Caspase-8 Promotes Pulmonary Hypertension by Activating Macrophage-Associated Inflammation and IL-1ß (Interleukin 1ß) Production.

BACKGROUND: Macrophages are involved in the pathogenesis of pulmonary arterial hypertension (PAH). Caspase-8, an apical component of cell death pathways, is significantly upregulated in macrophages of PAH animal models. However, its role in PAH remains unclear. Caspase-8 plays a critical role in regulating inflammatory responses via inflammasome activation, cell death, and cytokine induction. This study investigated the mechanism of regulation of IL-1ß (interleukin 1ß) activation in macrophages by caspase-8. METHODS: A hypoxia + SU5416-induced PAH mouse model and monocrotaline-induced rat model of PAH were constructed and the role of caspase-8 was analyzed. RESULTS: Caspase-8 and cleaved-caspase-8 were significantly upregulated in the lung tissues of SU5416 and hypoxia-treated PAH mice and monocrotaline-treated rats. Pharmacological inhibition of caspase-8 alleviated PAH compared with wild-type mice, observed as a significant reduction in right ventricular systolic pressure, ratio of right ventricular wall to left ventricular wall plus ventricular septum, pulmonary vascular media thickness, and pulmonary vascular muscularization; caspase-8 ablated mice also showed significant remission. Mechanistically, increased proliferation of pulmonary arterial smooth muscle cellss is closely associated with activation of the NLRP3 (NOD [nucleotide oligomerization domain]-, LRR [leucine-rich repeat]-, and PYD [pyrin domain]-containing protein 3) inflammasome and the IL-1ß signaling pathway. Although caspase-8 did not affect extracellular matrix synthesis, it promoted inflammatory cell infiltration and pulmonary arterial smooth muscle cell proliferation via NLRP3/IL-1ß activation during the development stage of PAH. CONCLUSIONS: Taken together, our study suggests that macrophage-derived IL-1ß via caspase-8-dependent canonical inflammasome is required for macrophages to play a pathogenic role in pulmonary perivascular inflammation.

ABIN1 (Q478) is Required to Prevent Hematopoietic Deficiencies through Regulating Type I IFNs Expression.

A20-binding inhibitor of NF-κB activation (ABIN1) is a polyubiquitin-binding protein that regulates cell death and immune responses. Although Abin1 is located on chromosome 5q in the region commonly deleted in patients with 5q minus syndrome, the most distinct of the myelodysplastic syndromes (MDSs), the precise role of ABIN1 in MDSs remains unknown. In this study, mice with a mutation disrupting the polyubiquitin-binding site (Abin1Q478H/Q478H ) is generated. These mice develop MDS-like diseases characterized by anemia, thrombocytopenia, and megakaryocyte dysplasia. Extramedullary hematopoiesis and bone marrow failure are also observed in Abin1Q478H/Q478H mice. Although Abin1Q478H/Q478H cells are sensitive to RIPK1 kinase-RIPK3-MLKL-dependent necroptosis, only anemia and splenomegaly are alleviated by RIPK3 deficiency but not by MLKL deficiency or the RIPK1 kinase-dead mutation. This indicates that the necroptosis-independent function of RIPK3 is critical for anemia development in Abin1Q478H/Q478H mice. Notably, Abin1Q478H/Q478H mice exhibit higher levels of type I interferon (IFN-I) expression in bone marrow cells compared towild-type mice. Consistently, blocking type I IFN signaling through the co-deletion of Ifnar1 greatly ameliorated anemia, thrombocytopenia, and splenomegaly in Abin1Q478H/Q478H mice. Together, these results demonstrates that ABIN1(Q478) prevents the development of hematopoietic deficiencies by regulating type I IFN expression.

Therapeutic potential and protective role of GRK6 overexpression in pulmonary arterial hypertension.

