GSDMD contributes to host defence against Staphylococcus aureus skin infection by suppressing the Cxcl1-Cxcr2 axis.

Gasdermin D (GSDMD), a member of the gasdermin protein family, is a caspase substrate, and its cleavage is required for pyroptosis and IL-1ß secretion. To date, the role and regulatory mechanism of GSDMD during cutaneous microbial infection remain unclear. Here, we showed that GSDMD protected against Staphylococcus aureus skin infection by suppressing Cxcl1-Cxcr2 signalling. GSDMD deficiency resulted in larger abscesses, more bacterial colonization, exacerbated skin damage, and increased inflammatory cell infiltration. Although GSDMD deficiency resulted in defective IL-1ß production, the critical role of IL-1ß was counteracted by the fact that Caspase-1/11 deficiency also resulted in less IL-1ß production but did not aggravate disease severity during S. aureus skin infection. Interestingly, GSDMD-deficient mice had increased Cxcl1 secretion accompanied by increased recruitment of neutrophils, whereas Caspase-1/11-deficient mice presented similar levels of Cxcl1 and neutrophils as wild-type mice. Moreover, the absence of GSDMD promoted Cxcl1 secretion in bone marrow-derived macrophages induced by live, dead, or different strains of S. aureus. Corresponding to higher transcription and secretion of Cxcl1, enhanced NF-κB activation was shown in vitro and in vivo in the absence of GSDMD. Importantly, inhibiting the Cxcl1-Cxcr2 axis with a Cxcr2 inhibitor or anti-Cxcl1 blocking antibody rescued host defence defects in the GSDMD-deficient mice. Hence, these results revealed an important role of GSDMD in suppressing the Cxcl1-Cxcr2 axis to facilitate pathogen control and prevent tissue damage during cutaneous S. aureus infection.

Geniposide Enhances Macrophage Autophagy through Downregulation of TREM2 in Atherosclerosis.

Macrophage autophagy defect is closely related to the progression of atherosclerosis (AS) and is regulated by the triggering receptor expressed on myeloid cell 2 (TREM2). TREM2 is a key factor in the development of Alzheimer's disease (AD), the deficiency of which leads to anomalous autophagy in microglia. However, the role of TREM2 in the autophagy of plaque macrophages is still unclear. Geniposide (GP) can inhibit AS progression and enhance macrophage autophagy, although the underlying mechanisms remain unknown. We found that high-fat diet (HFD) feeding significantly increased TREM2 levels and inhibited autophagy in the macrophages of ApoE[Formula: see text] mice. TREM2 overexpression in RAW264.7 macrophages decreased autophagy via activation of mTOR signaling. GP inhibited the progression of AS in ApoE[Formula: see text] mice, reinforced macrophage autophagy, and downregulated TREM2 by inhibiting mTOR signaling. Taken together, augmenting the autophagy levels in plaque macrophages by inhibiting the TREM2/mTOR axis can potentially impede atherosclerotic progression. The promising therapeutic effects of GP seen in this study should be validated in future trials, and the underlying mechanisms have to be elucidated in greater detail.

DNA Sensor IFI204 Contributes to Host Defense Against Staphylococcus aureus Infection in Mice.

Interferon-inducible protein (IFI204) (p204, the murine homolog of human IFI16) is known as a cytosolic DNA sensor to recognize DNA viruses and intracellular bacteria. However, little is known about its role during extracellular bacterial infection. Here we show that IFI204 is required for host defense against the infection of Staphylococcus aureus, an extracellular bacterial pathogen. IFI204 deficiency results in decreased survival, increased bacterial loads, severe organs damage, and decreased recruitment of neutrophils and macrophages. Production of several inflammatory cytokines/chemokines including IFN-ß and KC is markedly decreased, as well as the related STING-IRF3 and NF-κB pathways are impaired. However, exogenous administration of recombinant KC or IFN-ß is unable to rescue the susceptibility of IFI204-deficient mice, suggesting that other mechanisms rather than KC and IFN-ß account for IFI204-mediated host defense. IFI204 deficiency leads to a defect in extracellular bacterial killing in macrophages and neutrophils, although bacterial engulf, and intracellular killing activity are normal. Moreover, the defect of bactericidal activity is mediated by decreased extracellular trap formation in the absence of IFI204. Adoptively transferred WT bone marrow cells significantly protect WT and IFI204-deficient recipients against Staphylococcus infection compared with transferred IFI204-deficient bone marrow cells. Hence, this study suggests that IFI204 is essential for the host defense against Staphylococcus infection.

Codonopsis tangshen Oliv. Amelioration Effect on Diabetic Kidney Disease Rats Induced by High Fat Diet Feeding Combined with Streptozotocin.

Diabetic kidney disease (DKD) is the most serious microvascular complication during the development of diabetes with the characterizations of glomerular basement membrane thickening, mesangial expansion, and glomerular sclerosis, eventually leading to end-stage renal disease. This study aimed to investigate the melioration effect of Codonopisis tangshen Oliv. (COD) on the DKD model, which was established by unilateral nephrectomy (UN)-high fat diet feeding (HFD) combined with streptozotocin (STZ). After the DKD rats were oral treated with COD at a dose of 2.7 mg/kg for 4 consecutive weeks, the blood glucose, lipid metabolism, renal function, inflammatory mediators, and fibrosis-associated proteins were examined. In vivo, the COD administration obviously relieved the weight loss, water intake, and blood glucose; decreased the total cholesterol, triglyceride, and low-density lipoprotein cholesterol levels; and improved the renal function by reducing the expression of serum creatinine, uric acid, and urinary protein compared with the model group. The levels of pro-inflammatory cytokines of tumor necrosis factor-α, interleukin-1ß, and IL-6 were significantly inhibited by COD. Meanwhile, the deposition of collagen fiber was markedly increased, and the protein and mRNA expressions of transforming growth factor-ß1 and α-smooth muscle actin were markedly elevated in DKD rats, but they were decreased to some extent after the COD treatment. In conclusion, COD exhibited a protective effect on the UN-HFD feeding combined with STZ-induced DKD model by improving the blood glucose and lipid metabolism, relieving the inflammatory response, and mitigating the renal fibrosis, which provided scientific evidence for its applications in clinic.

