Regulation of Leukocyte Recruitment to the Spleen and Peritoneal Cavity during Pristane-Induced Inflammation

Central obesity and fat-free mass are associated with a larger spleen volume in the general population

Background and aim

As the spleen plays a significant role in immunity, the aim was to investigate the associations of different body composition markers derived from various sources with spleen volume in a general population sample.

Materials and methods

Cross-sectional data of 1095 individuals (570 women; 52%) aged between 30 and 90 years were collected in the Study of Health in Pomerania (SHIP-START-2). We measured spleen volume by magnetic resonance imaging (MRI).Body composition markers were derived from classic anthropometry, bioelectrical impedance analysis, including absolute fat mass (FM) and fat-free mass (FFM), as well as from MRI, including visceral adipose tissue (VAT), subcutaneous adipose tissue (SAT), and liver fat content. Sex-stratified-adjusted linear regression models were used to analyze the associations of body composition markers with spleen volumes.

Results

We observed positive associations of body mass index, body weight, waist circumference, hip circumference, waist-to-height ratio, absolute FM, absolute FFM, and VAT and SAT with spleen volume in men and women. An 8.12 kg higher absolute FFM was associated with a 38.4 mL (95% confidence interval [CI]: 26.7-50.1) higher spleen volume in men and a 5.21 kg higher absolute FFM with a 42.6 mL (95% CI: 26.2-59.0) higher spleen volume in women.

Conclusion

Our findings indicate that obesity-related body composition markers and FFM are associated with a higher spleen volume. Particularly, higher absolute FFM showed a strong association with a larger spleen volume in both men and women. Further studies are warranted to understand the clinical significance of body composition markers on large spleen volume.

Null Function of Npr1 Disturbs Immune Response in Colonic Inflammation During Early Postnatal Stage

Natriuretic peptide receptor 1 (NPR1) is conventionally known as a regulator of vascular homeostasis. Here, we generated an Npr1 knockout mouse model with CRISPR/Cas9 technology and found that homozygous mice (Npr1-/-) exhibited weight loss and poor survival rate during early postnatal stage. Careful examination revealed unexpectedly that Npr1-/- mice developed colitis characterized by shortened colon, evident colonic mucosal damage, increased histopathological score, and higher colonic expression of proinflammatory cytokines interleukin-1B (IL1B) and -6 (IL6). RNA-sequencing analysis revealed that differentially expressed genes were prominently enriched in the biological pathways related to immune response in both spleen and colon of Npr1-/- mice. Cytofluorimetric analysis demonstrated that leukocytes in the spleen were significantly increased, particularly, the populations of neutrophil and CD3+ T cell were elevated but CD4+ T cells were decreased in Npr1-/- mice. Administration of 8-Br-cGMP, a downstream activator of NPR1, restored these immune-cell populations disturbed in Npr1-/- mice and lessened the colitis-related phenotypes. To validate the involvement of Npr1 in colitis, we examined another mouse model induced by dextran sodium sulfate (DSS) and found a decreased Npr1 expression and shifted immune-cell populations as well. Importantly, 8-Br-cGMP treatment exhibited a similar effect in the restoration of immune-cell populations and attenuation of colonic inflammation in DSS mice. Our data indicate that loss of Npr1 possibly interrupts immune response, which is critical to the pathogenesis of colitis in the early life.

IOX1 impedes host inflammation in imiquimod-triggered psoriasis

Psoriasis is a chronic autoimmune disease with an unknown etiology and highly limited treatment strategies. The drugs currently used in the treatment of psoriasis are rarely recommended for long-term use owing to the serious side effects. Although different targets have been identified for controlling psoriasis, the role of epigenetic modifications as therapeutic targets is yet to be elucidated. Here, we investigated the therapeutic potential of 8-hydroxyquinoline-5-carboxylic acid (IOX1), a novel drug with a genetic target, in psoriasis. The daily topical administration of IOX1 in a mouse model of imiquimod (IMQ)-induced psoriatic inflammation reduced inflammatory reactions in the skin and lowered the PASI score. Furthermore, intraperitoneally injected IOX1 repressed the inflammatory status induced by IMQ in psoriatic mice by reducing the mRNA levels of pro-inflammatory cytokines, restoring splenocyte populations, and regulating macrophage polarization. Our findings indicate the remedial effects of IOX1 on dermatitis psoriasis and the potential of IOX1 as a therapeutic compound in psoriasis.

The spleen size in patients undergoing hemodialysis

Introduction:

Inflammation promotes the progression of chronic renal failure, and the start of dialysis worsens inflammation. The enlargement of the spleen is associated with inflammation, and patients on hemodialysis may show a large spleen. The aim of the present study was to compare the spleen size of patients undergoing hemodialysis versus controls to update this thread.

Methods:

Controls and patients were eligible to participate in the study provided they were negative for serological markers of hepatitis B and C viruses and HIV, if they had no lymphoproliferative disorder, and if they were at least 18 years of age. Age, sex, and the duration of dialysis were recorded. Laboratory variables (hemoglobin, hematological cell count, serum creatinine) and the underlying cause of end-stage renal disease were analyzed. The spleen sizes of the patients were divided into tertiles.

Results:

The 75 controls and 168 patients selected were sex-matched. The patients were older, had larger spleens and lower platelet counts than controls. The relationship between spleen size and age in the controls and patients was quite similar. The patients in the first tertile of spleen size compared with those in the third were older and had a higher platelet counts. The underlying disease and dialysis vintage had no effect on spleen size.

