Chemoprotective effect of all-trans retinoic acid (ATRA) on oxidative stress and lung metastasis induced by benzo(a)pyrene

Extirpating the cancer stem cell hydra: Differentiation therapy and Hyperthermia therapy for targeting the cancer stem cell hierarchy

Ever since the discovery of cancer stem cells (CSCs), they have progressively attracted more attention as a therapeutic target. Like the mythical hydra, this subpopulation of cells seems to contribute to cancer immortality, spawning more cells each time that some components of the cancer cell hierarchy are destroyed. Traditional modalities focusing on cancer treatment have emphasized apoptosis as a route to eliminate the tumor burden. A major problem is that cancer cells are often in varying degrees of dedifferentiation contributing to what is known as the CSCs hierarchy and cells which are known to be resistant to conventional therapy. Differentiation therapy is an experimental therapeutic modality aimed at the conversion of malignant phenotype to a more benign one. Hyperthermia therapy (HT) is a modality exploiting the changes induced in cells by the application of heat produced to aid in cancer therapy. While differentiation therapy has been successfully employed in the treatment of acute myeloid leukemia, it has not been hugely successful for other cancer types. Mounting evidence suggests that hyperthermia therapy may greatly augment the effects of differentiation therapy while simultaneously overcoming many of the hard-to-treat facets of recurrent tumors. This review summarizes the progress made so far in integrating hyperthermia therapy with existing modules of differentiation therapy. The focus is on studies related to the successful application of both hyperthermia and differentiation therapy when used alone or in conjunction for hard-to-treat cancer cell niche with emphasis on combined approaches to target the CSCs hierarchy.

Concomitant inhibition of hedgehog signalling and activation of retinoid receptors abolishes bleomycin-induced lung fibrosis

Pulmonary fibrosis is a devastating disease with unknown treatment. All-trans retinoic acid (ATRA) attenuates bleomycin-induced lung fibrosis by different mechanistic pathways. However, the role of retinoid receptors in lung fibrosis is still unclear. Forskolin (FSK), a potent inhibitor for the revolutionary hedgehog (Hh) signalling pathway, has a promising antifibrotic effect on other organs such as the liver. This study investigates the interplay between the retinoid receptors modulation and the Hh signalling pathway in bleomycin (BLM)-induced pulmonary fibrosis. Rats were randomised and administrated a single dose of 7.5 mg/kg of BLM alone and with ATRA, FSK and both of them. The effects of FSK and ATRA on lung functions, oxidative stress markers (malondialdehyde [MDA], glutathione [GSH], superoxide dismutase [SOD] and catalase [CAT]), retinoid markers (retinoic acid receptors [RAR] and rexinoid X receptors [RXR]) and Hh signalling markers (patched homolog 1 [Ptch-1], Smoothened [Smo] and glioblastoma-2 [Gli-2]) were assessed. In single therapies, ATRA and FSK ameliorated BLM-induced lung fibrosis. On the contrary, a combination of both drugs synergistically reversed the effect of BLM-induced lung fibrosis, as indicated by the enhancement of lung functions and the decrease of the α-smooth muscle actin (α-SMA) expression and collagen deposition. Additionally, FSK and ATRA ameliorated oxidative stress and inflammation, reduced transforming growth factor β1 (TGF-β1) levels and reversed the effect of BLM on the mRNA expression of Ptch-1, Smo and Gli-2. FSK inhibited the Hh pathway and also activated protein kinase A (PKA) that is, in part, involved in phosphorylation of RAR/RXR heterodimer (a key step in retinoid receptor activation). The present results suggest that a combination of FSK and ATRA has a promising therapeutic value for lung fibrosis management.

Synergistic effect of co-treatment with all-trans retinoic acid and 9-cis retinoic acid on human lung cancer cell line at molecular level

The major challenge in treating cancers with ATRA is the limited availability inside the cell and resistance developed in prolonged treatment. We made an attempt for co-treatment of human NSCLC cell lines (A549) with ATRA and its isomeric precursor (9cisRA). In this study, the growth inhibitory effect of ATRA, 9cisRA and combination of both were tested in A549 cells by MTT and Trypan blue assays. As the effects of retinoid are mediated through their receptors, their gene expression levels were analyzed by RT-PCR. The target gene receptor, RAR-β protein expression, was analyzed by immunocytochemistry. The cancer cell (A549) growth inhibitory effect was significantly (p ≤ 0.001) enhanced in combination treatment when compared with the result of individual treatments. The mRNA expression levels of both RAR-β and RXR-β were found to be increased in co-treatment (band density of 0.75 and 0.806, respectively) when compared with 9cisRA treatment (0.25 and 0.112) and ATRA treatment (0.01 and 0.081). A concomitant enhancement in the target RAR-β protein expression was observed in co-treated cells when compared with individual treatments. We thus conclude that the co-treatment had increased the availability of ATRA, by isomerization of the 9cisRA which then resulted in an increased expression of both RAR-β and RXR-β receptors and the target protein RAR-β which in turn inhibited lung cancer cell growth. Our study results have explored the mechanism of synergistic effect of co-treatment with ATRA and 9cisRA and further preclinical studies are necessary to validate the application of co-treatment of retinoid in clinical use.

ATRA reduces inflammation and improves alveolar epithelium regeneration in emphysematous rat lung

INTRODUCTION

Pulmonary emphysema characterized by alveolar wall destruction is resultant of persistent chronic inflammation. All-trans retinoic acid (ATRA) has been reported to reverse elastase-induced emphysema in rats. However, the underlying molecular mechanisms are so far unknown.

