Deficiency of FHL2 attenuates airway inflammation in mice and genetic variation associates with human bronchial hyper-responsiveness

FHL2 regulates microglia M1/M2 polarization after spinal cord injury via PARP14-depended STAT1/6 pathway

Neuronal apoptosis and inflammation exacerbate the secondary injury after spinal cord injury (SCI). Four and a half domains 2 (FHL2) is a multifunctional scaffold protein with tissue- and cell-type specific effects on the regulation of inflammation, but its role in SCI remains unclear. The T10 mouse spinal cord contusion model was established, and the mice were immediately injected with lentiviruses carrying FHL2 shRNA after SCI. The results showed that FHL2 expression was increased following SCI, and then gradually decreased. Moreover, FHL2 depletion aggravated functional impairment, neuronal necrosis, and enlarged lesion cavity areas in the injured spinal cord. FHL2 deficiency facilitated neuronal apoptosis by elevating cleaved caspase 3/9 expression, neuroinflammation by regulating microglia polarization, and bone loss. Indeed, FHL2 deficiency increased the secretion of TNF-α and IL-6, M1 microglia polarization, and the activation of STAT1 pathway but decreased the secretion of IL-10 and IL-4, M2 microglia polarization, and the activation of the STAT6 pathway in the spinal cord. In vitro, FHL2 silencing promoted LPS + IFN-γ-induced microglia M1 polarization through activating the STAT1 pathway and alleviated IL-4-induced microglia M2 polarization via inhibiting the STAT6 pathway. FHL2 positively regulated the expression of poly (ADP-ribose) polymerase family member 14 (PARP14) by promoting its transcription. PARP14 overexpression inhibited FHL2 silencing-induced microglia M1 polarization and relieved the inhibitory effect of FHL2 silencing on microglia M2 polarization. Collectively, the study suggests that FHL2 reduces the microglia M1/M2 polarization-mediated inflammation via PARP14-dependent STAT1/6 pathway and thereby improves functional recovery after SCI.

The protective effect of solidagenone from Solidago chilensis Meyen in a mouse model of airway inflammation

Solidagenone is the main active constituent present in Solidago chilensis Meyen which is used in folk medicine to treat pain and inflammatory diseases. This study aimed to evaluate the anti-inflammatory activity of solidagenone in vitro and in a model of allergic airway inflammation. In vitro studies were performed in activated macrophages and lymphocytes. BALB/c mice were sensitized and challenged with ovalbumin and treated with solidagenone orally (30 or 90 mg/kg body weight) or dexamethasone, as a positive control in our in vivo analysis. Supernatant concentrations of nitrite, TNF and IL-1β, as well as gene expression of pro-inflammatory mediators in macrophages cultures, were reduced after solidagenone treatment, without affecting macrophages viability. Besides, solidagenone significantly decreased T cell proliferation and secretion of IFNγ and IL-2. Th2 cytokine concentrations and inflammatory cell counts, especially eosinophils, in bronchoalveolar lavage fluid were reduced in mice treated with solidagenone. Histopathological evaluation of lung tissue was performed, and morphometrical analyses demonstrated reduction of cellular infiltration and mucus hypersecretion. Altogether, solidagenone presented anti-inflammatory activity in vitro and in vivo in the OVA-induced airway inflammation model, suggesting its promising pharmacological use as an anti-inflammatory agent for allergic hypersensitivity.

How (Epi)Genetic Regulation of the LIM-Domain Protein FHL2 Impacts Multifactorial Disease

Susceptibility to complex pathological conditions such as obesity, type 2 diabetes and cardiovascular disease is highly variable among individuals and arises from specific changes in gene expression in combination with external factors. The regulation of gene expression is determined by genetic variation (SNPs) and epigenetic marks that are influenced by environmental factors. Aging is a major risk factor for many multifactorial diseases and is increasingly associated with changes in DNA methylation, leading to differences in gene expression. Four and a half LIM domains 2 (FHL2) is a key regulator of intracellular signal transduction pathways and the FHL2 gene is consistently found as one of the top hyper-methylated genes upon aging. Remarkably, FHL2 expression increases with methylation. This was demonstrated in relevant metabolic tissues: white adipose tissue, pancreatic β-cells, and skeletal muscle. In this review, we provide an overview of the current knowledge on regulation of FHL2 by genetic variation and epigenetic DNA modification, and the potential consequences for age-related complex multifactorial diseases.

