Inhibition of IKKβ by celastrol and its analogues - an in silico and in vitro approach

Context: Alzheimer's disease (AD) is the most common form of dementia affecting the aged population and neuroinflammation is one of the most observed AD pathologies. NF-kappa B is the central regulator of inflammation and inhibitor kappa B kinase (IKK) is the converging point in NF-kappa B activation. Celastrol is a natural triterpene used as a treatment for inflammatory conditions. Objective: This study determines the neuroprotective and inhibitory effect of celastrol on amyloid beta(1-42) (A beta(1-42)) induced cytotoxicity and IKK beta activity, respectively. Materials and methods: Retinoic acid differentiated IMR-32 cells were treated with celastrol (1 mu M) before treatment with A beta(1-42) (IC30 10 mu M) for 24 h. The cytotoxicity and IKK phosphorylation were measured by MTT and western blotting analysis, respectively. We screened 36 celastrol analogues for the IKK beta inhibition by molecular docking and evaluated their drug like properties to delineate the neuroprotective effects. Results: Celastrol (1 mu M) inhibited A beta(1-42) (10 lM) induced IjBa phosphorylation and protected IMR-32 cells from cell death. Celastrol and 25 analogues showed strong binding affinity with IKK beta as evidenced by strong hydrogen-bonding interactions with critical active site residues. All the 25 analogues displayed strong anti-inflammatory properties but only 11 analogues showed drug-likeness. Collectively, molecule 15 has highest binding affinity, CNS activity and more drug likeness than parent compound celastrol. Discussion and conclusion: The decreased expression of pI kappa B alpha in celastrol pretreated cells affirms the functional representation of inhibited IKK beta activity in these cells. The neuroprotective potentials of celastrol and its analogues may be related to IKK inhibition.