Protective Effect of Proteins Derived from Seed Explant Cultures of Calotropis procera in a Preclinical Model of Arthritis

Abstract

!Proteins isolated from the in vitro cultures of callus and roots developed from the germinating seed explants of Calotropis procera were evaluated for their protective effect in a rat model of arthritis at 1 and 5 mg/kg doses in two independent sets of experiments comprising of respective controls. Joint swelling, functional parameters, markers of inflammation, oxidative stress, tissue histology, and cyclooxygenase-2 expression in these rats were compared with those treated with the standard anti-inflammatory drug diclofenac on day 3. Both callus and root proteins produced a dose-dependent reduction in joint swelling, and at the 5-mg/kg dose, their inhibitory effect was more pronounced (57 and 55 % inhibition) than that of diclofenac (42 and 46% in two sets). Both of the protein fractions alleviated functional limitations in arthritic rats and normalized the levels of prostaglandin E 2 , tumor necrosis factor-α, and other biochemical markers of inflammation and oxidative stress, maintained tissue architecture, and suppressed cyclooxygenase-2 expression compared to arthritic controls. This study demonstrates that the proteins derived from the in vitro culture of C. procera explants have potential in the treatment of arthritis. Key wordsCalotropis procera · Apocynaceae · callus · inflammation · medicinal plant · roots Plants have served as living factories for time immemorial to meet the requirement of medicinal agents that have been used in various traditional systems for the prevention and cure of several diseases. Their demand for a medicinal purpose has been met either from wild growing or cultivated plants, and various environmental factors, methods of collection, and processing are well known to result in variability in efficacy and safety of medicinal preparations derived from them [1]. In this regard, their correct identification, documentation, and conservation are important aspects to be considered in order to have a sustainable resource [2]. Thus, growing the medicinal plants in a controlled environment is an alternative option to minimize variability, and plant tissue cultures have been used as a source of pharmacologically active secondary metabolites [3,4]. Calotropis procera Ait. R. Br., a member of the Apocynaceae family, is a wild-growing plant that has been used for the treatment of various diseases of the liver, abdomen, and those involving inflammation. Different parts of this plant, including its latex, have been shown to possess medicinal properties [5]. Both the nonprotein constituents present in the aqueous and organic extracts of latex and the proteins isolated from the latex have been reported to produce anti-inflammatory and antinociceptive effects in rodent models [6][7][8][9]. Recently, proteins isolated from the callus and roots developed from in vitro explants of the germinating seeds of this plant have also been shown to inhibit an acute inflammatory response [10,11]. The present study was carried out to investigate the efficacy of these proteins in a preclinical model of ...