The molecular and epigenetic mechanisms of innate lymphoid cell (ILC) memory and its relevance for asthma

Repetitive exposure of Rag1^−/− mice to the Alternaria allergen extract generated a form of memory that elicited an asthma-like response upon a subthreshold recall challenge 3–15 wk later. This memory was associated with lung ICOS⁺ST2⁺ ILC2s. Genetic, pharmacologic, and antibody-mediated inhibition and adoptive transfer established an essential role for ILC2s in memory-driven asthma. ATAC-seq demonstrated a distinct epigenetic landscape of memory ILC2s and identified Bach2 and AP1 (JunD and Fosl2) motifs as major drivers of altered gene accessibility. scRNA-seq, gene knockout, and signaling studies suggest that repetitive allergenic stress induces a gene repression program involving Nr4a2, Zeb1, Bach2, and JunD and a preparedness program involving Fhl2, FosB, Stat6, Srebf2, and MPP7 in memory ILC2s. A mutually regulated balance between these two programs establishes and maintains memory. The preparedness program (e.g., Fhl2) can be activated with a subthreshold cognate stimulation, which down-regulates repressors and activates effector pathways to elicit the memory-driven phenotype.

Mycobacterium tuberculosis-Specific Antigen Rv3619c Effectively Alleviates Allergic Asthma in Mice

Despite significant advances, asthma remains a cause of premature death, and current treatments are suboptimal. Antigen-specific Th2 cells and their cytokines are primary mediators of the pathophysiological changes seen in asthma. Studies in animal models have shown that mycobacteria can suppress the asthma phenotype by alteration of the Th1/Th2 cytokines ratio. In this study, utilizing a Th1 delivery system to modulate the allergic airway inflammation in a Th2-driven model of asthma, we evaluated the efficacy of immunization with Mycobacterium tuberculosis-specific antigen Rv3619c, either alone or in combination with low dose dexamethasone. The rv3619c gene was cloned in an expression plasmid pGES-TH-1, expressed in Escherichia coli, and the recombinant protein Rv3619c was purified to homogeneity using affinity chromatography. Mice were immunized with the recombinant protein emulsified in Freund's Incomplete Adjuvant (IFA) alone and in combination with low dose dexamethasone, and then challenged with ovalbumin (OVA). Airway inflammation was assessed by quantifying airway cytology, histological changes and Th2 cytokine (IL-5) secretion from splenocytes. OVA-specific IgE, IgG and IgG1 from sera was assessed, as well as pERK1/2 expression in the lung tissue. Immunization with recombinant Rv3619c alone inhibited the OVA-induced increase in total cell counts, eosinophil airway cell infiltration in BAL fluid, perivascular and peribronchial inflammation and fibrosis, and goblet cell hyper/metaplasia. In addition, Rv3619c/IFA inhibited the OVA-induced IL-5 in spleen cells, OVA-specific IgE, IgG, and IgG1 levels in sera, and pERK1/2 expression in lung tissue. Immunization with Rv3619c/IFA in combination with low dose dexamethasone resulted in an enhanced effect on some but not all the asthma features. Taken together, this study demonstrates that immunization with Rv3619c/IFA, alone or in combination with dexamethasone, may be an effective treatment strategy for the prevention of asthma.

Recent developments and highlights in allergic rhinitis

Allergic rhinitis (AR) is a disease with high prevalence all over the world and therefore needs to be thoroughly investigated and treated accordingly. The mechanisms underlying the pathology and treatment of AR have been widely studied, but many aspects remain unclear and warrant further investigations. This review presents an overview of recently published papers highlighting the risk factors, mechanisms, and treatment of AR. Additionally, recent studies discussing the role of single nucleotide polymorphism, DNA methylation, regulatory B cells, group 2 innate lymphoid cells, immunotherapy, and biologics in AR are also covered.

