Lobolide, a diterpene, blockades the NF-κB pathway and p38 and ERK MAPK activity in macrophages in vitro

Activities and Molecular Mechanisms of Diterpenes, Diterpenoids, and Their Derivatives in Rheumatoid Arthritis

Diterpenes and their derivatives have many biological activities, including anti-inflammatory and immunomodulatory effects. To date, several diterpenes, diterpenoids, and their laboratory-derived products have been demonstrated for antiarthritic activities. This study summarizes the literature about diterpenes and their derivatives acting against rheumatoid arthritis (RA) depending on the database reports until 31 August 2021. For this, we have conducted an extensive search in databases such as PubMed, Science Direct, Google Scholar, and Clinicaltrials.gov using specific relevant keywords. The search yielded 2708 published records, among which 48 have been included in this study. The findings offer several potential diterpenes and their derivatives as anti-RA in various test models. Among the diterpenes and their derivatives, andrographolide, triptolide, and tanshinone IIA have been found to exhibit anti-RA activity through diverse pathways. In addition, some important derivatives of triptolide and tanshinone IIA have also been shown to have anti-RA effects. Overall, findings suggest that these substances could reduce arthritis score, downregulate oxidative, proinflammatory, and inflammatory biomarkers, modulate various arthritis pathways, and improve joint destruction and clinical arthritic conditions, signs, symptoms, and physical functions in humans and numerous experimental animals, mainly through cytokine and chemokine as well as several physiological protein interaction pathways. Taken all together, diterpenes, diterpenoids, and their derivatives may be promising tools for RA management.

Nuclear factor-κB plays an important role in Tamarixetin-mediated inhibition of matrix metalloproteinase-9 expression

Flavonoids possess a broad spectrum of pharmacological properties, including anti-cancer, anti-oxidant and immunomodulatory activities. The current study explored the potential of some less-studied flavonoids in inhibiting Matrix Metalloproteinase-9 (MMP-9), a prominent biomarker, upregulated in a variety of cancers and known to promote migration and invasion of cancer cells. Amongst these, Tamarixetin, a naturally occurring flavonoid derivative of Quercetin, demonstrated significant dose-dependent inhibition of MMP-9 expression. Furthermore, a substantial inhibition of migration, invasion and clonogenic potential of HT1080 cells was also observed in the presence of Tamarixetin, which further suggests its role as a potential anti-cancer agent. It is noteworthy that Tamarixetin inhibits nuclear translocation as well the activity of nuclear factor kappa B (NFκB), both of which are functions essential for the activation of MMP-9 in promoting tumorigenesis. Additionally, the endogenous regulators of MMP-9 that tightly control its activity were also modulated by Tamarixetin, as evident from the 1.9 fold increase in the expression of Tissue Inhibitor of Metalloproteinase-1 (TIMP-1), with a concomitant 2.2 fold decrease in Matrix Metalloproteinase-14 (MMP-14) expression. The results obtained were further corroborated in three dimensional (3D) tumor models, which showed significant inhibition of MMP-9 activity as well as reduced invasive potential in the presence of Tamarixetin. Taken together, our observations demonstrate for the first time, the anti-invasive potential of Tamarixetin in cancer cells, indicating its possible use as a template for novel therapeutic applications.

TAK1 mediates excessive autophagy via p38 and ERK in cisplatin-induced acute kidney injury

