Protective effect of cinnamicaldehyde in endotoxin poisoning mice

Effect of pulegone on the NLPR3 inflammasome during inflammatory activation of THP-1 cells

Pulegone is a key active component of Schizonepeta essential oil and has been determined to have anti-inflammatory properties. However, the underlying molecular mechanisms with regard to the NLR family pyrin domain containing 3 (NLRP3) inflammasome, also known as the NALP3 inflammasome, have remained to be elucidated. NLRP3 represents a potential link between inflammation and immunity and may play possible key role in various pathologies. In the present study, the modulatory effects of pulegone on the NLRP3 inflammasome were investigated. THP-1 cells induced with phorbol myristate acetate were divided into various groups, including the Normal (control), lipopolysaccharide (LPS), LPS + ATP/nigericin, LPS + ATP/nigericin + 0.2% DMSO and pulegone (0.2, 0.1 and 0.05 mg/ml) groups. ELISA was used to detect the levels of interleukin (IL)-1β and IL-18 in the cell supernatants and the influence of potassium ions was assessed. PCR was used to determine the expression levels of NLRP3, caspase-1, IL-1β and IL-1α in the cell lysates. Furthermore, NLRP3 and apoptosis-associated speck-like protein (ASC) were detected via immunofluorescence assays and fluorescence microscopy was employed to determine the reactive oxygen species (ROS) levels in the THP-1 cells. The results indicated reduced levels of IL-18 and IL-1β in the supernatant of the cells of the pulegone groups when compared with those in the LPS + ATP/nigericin group. In addition, reduced mRNA production of inflammasome-associated genes was detected in the cell lysates after pulegone treatment. The immunofluorescence analyses indicated significantly reduced protein expression levels of NLRP3 and ASC in the pulegone groups, as well as co-localization of the NLRP3 and ASC proteins. The pulegone groups also exhibited significantly reduced ROS levels. Furthermore, a high concentration of potassium ions significantly reduced the secretion of IL-1β after induction/stimulation. In conclusion, the present study suggested that pulegone exerts its anti-inflammatory effects on LPS + ATP/nigericin-induced THP-1 cells via inhibition of NLRP3 expression, and its regulatory mechanism is associated with potassium channel and ROS pathways. It was hypothesized that pulegone first inhibits ROS signaling, to then inhibit NLRP3 expression as a downstream event. It appeared that NLRP3 may be situated further downstream and represented the link between inflammation and immunity.

Protective effects of ethyl acetate extracts of Rimulus Cinnamon on systemic inflammation and lung injury in endotoxin-poisoned mice

Rimulus cinnamon is the dried twig of Cinnamomum cassia Presl. It is widely used in China for the treatment of inflammatory processes, amenorrhea, and other diseases. We aimed to study the protective effects of ethyl acetate extracts of R. cinnamon (EAE) on systemic inflammation and lung injury in endotoxin-poisoned mice. EAE was administered 5 d prior to lipopolysaccharide (LPS) challenge with 15 mg/kg LPS. The administration of EAE increased the levels of interferon-γ (IFN-γ) and decreased the levels of interleukin-18 (IL-18) and tumor necrosis factor-α (TNF-α) in the serum. Additionally, EAE relieved the pathological changes in the tissues of the lungs and spleen, and significantly reduced the number of neutrophils in the lung tissues. In addition, treatment with EAE decreased the mRNA expression of the NLR family, pyrin domain-containing protein 3 (NLRP3), caspase-1, and interleukin-1β (IL-1β) in the lungs, as well as the expression of NLRP3, caspase-1 (p20), and pro-IL-1β proteins. These results demonstrated the promising anti-inflammatory effects of EAE in endotoxin-poisoned mice. Furthermore, EAE could alleviate the lung injury of endotoxin-poisoned mice by antagonizing the activation of the NLRP3 inflammasome.