Abnormal proliferation of pulmonary arterial smooth muscle cells (PASMCs) is a key mechanism in the development of pulmonary arterial hypertension (PAH). Signal transducer and activator of transcription 3 (STAT3) signalling plays a critical role in modulating PASMC proliferation, and G-protein-coupled receptor kinase 6 (GRK6) regulates the STAT3 pathway. However, the mechanism underlying the relationship between GRK6 and PAH remains unclear. In this study, we aimed to investigate the role of GRK6 in PAH and determine its potential as a therapeutic target. We utilised hypoxia- and SU5416-induced PAH mouse models and a monocrotaline-induced PAH rat model to analyse the involvement of GRK6. We conducted gain- and loss-of-function experiments using mouse PASMCs. Modulation of GRK6 expression was achieved via a lentiviral vector in vitro and an adeno-associated virus serotype 1 encoding GRK6 in vivo. GRK6 was significantly downregulated in the lung tissues of PAH mice and rats, predominantly in PASMCs. Knockout of GRK6 exacerbated PAH, while both therapeutic and prophylactic overexpression of GRK6 alleviated PAH, as evidenced by a reduction in right ventricular systolic pressure, right ventricular wall to left ventricular wall plus ventricular septum ratio, pulmonary vascular media thickness, and pulmonary vascular muscularisation. Mechanistically, GRK6 overexpression attenuated hypoxia-induced PASMC proliferation and STAT3 phosphorylation. Conversely, knockdown of GRK6 promoted hypoxia-induced proliferation, which was mitigated by a STAT3 inhibitor. Our findings highlight the potential protective and beneficial roles of GRK6 in PAH; we propose a lung-targeted GRK6 gene therapy utilizing adeno-associated virus serotype 1 as a potential treatment approach for patients with PAH.

Environmental eustress improves postinfarction cardiac repair via enhancing cardiac macrophage survival.

Macrophages play a vital role in cardiac repair following myocardial infarction (MI). An enriched environment (EE) is involved in the regulation of macrophage-related activities and disease progression; however, whether EE affects the phenotype and function of macrophages to improve postinfarction cardiac repair remains unknown. In this study, we found that EE improved cardiac function, decreased mortality, and ameliorated adverse ventricular remodeling in mice after MI, with these outcomes closely related to the increased survival of Ly6Clow macrophages and their CCR2-MHCIIlow subsets. EE increased the expression of brain-derived neurotrophic factor (BDNF) in the hypothalamus, leading to higher circulating levels of BDNF, which, in turn, regulated the cardiac macrophages. BDNF bound to tropomyosin receptor kinase B to activate downstream ERK1/2 and AKT pathways, promoting macrophage survival. These findings demonstrate that EE optimizes postinfarction cardiac repair and highlights the significance of EE as a previously unidentified strategy for impeding adverse ventricular remodeling.

Ubiquitin-binding domain in ABIN1 is critical for regulating cell death and inflammation during development.

ABIN1 is a polyubiquitin-binding protein known to regulate NF-κB activation and cell death signaling. Mutations in Abin1 can cause severe immune diseases in human, such as psoriasis, systemic lupus erythematosus, and systemic sclerosis. Here, we generated mice that disrupted the ubiquitin-binding domain of ABIN1 (Abin1UBD/UBD) died during later embryogenesis owing to TNFR1-mediated cell death, similar to Abin1-/- mice. Abin1UBD/UBD cells were rendered sensitive to TNF-α-induced apoptosis and necroptosis as the inhibition of ABIN1UBD and A20 recruitment to the TNF-RSC complex leads to attenuated RIPK1 deubiquitination. Accordingly, the embryonic lethality of Abin1UBD/UBD mice was rescued via crossing with RIPK1 kinase-dead mice (Ripk1K45A/K45A) or the co-deletion of Ripk3 and one allele of Fadd, but not by the loss of Ripk3 or Mlkl alone. Unexpectedly, Abin1UBD/UBD mice with the co-deletion of Ripk3 and both Fadd alleles died at E14.5. This death was caused by spontaneous RIPK1 ubiquitination-dependent multiple inflammatory cytokines over production and could be rescued by the co-deletion of Ripk1 or Tnfr1 combined with Ifnar. Collectively, these data demonstrate the importance of the ABIN1 UBD domain, which mediates the ABIN1-A20 axis, at limiting RIPK1 activation-dependent cell death during embryonic development. Furthermore, our findings reveal a previously unappreciated ubiquitin pathway that regulates RIPK1 ubiquitination by FADD/Casp8 to suppress spontaneous IKKε/TBK1 activation.

