The GTPase Rab1 Is Required for NLRP3 Inflammasome Activation and Inflammatory Lung Injury

Deciphering the molecular regulatory of RAB32/GPRC5A axis in chronic obstructive pulmonary disease

BACKGROUND

Chronic obstructive pulmonary disease (COPD) is a significant public health problem characterized by persistent airflow limitation. Despite previous research into the pathogenesis of COPD, a comprehensive understanding of the cell-type-specific mechanisms in COPD remains lacking. Recent studies have implicated Rab GTPases in regulating chronic immune response and inflammation via multiple pathways. In this study, the molecular regulating mechanism of RAB32 in COPD was investigated by multiple bioinformatics mining and experimental verification.

METHODS

We collected lung tissue surgical specimens from Zhongshan Hospital, Fudan University, and RT-qPCR and western blotting were used to detect the expression of Rabs in COPD lung tissues. Four COPD microarray datasets from the Gene Expression Omnibus (GEO) were analyzed. COPD-related epithelial cell scRNA-seq data was obtained from the GSE173896 dataset. Weighted gene co-expression network analysis (WGCNA), mfuzz cluster, and Spearman correlation analysis were combined to obtain the regulatory network of RAB32 in COPD. The slingshot algorithm was used to identify the regulatory molecule, and the co-localization of RAB32 and GPRC5A was observed with immunofluorescence.

RESULTS

WGCNA identified 771 key module genes significantly associated with the occurrence of COPD, including five Rab genes. RAB32 was up-regulated in lung tissues from subjects with COPD as contrast to those without COPD on both mRNA and protein levels. Integrating the results of WGCNA, Mfuzz clusters, and Spearman analysis, nine potential interacting genes with RAB32 were identified. Among these genes, GPRC5A exhibited a similar molecular expression pattern to RAB32. Co-expression density analysis at the cell level demonstrated that the co-expression density of RAB32 and GPRC5A was higher in type I alveolar epithelial cells (AT1s) than in type II alveolar epithelial cells (AT2s). The immunofluorescence also confirmed the co-localization of RAB32 and GPRC5A, and the Pearson correlation analysis found the relationship between RAB32 and GPRC5A was significantly stronger in the COPD lungs (r = 0.65) compared to the non-COPD lungs (r = 0.33).

CONCLUSIONS

Our study marked endeavor to delineate the molecular regulatory axis of RAB32 in COPD by employing diverse methods and identifying GPRC5A as a potential interacting molecule with RAB32. These findings offered novel perspectives on the mechanism of COPD.

Rab26 alleviates sepsis-induced immunosuppression as a master regulator of macrophage ferroptosis and polarization shift

Macrophage dysfunction is a significant contributor to more than 70 % of sepsis-related deaths, specifically secondary bacterial infections, during the immunosuppression stage of sepsis. Nevertheless, the role of Rab26 in this context remains unclear. In this study, we observed a substantial decrease in Rab26 expression in macrophages during the immunosuppressive phase of sepsis, which was also found to be suppressed by high extracellular levels of HMGB1. During the progression of sepsis, Rab26 deficiency promotes a polarization shift from the M1 to the M2-like phenotype in macrophages, rendering them susceptible to ferroptosis. Subsequent experimentation has revealed that Rab26 deficiency facilitates the degradation of GPX4, thereby aggravating macrophage ferroptosis through the upregulation of levels of lipid ROS, MDA, and ferrous iron induced by RSL3, a ferroptosis inducer. Additionally, Rab26-deficient mice in the immunosuppressed phase of sepsis exhibit heightened susceptibility to secondary infections, leading to exacerbated lung tissue damage and increased mortality rate. Overall, these findings indicate that Rab26 plays a crucial role in sepsis-induced macrophage immunosuppression by regulating macrophage ferroptosis and polarization. Hence, it represents a potential novel target for sepsis therapy.

