Roxadustat protects rat renal tubular epithelial cells from hypoxia-induced injury through the TGF-ß1/Smad3 signaling pathway.

OBJECTIVE: Roxadustat is used to treat renal anemia. The renoprotective effect of roxadustat needs to be further confirmed, and the mechanism of action is unknown. This study aims to evaluate the effect and mechanism of roxadustat in hypoxia-related nephropathy with the renal tubular epithelial cell line NRK-52E. MATERIALS AND METHODS: The cell Counting Kit-8 (CCK-8) assay was employed to assess cellular proliferation in the current investigation. Flow cytometry was used to conduct cell apoptosis analysis. The utilization of electron microscopy facilitated the identification of changes in cellular ultrastructure. Immunofluorescence was used to detect the expression trend of hypoxia-inducible factor-1α (HIF-1α). The connective tissue growth factor (CTGF), transforming growth factor-ß1 (TGF-ß1), Smad family member 3 (Smad3), p-Smad3, α-smooth muscle actin (α-SMA), collagen I, and HIF-1α were assessed by western blotting. Real-time fluorescent quantitative PCR (RT-qPCR) was used to measure TGF-ß1 and Smad3 mRNA. RESULTS: Significant growth inhibition and increased apoptosis were observed in NRK-52E cells cultured under hypoxic conditions (1% and 5% O2), which can be rescued by roxadustat. From a morphological perspective, it has been observed that roxadustat can counteract cellular damage features produced by hypoxia. These features include the contraction of the nuclear envelope and an increase in the formation of apoptotic bodies. Roxadustat increases HIF-1α expression acutely at 24 h, followed by a gradual reduction of HIF-1α expression to levels significantly below that of the hypoxia group by 72 h. Roxadustat can also inhibit hypoxia-induced increased expression of CTGF, TGF-ß1, p-Smad3, α-SMA, collagen I, and HIF-1α. Combined treatment with roxadustat and siRNA against TGF-ß1 synergistically reduced the expression of CTGF and HIF-1α, while the effect on TGF-ß1 and p-Smad3 were comparable to that of the individual treatment alone. Comparably, the combined administration of roxadustat and siRNA targeting Smad3 had a synergistic impact on diminishing the expression of CTGF. CONCLUSIONS: These findings indicate that roxadustat attenuates experimental renal fibrosis likely by inhibiting the TGF-ß1/Smad3 pathways, while its effect on CTGF and HIF-1α may involve other signaling pathways.

A small molecule designed to bind to the adenine nucleotide pocket of Hsp90 causes Her2 degradation and the growth arrest and differentiation of breast cancer cells.

BACKGROUND: The Hsp90s contain a conserved pocket that binds ATP/ADP and plays an important role in the regulation of chaperone function. Occupancy of this pocket by several natural products (geldanamycin (GM) and radicicol) alters Hsp90 function and results in the degradation of a subset of proteins (i.e. steroid receptors, Her2, Raf). We have used the structural features of this pocket to design a small molecule inhibitor of Hsp90. RESULTS: The designed small molecule PU3 competes with GM for Hsp90 binding with a relative affinity of 15-20 microM. PU3 induces degradation of proteins, including Her2, in a manner similar to GM. Furthermore, PU3 inhibits the growth of breast cancer cells causing retinoblastoma protein hypophosphorylation, G1 arrest and differentiation. CONCLUSIONS: PU3 is representative of a novel class of synthetic compounds that binds to Hsp90 and inhibits the proliferation of cancer cells. These reagents could provide a new strategy for the treatment of cancers.

Synthesis and evaluation of geldanamycin-testosterone hybrids.

Geldanamycin (GDM) binds to the Hsp90 chaperone protein resulting in the degradation of several important signaling proteins. A series of GDM-testosterone linked hybrids has been synthesized and evaluated for activity against prostate cancer cell lines. The hybrid with the greatest activity exhibits potent and selective cytotoxicity against prostate cancer cells containing the androgen receptor.

Identification of a geldanamycin dimer that induces the selective degradation of HER-family tyrosine kinases.

Geldanamycin (GM) is a natural antibiotic that binds Hsp90 and induces the degradation of receptor tyrosine kinases, steroid receptors, and Raf. It is a potent inhibitor of cancer cells that overexpress HER-kinases, but its effects on other important proteins may cause significant toxicity and limit its clinical use. We report the synthesis and identification of a GM dimer, GMD-4c, which had selective activity against HER-kinases. Selectivity was a function of linker length and required two intact GM moieties. GMD-4c is a potent inducer of G1 block and apoptosis of breast cancer cell lines that overexpress HER2, but does not appreciably inhibit the growth of 32D cells that lack HER-kinases. GMD-4c could be useful in the treatment of carcinomas dependent on HER-kinases.

Synthesis and evaluation of geldanamycin-estradiol hybrids.

Geldanamycin (GDM) binds to the Hsp90 chaperone protein and causes the degradation of several important signalling proteins. A series of novel estradiol-geldanamycin hybrids has been synthesized and evaluated for their ability to induce the selective degradation of the estrogen receptor (ER). The hybrid compounds are active and more selective than the parent causing degradation of ER and HER2, but not other GDM targets.