Tregs-derived interleukin 35 attenuates endothelial proliferation through STAT1 in pulmonary hypertension.

BACKGROUND: To explore the source, the role and the specific mechanism of IL-35 and its downstream molecules in the development of pulmonary hypertension. METHODS: 8-10 weeks male mice were undergoing hypoxia combined with SU5416 (HySu) to establish a pulmonary hypertension (PH) model. The phenotype of PH mice was measured by immunohistochemistry and immunofluorescence staining. The levels of two subunits (EBI3 and p35 subunits) in lung tissue were measured by real-time PCR and western blotting. EBI3 monoclonal antibody was administrated as IL-35 neutralization to offset systemic IL-35 expression. Fludarabine, an inhibitor of STAT1 (signal transducer and activator of transcription 1) was used to clarify the role of STAT1 under IL-35 treatment. RESULTS: After pulmonary hypertension, the expression of IL-35 and its two subunits (EBI3 and p35 subunits) in lung tissue were significantly increased. And the two subunits of IL-35 are highly expressed in Treg cells. Compared with the controlled PH mice, the IL-35 neutralization PH mice showed aggravated pulmonary hypertension phenotype. The specific manifestations are the increase of right ventricular systolic pressure (RVSP), the growing proportion of right heart [RV/(LV+S)], and the remodeling of pulmonary blood vessels increases. The expression of pulmonary vascular endothelium (CD31) in PH mice increased, and the proliferation ability of vascular endothelium enhanced after IL-35 was inhibited. IL-35 phosphorylates STAT1 through the receptor GP130 on pulmonary vascular endothelial cells, which in turn inhibits endothelial cell proliferation. IL-35 recombinant protein can reduce the expression of CD31 in lung tissues of PH mice. But the administration of STAT1 inhibitor made it invalid from the IL-35 effect of reversing pulmonary hypertension. CONCLUSIONS: Tregs-derived IL-35 can reverse the remodeling of pulmonary blood vessels and alleviate the progression of pulmonary hypertension by reducing the proliferation of endothelial cells.

Impact of Long-Term Home Quarantine on Mental Health and Physical Activity of People in Shanghai During the COVID-19 Pandemic.

This study aimed to investigate the effects of long-term home quarantine on the mental health of people during the COVID-19 epidemic in Shanghai. We conducted an online questionnaire survey on March 26 2020 and collected data on demographics, level of physical activity (PA), and mental health status of the participants. We assessed the mental health status using the Patient Health Questionnaire (PHQ-9) and Generalized Anxiety Disorder Scale (GAD-7), whereas PA was assessed using International Physical Activity Questionnaire Short Form (IPAQ-SF). Of all 2,409 valid samples, participants reported performing a total of 2015.20 metabolic equivalent of task (MET)-minutes/week of total PA before the outbreak period and 1720.29 MET-minutes/week of total PA during the outbreak period (p < 0.001). Participants who spent a longer time at home reported to have a better performance on the PHQ-9 (p = 0.087) and GAD-7 (p < 0.001). A high level of PA was considered an protective factor against depression (OR = 0.755, 95% CI 0.603-0.944, p < 0.001). Additionally, a high level of PA had a preventative effect on anxiety (OR = 0.741, 95% CI 0.568-0.967, p < 0.001), and a longer working period during the outbreak was shown to be a risk factor for anxiety (11-29 days, OR 1.455, 95% CI 1.110-1.909; 30-60 days OR 1.619, 95% CI 1.227-2.316). Home confinement during the pandemic might not have a negative effect on mental health provided that people engage in more PA indoors. This study encourages interventions for mental health problems through physical exercise.