Grouper Rab1 inhibits nodovirus infection by affecting virus entry and host immune response

Rab1, a GTPase, is present in all eukaryotes, and is mainly involved in vesicle trafficking between the endoplasmic reticulum and Golgi, thereby regulating many cellular activities and pathogenic infections. However, little is known of how Rab1 functions in fish during virus infection. Groupers (Epinephelus spp.) are high in economic value and widely cultivated in China and Southeast Asia, although they often suffer from diseases. Red-spotted grouper nervous necrosis virus (RGNNV), a highly pathogenic RNA virus, is a major pathogen in cultured groupers, and causes huge economic losses. A series of host cellular proteins involved in RGNNV infection was identified. However, the impact of Rab1 on RGNNV infection has not yet been reported. In this study, a novel Rab1 homolog (EcRab1) from Epinephelus coioides was cloned, and its roles during virus infection and host immune responses were investigated. EcRab1 encoded a 202 amino acid polypeptide, showing 98% and 78% identity to Epinephelus lanceolatus and Homo sapiens, respectively. After challenge with RGNNV or poly(I:C), the transcription of EcRab1 was altered both in vitro and in vivo, implying that EcRab1 was involved in virus infection. Subcellular localization showed that EcRab1 was displayed as punctate structures in the cytoplasm, which was affected by EcRab1 mutants. The dominant negative (DN) EcRab1, enabling EcRab1 to remain in the GDP-binding state, caused EcRab1 to be diffusely distributed in the cytoplasm. Constitutively active (CA) EcRab1, enabling EcRab1 to remain in the GTP-binding state, induced larger cluster structures of EcRab1. During the late stage of RGNNV infection, some EcRab1 co-localized with RGNNV, and the size of EcRab1 clusters was enlarged. Importantly, overexpression of EcRab1 significantly inhibited RGNNV infection, and knockdown of EcRab1 promoted RGNNV infection. Furthermore, EcRab1 inhibited the entry of RGNNV to host cells. Compared with EcRab1, overexpression of DN EcRab1 or CA EcRab1 also promoted RGNNV infection, suggesting that EcRab1 regulated RGNNV infection, depending on the cycles of GTP- and GDP-binding states. In addition, EcRab1 positively regulated interferon (IFN) immune and inflammatory responses. Taken together, these results suggest that EcRab1 affects RGNNV infection, possibly by regulating host immunity. Our study furthers the understanding of Rab1 function during virus infection, thus helping to design new antiviral strategies.

CD83+ B cells alleviate uveitis through inhibiting DCs by sCD83

Soluble CD83 (sCD83) exerts immunosuppressive functions in many autoimmune diseases, including experimental autoimmune uveitis (EAU), but the cells and mechanisms involved are unclear. This study showed that CD83+ B cells were the main sources of sCD83. They alleviated the symptoms of EAU and decreased the percentage of T cells and DCs in the eyes and lymph nodes. These CD83+ B cells decreased IL-1β, IL-18 and IFN-γ secretion by DCs through sCD83. sCD83 interacted with GTPase Ras-related protein (Rab1a) in DCs to promote Rab1a accumulation in autolysosomes and inhibit mTORC1 phosphorylation and NLRP3 expression. Hence, CD83+ B cells play a regulatory role in EAU by secreting sCD83. The lack of regulation of CD83+ B cells might be an important factor leading to hyperimmune activation in patients with autoimmune uveitis. CD83+ B cells suppress activated DCs in uveitis, indicating the potential therapeutic role of CD83+ B cells in uveitis.

Mapping Research Trends and Hotspots in the Link between Alzheimer's Disease and Gut Microbes over the Past Decade: A Bibliometric Analysis

Alzheimer's disease (AD) is a globally prevalent neurodegenerative disorder, the underlying causes and mechanisms of which remain elusive. The emerging interest in the potential connection between gut microbes and AD prompted our study to investigate this field through bibliometric analysis. To examine research trends over the past decade, we collected relevant data using search terms associated with gut microbiota and AD from the Web of Science Core Collection. Our analysis involved various tools, including R (version 4.2.2), VOSviewer (version 1.6.18), CiteSpace software (version 6.2.R1), and an online bibliometric platform. Our findings identified a total of 1170 articles published between 2012 and 2022, indicating a consistent growth of research interest in this area. Notably, China significantly contributed with 40.7% (374) of the publications, signifying its prominent role in this field. Among the journals, the Journal of Alzheimer's Disease published the highest number of articles (57; 4.9%). In terms of author influence, Wang Y, with an H-index of 13, emerged as the most influential author. Additionally, Shanghai Jiaotong University was the most productive institution, accounting for 66 articles (5.6%). Through keyword analysis, we grouped high-frequency keywords into six clusters: gut microbiota, AD, neuroinflammation, gut-brain axis, oxidative stress, and chain fatty acids. Chain fatty acids, oxidative stress, and the gut-brain axis emerged as dominant research topics in the past five years. Recent studies have specifically focused on "nlrp3 inflammasome" and "clearance" (2020-2022), indicating shifting research interests within this field. This bibliometric analysis aims to provide insights into the evolving landscape of research on the gut microbiota and AD. Our results identify key research trends and themes while highlighting potential research gaps. The findings offer valuable perspectives for future investigations, advancing our understanding of AD and exploring potential therapeutic strategies.

