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CD4 T Follicular Helper Cells Prevent Depletion of Follicular B Cells in Response to Cecal Ligation and Puncture.

ABSTRACT: Recent studies have demonstrated that induction of a diverse repertoire of memory T cells ("immune education") affects responses to murine cecal ligation and puncture (CLP), the most widely - used animal model of sepsis. Among the documented effects of immune education on CLP are changes in T cell, macrophage and neutrophil activity, more pronounced organ dysfunction and reduced survival. Little is known, however, about the effects of CLP on B cell responses, and how these responses might be altered by immune education. Importantly, effective B cell responses are modulated by IL21 produced by CD4⁺/CXCR5⁺/PD1⁺ T follicular helper (Tfh) cells. We examined the B cell population in control and immune educated mice 24 h and 60 days after CLP. Education alone increased Tfh cells. Twenty-four hours after CLP, Tfh cells were depleted. However, this reduction was less pronounced in immune educated mice than in controls and the percentage of CD4 T cells expressing a Tfh phenotype increased in the animals. CLP did not alter splenic architecture and decreased numbers of follicular, marginal, and germinal center B cells. CLP induced changes were not, however, noted following CLP in immune educated mice. At 60 days post - CLP, numbers of follicular, germinal center and marginal zone B cells were increased; this increase was more pronounced in immune educated mice. Finally, while CLP reduced the induction of antigen specific B cells in controls, this response was maintained following CLP in immune educated mice. Our data suggest that preexisting Tfh assists in rescuing the B cell response to CLP.

SUBMITTER: Taylor MD

PROVIDER: S-EPMC7434988 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Sepsis is the leading cause of death in intensive care units. MicroRNA-34a (miR-34a) is involved in sepsis progression, while its underlying mechanisms on sepsis-induced lung injury remain obscure. Oxidative stress, pyroptosis, and inhibition of autophagy can result in organ injury. MiR-34a has been reported to regulate oxidative stress and autophagy via inhibiting silent information regulator T1 (SIRT1) and autophagy gene 4B (ATG4B) signaling. This study aimed at identifying the function of miR-34a in oxidative stress, inflammation, pyroptosis, and autophagy in sepsis-induced lung injury. Male 8-week-old C57BL/6 mice were subjected to cecal ligation and puncture and treated with miR-34a antagomir/agomir. Survival (n = 10), histopathological changes (n = 6), and lung wet-to-dry ratio (n = 6) were recorded and assayed. Other detection (n = 6) was performed to investigate the level of oxidative stress, inflammation, pyroptosis, and autophagy in lung tissues. Results showed that miR-34a down-regulation ameliorated lung injury in septic mice as reflected by decreased lung injury scores (decrease from 3.00 ± 0.32 to 2.00 ± 0.32) and wet-to-dry ratio (0.36-fold decrease). MiR-34a down-regulation also decreased reactive oxygen species accumulation (0.36-fold decrease), and promoted superoxide dismutase activity and the expression of SIRT1 (1.24-fold increase), heme oxygenase-1 and nuclear factor erythroid 2 like 2 to inhibit oxidative stress in septic mice. Moreover, miR-34a down-regulation suppressed inflammatory response and pyroptosis in septic mice, as evidenced by decreased level of pro-inflammatory factors including tumor necrosis factor ?, interleukin-6 (IL-6), IL-1?, and IL-18, activity of caspase-1 (0.51-fold decrease) and expression of nucleotide-binding domain and leucine-rich repeat protein-3 (0.48-fold decrease), apoptosis-associated speck-like protein containing a CARD, cleaved-caspase-1, and cleaved-gasdermin D (0.36-fold decrease), and increased level of anti-inflammatory factors IL-10. MiR-34a down-regulation also enhanced autophagy in septic mice as evidenced by more autolysosomes and elevated expressions of ATG4B (0.90-fold increase), beclin1, ATG9, and LC3 II/I. Among these experiments, miR-34a up-regulation showed opposite effects on oxidative stress, inflammatory response, pyroptosis, and autophagy in septic mice. Additionally, miR-34a could bind to the 3'-untranslated region of SIRT1 and ATG4B. In conclusion, our findings demonstrated that miR-34a was implicated in oxidative stress, inflammation, pyroptosis, and autophagy in the development of sepsis. MiR-34a inhibition had a potential to alleviate sepsis-induced lung injury.

Project description:BACKGROUND:The paradigm shift from crystalloid to plasma resuscitation of traumatic hemorrhagic shock has improved patient outcomes due in part to plasma-mediated reversal of catecholamine and inflammation-induced endothelial injury, decreasing vascular permeability and attenuating organ injury. Since sepsis induces a similar endothelial injury as seen in hemorrhage, we hypothesized that plasma resuscitation would increase 48-h survival in a rat sepsis model. METHODS:Adult male Sprague-Dawley rats (375-425?g) were subjected to 35% cecal ligation and puncture (CLP) (t?=?0?h). Twenty-two hours post-CLP and prior to resuscitation (t?=?22?h), animals were randomized to resuscitation with normal saline (NS, 10?cc/kg/h) or pooled rat fresh frozen plasma (FFP, 3.33?cc/kg/h). Resuscitation under general anesthesia proceeded for the next 6 h (t?=?22?h to t?=?28?h); lactate was checked every 2?h, and fluid volumes were titrated based on lactate clearance. Blood samples were obtained before (t?=?22?h) and after resuscitation (t?=?28?h), and at death or study conclusion. Lung specimens were obtained for calculation of wet-to-dry weight ratio. Fisher exact test was used to analyze the primary outcome of 48-h survival. ANOVA with repeated measures was used to analyze the effect of FFP versus NS resuscitation on blood gas, electrolytes, blood urea nitrogen (BUN), creatinine, interleukin (IL)-6, IL-10, catecholamines, and syndecan-1 (marker for endothelial injury). A two-tailed alpha level of <0.05 was used for all statistical tests. RESULTS:Thirty-three animals were studied: 14 FFP, 14 NS, and 5 sham. Post-CLP but preresuscitation (t?=?22?h) variables between FFP and NS animals were similar and significantly deranged compared with sham animals. FFP significantly increased 48-h survival compared to NS (n?=?8 [57%] vs n?=?2 [14%]), attenuated the post-resuscitation (t?=?28?h) levels of epinephrine (mean 2.2 vs 7.0?ng/mL), norepinephrine, (3.8 vs 8.9?ng/mL), IL-6 (3.8 vs 18.7?ng/mL), and syndecan-1 (21.8 vs 31.0?ng/mL) (all P?<?0.05), improved the post-resuscitation PO2 to FiO2 ratio (353 vs 151), and reduced the pulmonary wet-to-dry weight ratio (5.28 vs 5.94) (all P?<?0.05). CONCLUSION:Compared to crystalloid, plasma resuscitation increased 48-h survival in a rat sepsis model, improved pulmonary function and decreased pulmonary edema, and attenuated markers for inflammation, endothelial injury, and catecholamines.

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CD4 T Follicular Helper Cells Prevent Depletion of Follicular B Cells in Response to Cecal Ligation and Puncture.

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