Protective effects of essential oils from Rimulus cinnamon on endotoxin poisoning mice

The essential oils from Rimulus cinnamon (EORC) have anti-inflammation activities, but the effects of EORC on endotoxin poisoning mice remain to be explored, the mechanism is still unclear. This study was designed to investigate the protective effects and mechanism of EORC on lipopolysaccharide (LPS)-induced endotoxin poisoning mice. Pre-treatment with EORC decreased the production of pro-inflammatory cytokines (Interleukin-1β, Interleukin-18, Interleukin-5, and Interferon-γ) and chemokines (Monocyte chemotactic protein-1, Macrophage colony-stimulating factor, and Macrophage inflammatory protein-1β) in serum of endotoxin poisoning mice. The histopathological study showed that the lung injury was improved and EORC decreased the numbers of neutrophils and Nitric oxide (NO) levels in lung. EORC could reduce the mRNA expression of NLR family, pyrin domain-containing 3 (NLRP3), Interleukin (IL)-1β, and nitric oxide synthase (iNOS). In addition, EORC decreased the protein expression of NLRP3, Caspase-1 (p20), Pro-IL-1β, and purinergic P2 × 7 receptor (P2 × 7R) in the lung tissues. The results above indicated that the EORC may have protective effects on LPS-induced endotoxin poisoning mice via inhibiting the activation of P2 × 7R/NLRP3 inflammasome.

Protective effect of cinnamic acid in endotoxin-poisoned mice

In this work, we aimed to evaluate the protective effect of cinnamic acid (CD) on lipopolysaccharide (LPS; Escherichia coli 055:B5)-induced endotoxin-poisoned mice and clarify the underlying mechanisms. The mice were administrated CD 5 d before 15 mg/kg LPS challenge. 12 hr later, thymus was separated for determination of thymus indexes. Lung and spleen tissues were collected for histologic examination and the wet/dry weight ratio of lung was calculated, and serum was acquired for tumor necrosis factor-α (TNF-α), interleukin (IL)-18, and IL-1β measurement. Moreover, the expression of NOD-like receptor (NLR) family, pyrin domain-containing 3 (NLRP3) inflammasome was determined in lung. CD increased the thymus indexes and decreased lung wet/dry weight ratio. In addition, CD improved the lung and spleen histopathological changes induced by LPS and decreased the number of neutrophils in lung tissues. CD also inhibited the pro-inflammatory cytokines (TNF-α, IL-18, and IL-1β) production in serum. Furthermore, CD suppressed the LPS-induced NLRP3, Caspase-1, and IL-1β mRNA expression in lung, as well as the expression of NLRP3 and Caspase-1 (p20) protein. CD may have protective effects in endotoxin-poisoned mice via inhibiting the activation of NLRP3 inflammasome, and can be considered as a potential therapeutic candidate for diseases involved in endotoxin poisoning such as sepsis.

Inhibition of NLRP3 inflammasome: a new protective mechanism of cinnamaldehyde in endotoxin poisoning of mice

CONTEXT

Cinnamaldehyde (CA) has a protective effect in endotoxin poisoning of mice, but there is no direct evidence for the protective effect of CA through inhibition of NLRP3 inflammasome activation in endotoxin poisoning of mice.

OBJECTIVE

We aimed to investigate the protective mechanism of CA in endotoxin poisoned mice through NLRP3 inflammasome.

MATERIALS AND METHODS

First, we evaluated the anti-inflammatory effect of CA in phorbol-12-myristate acetate-differentiated THP-1 cells through the NLRP3 inflammasome. Second, in a mouse model of lipopolysaccharide (LPS)-induced endotoxin poisoning, CA was administrated for 5 d (once a day) before the 15 mg/kg LPS challenge. Then, the levels of IL-1β in serum were measured, and the effect of CA on the NLRP3 inflammasome activation and the expression of cathepsin B and P2X7R proteins in lung were explored.

RESULTS

In vitro, CA decreased the levels of p20, pro-IL-1β and IL-1β in cell culture supernatants, as well as the expression of NLRP3 and IL-1β mRNA in cells. In vivo, CA decreased IL-1β production in serum. Furthermore, CA suppressed LPS-induced NLRP3, p20, Pro-IL-1β, P2X7 receptor (P2X7R) and cathepsin B protein expression in lung, as well as the expression of NLRP3 and IL-1β mRNA.

CONCLUSIONS

CA has a protective effect in the endotoxin poisoned mice through the inhibition of NLRP3 inflammasome activation. Furthermore, CA suppresses the NLRP3 inflammasome activation by inhibiting the expression of cathepsin B and P2X7R protein expression. CA can be considered as a potential therapeutic candidate for diseases involved in endotoxin poisoning such as sepsis.