The conventional supposition made by scientists is that in cases of type 1 diabetes (T1D), the pancreatic beta cells take a back seat to the assault by immune cells. Researchers suggest that upon cell aging, certain beta cells may end up supporting the immune system’s destruction pathways. Researchers are exploring the hypothesis that type 1 diabetes may potentially be prevented by removing old beta cells with small-molecule inhibitors. Studies in aging beta cells in type 1 diabetic research models and non-obese diabetic mice suggested that aged beta cells secretory phenotype may have a correlation with aging. Beta cells that are becoming old may increase their Bcl-2 levels, and senolytic compounds cause them to die off. In this case, beta cell mass may be preserved, and diabetes may be prevented by clearing out senescent beta cells.
When pancreatic beta cells gradually die off, a condition known as type 1 diabetes (T1D) may become primed for development. This autoimmune disorder is characterized by its targeting of particular organs and inducing hyperglycemia. Eliminating beta cells by the immune system appears to be the driving force behind the illness, although it is still unknown if they have a role in the pathogenesis. One study indicates that a fraction of beta cells may develop a senescence-associated secretory phenotype (SASP) as type 1 diabetes progresses in the non-obese diabetic (NOD) mice model observed. Exposing NOD mice with Bcl-2 inhibitors appeared to have selectively removed senescent beta cells without affecting the quantity of the immune cell types implicated in the illness. This was purportedly achieved by reducing the upregulation of the pro-survival mediator Bcl-2. Importantly, preventing diabetes may be as simple as removing old beta cells and ending immune-mediated cell death. Research suggests that aging beta cells contribute significantly to type 1 diabetes pathogenesis and suggests that removing these cells might be a novel way to mitigate or prevent the disease.
Preliminary research has suggested that beta cell UPR activation occurs before overt type 1 diabetes symptoms. The standard model for spontaneous autoimmune diabetes, the non-obese diabetic (NOD) mouse model, which mimics most of the characteristics of type 1 diabetes, may be reversed by inhibitors of the terminal UPR, which preserves beta cell mass. Infiltrating lymphocytes expose beta cells to several inflammatory cytokines in addition to endoplasmic reticulum (ER) stress. There is mixed data concerning the method by which these variables cause stress responses and apoptotic pathways in living organisms. However, it is believed to occur. Although apoptosis is considered to be the primary response to terminal UPR, the kind and length of the stress and the beta cell’s competence may determine whether the cell produces a protective or destructive stress response. The results of beta cell stress responses in type 1 and type 2 diabetes are being examined more closely in light of recent research speculating that intrinsic beta cell fragility is a hallmark of both types of diabetes.
Researchers present that a subset of beta cells in the NOD mouse model and T1D experiences stress-induced senescence and SASP. These aged beta cells’ secretory phenotype displayed non-cell-autonomous behaviors such as inducing paracrine senescence and stimulating monocyte chemotaxis, typical of SASP from other cell types. They employed senolytic substances, which may selectively cause apoptosis in senescent cells, to take advantage of the dependency on Bcl-2 overexpression that they found to be the pro-survival strategy of senescent beta cells. This subgroup of cells may have contributed to the course of illness since the elimination of senescent beta cells from NOD mice provided substantial protection against diabetes. The remarkable thing is that the main lymphoid and myeloid populations invading the islets, spleen, and pancreatic lymph nodes appeared to be unaffected by senolytic exposure. This might mean that the immune cells were unaffected by the ablation of senescent beta cells in these tests. The results indicate that SASP is a harmful process in type 1 diabetes and that removing old beta cells may specifically impede the illness.
FOXO4-DRI and Fibrosis
This investigation aimed to examine the potential of FOXO4-DRI on a mouse model of bleomycin (BLM)-induced PF. FOXO4-DRI has been hypothesized to reduce senescent cells, suppress the senescence-associated secretory phenotype (SASP) expression, and reduce the morphological alterations and collagen deposition caused by BLM. In a mouse model of bleomycin-induced pulmonary fibrosis (BLM-PF), FOXO4-DRI also appeared to be able to raise the proportion of fibroblasts and type 2 alveolar epithelial cells (AEC2) while lowering the proportion of myofibroblasts.
When tested in vitro, FOXO4‐DRI was theorized as more likely to destroy TGF‐β‐induced myofibroblasts than mouse lung fibroblast cell lines. Research suggests that in BLM-induced PF, the downregulation of the extracellular matrix (ECM) receptor interaction pathway occurred because the inhibitory impact of FOXO4-DRI on myofibroblast was blocked. The most important thing is that FOXO4-DRI has been speculated to improve BLM-induced PF in mice, which might help PF.
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References
[i] Thompson, Peter J., et al. “Targeted Elimination of Senescent Beta Cells Prevents Type 1 Diabetes.” Cell Metabolism, vol. 29, no. 5, May 2019, pp. 1045-1060.e10, https://www.cell.com/cell-metabolism/pdfExtended/S1550-4131(19)30021-X, 10.1016/j.cmet.2019.01.021.
[ii] Culley, Miranda K., and Stephen Y. Chan. “Endothelial Senescence: A New Age in Pulmonary Hypertension.” Circulation Research, vol. 130, no. 6, 18 Mar. 2022, pp. 928–941, pubmed.ncbi.nlm.nih.gov/35298304/, 10.1161/CIRCRESAHA.121.319815.
[iii] Han, Xiaodan, et al. “FOXO4 Peptide Targets Myofibroblast Ameliorates Bleomycin‐Induced Pulmonary Fibrosis in Mice through ECM‐Receptor Interaction Pathway.” Journal of Cellular and Molecular Medicine, vol. 26, no. 11, 5 May 2022, pp. 3269–3280, 10.1111/jcmm.17333.
[iv] Tan, Huishi, et al. “Ageing, Cellular Senescence and Chronic Kidney Disease: Experimental Evidence.” Current Opinion in Nephrology & Hypertension, vol. 31, no. 3, 9 Feb. 2022, pp. 235–243, 10.1097/mnh.0000000000000782.
[v] Calissi G, Lam EW, Link W. Therapeutic strategies targeting FOXO transcription factors. Nat Rev Drug Discov. 2021 Jan;20(1):21-38. doi: 10.1038/s41573-020-0088-2. Epub 2020 Nov 10. PMID: 33173189.
