Computational analysis followed by in vitro studies to explore cytokines (TNF-α, IL-6 and IL-1β) inhibition potential of the new natural molecule polonilignan

Targeting pro-inflammatory cytokines and their production is found to be of therapeutic benefit for the regulation of inflammation in various chronic autoimmune diseases. Our continued efforts to discover small molecular-weight pro-inflammatory cytokine inhibitors resulted in identifying a novel natural lignan molecule named polonilignan, isolated from the culture broth extract of an endophytic fungus Penicillium polonicum. An in silico study (molecular docking, ADME predictions, binding free energy calculation and molecular dynamics simulation) of the polonilignan over the pro-inflammatory cytokines proteins TNF-α, IL-6 and IL-1β was performed using Schrodinger LLC software to understand the binding interactions, drug-like properties, and stability of the ligand-protein complex. Further, in-vitro testing of inhibition of TNF-α, IL-6 and IL-1β by polonilignan was carried out using ELISA and RT-PCR on LPS-induced RAW 264.7 cell lines along with the testing of nitrite production effect (Griess assay) and cytotoxicity (MTT) analysis. Under the computational study, polonilignan revealed good docking scores, binding interactions, and stability under MDS and desirable in silico ADME results over the proteins TNF-α, IL-1β and IL-6. Poloniligan showed significant inhibition of IL-1β, IL-6 and TNF-α with IC50 values of 2.01 μM, 6.59 μM and 42.10 μM, respectively. Also, it reduced the translocation of the NF-κB subunit p65 to the nucleus (confocal microscopy). The mRNA expression levels of pro-inflammatory markers IL-1β, TNF-α and IL-6 levels were lowered significantly (p < .001) by the compound, and the diminution was higher with IL-1β. Further, the lignan was non-cytotoxic and effective in attenuating nitrite release (IC50 48.56 μM). Thus, polonilignan has been identified as a new pan-cytokine and NO inhibitor, it is recommended to optimise a method for the synthesis of this small molecular weight lignan and explore its pharmacokinetic characteristics, toxicity and therapeutic effect under various chronic inflammatory disease models.

New natural pro-inflammatory cytokines (TNF-α, IL-6 and IL-1β) and iNOS inhibitors identified from Penicillium polonicum through in vitro and in vivo studies

Overexpression of pro-inflammatory cytokines and iNOS have been found to be concomitant with several chronic inflammatory diseases and hence targeting their inhibition would be a useful therapy for inflammation. In view of this, study on discovery of natural pro-inflammatory cytokines inhibitory lead molecules from Penicillium polonicum, an endophytic fungus isolated from the fresh fruits of Piper nigrum was performed. When the culture broth extract of P. polonicum (EEPP) was subjected to LPS-induced cytokines expression (ELISA in RAW 264.7 cells), it exhibited inhibition of TNF-α, IL-6 and IL-1β and this encouraged us to do chemical investigation on EEPP to explore the bioactive components. Four compounds isolated and characterised as 3,5-di-tert-butyl-4-hydroxy-phenyl propionic acid (1), 2,4-di-tert-butyl phenol (2), indole 3-carboxylic acid (3) and tyrosol (4) were tested for their effect on the production of TNF-α, IL-1β and IL-6 in RAW 264.7 cells (ELISA). All the compounds exhibited a highly significant (P < 0.0001) inhibition effect, particularly against IL-1β (IC₅₀: 4-0.91 μM, 1-2.81 μM, 3-4.38 μM, and 2-5.54 μM). Tyrosol (4) was most active with IC₅₀ values of 0.91, 2.67 and 4.60 μM against IL-1β, IL-6 and TNF-α, respectively. On observing the potential activity of the compounds, two compositions C1 and C2 were prepared by mixing equimolar concentrations of compounds 1, 2, 3 & 4 (C1) and compounds 1, 2, 3, 4 & piperine (C2) in equal ratio. A synergistic effect was observed with C1 exhibiting potential suppression of IL-6 secretion (IC₅₀ 1.91 μM) and C2 against IL-1β (IC₅₀ 5.98 μM). Also, the individual compounds and C1 were effective in controlling iNOS expressions in RAW 264.7 cells (RTPCR). Further, the in vivo performance of the compounds and compositions were studied under two in vivo inflammatory models (LPS-induced endotoxaemia and carrageenan-induced paw oedema). Compounds 1, 2, 3, 4, C1 and C2 at 50 mg/kg oral dose showed a significant control over the LPS-stimulated TNF-α, IL-1β and IL-6 levels in plasma. C1, C2 and 1 exhibited > 50% pan-cytokine inhibition effect. Under the carrageenan-induced anti-inflammatory model, a significant reduction in the paw oedema measured in terms of the difference in the paw thickness was observed. Further, attenuation of pro-inflammatory cytokines levels following ELISA and RT-PCR experiments in the paw tissue homogenate was in agreement with paw thickness results. All compounds and C1 decreased the iNOS gene expression levels, and also the MPO activity and NO production in the paw tissue homogenate with tyrosol (4) as the most active molecule. Further, the mechanism of action was explored by testing the effect of the compounds on the expression of inflammatory markers using western blot analysis (in vitro). They were found to regulate the expression of pro-form and matured-form of IL-1β by inhibiting NFκB. Also, the compounds reduced the translocation of the NF-κB subunit p65 to the nucleus. Thus, compounds 3,5-di-tert-butyl-4-hydroxy-phenyl propionic acid (1), 2,4-di-tert-butyl phenol (2), indole 3-carboxylic acid (3) and tyrosol (4) are reported as new natural multiple pro-inflammatory cytokines inhibitory leads. The interesting results of C1 might lay a footing for the development of a new anti-inflammatory composition.

