Controlling innate immune memory

HG-9-91-01 Attenuates Murine Experimental Colitis by Promoting Interleukin-10 Production in Colonic Macrophages Through the SIK/CRTC3 Pathway

BACKGROUND

Interleukin-10 (IL-10) is a potent immunoregulatory cytokine that plays a pivotal role in maintaining mucosal immune homeostasis. As a novel synthetic inhibitor of salt-inducible kinases (SIKs), HG-9-91-01 can effectively enhance IL-10 secretion at the cellular level, but its in vivo immunoregulatory effects remain unclear. In this study, we investigated the effects and underlying mechanism of HG-9-91-01 in murine colitis models.

METHODS

The anti-inflammatory effects of HG-9-91-01 were evaluated on 2, 4, 6-trinitrobenzene sulfonic acid (TNBS)-, dextran sulfate sodium-induced colitis mice, and IL-10 knockout chronic colitis mice. The in vivo effector cell of HG-9-91-01 was identified by fluorescence-activated cell sorting and quantitative real-time polymerase chain reaction. The underlying mechanism of HG-9-91-01 was investigated via overexpressing SIKs in ANA-1 macrophages and TNBS colitis mice.

RESULTS

Treatment with HG-9-91-01 showed favorable anticolitis effects in both TNBS- and DSS-treated mice through significantly promoting IL-10 expression in colonic macrophages but failed to protect against IL-10 KO murine colitis. Further study indicated that HG-9-91-01 markedly enhanced the nuclear level of cAMP response element-binding protein (CREB)-regulated transcription coactivator 3 (CRTC3), whereas treatment with lentiviruses encoding SIK protein markedly decreased the nuclear CRTC3 level in HG-9-91-01-treated ANA-1 macrophages. In addition, intracolonic administration with lentiviruses encoding SIK protein significantly decreased the nuclear CRTC3 level in the lamina propria mononuclear cells and ended the anti-inflammatory activities of HG-9-91-01.

CONCLUSIONS

We found that HG-9-91-01 promoted the IL-10 expression of colonic macrophages and exhibited its anticolitis activity through the SIK/CRTC3 axis, and thus it may represent a promising strategy for inflammatory bowel disease therapy.

Mesenchymal stem cells transfected with anti-miRNA-204-3p inhibit acute rejection after heart transplantation by targeting C-X-C motif chemokine receptor 4 (CXCR4) in vitro

Background

Mesenchymal stem cells (MSCs) are a promising treatment for acute rejection (AR) after heart transplantation (HTx) owing to their immunomodulatory functions by promoting the transformation of macrophages from the M0 to M2 phenotype. However, it is undetermined whether surface expression of C-X-C motif chemokine receptor 4 (CXCR4) by MSCs influences macrophage polarization. In this study, we investigated the effects of MSCs on macrophages caused by CXCR4, and detected the underlying mechanism, which may contribute to improving HTx outcomes.

Methods

The MSCs were extracted from rat bone marrow and identified using flow cytometry. We subsequently observed the effects of CXCR4 and anti-miRNA-204-3p on cell proliferation and migration, and the effects on macrophage polarization. Dual luciferase reporter assay was used to explore whether miRNA-204-3p was an upstream microRNA (miRNA) of CXCR4. A series of rescue experiments were performed to further confirm the inhibitory effect of miRNA-204-3p on CXCR4.

Results

The results showed that CXCR4 could promote the proliferation and migration of MSCs. Furthermore, it facilitated MSC-mediated macrophage transformation from the M0 to M2 phenotype. In addition, miRNA-204-3p inhibited the function of CXCR4 of MSCs.

Conclusions

Regulated by miRNA-204-3p, CXCR4 could inhibit the progression of AR after HTx. This study provides a new insight of the treatment of AR after HTx.

The Role of Microbiota in Neutrophil Regulation and Adaptation in Newborns

Newborns are highly susceptible to infections and mainly rely on innate immune functions. Reduced reactivity, delayed activation and subsequent failure to resolve inflammation however makes the neonatal immune system a very volatile line of defense. Perinatal microbiota, nutrition and different extra-uterine factors are critical elements that define long-term outcomes and shape the immune system during the neonatal period. Neutrophils are first responders and represent a vital component of the immune system in newborns. They have long been regarded as merely executive immune cells, however this notion is beginning to shift. Neutrophils are shaped by their surrounding and adaptive elements have been described. The role of “innate immune memory” and the main triangle connection microbiome—neutrophil—adaptation will be discussed in this review.

