Bio Actives from Albizia Lebbeck on Acute Lung Injury/ Acute Respiratory Distress Syndrome Molecular Targets: In-Silico Study

This contemporary work is prepared with the aim of presenting natural phytoconstituents obtained from Albizia lebbeck (Bronco T) as a remedial option against Acute Lung Injury / Acute Respiratory Distress Syndrome (ARDS). The early onset of non-cardiogenic edema and subsequent gas-exchange impairment caused by a severe inflammatory process known as cytokine storm is acute respiratory distress syndrome (ARDS). The existing strategy includes mechanical ventilation and glucocorticosteroid. However, they pose problems like diaphragm atrophy and down regulated immune response of the host in the lungs of patients with acute respiratory distress syndrome (ARDS), the nuclear regulatory factor NF-kappaB and TLR-4 is activated, which may contribute to increased expression of immune regulatory cytokines and other pro inflammatory mediators including IL-6 and TNF-alpha. Natural products play a pivotal role as it offers minimal and in some cases no toxicity. Albizia lebbeck is the folk language and is known for its anti-inflammatory properties. Targeting the above-mentioned receptors with bioactives from Albizia lebbeck would down regulate the signaling pathway and its associated mediators in ARDS. Through in- silico study including molecular docking, ADMET and Lipinski analysis, we are trying to narrow down the active phytoconstituent from Albizia lebbeck against ARDS.


Annals of Reviews and Research
ventilator-associated pneumonia (VAP) [9]. Alveolar epithelial cells are divided into two types: alveolar type I (ATI) and alveolar type II (ATI) (ATII). AT1 cells are common in the body and can be readily harmed. When type I cells are damaged, fluid leaks into the alveoli, disrupting regular alveolar clearance. Surfactant secretion is controlled by ATII cells, which is an important role in lowering alveolar tension. In addition, ATII cells have a role in ion transport. Although ATII cells are few in number, they are more resistant to injury [10,11].
A combination of alveolar epithelial cells and capillary vascular cells may be involved in the condition. Endothelial injury, on the other hand, is more common. There is a leakage of fluids and proteins into the interstitium in ARDS due to increased permeability of the capillaries. Fluids, red blood cells, and neutrophils enter the alveolar space through the injured epithelial cells after that. In the exudative phase of ARDS, interstitial and alveolar edema are common [12]. TLR4 is found on both alveolar macrophages and epithelial cells in the lungs. TLR4 detects key ligands like as hyaluronic, LPS, heat shock proteins, and the high mobility group box-1 (HMGB) protein during ARDS propagation [13]. TLR4 activation causes the generation of pro-inflammatory cytokines, which can increase the severity of injuries, as previously stated. Many studies have been conducted in recent years to determine TLR4's exact role in ARDS. The TLR4/nuclear factor (NF)-B pathway could be a key target for inflammatory damage. TLR4 is a pattern recognition receptor from the TLR protein family that activates NF-B and causes the production of inflammatory cytokines and chemokines including TNF-and IL-6 in lung cells. Medicinal plants can be used in this direction as they come with minimum and in some cases no toxicity as well as strengthen immune system via various pathways. Abizia lebbeck, a native tree to Asian and subtropical regions across the world, is a perennial, deciduous tree which is used as a shelter tree for cash crops, for erosion control, as a forage crop and as a source of hardwood [14]. In Ayurveda it is used for various medicinal purposes as it is a non-toxic tree. This tree contains alkaloids, tannins, saponins and flavonoids which have medicinal action, and it is used especially in treating bites and stings from poisonous animals such as snake. Pharmacologically A. lebbeck is used in treatment of various respiratory ailments including bronchial asthma (Table 1 & 2). In the present study, phytoconstituents of A. lebbeck were analyzed using molecular docking software and the best docked compounds were further processed for druglikeness and ADMET profile analysis using Lipinski Rule of Five and ADMET SAR studies.  Table 2 Kingdom Plantae

Order Fabales
Family Fabaceae

Preparation of protein
RCSB Protein Data Bank (https://www.rcsb.org/) [15] was used to retrieve the crystal structure of TNF-alpha (PDB ID: 2AZ5), TLR4 (PDB ID: 3FXI), NfkB (PDB ID: 1NFK), IL-6(PDB ID: 1ALU). Protein preparation was done with the help of Discovery studio 4.0 by the removal of water molecule and other heteroatoms present in the crystal structure. Further, the active site identification was done for the prepared protein model with the help of Discovery studio 4.0.

Selection of active phytochemicals-Ligands
Total 59 active phytochemicals from medicinal plant Albizzia lebbeck were retrieved from literature and database. PubChem compound database (https://pubchem.ncbi.nlm.nih.gov/) was used for retrieval of structure in 2D SDF format. Ligand optimization, energy minimization and conversion of retrieved ligands to 3D PDB formatwere done with the help of Discovery Studio 4.0.

