Polyphenols of Hibiscus sabdariffa improved diabetic nephropathy via attenuating renal epithelial mesenchymal transition.

We previously reported that Hibiscus sabdariffa polyphenol extracts (HPE) are beneficial for diabetic nephropathy. Since an epithelial to mesenchymal transition (EMT) is critical in renal fibrosis, the present study aimed to investigate whether HPE could prevent EMT of tubular cells. Treatment of HPE reduced angiotensin II receptors (AT)-1 and transforming growth factor ß1 (TGF-ß1) evoked by high glucose and recovered the increased vimentin and decreased E-cadherin. HPE decreased fibronectin, thus avoiding EMT and accompanying fibrosis. AT-1 was upstream to TGF-ß1, while there were recruitment signals between AT-1 and TGF-ß1. Scan electron microscopy (SEM) and immunohistochemistry (IHC) revealed that the interacting filaments of tubular cells disappeared when treated with high glucose, and type IV collagen of tubulointerstitial decreased in diabetic kidneys. Treatment of HPE recovered morphological changes of cell junction and basement membrane. We suggest that HPE has the potential to be an adjuvant for diabetic nephropathy by regulating AT-1/TGF-ß1 and EMT.

A system for purification of recombinant proteins in Escherichia coli via artificial oil bodies constituted with their oleosin-fused polypeptides.

An expression/purification system was developed using artificial oil bodies (AOB) as carriers for producing recombinant proteins. A target protein, green fluorescent protein (GFP), was firstly expressed in Escherichia coli as an insoluble recombinant protein fused to oleosin, a unique structural protein of seed oil bodies, by a linker sequence susceptible to factor Xa cleavage. Artificial oil bodies were constituted with triacylglycerol, phospholipid, and the insoluble recombinant protein, oleosin-Xa-GFP. After centrifugation, the oleosin-fused GFP was exclusively found on the surface of artificial oil bodies presumably with correct folding to emit fluorescence under excitation. Proteolytic cleavage with factor Xa separated soluble GFP from oleosin embedded in the artificial oil bodies; thus after re-centrifugation, GFP of high yield and purity was harvested simply by concentrating the ultimate supernatant.

Method for bacterial expression and purification of sesame cystatin via artificial oil bodies.

A method was developed for production of sesame cystatin, a thermostable cysteine protease inhibitor. Sesame cystatin was first expressed in Escherichia coli as an insoluble recombinant protein fused to oleosin, a unique structural protein of seed oil bodies, by a short hydrophilic linker peptide. Stable artificial oil bodies were constituted with triacylglycerol, phospholipid, and the insoluble oleosin-cystatin fusion protein. After centrifugation, the oleosin-cystatin fusion protein was exclusively found in the artificial oil bodies. Proteolytic cleavage with papain, a cysteine protease effectively inhibited by cystatin, separated soluble cystatin from oleosin that was firmly embedded in the artificial oil bodies. After recentrifugation, papain that coexisted with cystatin in the collected supernatant was denatured by incubating at 55 degrees C for 30 min. The insoluble denatured papain was removed by one more centrifugation, and the expressed cystatin of high yield and purity was harvested simply by concentrating the ultimate supernatant. Comparable inhibitory activity toward papain was observed between the expressed cystatin and the native one purified from sesame seeds. This method is presumably applicable to production of other protease inhibitors whose target proteases are economically available.