Bitter melon protects against ER stress in LS174T colonic epithelial cells

Dale A Kunde,Wai Chin Chong,Jason A Smith,Nuri Guven,Kiran D.K Ahuja,Rajaraman D Eri,Prathiba V Nerurkar,Jeremy Just

doi:10.1186/s12906-016-1522-1

Dale A Kunde, Wai Chin Chong + Show 6 more

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https://doi.org/10.1186/s12906-016-1522-1

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Abstract

BackgroundBitter Melon (BM) has been used as a functional food in traditional Chinese and Indian medicine for many generations and has gained a great deal of attention due to its apparent benefits in moderating some of the pathogenic processes in a variety of inflammatory conditions. BM extract (BME) has been shown to possess strong anti-oxidant properties. In addition, it can ameliorate oxidative stress and potentially ER stress. There is increasing evidence that oxidative and ER stress are major contributors for intestinal secretory cell dysfunction which leads to local inflammation and disease pathogenesis that are hallmarks of inflammatory bowel diseases (IBD). Hence, the search for potential therapeutics against ER stress and oxidative stress in intestinal epithelial secretory cells may provide valuable resources for the management of IBD. The aim of the present study was to investigate the effects of BME in ameliorating ER stress in colonic epithelial cells.MethodsHuman colonic adenocarcinoma LS174T cells were used for the assessment of BME effects on colonic epithelial cells in vitro. Cell viability was assessed using trypan blue exclusion and the effect of BME in ameliorating tunicamycin (TM)-induced ER stress was determined by analysing the mRNA expression of the common ER stress markers; ATF6, XBP1, GRP78, CHOP and PERK by quantitative RT-PCR and GRP78 and CHOP by western blot.ResultsIn the absence of ER stress, BME exhibited no cell toxicity up to 2.0% w/v and no significant effect on the basal mRNA expression of ER stress markers in LS174T cells. In contrast, pre-treatment of LS174T cells with BME followed by induction of ER stress resulted in a significant decrease in mRNA expression of ATF6, XBP1, GRP78, CHOP and PERK and protein expression of GRP78 and CHOP. Co-treatment during induction of ER stress and post- treatment following induction of ER Stress in LS174T cells resulted in a lower but still significant reduction in mRNA expression levels of most ER stress markers.ConclusionsThis is one of the first studies demonstrating the efficacy of BME in reducing expression of ER stress markers in colonic epithelial cells suggesting the potential of BME as a dietary intervention in ameliorating ER stress and oxidation in IBD. Interestingly, while the most significant effect was seen with pre-treatment of cells with BME there was a reduced but still significant effect when co-treated or even post-treated. This suggests that BME may even be effective in modulating ER stress in the face of an existing cell stress environment.

Highlights

Bitter Melon (BM) has been used as a functional food in traditional Chinese and Indian medicine for many generations and has gained a great deal of attention due to its apparent benefits in moderating some of the pathogenic processes in a variety of inflammatory conditions
An increase in lag time of oxidation was observed with increasing concentrations of BM extract (BME) (Additional file 2 Table S1) where the lag time ranged from 144 ± 15 min for vehicle to >360 min for BME 0.75%
The maximum change in absorbance ranged from 0.570 ± 0.035 for the vehicle to 0.490 ± 0.0.038 abs at BME 0.25% (Additional file 2 Table S1) but was not significantly different, while the maximum change in absorbance for the BME treatments of 0.5% and 0.75% were significantly lower (0.295 ± 0.045 and 0.079 ± 0.009 respectively; p < 0.05) due to incomplete oxidation reaction resulting from an increased lag time

Summary

Introduction

Bitter Melon (BM) has been used as a functional food in traditional Chinese and Indian medicine for many generations and has gained a great deal of attention due to its apparent benefits in moderating some of the pathogenic processes in a variety of inflammatory conditions. There is increasing evidence that oxidative and ER stress are major contributors for intestinal secretory cell dysfunction which leads to local inflammation and disease pathogenesis that are hallmarks of inflammatory bowel diseases (IBD). Bitter melon (BM; Momordica charantia), known as bitter gourd, karela or balsam pear, belongs to the Cucurbitaceae family and is widely cultivated in tropical regions including Asia, Africa and South America. It has been used in traditional Chinese and Indian medicines for gastrointestinal disorders as well as diabetes and its complications [1,2,3,4]. Intestinal barrier dysfunction due to defects in the intestinal secretory cells as a result of increased oxidative and ER stress has been recognised as a major contributor to the pathogenesis of IBD [13, 15]

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