Annals of Reviews and Research
software. For the calculation of interaction energy between receptor and selected ligands individually, the macro file dockrun_ mcr was used. Afterward, with the help of YASARA software, docked complexes visualize and changed in PDB files for 2D-3D interaction visualization study using Discovery studio 4.0. For the docking calculation study, the result log files from YASARA were taken. Shortening on the basis of binding energy [kcal/mol] and dissociation constant [pM], 25 VINA docking runs of the ligand object 2 to the receptor object 1 was done. The compound having more positive binding energies indicates stronger binding, and negative energies indicate no binding.

Molecular docking
Molecular docking study revealed that 19 out of 59 phytochemicals from A. lebbeck showed significant binding affinity with TLR-4, Nf-kB IL-6, TNF-alpha, of inflammatory cascade. Table  3 shows the list of phytochemicals showing significant binding energy (≥7.0 kcal/mol) with above mentioned targets (Figure 1).

Drug-likeness and ADMET analysis
Drug-likeness test for best docked compounds was predicted using Lipinski's filter and ADMET molecular property prediction test was performed out by admetSAR server. Lipinski rule of five is a thumb rule of five which helps in differentiating between drug like and non-drug like molecules by obeying its five parameters (Molecular mass, Hydrogen bond donor, Hydrogen bond acceptor, Log P, and Molar refractivity), it must obey 2 or more of their parameters. Consequently, our best docked compounds (Table 4) follow more than 2 parameters of Lipinski rule of five. admetSAR server provides ADMET profiles of drug candidates. The molecular property profile results indicate positive sign towards human intestinal absorption (HIA) and have no carcinogenic effects, indicating all drugs like properties (Table 4).

Discussion
Since its original description 50 years ago, molecular aetiology and pathophysiology for the development of ALI/ARDS have become better understood. However, "lung-protective ventilation" in mechanically ventilated patients with ARDS is now the best practice, with no specific therapy aimed at lung inflammation. A complex network of proinflammatory signaling pathways and oxidative stress created by a range of cell types in the lungs initiate, amplify, and control the inflammatory response in patients with ARDS. Here in this work we have used in-silico study to screen out the bio actives from the Albizia lebbeck against molecular target of acute lung injury. A. lebbeck is an astringent that is used to cure boils, coughs, eye infections, flu, gingivitis, lung difficulties, chest problems, as a tonic, and to treat abdominal tumors in some cultures [19]. It is a medicinal plant as per Ayurveda the bark can be used to treat inflammations [20]. This formed the hypothesis of the present work as ALI is a clinical condition of respiratory distress involving deregulated inflammatory system. It begins with accumulation of fluid in the alveolar region due to infiltration of neutrophil. Neutrophils serve as the defense mechanism regulated by macrophage polarization [21] in normal condition.However, under the influence of endotoxins the toll like receptors (TLR-4) are activated and they secrete chemokine to flush out the invading pathogens. In ALI/ARDS this mechanism goes out of control especially in cases of septicemia influenced ARDS and creates storm of inflammatory cytokines [22]. From the molecular docking study we found that phytoconstituents from A.lebbeck such as Globularicitrin (9.94 kcal) and Vicenin-2 (9.64 kcal) showed significant binding energy suggesting that they can down regulate TLR-4 receptors in ARDS condition and can save the patient from deleterious effects. Another pathway involved in pathogenesis of ARDS in Nf-KB. In the lungs of patients with acute respiratory distress syndrome (ARDS), the nuclear regulatory factor NF-kappaB is activated, which may contribute to increased expression of immune-regulatory cytokines and other pro inflammatory mediators [23]. In our study we found that Terpenoids and Tannins have significant binding interaction with Nf-kB suggesting it could control the inflammatory cytokine storm. The major inflammatory cytokines responsible for destructive effect of ARDS are Il-6 and TNF-α [24]. From this in-silico work we found that Friedelin (IL-6), Lupeol (IL-6), Albigenin (TNF-alpha) and Alpha Amyrin (TNF-alpha) were able to inhibit these cytokines by binding with them. All the reported bio actives (Figure 2) from A. lebbeck showed drug-like property as per LPINSKI RULE OF FIVE and were safe as per optimal scoring by ADMETSar software. Despite significant progress in delineating molecular pathways for ALI and ARDS over the previous several decades, these discoveries have not resulted in substantial advances in medical treatment for ARDS patients. From this in-silico work we are reporting for the first time that a medicinal plant from Indian traditional system could be utilized as add on therapy under clinical supervision for management of acute lung injury/acute respiratory distress syndrome.