Gasdermin D mediates host cell death but not interleukin-1ß secretion in Mycobacterium tuberculosis-infected macrophages.

Necrotic cell death represents a major pathogenic mechanism of Mycobacterium tuberculosis (Mtb) infection. It is increasingly evident that Mtb induces several types of regulated necrosis but how these are interconnected and linked to the release of pro-inflammatory cytokines remains unknown. Exploiting a clinical cohort of tuberculosis patients, we show here that the number and size of necrotic lesions correlates with IL-1ß plasma levels as a strong indicator of inflammasome activation. Our mechanistic studies reveal that Mtb triggers mitochondrial permeability transition (mPT) and subsequently extensive macrophage necrosis, which requires activation of the NLRP3 inflammasome. NLRP3-driven mitochondrial damage is dependent on proteolytic activation of the pore-forming effector protein gasdermin D (GSDMD), which links two distinct cell death machineries. Intriguingly, GSDMD, but not the membranolytic mycobacterial ESX-1 secretion system, is dispensable for IL-1ß secretion from Mtb-infected macrophages. Thus, our study dissects a novel mechanism of pathogen-induced regulated necrosis by identifying mitochondria as central regulatory hubs capable of delineating cytokine secretion and lytic cell death.

Long-lived macrophage reprogramming drives spike protein-mediated inflammasome activation in COVID-19.

Innate immunity triggers responsible for viral control or hyperinflammation in COVID-19 are largely unknown. Here we show that the SARS-CoV-2 spike protein (S-protein) primes inflammasome formation and release of mature interleukin-1ß (IL-1ß) in macrophages derived from COVID-19 patients but not in macrophages from healthy SARS-CoV-2 naïve individuals. Furthermore, longitudinal analyses reveal robust S-protein-driven inflammasome activation in macrophages isolated from convalescent COVID-19 patients, which correlates with distinct epigenetic and gene expression signatures suggesting innate immune memory after recovery from COVID-19. Importantly, we show that S-protein-driven IL-1ß secretion from patient-derived macrophages requires non-specific monocyte pre-activation in vivo to trigger NLRP3-inflammasome signaling. Our findings reveal that SARS-CoV-2 infection causes profound and long-lived reprogramming of macrophages resulting in augmented immunogenicity of the SARS-CoV-2 S-protein, a major vaccine antigen and potent driver of adaptive and innate immune signaling.

Chemical p38 MAP kinase inhibition constrains tissue inflammation and improves antibiotic activity in Mycobacterium tuberculosis-infected mice.

Host-modulating therapies have become an important focus in the development of novel concepts for improved management of tuberculosis (TB). Previous in vitro studies revealed that the p38 MAP kinase signaling pathway coordinates several inflammatory and stress responses in Mycobacterium tuberculosis (Mtb)-infected host cells. Here we extend these findings and show that in vivo treatment of Mtb-infected C57BL/6 mice with doramapimod, a p38 MAP-kinase inhibitor, results in reduced inflammation, granuloma formation and lung pathology. Moreover, doramapimod, together with standard antibiotic treatment, significantly reduced lung and spleen mycobacterial loads compared to antibiotic treatment alone. Our in vivo data suggest the opportunity to repurpose p38 MAPK inhibitors for adjunct host directed therapies. We also provide first data on safety of p38 MAPK inhibition which is of relevance for future application of these substances in inflammatory diseases and concomitant TB.

The Expanding Role of p38 Mitogen-Activated Protein Kinase in Programmed Host Cell Death.

The p38 mitogen-activated protein kinase (MAPK) is involved in a multitude of essential cellular processes. The kinase is activated in response to environmental stresses, including bacterial infections and inflammation, to regulate the immune response of the host. However, recent studies have demonstrated that pathogens can manipulate p38 MAPK signaling for their own benefit to either prevent or induce host cell apoptosis. In addition, there is evidence demonstrating that p38 MAPK is a potent trigger of pathogen-induced necrosis driven by mitochondrial membrane disruption. Given the large number of p38 MAPK inhibitors that have been tested in clinical trials, these findings provide an opportunity to repurpose these drugs for improved control of infectious diseases.

Corticosteroids inhibit Mycobacterium tuberculosis-induced necrotic host cell death by abrogating mitochondrial membrane permeability transition.

Corticosteroids are host-directed drugs with proven beneficial effect on survival of tuberculosis (TB) patients, but their precise mechanisms of action in this disease remain largely unknown. Here we show that corticosteroids such as dexamethasone inhibit necrotic cell death of cells infected with Mycobacterium tuberculosis (Mtb) by facilitating mitogen-activated protein kinase phosphatase 1 (MKP-1)-dependent dephosphorylation of p38 MAPK. Characterization of infected mixed lineage kinase domain-like (MLKL) and tumor necrosis factor receptor 1 (TNFR1) knockout cells show that the underlying mechanism is independent from TNFα-signaling and necroptosis. Our results link corticosteroid function and p38 MAPK inhibition to abrogation of necrotic cell death mediated by mitochondrial membrane permeability transition, and open new avenues for research on novel host-directed therapies (HDT).