The ability of cisplatin (cis-diamminedichloroplatinum II) toxicity to induce acute kidney injury (AKI) has attracted people's attention and concern for a long time, but its molecular mechanisms are still widely unknown. We found that the expression of transforming growth factor-β (TGF-β)-activated kinase 1 (TAK1) could be increased in kidneys of mice administrated with cisplatin. Autophagy is an evolutionarily conserved catabolic pathway and is involved in various acute and chronic injuries. Moreover, p38 MAPK (mitogen-activated protein kinase) and ERK regulate autophagy in response to various stimuli. Therefore, our hypothesis is that cisplatin activates TAK1, which phosphorylates p38 and ERK, leading to excessive autophagy of tubular epithelial cells and thus exacerbating kidney damage. Here, BALB/c mice were intraperitoneally injected with a TAK1 inhibitor and were then administrated with sham or cisplatin at 20 mg/kg by intraperitoneal injection. Compared with mice in the vehicle cisplatin group, mice intraperitoneally injected with a TAK1 inhibitor were found to have lower serum creatinine and less tubular damage following cisplatin-induced AKI. Furthermore, inhibition of TAK1 reduced p38 and Erk phosphorylation, decreased expression of LC3II and reversed the down-regulation of P62 expression induced by cisplatin. The hypothesis was verified with tubular epithelial cells administrated with cisplatin in vitro. Finally, p38 inhibitor or ERK inhibitor abated autophagy activation and cell viability reduction in tubular epithelial cells treated with cisplatin plus TAK1 overexpression vector. Taken together, our results show that cisplatin activates TAK1, which phosphorylates p38 and ERK, leading to excessive autophagy of tubular epithelial cells that exacerbates kidney damage.

Anti-inflammatory effect of diterpenes-enriched fractions from Pterodon polygalaeflorus through inhibition of macrophage migration and cytokine production

Objectives

To evaluate the anti-inflammatory potential of Pterodon polygalaeflorus hexane extract (HE) and its fractions on macrophage migration in vitro and in vivo.

Methods

Hexane extract from P. polygalaeflorus fruits was fractionated and yielded four fractions. RAW 264.7 cells were treated with samples to evaluate cell viability (MTT assay), cell migration (wound healing and transwell assays), CD14 expression (flow cytometry), iNOS and cytokine mRNA expression (RT-qPCR), NO (Griess reaction) and cytokine (ELISA) production. In vivo migration was evaluated on the thioglycollate-induced peritonitis model. Qualitative analysis was performed by GC-MS.

Key findings

All fractions inhibited the NO production by LPS-stimulated RAW 264.7 cells. Fr3 and Fr4 presented the lowest IC50 values. The expressions of iNOS and IL-1β, TNF-α and IL-10 cytokines were inhibited by Fr3 and Fr4, whereas the CD14 expression was only inhibited by Fr3. All the samples inhibited RAW 264.7 migration in the wound healing and transwell assays. Fr3 and Fr4 reduced the migration of Mac-1+Gr-1− cells to the peritoneum and presented in their compositions: 6α-hydroxy-7β-acetoxyvouacapan-17β-oate, methyl 6α,7β-dihydroxyvouacapan-17β-oate, methyl 6α-acetoxy-7β-hydroxyvouacapan-17β-oate, geranylgeraniol and 14,15-epoxy-geranylgeraniol.

Conclusions

The anti-inflammatory effects of Fr3 and Fr4 involve inhibition of cell migration, iNOS expression and NO production, cytokine expression (mRNA and proteins) and CD14 expression (Fr3).

6-O-Veratroyl catalpol suppresses pro-inflammatory cytokines via regulation of extracellular signal-regulated kinase and nuclear factor-κB in human monocytic cells

The compound 6-O-veratroyl catalpol (6-O) is a bioactive iridoid glucoside that was originally isolated from Pseudolysimachion rotundum var. subintegrum. It has been demonstrated that catapol derivative iridoid glucosides including 6-O, possess anti-inflammatory activity in carragenan-induced paw edema mouse model as well as bronchoalveolar lavage fluid of ovalbumin-induced mouse model. In the present study, we investigated whether 6-O modulates inflammatory responses in THP-1 monocytic cells stimulated with phorbol12-myristate-13-acetate (PMA). Our data showed that 6-O inhibited PMA induced interleukin (IL)-1β and tumor necrosis factor (TNF)-α expression in THP-1 monocytic cells. Mechanistic studies revealed that 6-O suppressed the activity of protein kinase C (PKC), which further resulted in downstream inactivation of extracellular signal-regulated kinase (ERK) and nuclear factor-κB (NF-κB) inflammatory pathway. The results implied that 6-O may protect against inflammatory responses that could be a potential compound in treating inflammatory diseases.