The Interactive Roles of Lipopolysaccharides and dsRNA/Viruses on Respiratory Epithelial Cells and Dendritic Cells in Allergic Respiratory Disorders: The Hygiene Hypothesis

Advances in Mechanisms of Anaphylaxis in Wheat Allergy: Utility of Rodent Models

Wheat is a staple and nutritious food that is consumed globally. However, it is identified as a major allergenic food because of its capacity to trigger life-threatening systemic anaphylaxis. The specific mechanisms that underlie this systemic anaphylaxis in wheat allergy are incompletely understood. As a result, several rodent models have been developed to study anaphylaxis in wheat allergies. In this paper, we have conducted a comprehensive review of wheat-induced anaphylaxis using Google Scholar and PubMed databases with relevant keywords. The following objectives were addressed: (1) to determine the complexity of wheat-induced anaphylaxis; (2) to summarize the role of genetic susceptibility in wheat anaphylaxis; (3) to identify the environmental factors involved in the development of wheat anaphylaxis; (4) to map the current status of mechanisms involved in wheat anaphylaxis; (5) to identify the approaches, strengths, and limitations of rodent models of wheat anaphylaxis; and (6) to identify challenges and opportunities in this area of science. Our findings provide a comprehensive updated critical resource for the future research agenda in wheat allergy-associated anaphylaxis, particularly using rodent models as attractive pre-clinical tools.

Targeting exosomal double-stranded RNA-TLR3 signaling pathway attenuates morphine tolerance and hyperalgesia

Long-term morphine use leads to tolerance and hyperalgesia in patients with chronic pain, with neuroinflammation playing a key role, but its underlying mechanisms remain elusive. This study determines that repeated intrathecal morphine injections increase double-stranded RNA (dsRNA) production in spinal neurons, due to downregulated adenosine deaminase RNA specific 1 (ADAR1) expression. Lentivirus-induced ADAR1 elevation decreases the high levels of intracellular dsRNA and attenuates morphine tolerance and hyperalgesia. dsRNA is released into cerebrospinal fluid via exosomes (Exos) after repeated morphine injections and is taken up by microglia for TLR3-TRIF-IL-6 signaling activation. Blocking Exos release with GW4869 or inhibition of TLR3 signaling mitigates neuroinflammation, preventing the development of morphine tolerance and hyperalgesia. Intrathecal injection of TLR3 inhibitor alone shows analgesic effects in neuropathic pain, and co-administration with morphine amplifies the analgesic efficacy of morphine. These findings demonstrate that targeting dsRNA-TLR3 signaling to mitigate neuroinflammation could be a promising treatment for morphine tolerance.

Extracellular RNAs-TLR3 signaling contributes to cognitive impairment after chronic neuropathic pain in mice

Chronic pain is often associated with cognitive decline, which could influence the quality of the patient's life. Recent studies have suggested that Toll-like receptor 3 (TLR3) is crucial for memory and learning. Nonetheless, the contribution of TLR3 to the pathogenesis of cognitive decline after chronic pain remains unclear. The level of TLR3 in hippocampal neurons increased in the chronic constriction injury (CCI) group than in the sham group in this study. Importantly, compared to the wild-type (WT) mice, TLR3 knockout (KO) mice and TLR3-specific neuronal knockdown mice both displayed improved cognitive function, reduced levels of inflammatory cytokines and neuronal apoptosis and attenuated injury to hippocampal neuroplasticity. Notably, extracellular RNAs (exRNAs), specifically double-stranded RNAs (dsRNAs), were increased in the sciatic nerve, serum, and hippocampus after CCI. The co-localization of dsRNA with TLR3 was also increased in hippocampal neurons. And the administration of poly (I:C), a dsRNA analog, elevated the levels of dsRNAs and TLR3 in the hippocampus, exacerbating hippocampus-dependent memory. In additon, the dsRNA/TLR3 inhibitor improved cognitive function after CCI. Together, our findings suggested that exRNAs, particularly dsRNAs, that were present in the condition of chronic neuropathic pain, activated TLR3, initiated downstream inflammatory and apoptotic signaling, caused damage to synaptic plasticity, and contributed to the etiology of cognitive impairment after chronic neuropathic pain.