Intestinal helminth infection drives carcinogenesis in colitis-associated colon cancer.

Inflammatory bowel diseases (IBD) are chronic inflammatory disorders of the gastrointestinal tract, strongly associated with an increased risk of colorectal cancer development. Parasitic infections caused by helminths have been shown to modulate the host's immune response by releasing immunomodulatory molecules and inducing regulatory T cells (Tregs). This immunosuppressive state provoked in the host has been considered as a novel and promising approach to treat IBD patients and alleviate acute intestinal inflammation. On the contrary, specific parasite infections are well known to be directly linked to carcinogenesis. Whether a helminth infection interferes with the development of colitis-associated colon cancer (CAC) is not yet known. In the present study, we demonstrate that the treatment of mice with the intestinal helminth Heligmosomoides polygyrus at the onset of tumor progression in a mouse model of CAC does not alter tumor growth and distribution. In contrast, H. polygyrus infection in the early inflammatory phase of CAC strengthens the inflammatory response and significantly boosts tumor development. Here, H. polygyrus infection was accompanied by long-lasting alterations in the colonic immune cell compartment, with reduced frequencies of colonic CD8+ effector T cells. Moreover, H. polygyrus infection in the course of dextran sulfate sodium (DSS) mediated colitis significantly exacerbates intestinal inflammation by amplifying the release of colonic IL-6 and CXCL1. Thus, our findings indicate that the therapeutic application of helminths during CAC might have tumor-promoting effects and therefore should be well-considered.

Clinical prognosticators of survival in patients with urothelial carcinoma of the bladder and lymph node metastases after cystectomy with curative intent.

INTRODUCTION: Patients with lymph node-positive urothelial carcinoma of the bladder generally have a poor prognosis. Nevertheless, long-term survival in up to 30% of patients is reported. In the absence of established prognostic molecular markers, an assessment of the prognosis with clinical parameters is mandatory. PATIENTS AND METHODS: All patients from one high-volume center with a curatively intended cystectomy for lymph node-positive urothelial carcinoma were evaluated. Patients' overall and cancer-specific survival were correlated with clinicopathological parameters. Pathological lymph node staging was performed with both the 2002 and 2010 TNM classification of the AJCC. RESULTS: Lack of a perioperative chemotherapy (p < 0.001), higher numbers of positive nodes (p = 0.002), a higher lymph node density (p = 0.003), a higher pathological T stage (p = 0.006) and urinary diversion with an ileal conduit compared to an ileal neobladder (p = 0.023) were prognostic of a shorter overall survival while the number of removed lymph nodes showed no significant association with survival. Both with the 2002 and 2010 TNM classifications patients staged pN1 had a longer overall survival and time to cancer-specific death in comparison to patients with more extensive lymph node disease. According to the 2002 classification, there was a significant survival difference between patients with lymph node metastases in regional and distant lymph nodes. DISCUSSION: Patients with a low lymph node density and an early pT stage present with the best prognosis among LN positive patients. The value of perioperative chemotherapy is emphasized. Which lymph node metastases are to be considered regional or distant remains a matter of debate.

Antitumor T cell responses in bladder cancer are directed against a limited set of antigens and are modulated by regulatory T cells and routine treatment approaches.

Regulatory T cells (Tregs) play a key role in cancer immune escape. We identified target antigens of spontaneous tumor-specific T cell responses in urothelial carcinoma (UC) and evaluated their modulation by treatment and Treg. We determined Treg target antigens in UC. Fifty-six UC and 13 control patients were prospectively enrolled. Blood was drawn before and after routine treatment. Changes in Treg frequency were measured by fluorescence cytometry and the T effector cell (Teff) response against a set of nine tumor-associated antigens (TAAs) was monitored with an interferon-gamma ELISpot. Antigen specificity of Treg was determined by their increased capacity to inhibit after TAA-specific activation the proliferation of an autologous T cell population. The highest difference in the overall response rate for the total T cell population was observed for epidermal growth factor receptor (EGFR) (UC: 23% and controls: 0%). After depleting Treg, also new york esophageal (NYES)O1 (19 and 0%) and MUC20 (27 and 0%) were more frequently recognized in UC patients. In metastasized patients, the TAA-directed T cell response was augmented by Treg depletion. Tumor resection seemed to diminish Treg suppression of TAA-specific immunity, whereas chemotherapy had no effect. We demonstrated the existence of TAA-specific Treg in UC, which share antigen specificities with Teff. The coexistence of TAA-specific Treg and Teff was very rare. Treg frequencies in the peripheral blood were not changed by therapy. In summary, we identified potentially immunologically relevant TAA in UC. TAA-specific T cell responses against these antigens are suppressed by Treg. We identified TAA-specific Treg in UC patients, which do not cooccur with TAA-specific Teff.