Non-Hematopoietic MLKL Protects Against Salmonella Mucosal Infection by Enhancing Inflammasome Activation.

The intestinal mucosal barrier is critical for host defense against pathogens infection. Here, we demonstrate that the mixed lineage kinase-like protein (MLKL), a necroptosis effector, promotes intestinal epithelial barrier function by enhancing inflammasome activation. MLKL-/- mice were more susceptible to Salmonella infection compared with wild-type counterparts, with higher mortality rates, increased body weight loss, exacerbated intestinal inflammation, more bacterial colonization, and severe epithelial barrier disruption. MLKL deficiency promoted early epithelial colonization of Salmonella prior to developing apparent intestinal pathology. Active MLKL was predominantly expressed in crypt epithelial cells, and experiments using bone marrow chimeras found that the protective effects of MLKL were dependent on its expression in non-hematopoietic cells. Intestinal mucosa of MLKL-/- mice had impaired caspase-1 and gasdermin D cleavages and decreased interleukin (IL)-18 release. Moreover, administration of exogenous recombinant IL-18 rescued the phenotype of increased bacterial colonization in MLKL-/- mice. Thus, our results uncover the role of MLKL in enhancing inflammasome activation in intestinal epithelial cells to inhibit early bacterial colonization.

[Antioxidant effects of celastrol against hydrogen peroxide-induced oxidative stress in the cell model of amyotrophic lateral sclerosis].

To investigate the anti-oxidative effect of celastrol on H2O2-induced oxidative stress in the cell model of amyotrophic lateral sclerosis (ALS) and its molecular mechanism, NSC34 motor neuron-like cells were transfected with EGFP-G93A-SOD1 plasmid and used as in vitro ALS cell model. SOD1G93A transfected NSC34 cells were treated with different doses of H2O2 and celastrol. The survival rate of the cells was detected by CCK-8 assay, and malondialdehyde (MDA) content was detected by corresponding kit. The mRNA expression of glutamate-cysteine ligase catalytic subunit (GCLC) and glutathione S-transferases (GST) were detected by real-time PCR. The activation of intracellular MEK/ERK and PI3K/Akt signal pathways was detected by Western blot. The results showed that pre-incubation of celastrol (50 nmol/L) for 4 h prior to H2O2 (10 µmol/L) co-treatment for another 24 h significantly attenuated H2O2-induced cell death and MDA level in SOD1G93A transfected NSC34 cells. Real-time PCR showed that the mRNA expressions of GCLC and GST were enhanced with pre-incubation of celastrol. Celastrol quickly induced phosphorylation of ERK1/2 and Akt within 30 min and 1 h respectively in SOD1G93A transfected NSC34 cells. Pharmacological inhibitors of MEK (PD98059, 10 µmol/L) or Akt (MK2206, 10 µmol/L) could reverse the phosphorylation of ERK1/2 and Akt, and abolish up-regulation of GCLC and GST induced by celastrol at mRNA levels. Taken together, we conclude that celastrol exerts a beneficial antioxidant effect in SOD1G93ANSC34 cells, which might be dependent on MEK/ERK and PI3K/Akt signaling pathway activation.

Posterior fixation and fusion with atlas pedicle screw system for upper cervical diseases.

OBJECTIVE: To evaluate the feasibility, safety and efficacy of atlas pedicle screws system fixation and fusion for the treatment of upper cervical diseases. METHODS: Twenty-three consecutive patients with upper cervical disorders requiring stabilization, including 19 cases of atlantoaxial dislocation (4 congenital odontoid disconnections, 6 old odontoid fractures, 4 fresh odontoid fractures of Aderson II C, 3 ruptures of the C(1) transverse ligament, and 2 fractures of C(1)), 2 cases of C2 tumor (instability after the resection of the tumors), and 2 giant neurilemomas of C(2)-C(3)(instability after resection of the tumors), were treated by posterior fixation and fusion with the atlas pedicle screw system, in which the screws were inserted through the posterior arch of C1. The operative time, bleeding volume and complications were reported. All patients were immobilized without external fixation or with rigid cervical collars for 1-3 months. All patients were followed up and evaluated with radiographs and CT. RESULTS: In the 23 patients, 46 C(1) pedicle screws, 42 C(2) pedicle screws and 6 lower cervical lateral mass screws and 2 lower cervical pedicle screws were placed. The mean operative time and bleeding volume was 2.7 hours and 490 ml respectively. No intraoperative complications were directly related to surgical technique. No neurological, vascular or infective complications were encountered. All patients were followed up for 3-36 months (average 15 months). Firm bony fusion was documented in all patients after 3-6 months. One patient with atlas fracture showed anterior occipitocervical fusion. There was no implant failure. CONCLUSIONS: Posterior fixation and fusion of the atlas pedicle screw system is feasible and safe for the treatment of upper cervical diseases, and may be applicable to a larger number of patients.