Long noncoding RNA signatures in intrauterine infection/inflammation-induced lung injury: an integrative bioinformatics study

BACKGROUND

Intrauterine infection/inflammation can result in fetal and neonatal lung injury. However, the biological mechanisms of intrauterine infection/inflammation on fetal and neonatal lung injury and development are poorly known. To date, there are no reliable biomarkers for improving intrauterine infection/inflammation-induced lung injury.

METHODS

An animal model of intrauterine infection/inflammation-induced lung injury was established with pregnant Sprague-Dawley rats inoculated with Escherichia coli suspension. The intrauterine inflammatory status was assessed through the histological examination of the placenta and uterus. A serial of histological examinations of the fetal and neonatal rats lung tissues were performed. The fetal and neonatal rat lung tissues were harvested for next generation sequencing at embryonic day 17 and postnatal day 3, respectively. Differentially expressed mRNAs and lncRNAs were identified by conducting high-throughput sequencing technique. The target genes of identified differentially expressed lncRNAs were analyzed. Homology analyses for important differentially expressed lncRNAs were performed.

RESULTS

The histopathological results showed inflammatory infiltration, impaired alveolar vesicular structure, less alveolar numbers, and thickened alveolar septa in fetal and neonatal rat lung tissues. Transmission electron micrographs revealed inflammatory cellular swelling associated with diffuse alveolar damage and less surfactant-storing lamellar bodies in alveolar epithelial type II cells. As compared with the control group, there were 432 differentially expressed lncRNAs at embryonic day 17 and 125 differentially expressed lncRNAs at postnatal day 3 in the intrauterine infection group. The distribution, expression level, and function of these lncRNAs were shown in the rat genome. LncRNA TCONS_00009865, lncRNA TCONS_00030049, lncRNA TCONS_00081686, lncRNA TCONS_00091647, lncRNA TCONS_00175309, lncRNA TCONS_00255085, lncRNA TCONS_00277162, and lncRNA TCONS_00157962 may play an important role in intrauterine infection/inflammation-induced lung injury. Fifty homologous sequences in Homo sapiens were also identified.

CONCLUSIONS

This study provides genome-wide identification of novel lncRNAs which may serve as potential diagnostic biomarkers and therapeutic targets for intrauterine infection/inflammation-induced lung injury.

p120-Catenin suppresses NLRP3 inflammasome activation in macrophages

Inflammasome activation is of central importance for the process of generation of overwhelming inflammatory response and the pathogenesis of sepsis. The intrinsic molecular mechanism for controlling inflammasome activation is still poorly understood. Here we investigated the role of p120-catenin expression in macrophages in regulating nucleotide-binding oligomerization domain (NOD) and leucine-rich repeat (LRR)- and pyrin domain-containing proteins 3 (NLRP3) inflammasome activation. Depletion of p120-catenin in murine bone marrow-derived macrophages enhanced caspase-1 activation and secretion of active interleukin (IL)-1β in response to ATP stimulation following LPS priming. Coimmunoprecipitation analysis showed that p120-catenin deletion promoted NLRP3 inflammasome activation by accelerating the assembly of the inflammasome complex comprised of NLRP3, apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC), and pro-caspase-1. Depletion of p120-catenin also increased the production of mitochondrial reactive oxygen species. Pharmacological inhibition of mitochondrial reactive oxygen species nearly completely abolished NLRP3 inflammasome activation, caspase-1 activation, and the production of IL-1β in p120-catenin-depleted macrophages. Furthermore, p120-catenin ablation significantly disrupted mitochondrial function, evidenced by decreased mitochondrial membrane potential and lower production of intracellular ATP. In alveolar macrophage-depleted mice challenged with cecal ligation and puncture, pulmonary transplantation of p120-catenin-deficient macrophages dramatically enhanced the accumulation of IL-1β and IL-18 in bronchoalveolar lavage fluid. These results demonstrate that p120-catenin prevents NLRP3 inflammasome activation in macrophages by maintaining mitochondrial homeostasis and reducing the production of mitochondrial reactive oxygen species in response to endotoxin insult. Thus, inhibition of NLRP3 inflammasome activation by stabilization of p120-catenin expression in macrophages may be a novel strategy to prevent an uncontrolled inflammatory response in sepsis.

