The Immunoprotective Activity of Baicalin in Mouse Model of Cecal Ligation and Puncture-Induced Sepsis

The effects of flavonoids in experimental sepsis: A systematic review and meta-analysis

Sepsis is a host's dysregulated immune response to an infection associated with systemic inflammation and excessive oxidative stress, which can cause multiple organ failure and death. The literature suggests that flavonoids, a broad class of secondary plant metabolites, have numerous biological activities which can be valuable in the treatment of sepsis. This study aimed to review the effects of flavonoids on experimental sepsis, focusing mainly on survival rate, and also summarizing information on its mechanisms of action. We searched in the main databases up to November 2022 using relevant keywords, and data were extracted and analyzed qualitatively and quantitatively. Thirty-two articles met the study criteria for review and 29 for meta-analysis. Overall, 30 different flavonoids were used in the studies. The flavonoids were able to strongly inhibit inflammatory response by reducing the levels of important pro-inflammatory mediators, for example, tumor necrosis factor-alpha and interleukin-1β, oxidative stress, and showed antibacterial and anti-apoptotic actions. The meta-analysis found an increase of 50% in survival rate of the animals treated with flavonoids. They appear to act as multi-target drugs and may be an excellent therapeutic alternative to reduce a number of the complications caused by sepsis, and consequently, to improve survival rate.

Baicalein Attenuates Severe Polymicrobial Sepsis via lleviating Immune Dysfunction of T Lymphocytes and Inflammation

OBJECTIVE

To investigate the effect of baicalein on polymicrobial sepsis-induced immune dysfunction and organ injury.

METHODS

A sepsis model was induced in Sprague-Dawley rats via caecal ligation and puncture (CLP). Specific pathogen free rats were randomly divided into a sham group, CLP group and CLP + baicalein (Bai) group (n=16 each). Rats in the CLP + Bai group were intravenously injected with baicalein (20 mg/kg) at 1 and 10 h after CLP. Survival rate, bacterial load, and organ damage were assessed. Then each group was evaluated at 6, 12, and 24 h to investigate the effect of baicalein on immune cells and inflammatory cytokines in septic rats.

RESULTS

Baicalein treatment significantly improved the survival of septic rats, decreased the bacterial burden, and moderated tissue damage (spleen, liver, and lung), as observed by haematoxylin and eosin staining. Septic rats treated with baicalein had strikingly increased proportions of CD3⁺CD4⁺ T cells and ratios of CD4⁺/CD8⁺ T cells in the peripheral blood and spleen (all P<0.05). Moreover, baicalein treatment decreased the apoptotic rate of whole white blood cells and spleen cells at 24 h after surgery (P<0.05). Baicalein significantly reduced the levels of tumor necrosis factor α and interleukin-6 (IL-6) and increased IL-10, and the expression levels of galectin 9 were also raised in the spleen (P<0.01).

CONCLUSION

Baicalein may be an effective immunomodulator that attenuates overwhelming inflammatory responses in severe abdominal sepsis.

Application of enzyme-assisted extraction of baicalin from Scutellaria baicalensis Georgi

Endophytes may depend on degrading the plant cell wall with cellulases for their survival. Therefore, cellulase produced by endophytes may be useful in releasing the active ingredient of medicinal plants. Scutellaria baicalensis Georgi is a traditional Chinese medicinal plant widely used in China and baicalin is one of its main active ingredients. In this study, fresh S. baicalensis Georgi was used to isolate endophytes, Congo red staining was used to screen cellulase-producing strains, and HPLC was used to determine the content of baicalin in S. baicalensis Georgi. As a result, a highly active strain of endophyte capable of the extraction of high levels of baicalin was obtained. The strain was named HG-5 and identified as Bacillus sp. Scanning electron microscopy analysis confirmed that the enzyme better promotes the dissolution of plant active ingredients. After optimizing the enzyme production and extraction processes, we found that when compared with the traditional extraction method, the baicalin yield was increased 79.31% after extraction with the HG-5 enzyme. The current study provides a novel approach and method for the use of endophyte cellulase to improve the extraction of compounds from medicinal plants.

