Improved lymphocyte response to H2O2 after regular intake of Sage tea (Salvia officinalis) involves induction of HSP70

Abstract

Sage (Salvia officinalis) has recently been shown to have plasma glucose lowering potential. This suggests an antidiabetic potential for this plant alongside with other well-known properties that include antioxidant, anti-inflammatory and anti-mutagenic activities. Diabetes, a disease caused by loss of control of glucose homeostasis, also involves imbalances in the internal metabolic environment that can lead to irreversible oxidative damage in some cell populations. In the present study, we investigated the protective effect of the regular intake of Sage tea on the antioxidant response of peripheral blood lymphocytes (PBLs) challenged with H2O2. Lymphocytes were isolated from six healthy human volunteers at several times during a pilot trial of four weeks of sage tea treatment (twice a day). We also collected blood samples in the pre- and post-treatment periods referred to as baseline and wash-out, respectively. Damage to DNA was evaluated by Comet Assay. Significant reduction of damage induced by 200 μM H2O2 after two weeks of treatment were observed, indicative of improved cell defences. To further explore the mechanisms of cellular protection conferred by tea drinking to lymphocytes, we assessed effects on Hsp70 expression levels in PBLs by use of Western Blotting analysis. Besides being associated with improved stress resistance, the increased expression of Hsp is regarded as one of the most powerful means of cytoprotection against protein misfolding and aggregation. Our results show Hsp70 levels were significantly elevated in treatment compared with the baseline, which suggests that an induction of Hsp70 may be, at least in part, responsible for the improved cellular response to H2O2 induced damage.