Search

Matrix metalloproteinases (MMPs), which are proteolytic enzymes, promote blood–brain barrier (BBB) disruption, leading to neuronal damage and neuroinflammation. Among them, MMP-9 upregulation serves as an inflammatory biomarker in the central nervous system (CNS). Currently, the development of marine organism-derived bioactive compounds or metabolites as anti-inflammatory drugs has received considerable attention. The 9,11-secosteroid, 3β,11-dihydroxy-9,11-secogorgost-5-en-9-one (4p3f), is a novel sterol compound extracted from the soft coral Sinularia leptoclado with potential anti-inflammatory activity. However, the effect of and potential for brain protection of 4p3f on brain astrocytes remain unclear. Herein, we used rat brain astrocytes (RBAs) to investigate the effects and signaling mechanisms of 4p3f on lipopolysaccharide (LPS)-induced MMP-9 expression via zymographic, quantitative reverse transcription–polymerase chain reaction (qRT-PCR), Western blot, immunofluorescence staining, promoter–reporter, and cell migration analyses. We first found that 4p3f blocked LPS-induced MMP-9 expression in RBAs. Next, we demonstrated that LPS induced MMP-9 expression via the activation of ERK1/2, p38 MAPK, and JNK1/2, which is linked to the STAT3-mediated NF-κB signaling pathway. Finally, 4p3f effectively inhibited LPS-induced upregulation of MMP-9-triggered RBA cell migration. These data suggest that a novel sterol from soft coral, 4p3f, may have anti-inflammatory and brain-protective effects by attenuating these signaling pathways of MMP-9-mediated events in brain astrocytes. Accordingly, the soft coral-derived sterol 4p3f may emerge as a potential candidate for drug development or as a natural compound with neuroprotective properties.

Lung inflammation is a pivotal event in the pathogenesis of acute lung injury. Heme oxygenase-1 (HO-1) is a key antioxidant enzyme that could be induced by kaempferol (KPR) and exerts anti-inflammatory effects. However, the molecular mechanisms of KPR-mediated HO-1 expression and its effects on inflammatory responses remain unknown in human pulmonary alveolar epithelial cells (HPAEpiCs). This study aimed to verify the relationship between HO-1 expression and KPR treatment in both in vitro and in vivo models. HO-1 expression was determined by real time-PCR, Western blotting, and promoter reporter analyses. The signaling components were investigated by using pharmacological inhibitors or specific siRNAs. Chromatin immunoprecipitation (ChIP) assay was performed to investigate the interaction between nuclear factor erythroid-2-related factor (Nrf2) and antioxidant response elements (ARE) binding site of HO-1 promoter. The effect of KPR on monocytes (THP-1) binding to HPAEpiCs challenged with lipopolysaccharides (LPS) was determined by adhesion assay. We found that KPR-induced HO-1 level attenuated the LPS-induced intercellular cell adhesion protein 1 (ICAM-1) expression in HPAEpiCs. KPR-induced HO-1 mRNA and protein expression also attenuated ICAM-1 expression in mice. Tin protoporphyrin (SnPP)IX reversed the inhibitory effects of KPR in HPAEpiCs. In addition, in HPAEpiCs, KPR-induced HO-1 expression was abolished by both pretreating with the inhibitor of NADPH oxidase (NOX, apocynin (APO)), reactive oxygen species (ROS) (N-acetyl-L-cysteine (NAC)), Src (Src kinase inhibitor II (Srci II)), Pyk2 (PF431396), protein kinase C (PKC)α (Gö6976), p38 mitogen-activated protein kinase (MAPK) inhibitor (p38i) VIII, or c-Jun N-terminal kinases (JNK)1/2 (SP600125) and transfection with their respective siRNAs. The transcription of the homx1 gene was enhanced by Nrf2 activated by JNK1/2 and p38α MAPK. The binding activity between Nrf2 and HO-1 promoter was attenuated by APO, NAC, Srci II, PF431396, or Gö6983. KPR-mediated NOX/ROS/c-Src/Pyk2/PKCα/p38α MAPK and JNK1/2 activate Nrf2 to bind with ARE on the HO-1 promoter and induce HO-1 expression, which further suppresses the LPS-mediated inflammation in HPAEpiCs. Thus, KPR exerts a potential strategy to protect against pulmonary inflammation via upregulation of the HO-1.