Discussion:

The patients had larger spleens and a greater range of spleen sizes than the controls. In patients, the association between larger and smaller spleen with lower and higher platelet counts, respectively, sparked the speculation of occurrence of hypersplenism and hyposplenism.

Marginal Zone B Cells Assist With Neutrophil Accumulation to Fight Against Systemic Staphylococcus aureus Infection

In addition to regulating immune responses by producing antibodies that confer humoral immunity, B cells can also affect these responses by producing cytokines. How B cells participate in the clearance of pathogenic infections via functions other than the production of pathogen-specific antibodies is still largely unknown. Marginal zone (MZ) B cells can quickly respond to bacterial invasion by providing the initial round of antibodies. After a bloodborne bacterial infection, neutrophils promptly migrate to the MZ. However, the mechanisms regulating neutrophil accumulation in the MZ during the initial phase of infection also remain obscure. Here, we found that MZ B cell-deficient mice are more susceptible to systemic Staphylococcus aureus (S. aureus) infection compared with wildtype mice. The expression levels of interleukin (IL)-6 and CXCL1/CXCL2 in MZ B cells increased significantly in mice at 3–4 h after infection with S. aureus, then decreased at 24 h post-infection. After systemic S. aureus infection, splenic neutrophils express increased CXCR2 levels. Our results from confocal microscopy imaging of thick-section staining demonstrate that neutrophils in wildtype mice form cell clusters and are in close contact with MZ B cells at 3 h post-infection. This neutrophil cluster formation shortly after infection was diminished in both MZ B cell-deficient mice and IL-6-deficient mice. Blocking the action of CXCL1/CXCL2 by injecting anti-CXCL1 and anti-CXCL2 antibodies 1 h before S. aureus infection significantly suppressed the recruitment of neutrophils to the MZ at 3 h post-infection. Compared with peptidoglycan stimulation alone, peptidoglycan stimulation with neutrophil co-culture further enhanced MZ B-cell activation and differentiation. Using a Förster resonance energy transfer by fluorescence lifetime imaging (FLIM-FRET) analysis, we observed evidence of a direct interaction between neutrophils and MZ B cells after peptidoglycan stimulation. Furthermore, neutrophil depletion in mice resulted in a reduced production of S. aureus-specific immunoglobulin (Ig)M at 24 h post-infection. Together, our results demonstrate that MZ B cells regulate the rapid neutrophil swarming into the spleen during the early phase of systemic S. aureus infection. Interaction with neutrophils assists MZ B cells with their differentiation into IgM-secreting cells and contributes to the clearance of systemic bacterial infections.

Retinoic Acid Exerts Disease Stage-Dependent Effects on Pristane-Induced Lupus

We previously showed that all-trans-retinoic acid (tRA), an active metabolite of vitamin A, exacerbated pre-existing autoimmunity in lupus; however, its effects before the development of autoimmunity are unknown. Here, using a pristane-induced model, we show that tRA exerts differential effects when given at the initiation vs. continuation phase of lupus. Unlike tRA treatment during active disease, pre-pristane treatment with tRA aggravated glomerulonephritis through increasing renal expression of pro-fibrotic protein laminin β1, activating bone marrow conventional dendritic cells (cDCs), and upregulating the interaction of ICAM-1 and LFA-1 in the spleen, indicating an active process of leukocyte activation and trafficking. Transcriptomic analysis revealed that prior to lupus induction, tRA significantly upregulated the expression of genes associated with cDC activation and migration. Post-pristane tRA treatment, on the other hand, did not significantly alter the severity of glomerulonephritis; rather, it exerted immunosuppressive functions of decreasing circulatory and renal deposition of autoantibodies as well as suppressing the renal expression of proinflammatory cytokines and chemokines. Together, these findings suggest that tRA differentially modulate lupus-associated kidney inflammation depending on the time of administration. Interestingly, both pre- and post-pristane treatments with tRA reversed pristane-induced leaky gut and modulated the gut microbiota in a similar fashion, suggesting a gut microbiota-independent mechanism by which tRA affects the initiation vs. continuation phase of lupus.

Knockdown of microRNA-135b in Mammary Carcinoma by Targeted Nanodiamonds: Potentials and Pitfalls of In Vivo Applications

Nanodiamonds (ND) serve as RNA carriers with potential for in vivo application. ND coatings and their administration strategy significantly change their fate, toxicity, and effectivity within a multicellular system. Our goal was to develop multiple ND coating for effective RNA delivery in vivo. Our final complex (NDA135b) consisted of ND, polymer, antisense RNA, and transferrin. We aimed (i) to assess if a tumor-specific coating promotes NDA135b tumor accumulation and effective inhibition of oncogenic microRNA-135b and (ii) to outline off-targets and immune cell interactions. First, we tested NDA135b toxicity and effectivity in tumorospheres co-cultured with immune cells ex vivo. We found NDA135b to target tumor cells, but it binds also to granulocytes. Then, we followed with NDA135b intravenous and intratumoral applications in tumor-bearing animals in vivo. Application of NDA135b in vivo led to the effective knockdown of microRNA-135b in tumor tissue regardless administration. Only intravenous application resulted in NDA135b circulation in peripheral blood and urine and the decreased granularity of splenocytes. Our data show that localized intratumoral application of NDA135b represents a suitable and safe approach for in vivo application of nanodiamond-based constructs. Systemic intravenous application led to an interaction of NDA135b with bio-interface, and needs further examination regarding its safety.