Search

Failures of self-control during conflicts between long-term goals and immediate desires are a key characteristic of many harmful behaviours, including unhealthy eating habits, lack of exercise and problematic substance use, which often have adverse personal consequences and incur great societal costs. The project aims to elucidate neurocognitive mechanisms mediating deficient self-control, both in daily self-control failures and in substance use disorders and behavioural addictions, which are characterized by a loss of control despite awareness of adverse consequences. We launched a prospective cohort study using a multi-level approach that combines (i) a comprehensive clinical assessment, (ii) behavioural task batteries assessing cognitive control and decision-making functions, (iii) task-related and resting state fMRI, and (iv) smartphone-based ecological momentary assessment of daily self-control failures. From a representative community sample, we recruited three groups of participants (n = 338; age 19 – 27 years) with (a) symptoms of non-substance related (n=118) and (b) substance-related addictive disorders (n=100) and (c) syndrome-free controls (n=120. Participants are invited to yearly clinical follow-up assessments and further multi-level assessments 3 and 6 years after initial recruitment. Results obtained so far (until 09/2021) provide converging evidence that task performance as well as brain activity in monitoring, control, and valuation networks is reliably associated with the propensity to commit real-life self-control failures. Results support a process model, according to which deficient performance-monitoring leads to an insufficient recruitment of control networks, which attenuates the impact of long-term goals on neural value signals and increases the likelihood of self-control failures. In the final funding period (until 06/2024), we will extend the clinical follow-up period to 7 years. In addition, we will assess stress markers as possible moderators of self-control. With our cross-lagged panel design we expect the project to make a substantial contribution to the central unresolved question whether dysfunctions of cognitive control are causally involved in the development and trajectories of self-control failures and addictive behaviours, as well as to the disputed question of communalities and differences between different addictive disorders. Thereby, we hope to contribute to mechanism-based models of self-control impairments as a foundation for improved prevention and therapy.

Please note that this is a detailed description of a part of the hypotheses from the project ‘Volitional Dysfunction in Self-control Failures and Addictive Behaviours’, which you can find on OSF at https://osf.io/rhjb4. As we have various hypotheses with complex operationalisations in this project, we planned to present separate analysis plans for each hypothesis. The separate analysis plans are and will be added to the main OSF project and numbered according to the hypotheses under section ‘4 Hypotheses’ in the main document ‘OSF Registration C1_23.09.21’.

Salmonella enterica serovar Typhimurium (S. Typhimurium) is a Gram-negative bacterium that induces cell death of macrophages as a key virulence strategy. We have previously demonstrated that the induction of macrophage death is dependent on the host’s type I IFN (IFN-I) response. IFN-I signaling has been shown to induce tripartite motif (TRIM) 21, an E3 ubiquitin ligase with critical functions in autoimmune disease and antiviral immunity. However, the importance and regulation of TRIM21 during bacterial infection remains poorly understood. In this study, we investigated the role of TRIM21 upon S. Typhimurium infection of murine bone marrow–derived macrophages. Although Trim21 expression was induced in an IFN-I–dependent manner, we found that TRIM21 levels were mainly regulated posttranscriptionally. Following TLR4 activation, TRIM21 was transiently degraded via the lysosomal pathway by chaperone-mediated autophagy (CMA). However, S. Typhimurium–induced mTORC2 signaling led to phosphorylation of Akt at S473, which subsequently impaired TRIM21 degradation by attenuating CMA. Elevated TRIM21 levels promoted macrophage death associated with reduced transcription of NF erythroid 2–related factor 2 (NRF2)–dependent antioxidative genes. Collectively, our results identify IFN-I–inducible TRIM21 as a negative regulator of innate immune responses to S. Typhimurium and a previously unrecognized substrate of CMA. To our knowledge, this is the first study reporting that a member of the TRIM family is degraded by the lysosomal pathway.

Type I interferon (IFN-I) triggers necroptosis in macrophages infected with S. Typhimurium by an unclear mechanism. Hos et al. now demonstrate that RIP3 enhances the interaction of Nrf2 with Pgam5 in response to IFN-I signaling in S. Typhimurium–infected macrophages, which abates Nrf2-dependent cytoprotective pathways and increases cell death., Salmonella enterica serovar Typhimurium exploits the host’s type I interferon (IFN-I) response to induce receptor-interacting protein (RIP) kinase–mediated necroptosis in macrophages. However, the events that drive necroptosis execution downstream of IFN-I and RIP signaling remain elusive. In this study, we demonstrate that S. Typhimurium infection causes IFN-I–mediated up-regulation of the mitochondrial phosphatase Pgam5 through RIP3. Pgam5 subsequently interacts with Nrf2, which sequesters Nrf2 in the cytosol, thereby repressing the transcription of Nrf2-dependent antioxidative genes. The impaired ability to respond to S. Typhimurium–induced oxidative stress results in reactive oxygen species–mediated mitochondrial damage, energy depletion, transient induction of autophagy, and autophagic degradation of p62. Reduced p62 levels impair interaction of p62 with Keap1, which further decreases Nrf2 function and antioxidative responses to S. Typhimurium infection, eventually leading to cell death. Collectively, we identify impaired Nrf2-dependent redox homeostasis as an important mechanism that promotes cell death downstream of IFN-I and RIP3 signaling in S. Typhimurium–infected macrophages.

Bacterial capsular polysaccharides are virulence factors and are considered T cell–independent antigens. However, the capsular polysaccharide Sp1 from Streptococcus pneumoniae serotype 1 has been shown to activate CD4+ T cells in a major histocompatibility complex (MHC) class II–dependent manner. The mechanism of carbohydrate presentation to CD4+ T cells is unknown. We show in live murine dendritic cells (DCs) that Sp1 translocates from lysosomal compartments to the plasma membrane in MHCII-positive tubules. Sp1 cell surface presentation results in reduction of self-peptide presentation without alteration of the MHCII self peptide repertoire. In DM-deficient mice, retrograde transport of Sp1/MHCII complexes resulting in T cell–dependent immune responses to the polysaccharide in vitro and in vivo is significantly reduced. The results demonstrate the capacity of a bacterial capsular polysaccharide antigen to use DC tubules as a vehicle for its transport as an MHCII/saccharide complex to the cell surface for the induction of T cell activation. Furthermore, retrograde transport requires the functional role of DM in self peptide–carbohydrate exchange. These observations open new opportunities for the design of vaccines against microbial encapsulated pathogens., Author Summary Microorganisms are comprised of proteins, carbohydrates, lipids, and nucleic acids. Current immunologic paradigms state that activation of T lymphocytes required for humoral and cellular immune responses resulting in immunologic memory to the pathogens is solely brought about by proteinaceous antigens, processed and degraded to small peptides, loaded onto major histocompatibility complex (MHC) molecules, and transported as MHC/peptide complexes to the cell surface, where the MHC/peptide complex is recognized by the T cell antigen receptor. The findings of the present study elucidate the mechanism of MHC class II (MHCII)–dependent presentation of the bacterial capsular polysaccharide of Streptococcus pneumoniae serotype 1 (Sp1) that results in effective T cell activation. Sp1 is transported in MHCII-positive tubules from lysosomal compartments to the plasma membrane for presentation. In the absence of the DM molecule, known as an editor and catalyst of self and foreign peptide exchange, retrograde transport of carbohydrate/MHCII complexes resulting in dendritic cell engagement with T cells in vitro and T cell–dependent immune responses to the polysaccharide in vivo fail. The results suggest a fundamental shift in the immunologic paradigm, offering previously unrecognized opportunities for the design of new classes of vaccines against infectious diseases.