Thoracic adipose tissue contributes to severe virus infection of the lung.

OBJECTIVE: Obesity is an independent risk factor for severe influenza virus and COVID-19 infections. There might be an interplay between adipose tissue and respiratory pathogens, although the mechanism is unknown. Proinflammatory factors secreted by the adipose tissue are often discussed to serve as indirect contributor to virus infection. However, the direct potential of adipose tissue to serve as a viral niche has not yet been investigated. METHODS: Two murine obesity models (DIO and ob/ob) were infected with influenza A virus (IAV) and monitored for 3 weeks. p.i. Lung and adipose tissue were harvested, and the viral load was analysed. Direct replication of IAV in vitro was investigated in human derived primary adipocytes and macrophages. The indirect impact of the secretory products of adipocytes during infection was analysed in a co-culture system with lung fibroblasts. Moreover, lung and adipose tissue was harvested from deceased patients infected with SARS-CoV-2 omicron variant. Additionally, replication of SARS-CoV-2 alpha, delta, and omicron variants was investigated in vitro in adipocytes and macrophages. RESULTS: Both murine obesity models presented high IAV titers compared to non-obese mice. Interestingly, adipose tissue adjacent to the lungs was a focal point for influenza virus replication in mice. We further detected IAV replication and antiviral response in human adipocytes. Co-cultivation of adipocytes and lung fibroblasts led to increased IL-8 concentration during infection. Though we observed SARS-CoV-2 in the thoracic adipose tissue of COVID-19 patients, no active replication was found in adipocytes in vitro. However, SARS-CoV-2 was detected in the macrophages and this finding was associated with increased inflammation. CONCLUSIONS: Our study revealed that thoracic adipose tissue contributes to respiratory virus infection. Besides indirect induction of proinflammatory factors during infection, adipocytes and macrophages within the tissue can directly support viral replication.

SARS-CoV-2 and its ORF3a, E and M viroporins activate inflammasome in human macrophages and induce of IL-1α in pulmonary epithelial and endothelial cells.

Inflammasome assembly is a potent mechanism responsible for the host protection against pathogens, including viruses. When compromised, it can allow viral replication, while when disrupted, it can perpetuate pathological responses by IL-1 signaling and pyroptotic cell death. SARS-CoV-2 infection was shown to activate inflammasome in the lungs of COVID-19 patients, however, potential mechanisms responsible for this response are not fully elucidated. In this study, we investigated the effects of ORF3a, E and M SARS-CoV-2 viroporins in the inflammasome activation in major populations of alveolar sentinel cells: macrophages, epithelial and endothelial cells. We demonstrated that each viroporin is capable of activation of the inflammasome in macrophages to trigger pyroptosis-like cell death and IL-1α release from epithelial and endothelial cells. Small molecule NLRP3 inflammasome inhibitors reduced IL-1 release but weakly affected the pyroptosis. Importantly, we discovered that while SARS-CoV-2 could not infect the pulmonary microvascular endothelial cells it induced IL-1α and IL-33 release. Together, these findings highlight the essential role of macrophages as the major inflammasome-activating cell population in the lungs and point to endothelial cell expressed IL-1α as a potential novel component driving the pulmonary immunothromobosis in COVID-19.

Influenza Virus-Induced Paracrine Cellular Senescence of the Lung Contributes to Enhanced Viral Load.

Aging is a major risk factor associated with increased morbidity and mortality rates observed during respiratory infections. In this study, we investigated the role of influenza virus infections in the establishment of premature cellular senescence and paracrine macrophage-activated inflammation. We observed in our murine model a premature aging by the appearance of senescent cells in the lungs after 21 d of influenza A virus infection. By using murine ex vivo lung models, the influence of TNF-α on the establishment of cellular senescence was detectable. Our findings were proven by using conditioned media of infected human monocyte-derived macrophages on primary lung fibroblasts. Here, a distinct expression of senescence-associated parameters could be confirmed. Furthermore, senescent cells in the lungs strongly influenced subsequent viral infections. Our data demonstrated a higher viral load in senescent primary lung fibroblasts, indicating an intracellular effect on viral replication. Transcriptomic data revealed an increased regulation of JAK/STAT signaling in senescent IAV-infected cells accompanied with increased TRAIL expression. Additionally, senescent cells indicating low pH values, accelerating viral replication. Our study provides new insights into pathomechanisms of virus-induced cellular senescence. Hence, IAV infection induces premature senescence and subsequent infections in senescent cells lead to an increased viral replication.