Glucose metabolism and glycosylation link the gut microbiota to autoimmune diseases

Carbohydrates serve as important energy sources and structural substances for human body as well as for gut microbes. As evidenced by the advances in immunometabolism, glucose metabolism and adenosine triphosphate (ATP) generation are deeply involved in immune cell activation, proliferation, and signaling transduction as well as trafficking and effector functions, thus contributing to immune response programming and assisting in host adaption to microenvironment changes. Increased glucose uptake, aberrant expression of glucose transporter 1 (e.g., GLU1), and abnormal glycosylation patterns have been identified in autoimmunity and are suggested as partially responsible for the dysregulated immune response and the modification of gut microbiome composition in the autoimmune pathogenesis. The interaction between gut microbiota and host carbohydrate metabolism is complex and bidirectional. Their impact on host immune homeostasis and the development of autoimmune diseases remains to be elucidated. This review summarized the current knowledge on the crosstalk of glucose metabolism and glycosylation in the host with intestinal microbiota and discussed their possible role in the development and progression of autoimmune diseases. Potential therapeutic strategies targeting glucose metabolism and glycosylation in modulating gut ecosystem and treating autoimmune diseases were discussed as well.

Pyroptosis in acute pancreatitis and its therapeutic regulation

Pyroptosis defines a new type of GSDMs-mediated programmed cell death, distinguishes from the classical concepts of apoptosis and necrosis-mediated cell death and is prescribed by cell swelling and membrane denaturation, leading to the extensive secretion of cellular components and low-grade inflammatory response. However, NLRP3 inflammasome activation can trigger its downstream inflammatory cytokines, leading to the activation of pyroptosis-regulated cell death. Current studies reveal that activation of caspase-4/5/11-driven non-canonical inflammasome signaling pathways facilitates the pathogenesis and progression of acute pancreatitis (AP). In addition, a large number of studies have reported that NLRP3 inflammasome-dependent pyroptosis is a crucial player in driving the course of the pathogenesis of AP. Excessive uncontrolled GSDMD-mediated pyroptosis has been implicated in AP. Therefore, the pyroptosis-related molecule GSDMD may be an independent prognostic biomarker for AP. The present review paper summarizes the molecular mechanisms of pyroptotic signaling pathways and their pathophysiological impacts on the progress of AP. Moreover, we briefly present some experimental compounds targeting pyroptosis-regulated cell death for exploring novel therapeutic directions for the treatment and management of AP. Our review investigations strongly suggest that targeting pyroptosis could be an ideal therapeutic approach in AP.

The extended farm effect: The milk protein β-lactoglobulin in stable dust protects against allergies

Background: The allergy- and asthma-protective farm effect is mediated by numerous factors. Especially dust from cattle stables and raw cow’s milk show beneficial properties, suggesting a bovine protein to be involved. As a major milk protein and member of the lipocalin family, β-lactoglobulin (BLG) binds small, hydrophobic ligands and thereby modulates the immune response. Empty BLG promotes allergy development, whereas BLG in association with ligands shows allergy-preventive as well as allergy-reducing effects in vivo and in vitro. Results: BLG has been identified as a major protein in stable dust (therein bound to zinc) as well as in the air around cattle stables. This association with zinc favors an allergy-protective immune profile. Conclusion: Its immune-modulating, allergy-protective characteristics together with its presence in raw cow’s milk as well as in stable dust and ambient air render BLG an essential contributor to the farm effect.

Bate palmas mutant mice as a model of Kabuki syndrome: Higher susceptibility to infections and vocalization impairments?

The recessive mutant mouse bate palmas (bapa) arose from N-ethyl-N-nitrosourea mutagenesis. Previous studies of our group revealed some behavioral impairments and a mutation in the lysine (K)-specific methyltransferase 2D (Kmt2d) gene. Because mutations in the KMT2D gene in humans are mainly responsible for Kabuki syndrome, this study was proposed to validate bapa mice as a model of Kabuki syndrome. Besides other symptoms, Kabuki syndrome is characterized by increased susceptibility to infections and speech impairments, usually diagnosed in the early childhood. Thus, juvenile male and female bapa mice were studied in different developmental stages (prepubertal period and puberty). To induce sickness behavior and to study infection susceptibility responses, lipopolysaccharide (LPS) was used. To study oral communication, ultrasonic vocalizations were evaluated. Behavioral (open-field test) and central (astrocytic glial fibrillary acidic protein [GFAP] and tyrosine hydroxylase [TH]) evaluations were also performed. Control and bapa female mice emitted 31-kHz ultrasounds on prepubertal period when exploring a novel environment, a frequency not yet described for mice, being defined as 31-kHz exploratory vocalizations. Males, LPS, and puberty inhibited these vocalizations. Bapa mice presented increased motor/exploratory behaviors on prepubertal period due to increased striatal TH expression, revealing striatal dopaminergic system hyperactivity. Combining open-field behavior and GFAP expression, bapa mice did not develop LPS tolerance, that is, they remained expressing signs of sickness behavior after LPS challenge, being more susceptible to infectious/inflammatory processes. It was concluded that bapa mice is a robust experimental model of Kabuki syndrome.

