Tobacco Smoke Carcinogens Induce DNA Repair Machinery Function Loss: Protection by Carbon Nanotubes

Abstract

Purpose: DNA damage is a continuous process occurring within the cells caused by intrinsic and extrinsic factors, but it gets repaired regularly. If the DNA repair process is faulty, the incidences of damages/mutations can accumulate in cells resulting in cell transformation. It is hypothesized that the negative variations in DNA repair pathways in even at one point viz. genetic, translational or posttranslational stage may fairly be crucial for the beginning and development of carcinogenesis. Therefore, we investigated the potential of tobacco specific nitrosamines (TSNs) related carcinogens to interact with the enzymes involved in DNA repair mechanisms in the current study.

Methods: The derivatives of cigarettes' smoke like NNK and NNAL are very well known and recognized carcinogens. Therefore, almost 120 enzymes playing crucial role in the DNA repair process have been analysed for their reactivity with NNK and NNAL.

Results: The molecular docking study helped to screen out, 07 possible DNA repair enzyme targets for NNK, and 12for NNAL. Present study revealed the loss of activity of DNA repair enzymes in the presence of NNK and NNAL, and this accumulation may induce the tendency of DNA damage which can lead the transformation of exposed normal cells in to cancerous cells. This study also demonstrated the protective potential of nanoparticles like SWCNTs/MWCNTs against TSN's induced toxicity; here SWCNT against NNK (-17.16 Kcal/Mol) and MWCNT against NNK -17.01 Kcal/Mol were showing maximum binding affinities than the known biomolecular target of NNK 1UGH (Uracil-DNA glycosylase,-7.82Kcal/Mol).

Conclusion: CNTs can be applied as chemo-preventive agents against environmental and tobacco induced carcinogens owing to their scavenging potential and warrants for in vivo and in vitro experimental validation of the results obtained from the present study.<br />.

Keywords: DNA damage; Molecular docking; NNAL; NNK; cancer.

Figure 1

Schematic Methodology of the Analyses

Figure 2

Chemical Structure of NNK [4-(Methylnitrosamino)-1-(3-pyridyl)-1-butanone] PubChem Compound ID- 47289, ChemSpider ID-43038

Figure 3

Chemical structure of NNAL [4-(methylnitrosamino)-1-(3-pyridyl)-1-butan-1-ol] PubChem Compound ID- 104856, ChemSpider ID- 94646

Figure 4

3D Structure of SWCNT, MWCNT and Fullerene

Figure 5

Protein–Protein Interaction of HUS1with Their Functional Partner RAD9,ZDOCK Score was Reduced from 14.06 to 12.7 and NNK Binds between the Interface ofHUS1 and RAD9. Orange and yellow coloured ribbon like structures represents the RAD9 andHUS1 proteins respectively and red and green coloured ball like structures shows binding residues of RAD9 and HUS1, which involve an intermolecular hydrogen bond. NNK is interfering between the interfaces of HUS1 andRAD9

Figure 6

Binding Pose of NNK & NNAL with SWCNT

Figure 7

Binding Pose of NNK & NNAL with MWCNT

Figure 8

Binding Pose of NNK & NNAL with Fullerene