Fundamental drivers of auto-immunity in metabolic diseases – the role of LC3 associated phagocytosis after regulated cell death

To our current understanding, type 1 diabetes mellitus (T1DM) is driven by autoimmunity and is characterized by T cell-mediated destruction of β-cells within the pancreas. It has been proposed that accumulation of necrotic cellular debris leads to chronic inflammation and autoimmunity if macrophages cannot properly remove this debris. According to the concept of necroinflammation, various forms of regulated cell death (RCD) are immunogenic to a different extent. Recently, it has been demonstrated that necrotic debris can drive autoimmunity in mice that are deficient in LC3-associated phagocytosis (LAP). It is however unclear which pathway of regulated necrosis might drive this phenotype. The only known protein that clearly distinguishes LAP from autophagy was named rubicon. Rubiconᴷᴼ mice are deficient for LAP. Therefore, in this project, we will investigate the contribution of two forms of regulated necrosis (necroptosis and pyroptosis) in the pathophysiological course of the LAP-deficient model of autoimmunity.

We generated mice that are double-deficient for LAP and pyroptosis or LAP and necroptosis. We aim to assess the autoimmune phenotype of these mice by observing them over a period of 52 weeks alongside with regular blood collections and weight measurements. We will monitor autoantibodies (ds-DNA antibodies, anti-nuclear antibodies (ANAs)) and cytokine levels (IL-1β, IL-18, MCP-1, IL-10, IP-10, IL-33, IL-6, MIP1β) as well as signs of diabetes (serum glucose) and chronic kidney disease (serum urea and serum creatinine). Aftewards, the mice will be sacrificed and dissected to perform histological analyses (PAS-staining of the kidneys, H&E staining of the pancreas).

Addiotionally, we are investigating the role of LAP during acute kidney injury (AKI). Necroptosis and pyroptosis have been implied to play a role in development of AKI, but the role of LAP has not been evaluated so far. AKI will be induced by injection of the chemotherapeutic agent cisplatin inducing toxic cell death in the kidney or by ischemia-perfusion injury (IRI), induced by bilateral clamping of the renal pedicles. The IRI model is often interpreted to mimick renal transplantation, but similar pathophysiological disease patterns have been observed in patients with septic and other causes of pre-renal AKI.

In conclusion, LAP is thought to contribute to the prevention of excessive immune responses after RCD.

Publications:

Precondition your donor pig for your successful allograft!  A. Schnieke, S. Locke, A. Linkermann. Am J Transplant. 2020;20:3275-3276.

Dysfunction of the key ferroptosis-surveilling systems hypersensitizes mice to tubular necrosis during acute kidney injury.  W. Tonnus, C. Meyer, C. Steinebach, A. Belavgeni, A. von Mässenhausen, N.Z. Gonzalez, F. Maremonti, F. Gembardt, N. Himmerkus, M. Latk, S. Locke, J. Marschner, W. Li, S. Short, S. DollS, I. Ingold, B. Proneth, C. Daniel, N. Kabgani, R. Kramann, S. Motika, P.J. Hergenrother, S.R. Bornstein, C. Hugo, J.U. Becker, K. Amann, H.J. Anders, D. Kreisel, D. Pratt, M. Gütschow, M. Conrad, A. Linkermann. Nat Commun. 2021;12(1):4402.