QSAR and Docking Studies on Capsazepine Derivatives for Immunomodulatory and Anti-Inflammatory Activity Aparna Shukla 1 , Pooja Sharma 1 , Om Prakash 1 , Monika Singh 2 , Komal Kalani 3 , Feroz Khan 1 *, Dnyaneshwar Umrao Bawankule 2 , Suaib Luqman 2 , Santosh Kumar Srivastava 3 1 Metabolic and Structural Biology Department, CSIR-Central Institute of Medicinal and Aromatic Plants, P.O.- CIMAP, Kukrail Picnic Spot Road, Lucknow (Uttar Pradesh), India, 2 Molecular Bio-Prospection Department, CSIR-Central Institute of Medicinal and Aromatic Plants, P.O.- CIMAP, Kukrail Picnic Spot Road, Lucknow (Uttar Pradesh), India, 3 Analytical Chemistry Division, CSIR-Central Institute of Medicinal and Aromatic Plants, P.O.- CIMAP, Kukrail Picnic Spot Road, Lucknow (Uttar Pradesh), India Abstract Capsazepine, an antagonist of capsaicin, is discovered by the structure and activity relationship. In previous studies it has been found that capsazepine has potency for immunomodulation and anti-inflammatory activity and emerging as a favourable target in quest for efficacious and safe anti-inflammatory drug. Thus, a 2D quantitative structural activity relationship (QSAR) model against target tumor necrosis factor-a (TNF-a) was developed using multiple linear regression method (MLR) with good internal prediction (r 2 = 0.8779) and external prediction (r 2 pred = 0.5865) using Discovery Studio v3.5 (Accelrys, USA). The predicted activity was further validated by in vitro experiment. Capsazepine was tested in lipopolysaccharide (LPS) induced inflammation in peritoneal mouse macrophages. Anti-inflammatory profile of capsazepine was assessed by its potency to inhibit the production of inflammatory mediator TNF-a. The in vitro experiment indicated that capsazepine is an efficient anti-inflammatory agent. Since, the developed QSAR model showed significant correlations between chemical structure and anti-inflammatory activity, it was successfully applied in the screening of forty-four virtual derivatives of capsazepine, which finally afforded six potent derivatives, CPZ-29, CPZ-30, CPZ-33, CPZ-34, CPZ-35 and CPZ- 36. To gain more insights into the molecular mechanism of action of capsazepine and its derivatives, molecular docking and in silico absorption, distribution, metabolism, excretion and toxicity (ADMET) studies were performed. The results of QSAR, molecular docking, in silico ADMET screening and in vitro experimental studies provide guideline and mechanistic scope for the identification of more potent anti-inflammatory & immunomodulatory drug. Citation: Shukla A, Sharma P, Prakash O, Singh M, Kalani K, et al. (2014) QSAR and Docking Studies on Capsazepine Derivatives for Immunomodulatory and Anti- Inflammatory Activity. PLoS ONE 9(7): e100797. doi:10.1371/journal.pone.0100797 Editor: Aamir Ahmad, Wayne State University School of Medicine, United States of America Received March 21, 2014; Accepted May 29, 2014; Published July 8, 2014 Copyright: ß 2014 Shukla et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Data Availability: The authors confirm that all data underlying the findings are fully available without restriction. All data are included within the manuscript. Supporting Information files are also available publically. Funding: This study was supported by the ‘Science and Engineering Research Board (SERB), Department of Science & Technology (DST)’, New Delhi, India for the financial support at CSIR – Central Institute of Medicinal and Aromatic Plants, Lucknow, India (SR/FT/LS-25/2010 dated May 2, 2012). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: The authors have declared that no competing interests exist. * Email: f.khan@cimap.res.in Introduction Capsicum species commonly known as chillies, relished as an important spice in the culinary art of the world and is known for its medicinal effect since the dawn of the human civilization. The medicinal property of ‘hot pepper’ has been attributed to the presence of capsaicin, a pungent principal ingredient produced as a secondary metabolite. Chemically known as 8-methyl-N-vanillyl- 6-nonenamide. Capsaicin and its related compounds, collectively referred as ‘capsaicinoids’ or ‘vanilloids’, which bind specifically to transient receptor cation channel subfamily V (TRPV), that carry sensation of pain and responds naturally to noxious stimuli like high temperature and acidic pH [1]. Prolonged exposure causes nociceptor terminals to become insensitive to capsaicin, as well to other noxious stimuli [2]. Hyper stimulation of TRPV1 by capsaicin has an analgesic effect, since it leads to long-term desensitization of the sensory neurons. The clinical uses of TRPV1 agonist like capsaicin, are limited due to side effects of a burning sensation, irritation and neurotoxicity [3]. On the other hand, blocking of the pain-signalling pathway with a TRPV1 antagonist capsazepine represents a promising strategy for the development of novel analgesics with potentially fewer side effects [4]. Several non-neuronal effects of capsaicin have also been reported viz., induction of apoptosis in transformed cells [5], stimulation of prostaglandin formation leading to inhibition of gastric lesion [6], antibacterial activity [7], inhibition of cardiac excitability [8] and platelet aggregation [9]. Capsazepine is a known analog of capsaicin, discovered as a result of structure-activity relationship (SAR) studies [10]. Capsazepine induced similar action as capsaicin and resiniferatoxin (RTX) and exhibits even twofold more potent inhibition of expression of iNOS gene in LPS- stimulated murine macrophages through inactivation of NF-kB [11,12]. NF-kB is a protein complex that control transcription of DNA and it is involved in cellular responses to stimuli such as stress, cytokines, free radicals, ultraviolet irradiations, oxidized low-density lipoprotein, and microbial antigens. NF-kB regulation of immune response and inflammation, cell lineage development, cell apoptosis, cell cycle progression and oncogenesis in response to stimuli have been shown to regulate the expression of several genes (bcl-2, bcl-xl), cellular inhibitor of apoptosis protein, tumor PLOS ONE | www.plosone.org 1 July 2014 | Volume 9 | Issue 7 | e100797