Baicalin suppresses Th1 and Th17 responses and promotes Treg response to ameliorate sepsis-associated pancreatic injury via the RhoA-ROCK pathway

Recent studies have reported that the imbalance of T helper 1 cell (Th1), Th17 and regulatory T cell (Treg) have been confirmed to play a vital role in the development of sepsis and other inflammatory diseases. Baicalin (BA) has anti-inflammatory properties and improves survival in sepsis. We investigated whether baicalin could regulate Th1, Th17 and Treg responses to ameliorate sepsis-associated pancreatic injury through the ras homolog family member A (RhoA)-Rho kinase (ROCK) pathway. The sepsis model was established by using the cecal ligation and puncture (CLP) method. Fifty mice were randomly divided into five groups (n = 10): sham group, model group, low-dose group (BA-L, 100 mg/kg of baicalin), medium-dose group (BA-M, 200 mg/kg of baicalin) and highdose group (BA-H, 300 mg/kg of baicalin). The effects of baicalin on the pancreatic injury, on changes of Th1, Th17 and Treg cells in vivo and in vitro, on RhoA, ROCK1 and signal transducer and activator of transcription (STAT) signaling pathways, and on levels of interferon-γ (IFN-γ), interleukin-17 (IL-17) and IL-10 were examined. Treatment of the CLP mice with baicalin significantly reduced the extent, scope and severity of the pathological changes of sepsis-associated pancreatic injury. Baicalin evidently reduced Th1 and Th17 cells and increased Treg cells in peripheral blood, spleen, pancreatic tissue and significantly inhibited T-box protein expressed in T cells (T-bet), retinoic acid receptor-related orphan receptor γt (RORγt) and increased forkhead/winged helix transcription factor (Foxp3) expressions in the pancreatic tissue. Baicalin reduced the expressions of RhoA, ROCK1, phosphorylated STAT4 (p-STAT4), p-STAT3 and increased the expression of p-STAT5 in peripheral blood, spleen and pancreatic tissue. Baicalin reduced the expressions of IFN-γ and IL-17 and increased the IL-10 in serum and pancreatic tissue. Baicalin is capable of ameliorating sepsis-associated pancreatic injury and regulating Th1, Th17 and Treg responses in sepsis. The present study provided a potential adjunctive therapy for treating pancreatic injury in sepsis, and further study is needed to reveal its deeper mechanisms.

Antimycobacterial and Anti-inflammatory Mechanisms of Baicalin via Induced Autophagy in Macrophages Infected with Mycobacterium tuberculosis

Tuberculosis (TB) remains a leading killer worldwide among infectious diseases and the effective control of TB is still challenging. Autophagy is an intracellular self-digestion process which has been increasingly recognized as a major host immune defense mechanism against intracellular microorganisms like Mycobacterium tuberculosis (Mtb) and serves as a key negative regulator of inflammation. Clinically, chronic inflammation surrounding Mtb can persist for decades leading to lung injury that can remain even after successful treatment. Adjunct host-directed therapy (HDT) based on both antimycobacterial and anti-inflammatory interventions could be exploited to improve treatment efficacy and outcome. Autophagy occurring in the host macrophages represents a logical host target. Here, we show that herbal medicine, baicalin, could induce autophagy in macrophage cell line Raw264.7 and caused increased killing of intracellular Mtb. Further, baicalin inhibited Mtb-induced NLRP3 inflammasome activation and subsequent inflammasome-derived IL-1β. To investigate the molecular mechanisms of baicalin, the signaling pathways associated with autophagy were examined. Results indicated that baicalin decreased the levels of phosphorylated protein kinase B (p-Akt) and phosphorylated mammalian target of rapamycin (p-mTOR) at Ser473 and Ser2448, respectively, but did not alter the phosphorylation of p38, JNK, or ERK both in Raw264.7 and primary peritoneal macrophages. Moreover, baicalin exerted an obvious inhibitory effect on nuclear factor-kappa B (NF-κB) activity. Finally, immunofluorescence studies demonstrated that baicalin promoted the co-localization of inflammasome with autophagosome may serve as the underlying mechanism of autophagic degradative effect on reducing inflammasome activation. Together, baicalin definitely induces the activation of autophagy on the Mtb-infected macrophages through PI3K/Akt/mTOR pathway instead of MAPK pathway. Furthermore, baicalin inhibited the PI3K/Akt/NF-κB signal pathway, and both autophagy induction and NF-κB inhibition contribute to limiting the NLRP3 inflammasome as well as subsequent production of pro-inflammatory cytokine IL-1β. Based on these results, we conclude that baicalin is a promising antimycobacterial and anti-inflammatory agent which can be a novel candidate for the development of new adjunct drugs targeting HDT for possible improved treatment.