Determination of the Salmonella intracellular lifestyle by the diversified interaction of Type III secretion system effectors and host GTPases

Intracellular bacteria have developed sophisticated strategies to subvert the host endomembrane system to establish a stable replication niche. Small GTPases are critical players in regulating each step of membrane trafficking events, such as vesicle biogenesis, cargo transport, tethering, and fusion events. Salmonella is a widely studied facultative intracellular bacteria. Salmonella delivers several virulence proteins, termed effectors, to regulate GTPase dynamics and subvert host trafficking for their benefit. In this review, we summarize an updated and systematic understanding of the interactions between bacterial effectors and host GTPases in determining the intracellular lifestyle of Salmonella. This article is categorized under: Infectious Diseases > Molecular and Cellular Physiology.

ROS induced the Rab26 promoter hypermethylation to promote cigarette smoking-induced airway epithelial inflammation of COPD through activation of MAPK signaling

Cigarette smoking (CS) exposure-induced airway inflammatory responses drive the occurrence and development of emphysema and chronic obstructive pulmonary disease (COPD). However, its precise mechanisms have not been fully elucidated. In this study, we explore the role of Rab26 in CS exposure modulating the inflammatory response of airway epithelium and the novel mechanism of CS exposure regulation Rab26. These data showed that CS exposure and H₂O₂ (a type of ROS) suppressed the expression of Rab26 and increased the expression of DNMT3b in vivo and in vitro. GEO data analysis found the level of Rab26 was decreased in the lung tissue of COPD patients. CSE-induced ROS promoted DNA methylation of the Rab26 promoter and inhibited its promoter activity by elevating the DNMT3b level. Antioxidants N-Acetyl-l-cysteine (NAC), 5-Aza-2'-deoxycytidine (5-AZA) (DNA methylation inhibitor) and DNMT3B siRNA alleviated CSE's inhibitory effect on Rab26 expression in vitro. Importantly, NAC alleviated the improved expression of Rab26 and reduced DNMT3B expression, in the airway of smoking exposure as well as attenuated the inflammatory response in vivo. Overexpression of Rab26 attenuated CSE-induced production of inflammatory mediators through part inactivation of p38 and JNK MAPK. On the contrary, silencing Rab26 enhanced p38 and JNK activation and aggravated inflammatory response. These findings suggest that ROS-mediated Rab26 promoter hypermethylation is a critical step in cigarette smoking-induced airway epithelial inflammatory response. Restoring Rab26 in the airway epithelium might be a potential strategy for treating airway inflammation and COPD.

Autophagy induced by Rab1a-ULK1 interaction promotes porcine reproductive and respiratory syndrome virus replication

Porcine reproductive and respiratory syndrome virus (PRRSV), an arterivirus from the Nidovirales order, continues to be a threat to the swine industry worldwide causing reproductive failure and respiratory disease in pigs. Previous studies have demonstrated that autophagy plays a positive role in PRRSV replication. However, its mechanism is less clearly understood. Herein, we report first that the protein level of Rab1a, a member of the Ras superfamily of GTPases, is upregulated during PRRSV infection. Subsequently, we demonstrate that Rab1a enhances PRRSV replication through an autophagy pathway as evidenced by knocking down the autophagy-related 7 (ATG7) gene, the key adaptor of autophagy. Importantly, we reveal that Rab1a interacts with ULK1 and promotes ULK1 phosphorylation dependent on its GTP-binding activity. These data indicate that PRRSV utilizes the Rab1a-ULK1 complex to initiate autophagy, which, in turn, benefits viral replication. These findings further highlight the interplay between PRRSV replication and the autophagy pathway, deepening our understanding of PRRSV infection.

SGOL2 promotes prostate cancer progression by inhibiting RAB1A ubiquitination

Prostate cancer is the most prevalent genitourinary malignant cancer in men worldwide. Patients with prostate cancer who progress to castration-resistant prostate cancer (CRPC) or metastatic CRPC have significantly poorer survival. Advanced prostate cancer is a clinical challenge due to the lack of effective treatment strategies. In the field of oncology, SGOL2 was an emerging and differentially expressed molecule, which enhanced the proliferation of cell populations in vitro in our studies. Mass spectrum and Co-IP validated the interaction of SGOL2 and RAB1A in a protein-protein manner. We further investigated the role of SGOL2 in the regulatory mechanism of RAB1A in prostate cancer cell lines. Furthermore, SGOL2 regulated RAB1A expression by inhibiting its ubiquitination. Rescue Experiments demonstrated that SGOL2 promoted prostate cancer cell proliferation and migration by upregulating RAB1A expression. Finally, we found that SGOL2 and RAB1A may regulate the tumor microenvironment (TME) in prostate cancer. In conclusion, our findings concluded that SGOL2 stabilized RAB1A expression to promote prostate cancer development. Both of them were of great importance in TME modulation.