LPS aggravates lung inflammation induced by RSV by promoting the ERK-MMP-12 signaling pathway in mice

Background

RSV can lead to persistent airway inflammation and airway hyperresponsiveness (AHR), and is intimately associated with childhood recurrent wheezing and asthma, but the underlying mechanisms remain unclear. Lipopolysaccharide (LPS) is also implicated in the onset and exacerbation of asthma. However, whether inhalation of LPS can boost airway inflammation induced by RSV is not clear. In this study, we utilized an LPS- and RSV-superinfected mouse model to explore underlying pathogenesis.

Methods

Mice were infected with RSV on day 0 and inoculated with LPS from day 35 to day 41, samples were collected on day 42. Inflammatory cells, lung histopathology and AHR were measured. Cytokines were detected by ELISA and ERK, JNK, p38 was determined by western blot. MMP408, PD98059, SP600125 and SB203580 were used to inhibit MMP-12, ERK, JNK and p38 respectively.

Results

LPS exposure superimposed on RSV-infected lungs could lead to more vigorous cellular influx, lung structures damage, augmented AHR and higher MMP-12 levels. Inhibition of MMP-12 or ERK signaling pathway in vivo both diminished LPS-driven airway inflammation and AHR.

Conclusions

Exposure to LPS in RSV-infected mice is associated with enhanced increases in ERK-MMP-12 expression that translates into increased lung inflammation and AHR. These findings contribute novel information to the field investigating the onset of post-RSV bronchiolitis recurrent wheezing as a result of LPS exposure.

Agaphelin modulates the activation of human bronchial epithelial cells induced by lipopolysaccharide and IL-4

Sand fly saliva presents molecules with potential to development of compounds for treatment of inflammatory diseases. Agaphelin, isolated from the saliva of the mosquito Anopheles gambiae, demonstrates anti-inflammatory properties such as neutrophils chemotaxis inhibition. Here, we extend these results and evaluated the role of agaphelin (0.1-100 nM) in an in vitro model consisting in the activation of human bronchial epithelial cells (BEAS-2B) by IL-4 (50 ng/mL) or lipopolysaccharide (LPS; 10 ng/mL). Agaphelin is non-cytotoxic for BEAS-2B cells. Notably, agaphelin markedly reduces CCL2 and IL-8 production induced by IL-4 or LPS, without altering the IL-10 production. The TLR4 expression and STAT1 phosphorylation induced by LPS were inhibited by agaphlin. In addition, agaphelin decreased the phosphorylation of STAT6 induce by IL-4, whose effect was independent of IL-4-binding activity. Taken together, these findings identify agaphelin as a potential anti-inflammatory therapeutic agent for airway inflammations.

Important Role of Immunological Responses to Environmental Exposure in the Development of Allergic Asthma

Allergic asthma is a public health problem that affects human health and socioeconomic development. Studies have found that the prevalence of asthma has significantly increased in recent years, which has become particularly pronounced in developed countries. With rapid urbanization in China in the last 3 decades, the prevalence of asthma has increased significantly in urban areas. As changes in genetic backgrounds of human populations are limited, environmental exposure may be a major factor that is responsible for the increased prevalence of asthma. This review focuses on environmental components of farms and rural areas that may have protective effects in reducing the development of asthma. Farm and rural related microorganism- and pathogen-associated molecular patterns are considered to be important environmental factors that modulate host's innate and adaptive immune system to induce protection effects later in life. Environmental microbial-related immunotherapy will also be discussed as the future research direction for the prevention of allergic asthma.

Combinatory antibiotic treatment protects against experimental acute pancreatitis by suppressing gut bacterial translocation to pancreas and inhibiting NLRP3 inflammasome pathway

Gut bacterial translocation following impaired gut barrier is a critical determinant of initiating and aggravating acute pancreatitis (AP). Antibiotic combination (ABX; vancomycin, neomycin and polymyxin b) is capable of reducing gut bacteria, but its efficacy in AP prevention and the underlying mechanism have not been investigated yet. AP was induced in BALB/c mice by caerulein (CAE) hyperstimulation. We found that ABX supplementation attenuated the severity of AP as evidenced by reduced pancreatic oedema and myeloperoxidase activity. The protective effect was also confirmed by improved histological morphology of the pancreas and decreased pro-inflammatory markers (IL-1β, TNF-α, MCP-1) in pancreas. ABX administration inhibits the activation of colonic TLR4/NLRP3 inflammasome pathway. Subsequently, down-regulated NLRP3 resulted in decreased colonic pro-inflammation (IL-1β, IL-6, MCP-1) and enhanced gut physical barrier as evidenced by up-regulation of tight junction proteins including occludin, claudin-1 and ZO-1, as well as improved histological morphology of the colon. Together, combinatory ABX therapy inhibited the translocation of gut bacteria to pancreas and its amplification effects on pancreatic inflammation by inhibiting the pancreatic NLRP3 pathway, and inhibiting intestinal-pancreatic inflammatory responses. The current study provides the basis for potential clinical application of ABX in AP.

