Quercetin reduces hydroxyurea induced cytotoxicity in immortalized mouse aortic endothelial cells

Abstract

Background: Chronic inflammation is a characteristic of sickle cell disease (SCD), and is invariably associated with vascular endothelial injury. Hydroxyurea (HU), a naturally cytotoxic chemotherapeutic agent, is the only FDA drug approved for SCD, and is therefore naturally cytotoxic. Quercetin (QCT) is a dietary flavonoid found ubiquitously in plants and foods that have anti-oxidative and anti-inflammatory characteristics. Our hypothesis is that dietary QCT will decrease cytotoxic effects of lipopolysaccharide (LPS) and HU induced vascular cell damage.

Methods: Lipopolysaccharide (LPS) was used to induce inflammation in immortalized mouse aortic endothelial cells (iMAECs), providing an in vitro model of inflamed endothelial cells. The cells were exposed to LPS throughout the entire experiment. Interventions included treating the LPS exposed cells with QCT, HU, or QCT + HU over 50 hours. The 50-hour period included 24 hours of varying treatments, followed by two hours of hypoxic exposure and then 24 hours under normal aerobic exposure.

Results: LDH level was significantly higher for LPS treated versus untreated cells (P = 0.0004). LPS plus 30 micromole QCT reduced the LDH (p = 0.1, trend), whereas LPS plus 100 micromoles HU, significantly increased LDH (p = 0.0004). However, LPS plus treatment with 30 micromoles QCT/100 micromoles HU, significantly reduced LDH, compared with HU alone (p = 0.0002).

Discussion: These results suggest that quercetin may be effective against vascular endothelial cell damage for iMAECs in vitro. In particular, it shows promise in preventing HU-induced cytotoxicity, surprisingly found from these results. This latter finding is important, and should be given more consideration, since HU is the only FDA-approved drug for treating sickle cell patients, and its use is rapidly increasing.

Keywords: Hydroxyurea; Quercetin; Sickle cell disease; Vascular endothelial cells.

Figure 1. Experimental outline.

Timeline of experimental procedure.

Figure 2. Comparing LDH release in LPS treated cells versus non-treated cells.

Values are means ± SD. The mean LDH release of the LPS treated cells was significantly higher than for the untreated cells.

Figure 3. The effect of various concentrations of quercetin on LDH release.

Values are means ± SD. The percentage of LDH released from the 30 µmol QCT-treated cells trended lower than the LDH release measured in the inflammatory model.

Figure 4. The effects of hydroxyurea and quercetin on LDH release.

Values are means ± SD. The addition of 30 µmol of QCT in combination with the HU treatment gleaned a significant reduction of LDH release, compared with only HU treatment.