Targeted disruption of Rab1a causes early embryonic lethality

Guanosine nucleotide diphosphate (GDP) dissociation inhibitor 2 (GDI2) regulates the GDP/guanosine triphosphate (GTP) exchange reaction of Rab proteins by inhibiting the dissociation of GDP and the subsequent binding of GTP. The present study aimed to determine the function of Rab1a in vivo, and thus generated mice with a trapped Rab1a gene. It was demonstrated that Rab1a is essential for embryonic development. It was also found that one functional Rab1a allele was sufficient for development in a heterozygous murine embryo, whereas a double mutant led to embryonic lethality. The dissection of uteri on embryonic day (E)10.5‑14.5 yielded no homozygous embryos, indicating that homozygotes die between E10.5 to E11.5. The gene trap construct contains a β‑galactosidase/neomycin reporter gene, allowing for heterozygotes to be stained for β‑galactosidase to determine the tissue‑specific expression of Rab1a. Rab1a was found to be highly expressed in the small intestine of both adult mice and embryos, although its expression levels were low in the brains of embryos. Moreover, there was no significant change in cytokine production and survival in wild‑type and heterozygous Rab1a+/‑ mice following a challenge with lipopolysaccharide. On the whole, the present study demonstrates that the disruption of the Rab1a gene causes embryonic lethality and homozygotes die between E10.5 and E11.5, suggesting that Rab1a is essential for the early development of mouse embryos.

The surface coating of iron oxide nanoparticles drives their intracellular trafficking and degradation in endolysosomes differently depending on the cell type

Magnetic nanoparticles (MNPs) are potential theranostic tools that are biodegraded through different endocytic pathways. However, little is known about the endolysosomal network through which MNPs transit and the influence of the surface coating in this process. Here, we studied the intracellular transit of two MNPs with identical iron oxide core size but with two distinct coatings: 3-aminopropyl-trietoxysilane (APS) and dimercaptosuccinic acid (DMSA). Using endolysosomal markers and a high throughput analysis of the associated proteome, we tracked the MNPs intracellularly in two different mouse cell lines, RAW264.7 (macrophages) and Pan02 (tumor cells). We did not detect differences in the MNP trafficking kinetics nor in the MNP-containing endolysosome phenotype in Pan02 cells. Nonetheless, DMSA-MNPs transited at slower rate than APS-MNPs in macrophages as measured by MNP accumulation in Rab7⁺ endolysosomes. Macrophage DMSA-MNP-containing endolysosomes had a higher percentage of lytic enzymes and catalytic proteins than their APS-MNP counterparts, concomitantly with a V-type ATPase enrichment, suggesting an acidic nature. Consequently, more autophagic vesicles are induced by DMSA-MNPs in macrophages, enhancing the expression of iron metabolism-related genes and proteins. Therefore, unlike Pan02 cells, the MNP coating appears to influence the intracellular trafficking rate and the endolysosome nature in macrophages. These results highlight how the MNP coating can determine the nanoparticle intracellular fate and biodegradation in a cell-type bias.

Getting out of crises: Environmental, social-ecological and evolutionary research is needed to avoid future risks of pandemics

The implementation of One Health/EcoHealth/Planetary Health approaches has been identified as key (i) to address the strong interconnections between risk for pandemics, climate change and biodiversity loss and (ii) to develop and implement solutions to these interlinked crises. As a response to the multiple calls from scientists on that subject, we have here proposed seven long-term research questions regarding COVID-19 and emerging infectious diseases (EIDs) that are based on effective integration of environmental, ecological, evolutionary, and social sciences to better anticipate and mitigate EIDs. Research needs cover the social ecology of infectious disease agents, their evolution, the determinants of susceptibility of humans and animals to infections, and the human and ecological factors accelerating infectious disease emergence. For comprehensive investigation, they include the development of nature-based solutions to interlinked global planetary crises, addressing ethical and philosophical questions regarding the relationship of humans to nature and regarding transformative changes to safeguard the environment and human health. In support of this research, we propose the implementation of innovative multidisciplinary facilities embedded in social ecosystems locally: ecological health observatories and living laboratories. This work was carried out in the frame of the European Community project HERA (www.HERAresearchEU.eu), which aims to set priorities for an environment, climate and health research agenda in the European Union by adopting a systemic approach in the face of global environmental change.