Nanoliposomes encapsulating immunostimulants modulate the innate immune system and elicit protection in zebrafish larvae

Here we present immunostimulant-loaded nanoliposomes (NL_c) as a strategy to protect zebrafish larvae against bacterial infection. The NL_c encapsulate crude lipopolysaccharide (LPS) from E. coli and polyinosinic:polycytidylic acid (Poly I:C), a synthetic analogue of viral dsRNA. Fluorescently-labeled NL_c were ingested by zebrafish larvae 4 days post fertilization, when administrated by bath immersion, and accumulated in the intestine. RT-qPCR analysis showed the expression of innate immune related genes (tnfα, il1β, nos2a, irf1a and ptgs2a) was significantly upregulated at 48 h post NL_c treatment. A zebrafish larvae infection model for Aeromonas hydrophila was set up by bath immersion, achieving bacterial-dose-dependent significant differences in survival at day 5 post infection in both injured and non-injured larvae. Using this model, NL_c protected non-injured zebrafish larvae against an A. hydrophila lethal infection. In contrast, neither the empty nanoliposomes nor the mixture of immunostimulants could protect larvae against lethal challenges. Our results demonstrate that nanoliposomes could be further developed as an efficient carrier, widening the scope for delivery of other immunostimulants in aquaculture.

Small RNA-mediated Cry toxin silencing allows Bacillus thuringiensis to evade Caenorhabditis elegans avoidance behavioral defenses

Pathogen avoidance behavior protects animal hosts against microbial pathogens. Pathogens have evolved specific strategies during coevolution in response to such host defenses. However, these strategies for combatting host avoidance behavioral defenses remain poorly understood. Here, we used Caenorhabditis elegans and its bacterial pathogen Bacillus thuringiensis as a model and determined that small RNA (sRNA)-mediated Cry toxin silencing allowed pathogens to evade host avoidance behavioral defenses. The B. thuringiensis strain YBT-1518, which encodes three nematicidal cry genes, is highly toxic to C. elegans. However, the expression of the most potent toxin, Cry5Ba, was silenced in this strain when YBT-1518 was outside the host. Cry5Ba silencing was due to the sRNA BtsR1, which bound to the RBS site of the cry5Ba transcript via direct base pairing and inhibited Cry5Ba expression. Upon ingestion by C. elegans, Cry5Ba was expressed in vivo by strain YBT-1518. Cry5Ba silencing may allow B. thuringiensis to avoid nematode behavioral defenses and then express toxins once ingested to kill the host and gain a survival advantage. Our work describes a novel model of sRNA-mediated regulation to aid pathogens in combating host avoidance behavioral defenses.

What vaccination studies tell us about immunological memory within the innate immune system of cultured shrimp and crayfish

The possibility of immunological memory in invertebrates is a topic that has recently attracted a lot of attention. Today, even vertebrates are known to exhibit innate immune responses that show memory-like properties, and since these responses are triggered by cells that are involved in the innate immune system, it seems that immune specificity and immune memory do not necessarily require the presence of B cells and T cells after all. This kind of immune response has been called "immune priming" or "trained immunity". In this report, we review recent observations and our current understanding of immunological memory within the innate immune system in cultured shrimp and crayfish after vaccination with live vaccine, killed vaccine and subunit vaccines. We also discuss the possible mechanisms involved in this immune response.

Macrophages as Effectors of Acute and Chronic Allograft Injury

Organ transplants give a second chance of life to patients with end-stage organ failure. However, the immuno-logical barriers prove to be very challenging to overcome and graft rejection remains a major hurdle to long-term transplant survival. For decades, adaptive immunity has been the focus of studies, primarily based on the belief that T cells are necessary and sufficient for rejection. With better-developed immunosuppressive drugs and protocols that effectively control adaptive cells, innate immune cells have emerged as key effector cells in triggering graft injury and have therefore attracted much recent attention. In this review, we discuss current understanding of macrophages and their role in transplant rejection, their dynamics, distinct phenotypes, locations, and functions. We also discuss novel therapeutic approaches under development to target macrophages in transplant recipients.