The role of FHL2 in wound healing and inflammation

The 4-and-a-half LIM domain protein 2 (FHL2) is a multifunctional adaptor protein that can interact with cell surface receptors, cytosolic adaptor and structural proteins, kinases, and nuclear transcription factors. It is involved in numerous functional activities, including the epithelial-mesenchymal transition, cell proliferation, apoptosis, adhesion, migration, structural stability, and gene expression. Despite this, FHL2-knockout (KO) mice are viable and fertile with no obvious abnormalities, rather suggesting a high capacity for fine-tuning adjustment and functional redundancy of FHL2. Indeed, challenging FHL2-KO cells or mice provided numerous evidences for the great functional significance of FHL2. In recent years, several reviews have been published describing the high capacity of FHL2 to bind diverse proteins as well as the versatile functions of FHL2, emphasizing in particular its role in cardiovascular diseases and carcinogenesis. Here, we view the function of FHL2 from a different perspective. We summarize the published data demonstrating the impact of FHL2 on wound healing and inflammation. FHL2 seems to be involved in numerous steps of these extremely complex and multidirectional but tightly regulated tissue remodeling processes, supporting tissue repair and coordinating inflammation. Deficiency of FHL2 not only slows down ongoing wound healing but also often turns it into a chronic condition.-Wixler, V. The role of FHL2 in wound healing and inflammation.

B Cell Presentation of Chlamydia Antigen Selects Out Protective CD4γ13 T Cells: Implications for Genital Tract Tissue-Resident Memory Lymphocyte Clusters

Surveillance and defense of the enormous mucosal interface with the nonsterile world are critical to protecting the host from a wide range of pathogens. Chlamydia trachomatis is an intracellular bacterial pathogen that replicates almost exclusively in the epithelium of the reproductive tract. The fallopian tubes and vagina are poorly suited to surveillance and defense, with limited immune infrastructure positioned near the epithelium. However, a dynamic process during clearing primary infections leaves behind new lymphoid clusters immediately beneath the epithelium. These memory lymphocyte clusters (MLCs) harboring tissue-resident memory (Trm) T cells are presumed to play an important role in protection from subsequent infections. Histologically, human Chlamydia MLCs have prominent B cell populations. We investigated the status of genital tract B cells during C. muridarum infections and the nature of T cells recovered from immune mice using immune B cells as antigen-presenting cells (APCs). These studies revealed a genital tract plasma B cell population and a novel genital tract CD4 T cell subset producing both gamma interferon (IFN-γ) and interleukin-13 (IL-13). A panel of CD4 T cell clones and microarray analysis showed that the molecular fingerprint of CD4γ13 T cells includes a Trm-like transcriptome. Adoptive transfer of a Chlamydia-specific CD4γ13 T cell clone completely prevented oviduct immunopathology without accelerating bacterial clearance. Existence of a CD4γ13 T cell subset provides a plausible explanation for the observation that human peripheral blood mononuclear cell (PBMC) Chlamydia-specific IFN-γ and IL-13 responses predict resistance to reinfection.

FHL2 Regulates Natural Killer Cell Development and Activation during Streptococcus pneumoniae Infection

Recent in silico studies suggested that the transcription cofactor LIM-only protein FHL2 is a major transcriptional regulator of mouse natural killer (NK) cells. However, the expression and role of FHL2 in NK cell biology are unknown. Here, we confirm that FHL2 is expressed in both mouse and human NK cells. Using FHL2^−/− mice, we found that FHL2 controls NK cell development in the bone marrow and maturation in peripheral organs. To evaluate the importance of FHL2 in NK cell activation, FHL2^−/− mice were infected with Streptococcus pneumoniae. FHL2^−/− mice are highly susceptible to this infection. The activation of lung NK cells is altered in FHL2^−/− mice, leading to decreased IFNγ production and a loss of control of bacterial burden. Collectively, our data reveal that FHL2 is a new transcription cofactor implicated in NK cell development and activation during pulmonary bacterial infection.