Structure-based design and synthesis of new 4-methylcoumarin-based lignans as pro-inflammatory cytokines (TNF-α, IL-6 and IL-1β) inhibitors

Suppression of pro-inflammatory cytokines (TNF-α, IL-1β and IL-6) along with nitric oxide reduction in RAW 264.7 cells by 7,8-dihydroxy-4-methylcoumarin, ethyl p-coumarate, ethyl caffeate and ethyl ferulate drove us to search structural-analogues of the aforementioned compounds through structure-based drug design. Docking studies revealed that substituted cinnamic acids and their ethyl esters (2-7c) showed higher GoldScore-fitness (GSF) and non-bonding interactions with target proteins than 7,8-dihydroxy-4-methylcoumarin (1a) and 7,8-dihydroxy-5-methylcoumarin (1b). With this background, the methylcoumarins (1a and 1b) and the cinnamic acid derivatives (2-7c) were fused in different permutations and combinations to generate sixty novel fused-cyclic coumarinolignans (FCLs) (8-13k). Docking studies on 8-13k indicated that several FCLs possess higher GSF, interesting active site interactions and distinctive π-π interactions compared to the standards (cleomiscosin A, diclofenac Na and prednisolone). Based on these findings, four novel FCLs (9d, 10d, 11d and 11e) were synthesized and tested for inhibition effect on TNF-α, IL-1β and IL-6 expressions in LPS and oxalate crystal-induced in-vitro models. Compound 10d exhibited significant effect (P < 0.0001 at 100 μM) with an IC₅₀ value of 8.5 μM against TNF-α. Compound 11e possessed IC₅₀ values of 13.29 μM and 17.94 μM against IL-6 and IL-1β, respectively. Study on SAR corroborated the requirement of C-4-methyl substituent in the coumarin moiety, dihydroxyl groups in the phenyl ring, and esterification of lignans for potent activity. Additionally, the reported excellent anti-inflammatory activity of cleomiscosin-A-glucoside was corroborated by from the higher GSF and better hydrophobic interactions than cleomsicosin A in the docking study. As an outcome, some novel and potentially active FCLs acting through NFκB and caspase 1 signaling pathways have been discovered as multiple cytokine inhibitors.

Hyosmin, a New Lignan from Hyoscyamus Niger L

Hyosmin (1) a new lignan has been isolated from the seeds of Hyoscyamus niger L. (Solanaceae), and its structure shown to be the 3-{[(2 R)-2-carbomethoxy-2-hydroxy]ethyl}benzoate ester of {(2 R,3 S,4 S)-2-(4-hydroxy-3-methoxyphenyl)-3-hydroxymethyl-4-[(4-hydroxy-3-methoxyphenyl)methyl]tetrahydrofuran

Attenuation of TNF-α secretion by L-proline-based cyclic dipeptides produced by culture broth of Pseudomonas aeruginosa

To identify small molecule inhibitors of TNF-α, bioassay- and LC-MS-guided chemical investigation on EtOAc extract of Pseudomonas aeruginosa ABS-36 culture broth (EEPA) was performed, which yielded four proline-based cyclic dipeptides, cyclo(Gly-l-Pro) (1), cyclo(l-Pro-l-Phe) (2), cyclo(trans-4-hydroxy-l-Pro-l-Phe) (3) and cyclo(trans-4-hydroxy-l-Pro-l-Leu) (4). Compounds 1 and 3 exhibited potent inhibition of TNF-α release with IC50 values of 4.5 and 14.2μg/mL, respectively, while EEPA showed IC50 of 38.8μg/mL under lipopolysaccharide treated RAW 264.7 cell ELISA assay. Also, marked attenuation of mRNA-expression of TNF-α was shown by all compounds. In vivo testing in rats of EEPA and chemically synthesized 4 validated significant TNF-α reduction with 51% (500mg/kg) and 79% (50mg/kg), respectively. In addition, all compounds exhibited significant diminution of IL-1β and IL-6 mRNA-expression levels and NO production. All samples displayed only weak toxicity to lipopolysaccharide-induced RAW 264.7 cells.