Baicalin Inhibits NOD-Like Receptor Family, Pyrin Containing Domain 3 Inflammasome Activation in Murine Macrophages by Augmenting Protein Kinase A Signaling

The flavonoid baicalin has been reported to possess potent anti-inflammatory activities by suppressing inflammatory signaling pathways. However, whether baicalin can suppress the activation of NOD-like receptor (NLR) family, pyrin containing domain 3 (NLRP3) inflammasome in macrophages is largely unknown. Here, we showed that baicalin treatment dose-dependently inhibited adenosine triphosphate (ATP) or nigericin-induced NLRP3 inflammasome activation, as revealed by the decreased release of mature interleukin (IL)-1β, active caspase-1p10, and high-mobility group box-1 protein from lipopolysaccharide (LPS)-primed bone marrow-derived macrophages. The formation of ASC specks, a critical marker of NLRP3 inflammasome assembly, was robustly inhibited by baicalin in the macrophages upon ATP or nigericin stimulation. All these inhibitory effects of baicalin could be partly reversed by MDL12330A or H89, both of which are inhibitors of the protein kinase A (PKA) signaling pathway. Consistent with this, baicalin strongly enhanced PKA-mediated phosphorylation of NLRP3, which has been suggested to prevent ASC recruitment into the inflammasome. Of note, the PKA inhibitor H89 could block baicalin-induced NLRP3 phosphorylation on PKA-specific sites, further supporting PKA’s role in this process. In addition, we showed that when administered pre and post exposure to Escherichia coli infection baicalin treatment significantly improved mouse survival in bacterial sepsis. Baicalin administration also significantly reduced IL-1β levels in the sera of bacterial infected mice. Altogether, our results revealed that baicalin inhibited NLRP3 inflammasome activation at least partly through augmenting PKA signaling, highlighting its therapeutic potential for the treatment of NLRP3-related inflammatory diseases.

The anti-inflammatory effects of baicalin through suppression of NLRP3 inflammasome pathway in LPS-challenged piglet mononuclear phagocytes

In this study, the anti-inflammatory effects and mechanisms of baicalin on LPS-induced NLRP3 inflammatory pathway were investigated in piglet mononuclear phagocytes (control, LPS stimulation, LPS stimulation + 12.5 µg/ml baicalin, LPS stimulation + 25 µg/ml baicalin, LPS stimulation + 50 µg/ml baicalin and LPS stimulation + 100 µg/ml baicalin). The levels of reactive oxygen species (ROS), the secretion levels of IL-1β, IL-18 and TNF-α, mRNA expression levels of IL-1β, IL-18, TNF-α and NLRP3, as well as the protein levels of cleaved caspase-1 p20 were significantly increased after LPS-challenge in vitro. However, LPS stimulation did not influence apoptosis-associated speck-like protein and caspase-1 mRNA levels, which are also components of the NLRP3 inflammasome. Baicalin at 50 µg/ml and 100 µg/ml could inhibit the production of ROS, TNF-α, IL-1β and IL-18, and down-regulate mRNA expression of IL-1β, IL-18, TNF-α and NLRP3, as well as expression of cleaved caspase-1 p20. These results showed that the anti-inflammatory effects of baicalin occurred via the regulation of the release of ROS and mRNA expression of NLRP3. The anti-inflammatory activity of baicalin could be related to the suppression of NLRP3 inflammasome pathway under LPS stimulation.