OBJECTIVE

To investigate the therapeutic potential effect of ATRA via the amelioration of the ERK/JAK-STAT pathways in the lungs of emphysematous rats.

METHODS

In silico analysis was done to find the binding efficiency of ATRA with receptor and ligands of ERK & JAK-STAT pathway. Emphysema was induced by porcine pancreatic elastase in Sprague-Dawley rats and ATRA was supplemented as therapy. Lungs were harvested for histopathological, genomics and proteomics analysis.

RESULTS AND DISCUSSION

In silico docking, analysis confirms that ATRA interferes with the normal binding of ligands (TNF-α, IL6ST) and receptors (TNFR1, IL6) of ERK/JAK-STAT pathways respectively. ATRA restored the histology, proteases/antiproteases balance, levels of inflammatory markers, antioxidants, expression of candidate genes of ERK and JAK-STAT pathways in the therapy group.

CONCLUSION

ATRA ameliorates ERK/JAK-STAT pathway in emphysema condition, resulting in alveolar epithelium regeneration. Hence, ATRA may prove to be a potential drug in the treatment of emphysema.

No beneficial effect of all-trans retinoic acid in previous non-responder patients with chronic hepatitis C: the ATRACTION study, a phase II randomised trial

BACKGROUND

Preclinical data suggested all-trans retinoic acid (tretinoin) as a potential antiviral agent against chronic hepatitis C infection.

AIMS

To assess efficacy, safety, and tolerability of tretinoin in combination with peg-interferon and ribavirin in genotype-1 infected patients with prior non-response.

METHOD

We performed an open-label multicentre clinical trial. Patients were randomised to either receive additional tretinoin (45mg/m(2)/day) for 12 weeks (arm A), or peg-interferon and ribavirin alone (arm B). Primary endpoint was the slope of the third phase of viral decline (Mδ) as determined in an established kinetic model known to correlate with treatment outcome. Secondary endpoints were additional kinetic parameters, viral response rates, safety, and tolerability.

RESULTS

27 patients in arm A and 30 patients in arm B were treated per protocol until week 12. Viral kinetic parameters did not differ. Rates of early virological response (>2log10 drop at week 12) were similar (10/27 versus 11/30 patients). In arm A, patients experienced a higher rate and intensity of adverse events, most commonly skin and mucosal dryness, and headache.

CONCLUSION

Addition of tretinoin was safe and acceptably well tolerated. However, it did not influence viral kinetics and thus cannot be further considered as a treatment option.

Relaxant effect of all-trans-retinoic acid via NO-sGC-cGMP pathway and calcium-activated potassium channels in rat mesenteric artery

Intraperitoneal injection of all-trans-retinoic acid (ATRA) results in a reduction of blood pressure in spontaneously hypertensive rats. However, the mechanisms involved in this effect are not clear. We hypothesized that ATRA may relax resistance arteries. In this study, we found that ATRA relaxed phenylephrine-preconstricted mesenteric arterial rings, which were abrogated by the removal of the endothelium. Pretreatment of endothelium-intact arterial rings with an inhibitor of endothelial nitric oxide (NO) synthase, N(G)-nitro-l-arginine methyl ester (l-NAME), or soluble guanylyl cyclase, 1H-[1,2,4]-oxadiazole-[4,3-α]-quinoxaline-1-one, reduced the vasorelaxant effect of ATRA. Incubation of mesenteric arterial rings with ATRA increased the production of NO and cGMP, which were blocked by N(G)-nitro-l-arginine methyl ester. The vasorelaxant effect of ATRA was markedly attenuated in the presence of an inhibitor of big conductance calcium-activated potassium channels (charybdotoxin), but not with an inhibitor of voltage-dependent potassium channel (4-aminopyridine) or ATP-sensitive potassium channel (glibenclamide). Activation of retinoic acid receptors (RARs) with CH55 or retinoic X receptors (RXRs) with LGD1069 induced the vasorelaxation of phenylephrine-preconstricted mesenteric arterial rings. The RAR (BMS493) and RXR (UVI3003) antagonists blocked the ATRA-induced vasorelaxation. The vasorelaxant effect ATRA is physiologically relevant because the intravenous infusion of ATRA decreased blood pressure in normotensive rats. We conclude that ATRA relaxes resistance vessels via both RARs and RXRs receptors that are mediated by the endothelium-dependent NO-cGMP pathway, which may participate in the control of blood pressure.

Purification and characterization of glutathione S-transferase from turkey liver and inhibition effects of some metal ions on enzyme activity

The glutathione S-transferases (EC 2.5.1.18) were purified and characterized from turkey liver for the first time. The enzyme was purified 252.7-fold with a yield of 45%, with a specific activity of 164.31 U/mg from turkey liver. The purity of the enzyme was determined by SDS-PAGE and showed two bands nearly 26 kDa and 24 kDa on the gel. The native molecular mass of the enzyme was found to be approximately 53 kDa by Sephadex G-100 gel filtration chromatography. Optimal pH, stable pH, optimal temperature, optimum ionic strength, K(m) and V(max) values for GSH and CDNB were also determined for the enzyme as 7.3, 8.5, 50 °C, 600 mM, 0.154 mM, 0.380 mM, 1.803 EU/ml, and 2.125 EU/ml, respectively. Additionally, inhibitory effects of metal ions (Cu(2+), Hg(2+), Fe(2+), Zn(2+), Ag(+), Mg(2+), Ni(2+), and Mn(2+)) were examined the enzyme's activity in vitro by performing Lineweaver-Burk graphs and plotting activity% vs., respectively.