Mechanism of Incisional Pain: Novel Finding on Long Noncoding RNA XIST/miR-340-5p/RAB1A Axis

The objective of this study is to investigate the effect of long noncoding RNA (lncRNA) XIST on postoperative pain and inflammation of plantar incision pain (PIP) in rats and its underlying mechanisms.

PIP rat models were established by plantar incision. Rats in the sham group were subjected to povidone-iodine scrubbing, and no incision was made. To explore the role of XIST/miR-340-5p/RAB1A in postoperative pain and inflammation, PIP rats were separately or simultaneously injected with lentivirus containing sh-NC, sh-XIST, mimic NC, miR-340-5p mimic, inhibitor NC, miR-340-5p inhibitor, pcDNA3.1, or pcDNA3.1-RAB1A through an intrathecal catheter. The paw withdrawal threshold (PWT) and paw withdrawal latency (PWL) values of rats in each group were assessed to evaluate the pain behavior. RT-qPCR and Western blot were utilized to determine the levels of XIST, miR-340-5p, RAB1A, and NF-κB pathway-related proteins (p-IκBα, IκBα, p-p65, and p65). The concentrations of inflammatory cytokines (TNF-α, IL-1β, and IL-6) in rat spinal dorsal horn tissues were inspected by ELISA. H and E staining was applied to observe the pathological changes of neurons in the spinal dorsal horn, TUNEL staining to detect neuronal apoptosis, and immunohistochemistry to measure RAB1A level.

Plantar incision surgery caused decreased PWT and PWL values, enhanced levels of XIST, RAB1A, and inflammatory cytokines, along with an increased proportion of apoptotic neurons. The pain sensitivity and inflammation of rats were motivated after plantar incision surgery. Intrathecal injection of sh-XIST or miR-340-5p mimic ameliorated the pain and inflammation of PIP rats, while silencing of miR-340-5p or overexpression of RAB1A partly reversed the effect of sh-XIST on PIP rats. XIST targeted miR-340-5p and miR-340-5p negatively regulated RAB1A. The XIST/miR-340-5p/RAB1A axis activated the NF-κB signaling pathway.

LncRNA XIST aggravates inflammatory response and postoperative pain of PIP rats by activating the NF-κB pathway via the miR-340-5p/RAB1A axis.

Surfactant protein A enhances the degradation of LPS-induced TLR4 in primary alveolar macrophages involving Rab7, β-arrestin2, and mTORC1

Respiratory infections by Gram-negative bacteria are a major cause of global morbidity and mortality. Alveolar macrophages (AMs) play a central role in maintaining lung immune homeostasis and host defense by sensing pathogens via pattern recognition receptors (PRR). The PRR Toll-like receptor (TLR) 4 is a key sensor of lipopolysaccharide (LPS) from Gram-negative bacteria. Pulmonary surfactant is the natural microenvironment of AMs. Surfactant protein A (SP-A), a multifunctional host defense collectin, controls LPS-induced pro-inflammatory immune responses at the organismal and cellular level via distinct mechanisms. We found that SP-A post-transcriptionally restricts LPS-induced TLR4 protein expression in primary AMs from healthy humans, rats, wild-type and SP-A^-/- mice by further decreasing cycloheximide-reduced TLR4 protein translation and enhances the co-localization of TLR4 with the late endosome/lysosome. Both effects as well as the SP-A-mediated inhibition of LPS-induced TNFα release are counteracted by pharmacological inhibition of the small GTPase Rab7. SP-A-enhanced Rab7 expression requires β-arrestin2 and, in β-arrestin2^-/- AMs and after intratracheal LPS challenge of β-arrestin2^-/- mice, SP-A fails to enhance TLR4/lysosome co-localization and degradation of LPS-induced TLR4. In SP-A^-/- mice, TLR4 levels are increased after pulmonary LPS challenge. SP-A-induced activation of mechanistic target of rapamycin complex 1 (mTORC1) kinase requires β-arrestin2 and is critically involved in degradation of LPS-induced TLR4. The data suggest that SP-A post-translationally limits LPS-induced TLR4 expression in primary AMs by lysosomal degradation comprising Rab7, β-arrestin2, and mTORC1. This study may indicate a potential role of SP-A-based therapeutic interventions in unrestricted TLR4-driven immune responses to lower respiratory tract infections caused by Gram-negative bacteria.

