and IL-12. Er-beta deficiency also significantly increased the UVB-induced expression of the immunosuppressive cytokine IL-10. Thus Er signalling via the Er-beta is evidently a major regulator of the UVA and UVB waveband interactions that determine the skin's immune functional status, and achieves this by normalization of the cutaneous cytokine array in the UV-irradiated skin.

Tryptanthrin is an indole quinazoline alkaloid from the indigo-bearing plants, such as Isatis indigotica Fort. Typically, this natural compound shows a variety of pharmacological activities such as antitumor, antibacterial, anti-inflammatory and antioxidant effects. This study was conducted to assess the antitumor activity of tryptanthrin in breast cancer models both in vitro and in vivo, and to explore the important role of the inflammatory tumor microenvironment (TME) in the antitumor effects of tryptanthrin. Human breast adenocarcinoma MCF-7 cells were used to assess the antitumor effect of tryptanthrin in vitro. MTT assay and colony formation assay were carried out to monitor the antiproliferative effect of tryptanthrin (1.56~50.0 μmol L−1) on inhibiting the proliferation and colony formation of MCF-7 cells, respectively. The migration and invasion of MCF-7 cells were evaluated by wound healing assay and Transwell chamber assay, respectively. Moreover, the 4T1 murine breast cancer model was established to examine the pharmacological activity of tryptanthrin, and three groups with different doses of tryptanthrin (25, 50 and 100 mg kg−1) were set in study. Additionally, tumor volumes and organ coefficients were measured and calculated. After two weeks of tryptanthrin treatment, samples from serum, tumor tissue and different organs from tumor-bearing mice were collected, and the enzyme-linked immunosorbent assay (ELISA) was performed to assess the regulation of inflammatory molecules in mouse serum. Additionally, pathological examinations of tumor tissues and organs from mice were evaluated through hematoxylin and eosin (H&E) staining. The expression of inflammatory proteins in tumor tissues was measured by immunohistochemistry (IHC) and Western blotting. Tryptanthrin inhibited the proliferation, migration and invasion of MCF-7 cells, up-regulated the protein level of E-cadherin, and down-regulated those of MMP-2 and Snail, as suggested by the MCF-7 cell experiment. According to the results from in vivo experiment, tryptanthrin was effective in inhibiting tumor growth, and it showed favorable safety without inducing the fluctuations of body mass and organ coefficient (p > 0.05). In addition, tryptanthrin also suppressed the expression levels of NOS1, COX-2 and NF-κB in mouse tumor tissues, and regulated those of IL-2, IL-10 and TNF-α in the serum of tumor cells-transplanted mice. Tryptanthrin exerted its anti-breast cancer activities through modulating the inflammatory TME both in vitro and in vivo.

Previous studies have found that signaling by the estrogen receptor-beta (Er-beta) attenuated solar-simulated UV radiation (SSUV)-induced immunosuppression. This study seeks evidence for a common mechanism for this immunoprotection for both Er-beta signaling and irradiation with the UVA waveband. In Skh:hr-1 hairless mice, the immunoprotection afforded by UVA exposure against subsequent UVB or cis-urocanic acid suppression of contact hypersensitivity (CHS) was abrogated by treatment with the antiestrogen, ICI 182,780. Furthermore, in normal C57BL mice, UVA enrichment of UVA/UVB sources provided protection against UVB-suppressed CHS and upregulated epidermal IL-10 expression, but this protection was inhibited in Er-beta-/- mice. These observations indicated that the immunoprotective response to UVA was dependent on Er-beta signaling. As earlier studies have established that UVA photoimmune protection depends on the induction of the stress enzyme, heme oxygenase (HO)-1, its activity was examined relative to Er-beta. Immunoprotection against SSUV by 17-beta-estradiol was prevented by inhibiting HO enzyme activity; immunoprotection against cis-urocanic acid by carbon monoxide (HO product) was prevented by ICI 182,780. In addition, the HO-1 gene was unresponsive to UVA induction in Er-beta-/- mice. Therefore, HO-1 inducibility and Er-beta signaling are interdependent requisite responses to the UVA waveband for its immunoprotective action against UVB exposure.

We have reported previously that a deficiency in signalling by the non-classical oestrogen receptor-beta (Er-beta) exacerbates immunosuppression by UV radiation in the mouse. Because photoimmune suppression is a risk factor for skin cancer development, we hypothesize that Er-beta deficiency will promote skin tumour growth. Therefore we have blocked Er signalling pharmacologically in the Skh:hr-1 hairless mouse by topical treatments with the Er antagonist ICI 182,780, and genetically in haired mice by using the specific Er-beta knockout mouse (targeted mutation of the Er-beta), and examined the growth rate of 3 transplantable skin tumour cell lines in their syngeneic host mice. Two UV-induced squamous cell carcinoma (SCC) cell lines transplanted into the Skh:hr-1 recipients were found to have regressor qualities that were delayed by prior immunosuppressive solar-simulated UV (SSUV) irradiation. For the T79 SCC, regression was significantly further delayed by combined pretreatment with SSUV+ICI 182,780, and the diameters of the surviving tumours were slightly larger. For the KL3.0 SCC, both SSUV and combined SSUV+ICI 182,780 pretreatments completely inhibited tumour regression, and resulted in significantly greater tumour diameters than in unirradiated recipient mice. In heterozygous Er-beta deficient mice (Er-beta+/-), the B16/F10 melanoma grew progressively and significantly faster than in the wild type control mice (C57BL/6), and growth rate was accelerated by prior SSUV irradiation. Homozygous Er-beta-/- mice supported the most rapid B16/F10 growth that was further accelerated by prior SSUV irradiation. Therefore Er signalling, specifically by Er-beta, has a natural endogenous protective role against skin tumour growth, probably mediated via immunological pathways.

Tetracyclic triterpenoids, including the dammarane, cucurbitane, cycloartane, lanostane and protostane groups, is a class of triterpenoids widely distributed in various medicinal plants, particularly those commonly used for the treatment of diabetes and its complications, such as Panax ginseng, Panax quinquefolium, Panax notoginseng, Gynostemma pentaphyllum, Astragalus membranaceus, Momordica charantia, and Ganoderma lucidum. This review highlights recent findings on the chemistry and bioactivities of tetracyclic triterpenoids from these plants and other popular herbal medicines.