Prediction of Possible Effects of Arsenic and Cadmium in Human Health Using Chemical-Protein and Protein-Protein Interaction Network

Arsenic and cadmium toxicity has demonstrated to be a crucial problem and there are many health issues interconnected with each other. The toxicity of these metals has no biological role even though remain present in some or the other form, hazardous for the human health and its proper functioning. As a result, from the very beginning, the researchers are trying to overcome the serious effects occurred by the heavy metals. The different procedures and methods are followed for minimizing the negative effects. The study was conducted to predict the probable effects and theirs targeted proteins in human body by recently developed advanced bioinformatics tools and subsequently found 10 proteins are interacted with arsenic and cadmium for each. However, these 10 proteins are independently associated with other 97 and 100 proteins. Finally, 25 common proteins have been identified which are affected by these two heavy metals. Our data mining search revealed that all of these 25 proteins are associated with the causing of cancer in human body.


Introduction
Heavy metals and their toxic forms are found in our environment due to natural and anthropogenic activities. It has toxic effects on human health exposure through foodstuff, water, air and soil [1,2]. Heavy metals pollution in water, air, crops, vegetables and other foodstuffs is a global risk for human health [3,4]. Bangladesh is a developing and overpopulated country, its industrialization is increasing day by day. Most of the industries are located in Dhaka, Gazipur and Narayanganj. All these three cities are surrounded by some rivers and lake. Everyday industrial untreated and waste water is discharged to the river and the lake [5]. Subsequently, river and lake water is becoming polluted with some heavy metals like arsenic (As), cadmium (Cd) etc. Intriguingly, the recent report shows that some lake water inside and peripheral rivers water of Dhaka, Gazipur and Narayanganj have been contaminated with some heavy metals like As, Cd, Pb, Cr, Hg, Zn [5]. These river water use for irrigation to cultivate some common agricultural crops like cereals, vegetables etc. Intriguingly, cereals and vegetables absorbed these heavy metals and subsequently contaminated. Now-a-days, it is very concerning issues that fishes, cereals and vegetables have been found toxic metals contaminated inside and surround the Dhaka city [6]. These fishes, cereals and vegetables use daily consumption in Dhaka city. Consequently, serious health problem has been occurring like cancer, Protein-Protein Interaction Network cardiovascular disease, and diabetes etc [7,8]. Considering above mentioned problem, our present study shows that probable proteins are being affected due to Arsenic (As) and Cadmium (Cd). We identified some common proteins by some Bioinformatics tools which are commonly responsible for some health hazards.

Network Retrieval
The interaction of As and Cd with human (Homo sapiens) proteins were searched through STITCH 4.0 (http://stitch.embl.de/) web server [9]. STITCH helps to predict the interactions of chemicals and proteins of specific species by evidence derived from experiments, databases and literature mining. The list of human (Homo sapiens) proteins interacting with As and Cd further considered to identify the protein-protein interaction (PPI). PPI was done through STRING 10.0 (http://string-db.org/) web server [10]. STRING is used to get all known and predicted protein interactions based on direct (physical) and indirect (functional) associations.

Sequence Collection
The sequences of proteins which were listed through PPI were downloaded in FASTA format for NCBI protein (http://www.ncbi.nlm.nih.gov/protein) database. The repetition was avoided during sequence collection. All the downloaded protein sequences were kept in one FASTA file for further analysis.

Blast 2 GO
Gene ontology of these sequences was done through Blast 2 GO software [11]. This tool was used for functional annotation and analysis of protein sequences. The correlation of sequences in biological process, molecular function and presence in cellular component were analyzed.

Venny
We used Venny (http://bioinfogp.cnb.csic.es/tools/venny/) web server to detect the common proteins in four targeted list. And the list of common protein was also collected from here.

Interaction Prediction
In our study, we found 10 potential proteins of Homo sapiens have been predicted by STITCH 4.0 for As and Cd ( Figure 1), respectively. During protein-protein interaction (PPI) prediction by STRING 10.0 bioinformatics tools 97, 100 proteins have been identified for As and Cd (Table 1 and 2), respectively.

Pathway Detection
Through Blast 2 GO software, we did following steps for a list of target protein sequences: protein Blast, mapping, retrieving Enzyme Codes (EC), tracking KEGG pathways and scanning motifs by Inter Pro Scan. These accomplished jobs helped to generate an overview of biological process, molecular function and cellular component of these listed proteins for As and Cd (Figure 2-4) and Cd ( Figure 5).

Common Targets Determination
These two heavy metals As and Cd have multiple targets and our study showed that 25 proteins (Table 3) are common target with As and Cd which was screened by Venny web server ( Figure 5).

BCL 2
Apoptosis regulator Bcl-2 Its role in regulation of apoptotic signaling pathways, is possibly related to carcinogenesis [15] TP 53 Cellular tumor antigen p53 Cell cycle regulation [16] XRCC 6 X-ray repair cross-complementing protein 6 Function as scaffolding protein in base excision repair and single strand break repair pathways. [17] FOS Proto-oncogene c-Fos A variety of biological processeses, including pro-liferation, differentiation, tumorigenesis, and apoptosis. [18] JUN Transcription factor AP-1 An important role in melanoma progression and development. [19] GSTA 2 Glutathione S-transferase A2 Upregulated during oxidative stress, overexpressed in many tumors and leading to causes during cancer chemotherapy [20] AKT 1 RAC-alpha serine/threonine-protein kinase Inhibits the apoptosis [21] NFE2 L 2 Nuclear factor erythroid 2-related factor 2 (No cancer related, blood heaomorrhage) Inflammatory disorder [22] ATF 2 Cyclic AMP-dependent transcription factor ATF-2 (Pregnancy related) Function in the control of uterine activity throughout pregnancy. [23]

Discussion
Heavy metals are always toxic to animal health in higher doses. Among the heavy metals As is one of most dangerous health hazard to human as because every fourth of the tube well is polluted with As in Bangladesh [12]. In addition that both of As and Cd polluted river and lake water is barning issues in Dhaka, Gazipur and Naraynagnj cities [13]. As a result, some life threatening diseases like cancer, metabolic disorders are common in Bangladesh. We found that some proteins are directly and indirectly affected by As and Cd and subsequently, life threatening diseases have been occurred. However, molecular mechanism of heavy metals has been extensively reported that oxidative DNA damage, inhibition of major DNA repair systems and inactivation of tumor suppressor genes are the main causes for increasing the health problem in human due to exposure of heavy metals [14]. Considering all of these preliminary published data, we investigated the target proteins for As and Cd which have been affected in human body by recent Bioinformatics tools. In our present study, we found total 25 common proteins for As and Cd enlisted in tabular form with their short description and probable functions which have the possibility to affect in the human body (Table 3). Interestingly, most of the identified proteins are responsible for occurring the cancer in the human body. For example, Apoptosis regulator Bcl-2 protein family was expressed in many types of cancer cell and related to cancer pathophysiology [15].

Conclusions
Effects of heavy metals such as As and Cd on living organism specially human beings is not constant in any locations, hence it is varies due to exposure in environment. Proper guidelines, government policy, rules can be reduced the level of contamination of heavy metals to be made safe and healthy living area for living organisms. Professional discharge to heavy metals can be declined by engineering solutions. Surveilling the exposure and possible intercession for decreasing additional exposure to heavy metals in the environment and in humans can become a momentous step towards prevention. National as well as international co-operation can play a vital role for framing appropriate tactics to prevent heavy metal toxicity.