Mazhar Noor

In vitro anti-fibrotic activities of herbal compounds and herbs

BACKGROUND We recently developed high-throughput assays of inflammation-independent anti-fibrotic activities based on TGF-beta1-induced total collagen accumulation and nodule formation in normal rat kidney fibroblasts. METHODS These assays were applied to examine the anti-fibrotic activities of 21 compounds isolated from plants used in Chinese medicine and methanol extracts of 12 Chinese herbs. Lactate dehydrogenase release assay and cell detachment index were used to monitor cytotoxicity. Changes in fibrogenic molecular markers were observed by reverse transcriptase quantitative polymerase chain reaction and high-content imaging analysis of immunofluorescence. RESULTS Three flavonoids (quercetin, baicalein and baicalin) and two non-flavonoids (salvianolic acid B and emodin) demonstrated anti-fibrotic activities in both total collagen accumulation and nodule formation assays. The remaining 16 compounds had little anti-fibrotic effect or were cytotoxic. The anti-fibrotic compounds suppressed collagen I expression at both mRNA and protein levels and also variably suppressed alpha-smooth muscle actin expression and bromodeoxyuridine incorporation. Methanol extracts of Scutellaria baicalensis Georgi, Salvia miltiorrhiza Bunge and Rheum palmatum L., which are rich sources of baicalein, baicalin, salvianolic acid B and emodin, respectively, also showed in vitro anti-fibrotic activities. CONCLUSIONS Five herbal compounds and three herbal extracts have in vitro anti-fibrotic activities. These data warrant further studies on these anti-fibrotic entities and suggest it a promising strategy to discover new anti-fibrotic drugs by screening more plant materials.

Knowledge-Based Discovery of Anti-Fibrotic and Pro-Fibrotic Activities from Chinese Materia Medica

Fibrosis, also known as scarring, sclerosis or cirrhosis, is characterised by excessive accumulation of extracellular matrix (ECM) proteins leading to tissue contraction, disruption of tissue architecture and eventually chronic organ failure (Wynn, 2007; Xu et al., 2007). Research and development of anti-fibrotic drugs are generally based on two distinct but interactive strategies, with one based on mechanism studies and another based on exploring efficacy. In principle, the mechanism-based strategy begins with identification of molecular targets through mechanistic studies, and then development of inhibitors or enhancers targeting the molecules. On the other hand, efficacy-based strategy starts with screening drug candidates in disease models to identify activities and efficacy, with less reliance on analysis of mechanisms of action. There are certain limitations in both the mechanism-based strategy and the efficacy-based strategy, which largely account for the lack of success in development of anti-fibrotic drugs. The former is often associated with identification of multiple molecular targets impeding development of a single drug that tackles multiple targets, while the latter is often hampered by establishment of apt models ideal for efficacy-driven drug screens. Efficacy-based strategy has been employed in development of both traditional and modern medicines. In the context of traditional medicine, the knowledge about efficacy of a given drug is largely derived from a trial-and-error process, namely by assessing patients’ response upon treatment with natural drug candidates. However, in modern medicine, it is impossible to directly test any new drugs in patients. Solid scientific evidence on efficacy and safety of a given drug in experimental models is required prior to clinical trials. Understandably, quality of these models would determine the specificity and efficiency of the tested drug.

Kidneys of Alb/TGF-β1 Transgenic Mice Are Deficient in Retinoic Acid and Exogenous Retinoic Acid Shows Dose-Dependent Toxicity

Background: Alb/TGF-β1 transgenic mice overexpress active transforming growth factor-β1 (TGF-β1) in the liver, leading to increased circulating levels of the cytokine and progressive renal fibrosis. This study was designed to explore if exogenous all-trans retinoic acid (tRA) prevents renal fibrosis in this animal model. Methods: The retinoid profile in kidney and liver of wild-type and Alb/TGF-β1 transgenic mice was examined by high-performance liquid chromatography and slow-release pellets containing different amounts of tRA were implanted subcutaneously to treat the Alb/TGF-β1 transgenic mice, starting at 1 week of age; mice were sacrificed 2 weeks later. Results: Kidneys of 3-week-old wild-type mice had abundant tRA, which was completely absent in kidneys of the transgenic mice. Low doses of tRA (6–10.7 mg/kg/day) failed to affect renal fibrosis although it tended to suppress the mRNA expression of some molecular markers of fibrosis and retinal dehydrogenase 2 (RALDH2), a gene encoding a key tRA-synthesising enzyme. These tendencies disappeared, mortality tended to increase and RALDH2 and connective tissue growth factor (CTGF) mRNAs significantly increased in the medium-dose group (12.7–18.8 mg/kg/day). High doses (20.1–27.4 mg/kg/day) showed even higher toxicity with increased renal fibrosis and significant mortality. Conclusions: Alb/TGF-β1 transgenic mice are characterised by depletion of endogenous renal tRA. Exogenous tRA dose-dependently increases mortality and kidney fibrosis, which is associated with dose-dependent regulation of renal RALDH2 and CTGF mRNA expression.