Cellular stress response in Eca-109 cells inhibits apoptosis during early exposure to isorhamnetin

Abstract

The flavonol aglycone isorhamnetin shows anti-proliferative activity in a variety of cancer cells. Previous work, from our laboratory showed that isorhamnetin inhibits the proliferation of human esophageal squamous carcinoma Eca-109 cells in vitro, but only after 72 h of exposure. This led us to propose that isorhamnetin exposure induces a cellular stress response that inhibits the antiproliferative and apoptotic effects of the compound during early exposure. To test this hypothesis, the present study examined the effects of isorhamnetin on Eca-109 cells during the first 72 h of exposure. Cell growth was assessed using the trypan blue exclusion assay, and expression of IκBα, NF-κB/p65, NF-κB/p50, phospho-Akt, Bcl-2, COX-2, Mcl-1, Bax, p53 and Id-1 were analyzed by Western blot. During the first 72 h of exposure, NF-κB/p65 and NF-κB/p50 accumulated in nuclei and expression of COX-2, Bcl-2 and Mcl-1 increased. In contrast, expression of IκBα and Bax fell initially but later increased. Expression of phospho-Akt and p53 showed no detectable change during the first 48 h. Pretreatment with the NF-κB inhibitor MG132 before exposure to isorhamnetin blocked the nuclear accumulation of p50 and p65, thereby inhibiting cell proliferation. These results show that during early exposure of Eca-109 cells to isorhamnetin, the NF-κB signaling pathway is activated and COX-2 expression increases, and this increase in expression partially inhibits isorhamnetin-induced apoptosis. Beyond 72 h of exposure, however, the apoptotic effect of isorhamnetin dominates, leading to inhibition of the NF-κB pathway and of cellular proliferation. These results will need to be taken into account when exploring the use of isorhamnetin against cancer in vivo.

Isorhamnetin Induces Melanoma Cell Apoptosis via the PI3K/Akt and NF-κB Pathways

“…[12,26,27] Interestingly, a study of esophageal squamous carcinoma reported that the NF-κB pathway showed activation in the first 72 h exposure of IH but became inhibited later. Explanation of this phenomenon was that cellular stress response (involving NF-κB activation) inhibited cell apoptosis in the early exposure [10]. However, cell apoptosis dominated later, leading to NF-κB inhibition.…”

“…[6,7] Isorhamnetin shows a variety of pharmacological activities such as cardiovascular protection, antioxidant, anticholinesterase, and antibacterial. [8,9] Besides, its anticancer effect has been proven in esophageal cancer [10], colon cancer [11], breast cancer [12], and lung cancer [13]. However, to the best of our knowledge, there is no research focusing on the inhibitory effect of IH in melanoma, and the mechanism underlying has not yet been clarified.…”

Protective Effects of Isorhamnetin on Cardiomyocytes Against Anoxia/Reoxygenation-induced Injury Is Mediated by SIRT1

“…1), a 3 0 -O-methylated metabolite of quercetin, is one of the naturally distributed flavonoids and has been confirmed that it can dilate coronary artery, protect cardiomocytes against oxidation, and has effects of antitumor and hemostasis functions. [1][2][3] Cardiovascular diseases are a leading cause of mortality around the world, and ischemia/reperfusion (I/R) injury plays a major role in cardiovascular diseases such as myocardial infarction. 4,5 Previous studies have demonstrated that IsoRN could prevent apoptosis of cardiomyocytes caused by anoxia/reoxygenation (A/R), an in vitro I/R model.…”

Isorhamnetin inhibits cell proliferation and induces apoptosis in breast cancer via Akt and mitogen-activated protein kinase kinase signaling pathways

“…These two herbs are administered for the treatment of rheumatism, hemorrhage and cancer in traditional medicine ( 20 – 22 ). Isorhamnetin is the active compound of these herbal medicinal plants, and is an immediate metabolite of quercetin, also termed 3′-O-methylquercetin, which has been shown to inhibit various types of cancer, including esophageal ( 23 ) and gastric cancer ( 24 ), leukemia ( 25 , 26 ), skin ( 27 ), colon ( 28 ) and lung cancer ( 29 ). However, to the best of our knowledge, no study to date has focused on the inhibitory effects of isorhamnetin on breast cancer, and the molecular mechanisms underlying its effects remain unclear.…”