Activation of NLRP3 Inflammasome and Onset of Alzheimer's Disease

The nucleotide-binding domain leucine-rich repeat and pyrin domain containing receptor protein 3 (NLRP3) is an important pattern recognition receptor in human innate immunity. Activation of the NLRP3 inflammasome play a key role in the pathogenesis of Alzheimer’s disease (AD). Theories explaining activation of the NLRP3 inflammasome include the reactive oxygen species theory, the lysosomal damage theory and the mitochondrial DNA theory. The NLRP3 activation promotes occurrence of AD by producing IL-1β, IL-18 and other cytokines, and then by affecting the deposition of Aβ and tau proteins. Over-activated NLRP3 inflammasome often impair cell function and induces immune-related diseases. Some mechanisms have been found to negatively regulate activation of the NLRP3 inflammasome, which may be through receptor binding blocking mechanism, autophagy related mechanism, abnormal cytokine secretion mechanism, or interference related gene expression regulation mechanism. In this review, we summarize the possible mechanisms by which the activation of NLRP3 inflammasomes affects the pathogenesis of AD, and the recent advances in the prevention and treatment of AD by controlling the activation of NLRP3 inflammasomes. By researching the activation or inactivation of NLRP3 inflammasome, it is possible to reveal the pathogenesis of AD from a new perspective and provide a new idea for the prevention and treatment of AD.

Targeting Small GTPases and Their Prenylation in Diabetes Mellitus

A fundamental role of pancreatic β-cells to maintain proper blood glucose level is controlled by the Ras superfamily of small GTPases that undergo post-translational modifications, including prenylation. This covalent attachment with either a farnesyl or a geranylgeranyl group controls their localization, activity, and protein–protein interactions. Small GTPases are critical in maintaining glucose homeostasis acting in the pancreas and metabolically active tissues such as skeletal muscles, liver, or adipocytes. Hyperglycemia-induced upregulation of small GTPases suggests that inhibition of these pathways deserves to be considered as a potential therapeutic approach in treating T2D. This Perspective presents how inhibition of various points in the mevalonate pathway might affect protein prenylation and functioning of diabetes-affected tissues and contribute to chronic inflammation involved in diabetes mellitus (T2D) development. We also demonstrate the currently available molecular tools to decipher the mechanisms linking the mevalonate pathway’s enzymes and GTPases with diabetes.

Exosome-inflammasome crosstalk and their roles in inflammatory responses

Inflammasome is a complex of multiple proteins found in cytoplasm of the cells activated by infectious and/or non-infectious stimuli. This complex involves caspase-1 activation, leading to unconventional secretion of interleukin-1β (IL-1β) and IL-18 and inflammatory cascade. Exosome is the nanoscale membrane-bound extracellular vesicle that plays significant roles in intercellular communications by carrying bioactive molecules, e.g., proteins, RNAs, microRNAs (miRNAs), DNAs, from one cell to the others. In this review, we provide the update information on the crosstalk between exosome and inflammasome and their roles in inflammatory responses. The effects of inflammasome activation on exosomal secretion are summarized. On the other hand, the (dual) effects of exosomes on inhibiting and promoting inflammasome activation are discussed. Finally, perspectives on therapeutic roles of exosomes in human diseases and future direction of the research on exosome-inflammasome crosstalk are provided.

When Rab GTPases meet innate immune signaling pathways

Ras-related protein in brain (Rab) GTPases, the subfamily of small GTP-binding proteins superfamily, play a vital role in regulating and controlling vesicles' transport between different membrane-bound organelles. As the first-line defense against invading pathogens, the host's innate immune system recognizes various pathogen-associated molecular patterns through a series of membrane-bound or cytoplasmic pathogen recognition receptors to activate the downstream signaling pathway and induce the type I interferons (IFN-I). Numerous studies have demonstrated that Rab GTPases participate in innate immunity by regulating transmembrane signals' transduction and the transport, adhesion, anchoring, and fusion of vesicles. However, the underlying mechanism of Rab GTPases regulating innate immunity is not entirely understood. A comprehensive understanding of the interplay between the Rab GTPases and innate immunity will help develop novel therapeutics against microbial infections and chronic inflammations.