Respiratory Infections in the Aging Lung: Implications for Diagnosis, Therapy, and Prevention.

Respiratory infections pose a significant health problem among elderly individuals, particularly during the COVID-19 pandemic. The increased mortality and morbidity rates among individuals over 65 highlight the criticality of these infections. The normal aging process in the lungs increases vulnerability to respiratory infections due to the accumulation of cellular damage and senescence. Consequently, the lung environment undergoes major changes in mechanical function and other systemic factors. This review aims to examine the influence of aging on respiratory infections from a clinical perspective by analyzing clinical studies. Additionally, the review will emphasize potential prevention and diagnostic developments to enhance therapy options available for elderly patients over 65 years of age.

Uncovering a unique pathogenic mechanism of SARS-CoV-2 omicron variant: selective induction of cellular senescence.

BACKGROUND: SARS-CoV-2 variants are constantly emerging with a variety of changes in the conformation of the spike protein, resulting in alterations of virus entry mechanisms. Solely omicron variants use the endosomal clathrin-mediated entry. Here, we investigate the influence of defined altered spike formations to study their impact on premature cellular senescence. METHODS: In our study, in vitro infections of SARS-CoV-2 variants delta (B.1.617.2) and omicron (B.1.1.529) were analyzed by using human primary small alveolar epithelial cells and human ex vivo lung slices. We confirmed cellular senescence in human lungs of COVID-19 patients. Hence, global gene expression patterns of infected human primary alveolar epithelial cells were identified via mRNA sequencing. RESULTS: Solely omicron variants of SARS-CoV-2 influenced the expression of cell cycle genes, highlighted by an increased p21 expression in human primary lung cells and human ex vivo lungs. Additionally, an upregulated senescence-associated secretory phenotype (SASP) was detected. Transcriptomic data indicate an increased gene expression of p16, and p38 in omicron-infected lung cells. CONCLUSIONS: Significant changes due to different SARS-CoV-2 infections in human primary alveolar epithelial cells with an overall impact on premature aging could be identified. A substantially different cellular response with an upregulation of cell cycle, inflammation- and integrin-associated pathways in omicron infected cells indicates premature cellular senescence.

Look at the Audience? A Randomized Controlled Study of Shifting Attention From Self-Focus to Nonsocial vs. Social External Stimuli During Virtual Reality Exposure to Public Speaking in Social Anxiety.

Background: Enhanced self-focused attention plays a central role in the maintenance and treatment of Social Anxiety and is targeted in contemporary cognitive behavioral therapy. Actual developments use Virtual Reality (VR) for behavioral training. However, no VR attention training combining exposure to public speaking with shifting attention from self-focus to external focus has been investigated, and no experimental evidence exists on different kinds of external cues as targets of attention. Therefore, we investigated the effects of an attention training during public speaking in VR and examined differential effects of an external focus on nonsocial vs. social stimuli. Methods: In this randomized controlled study, highly socially anxious participants were instructed to focus on either objects or the audience within a virtual speech task. We assessed the pre-post effects on affective reactions, self-perception, and attentional processes during public speaking as well as general Social Anxiety using subjective, physiological, and eye-tracking measures. Repeated-measures analyses of variance (ANOVAs) were calculated to detect changes from pretest to posttest over both groups, and time × group interaction effects. Results: Within the analysis sample (n = 41), anxiety during public speaking and fear of negative evaluation significantly decreased, with no significant differences between groups. No significant time effect, but a significant time × group effect, was found for the looking time proportion on the audience members' heads. Follow-up tests confirmed a significant increase in the social-focus group and a significant decrease in the nonsocial-focus group. For all other variables, except external focus and fear of public speaking, significant improvements were found over both groups. Further significant time x group effects were found for positive affect during public speaking, with a significant increase in the social focus, and no significant change in the nonsocial-focus group. Conclusion: Our findings suggest that attention training to reduce self-focus can be successfully conducted in VR. Both training versions showed positive short-term effects in the highly socially anxious, with particular advantages of an external social focus concerning eye contact to the audience and positive affect. Further research should investigate whether social focus is even more advantageous long term and if reinterpretations of dysfunctional beliefs could be achieved by not avoiding social cues.