Converging findings from linkage between periodontal pathogen with atopic and allergic immune response

This study aims to explore a relationship between exposures of whole-cell Porphyromonas gingivalis in various doses with atopic inflammatory responses at experimental mice. A pretest-posttest controlled group design, with 16 Wistar rats (Rattus novergicus) randomized into four groups. Group 1 was the control group. Group 2 was given low-dose (9 × 10⁷ colony-forming unit) of P. gingivalis. Group 3 was given medium-dose (9 × 10⁹ colony-forming unit) of P. gingivalis. Group 4 was given high-dose (9 × 10¹¹ colony-forming unit) of P. gingivalis. Interleukin-4, Interleukin-5, Interleukin-17F, Interleukin-21, Immunoglobulin-E, Immunoglobulin-G₄, and γ-Interferon were measured by direct-sandwich ELISA just before the treatments began, day-4, and day-11 after treatments. There is a sudden increase of Interleukin-4 in the group 4 (23.79 ± 0.91 pg/ml to 54.17 ± 0.79 pg/ml; p = 0.01) and slight increase of Interleukin-5 in the group 4 (207.60 ± 11.15 pg/ml to 243.40 ± 9.33 pg/ml; p = 0.03). No change was observed for Interleukin-17F in all groups. Serum concentration of Immunoglobulin-E was decreased in group 2 (-10.44 ± 8.13 pg/ml), but increased in group 4 (+1.03 ± 4.57 pg/ml). Taken together, some cytokines are up-regulated and others are down-regulated after exposure to whole-cell P. gingivalis. Moreover, study of host responses during periodontal infection may offer critical key insight that contribute to the development of atopy. CLINICAL IMPLICATIONS: We introduced and explained the potential role of periodontal pathogen Porphyromonas gingivalis in systemic immune responses, along with its virulence factor inside the oral cavity. Our results consider several changes and differences of cytokines and immunoglobulins following whole-cell Porphyromonas gingivalis exposure. However, results of the study need to be interpreted with caution due to its limitations. CAPSULE SUMMARY: Interleukin (IL)-4 and IL-5 had been found increase after exposure to the periodontal pathogens Porphyromonas gingivalis, whereas no or minimal change had been found in the level of IL-17F, Ig-G₄, and IFN-γ. The various cytokines and immunoglobulins shown in this study do not prove a causal relationship, and the precise role of Porphyromonas gingivalis in the regulation of atopic immune response warrants further investigation. Nevertheless, these findings may provide some critical key insight into the host responses following Porphyromonas gingivalis infection.

Trichinella spiralis Excretory-Secretory Products Induce Tolerogenic Properties in Human Dendritic Cells via Toll-Like Receptors 2 and 4

Trichinella spiralis, as well as its muscle larvae excretory–secretory products (ES L1), given either alone or via dendritic cells (DCs), induce a tolerogenic immune microenvironment in inbred rodents and successfully ameliorate experimental autoimmune encephalomyelitis. ES L1 directs the immunological balance away from T helper (Th)1, toward Th2 and regulatory responses by modulating DCs phenotype. The ultimate goal of our work is to find out if it is possible to translate knowledge obtained in animal model to humans and to generate human tolerogenic DCs suitable for therapy of autoimmune diseases through stimulation with ES L1. Here, the impact of ES L1 on the activation of human monocyte-derived DCs is explored for the first time. Under the influence of ES L1, DCs acquired tolerogenic (semi-matured) phenotype, characterized by low expression of HLA-DR, CD83, and CD86 as well as moderate expression of CD40, along with the unchanged production of interleukin (IL)-12 and elevated production of IL-10 and transforming growth factor (TGF)-β, compared to controls. The interaction with DCs involved toll-like receptors (TLR) 2 and 4, and this interaction was mainly responsible for the phenotypic and functional properties of ES L1-treated DCs. Importantly, ES L1 potentiated Th2 polarizing capacity of DCs, and impaired their allo-stimulatory and Th1/Th17 polarizing properties. Moreover, ES L1-treated DCs promoted the expansion of IL-10- and TGF-β- producing CD4⁺CD25^hiFoxp3^hi T cells in indolamine 2, 3 dioxygenase (IDO)-1-dependent manner and increased the suppressive potential of the primed T cell population. ES L1-treated DCs retained the tolerogenic properties, even after the challenge with different pro-inflammatory stimuli, including those acting via TLR3 and, especially TLR4. These results suggest that the induction of tolerogenic properties of DCs through stimulation with ES L1 could represent an innovative approach for the preparation of tolerogenic DC for treatment of inflammatory and autoimmune disorders.