Trimethylamine-N-oxide (TMAO) and basic fibroblast growth factor (bFGF) are possibly involved in corticosteroid resistance in adult patients with immune thrombocytopenia

PURPOSE

Immune thrombocytopenia (ITP) is an autoimmune disease characterized by accelerated platelet clearance. Gut dysbiosis was associated with its pathogenesis, but the underlying mechanisms have not been fully elucidated. Patients with ITP exhibit varying degrees of responsiveness to corticosteroid treatment. Therefore, prognostic indexes for corticosteroid responsiveness in ITP could offer valuable guidance for clinical practices.

METHODS

The present study examined the signature of six types of gut-microbiota metabolites and forty-eight types of cytokines, chemokines, and growth factors and their clinical significance in patients with ITP.

RESULTS

Both patients with good and poor corticosteroid responsiveness exhibited significantly elevated/suppressed secretion of twenty-two cyto(chemo)kins/growth factors in comparison to healthy controls. Additionally, patients with ITP demonstrated a significant decrease in plasma levels of trimethylamine-N-oxide (TMAO), which was found to be negatively correlated to circulating platelet counts, and positively correlated with Interleukin (IL)-1β and IL-18. Notably, patients who exhibited poor response to corticosteroid treatment displayed elevated levels of TMAO and basic fibroblast growth factor (bFGF) in comparison to responders. Additionally, we found that the amalgamation of TMAO, bFGF and interleukin (IL)-13 could serve as a valuable prognostic tool for predicting CS responsiveness.

CONCLUSION

Patients with ITP were characterized overall by an imbalanced secretion of cyto(cheo)kins/growth factors and inadequate levels of TMAO. The varying degrees of responsiveness to corticosteroid treatment can be attributed to different profiles of basic FGF and TMAO that might be related to overburdened oxidative stress and inflammasome overactivation, and ultimately mediate corticosteroid resistance.

Sulforaphane treatment reverses corticosteroid resistance in a mixed granulocytic mouse model of asthma by upregulation of antioxidants and attenuation of Th17 immune responses in the airways

Sulforaphane has received considerable attention in recent years due to its antioxidant and anti-inflammatory properties. Its preventive effect in the inhibition of airway inflammation is known; however, whether it affects mixed granulocyte asthma (corticosteroid resistance phenotype) is largely undiscovered. Therefore, we assessed the effect of pharmacological activation of Nrf2, a redox-sensitive transcription factor, using sulforaphane in a mouse model of mixed granulocyte airway inflammation. Mice were sensitized and challenged with cockroach allergen extract (CE), and airway inflammatory parameters and markers of steroid resistance [Nrf2 activity, oxidant-antioxidant balance in airway epithelial cells (AECs)/lung, and IL-17A-related pathway in Th17 cells and dendritic cells (DCs)] were investigated. Our results show that sulforaphane administration reduced neutrophilic airway inflammation, myeloperoxidase (MPO) activity, and Th17 immune responses in a mixed granulocyte mouse model of asthma through Nrf2 activation. On the other hand, corticosteroid treatment decreased Th2/eosinophilic immune responses but had little on Th17/neutrophilic immune responses. However, combined treatment with both almost completely blocked both neutrophilic/eosinophilic and Th17/Th2 immune responses in the lung. Sulforaphane treatment led to induction of antioxidant enzymes (SOD, GPx) in AECs and pulmonary non-enzymatic antioxidants. Further, it led to reduction in inflammatory cytokines (IL-6/IL-23/IL-17A) in Th17 cells/CD11c + DCs during mixed granulocytic inflammation. Collectively, our study presents the evidence that activation of Nrf2 by sulforaphane reduces neutrophilic airway inflammation by upregulation of antioxidants and downregulation of inflammatory cytokines in airways. This is possibly the basis for reversal of corticosteroid resistance in this model. This shows the therapeutic potential of sulforaphane in mixed granulocyte asthma.

Repeated lipopolysaccharide exposure causes corticosteroid insensitive airway inflammation via activation of phosphoinositide-3-kinase δ pathway

Corticosteroid resistance is one of major barriers to effective management of chronic inflammatory respiratory diseases, such as chronic obstructive pulmonary disease (COPD) and severe asthma. These patients often experience exacerbations with viral and/or bacterial infection, which may cause continuous corticosteroid insensitive inflammation. In this study, we observed that repeated exposure of lipopolysaccharide (LPS) intranasally attenuated the anti-inflammatory effects of the corticosteroid fluticasone propionate (FP) on neutrophils and CXCL1 levels in bronchoalveolar lavage (BAL) fluid in an in vivo murine model. Histone deacetylase-2 (HDAC2) and NF-E2 related factor 2 (Nrf2) levels in lungs after LPS administration for 3 consecutive days were significantly decreased to 38.9±6.3% (mean±SEM) and 77.5±2.7% of the levels seen after only one day of LPS exposure, respectively. In addition, 3 days LPS exposure resulted in an increase of Akt phosphorylation, indicating activation of the phosphoinositide-3-kinase (PI3K) pathway by 4-fold in lungs compared with 1 day of exposure. Furthermore, combination treatment with theophylline and FP significantly decreased the neutrophil accumulation and CXCL1 concentrations in BAL fluid from 22.5±1.8×10⁴ cells/mL and 214.6±20.6 pg/mL to 7.9±0.5×10⁴ cells/mL and 61.9±13.3 pg/mL, respectively. Combination treatment with IC87114, a selective PI3Kδ inhibitor, and FP also significantly decreased neutrophils and CXCL1 levels from 16.8±0.7×10⁴ cells/mL and 182.4±4.6 pg/mL to 5.9±0.3×10⁴ cells/mL and 71.4±2.7 pg/mL, respectively. Taken together, repeated exposure of LPS causes corticosteroid-insensitive airway inflammation in vivo, and the corticosteroid-resistance induced by LPS is at least partly mediated through the activation of PI3Kδ, resulting in decreased levels of HDAC2 and Nrf2. These findings provide a potentially new therapeutic approach to COPD and severe asthma.

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We first time proposed clinically relevant steroid insensitive exacerbation model.

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LPS caused corticosteroid insensitive airway inflammation via PI3Kδ activation.

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This murine model are useful to discover new therapies for airway inflammation.