Nlrp3 Deficiency Alleviates Angiotensin II-Induced Cardiomyopathy by Inhibiting Mitochondrial Dysfunction

Inflammation has been considered a key component in the pathogenesis and progression of angiotensin II- (Ang II-) induced cardiac hypertrophy and related cardiomyopathy. As a vital mediator of inflammation, the role of the Nlrp3 inflammasome in Ang II-induced cardiomyopathy remains unclear. This study was aimed to determine whether Nlrp3 inflammasome activation and its downstream pathway were involved in Ang II-induced cardiomyopathy. We established an Ang II infusion model in both wild-type and Nlrp3-/- mice to determine the contribution of Nlrp3 to cardiac function. Cardiac fibrosis was determined by Masson's trichrome staining, real-time PCR, and TUNEL assay; cardiac function was assessed by echocardiography. Nlrp3 inflammasome activation and related downstream cytokines were measured by Western blotting and enzyme-linked immunosorbent assays; mitochondrial dysfunction was examined by transmission electron microscopy and real-time PCR. We found that Ang II-infused mice showed impaired cardiac function, as evidenced by increased cardiac fibrosis, apoptosis, inflammation, and left ventricular dysfunction. However, these alterations were significantly alleviated in the mice with Nlrp3 gene deletion. Moreover, Ang II-infused mice showed increased Nlrp3 inflammasome activity relative to that of the cytokines IL-1β and IL-18, increased reactive oxygen species, mitochondrial abnormalities, and decreased mtDNA copy number and ATP synthase activity. These molecular and pathological alterations were also attenuated in Nlrp3 deficient mice. In conclusion, Nlrp3 inflammasome-induced mitochondrial dysfunction is involved in Ang II-induced cardiomyopathy. Nlrp3 gene deletion attenuated mitochondrial abnormalities, cardiac inflammation, oxidative stress, and fibrosis and thus alleviated heart dysfunction and hypertrophy. Targeting the Nlrp3 inflammasome and/or mitochondria may be a therapeutic approach for Ang II-induced cardiac diseases.

MicroRNA-3613-5p Promotes Lung Adenocarcinoma Cell Proliferation through a RELA and AKT/MAPK Positive Feedback Loop

Aberrant activation of nuclear factor κB (NF-κB)/RELA is often found in lung adenocarcinoma (LUAD). In this study, we determined that microRNA-3613-5p (miR-3613-5p) plays a crucial role in RELA-mediated post-transcriptional regulation of LUAD cell proliferation. Expression of miR-3613-5p in clinical LUAD specimens is associated with poor prognosis in LUAD. Upregulation of miR-3613-5p promotes LUAD cell proliferation in vitro and in vivo. Our results suggested a mechanism whereby miR-3613-5p expression is induced by RELA through its direct interaction with JUN, thereby stimulating the AKT/mitogen-activated protein kinase (MAPK) pathway by directly targeting NR5A2. In addition, we also found that phosphorylation of AKT1 and MAPK3/1 co-transactivates RELA, thus constituting a RELA/JUN/miR-3613-5p/NR5A2/AKT1/MAPK3/1 positive feedback loop, leading to persistent NF-κB activation. Our findings also revealed that miR-3613-5p plays an oncogenic role in LUAD by promoting cell proliferation and acting as a key regulator of the positive feedback loop underlying the link between the NF-κB/RELA and AKT/MAPK pathways.

Pro-inflammatory role of NLRP3 inflammasome in experimental sterile corneal inflammation

We evaluated the role of NLR family pyrin domain containing 3 (NLRP3) inflammasome in sterile corneal inflammation caused by lipopolysaccharide (LPS) or alkali burns in C57BL6 mice or NLRP3 KO (Nlrp3^−/−) mice. Various molecules related to the NLRP3 inflammasome were upregulated in C57BL6 mice after both alkali burn injury and LPS treatment. After alkali burn injury, the corneal opacity grade was significantly reduced in Nlrp3^−/− mice compared with C57BL6 mice. In Nlrp3^−/− mice, Gr-1 immunoreactivity and MMP-9 mRNA expression in the corneal stroma were significantly reduced by both LPS treatment and alkali burn injury. Quantitative PCR and immunohistochemistry revealed that IL-1β and MMP-9 expression in the corneal stroma were down-regulated in Nlrp3^−/− mice with both alkali burn injury and LPS treatment. These findings suggest that the NLRP3 inflammasome has a pro-inflammatory effect in the cornea by recruiting neutrophils to sites of inflammation.