Stress-induced pseudokinase TRB3 augments IL1ß signaling by interacting with Flightless homolog 1.

Interleukin-1ß is one of the most potent inducers of beta cell inflammation in the lead-up to type 1 diabetes. We have previously reported that IL1ß-stimulated pancreatic islets from mice with genetic ablation of stress-induced pseudokinase TRB3(TRB3KO) show attenuated activation kinetics for the MAP3K MLK3 and JNK stress kinases. However, JNK signaling constitutes only a portion of the cytokine-induced inflammatory response. Here we report that TRB3KO islets also show a decrease in amplitude and duration of IL1ß-induced phosphorylation of TAK1 and IKK, kinases that drive the potent NF-κB proinflammatory signaling pathway. We observed that TRB3KO islets display decreased cytokine-induced beta cell death, preceded by a decrease in select downstream NF-κB targets, including iNOS/NOS2 (inducible nitric oxide synthase), a mediator of beta cell dysfunction and death. Thus, loss of TRB3 attenuates both pathways required for a cytokine-inducible, proapoptotic response in beta cells. In order to better understand the molecular basis of TRB3-enhanced, post-receptor IL1ß signaling, we interrogated the TRB3 interactome using coimmunoprecipitation followed by mass spectrometry to identify immunomodulatory protein Flightless homolog 1 (Fli1) as a novel, TRB3-interacting protein. We show that TRB3 binds and disrupts Fli1-dependent sequestration of MyD88, thereby increasing availability of this most proximal adaptor required for IL1ß receptor-dependent signaling. Fli1 sequesters MyD88 in a multiprotein complex resulting in a brake on the assembly of downstream signaling complexes. By interacting with Fli1, we propose that TRB3 lifts the brake on IL1ß signaling to augment the proinflammatory response in beta cells.

The Impact of Sociodemographic Variables on Functional Recovery following Lower Extremity Amputation.

BACKGROUND: We hypothesize that sociodemographic variables, particularly disadvantaged financial environments, impact both rate of prosthetic utilization and the achievement of ambulation post major amputation. METHODS: All cases in the Vascular Quality Initiative amputation module were queried between April 2013 and January 2024. Inclusion was limited to patients who underwent below knee, through knee, and above knee amputation. Two primary outcomes were investigated: Nonambulatory status after amputation (minimum of 120 days follow-up); and, not having obtained a prosthetic limb (minimum of 90 days follow-up). The ambulation status and prosthetic status analyses had 6,984 and 6,793 patients meet inclusion, respectively. Multivariable binary logistic regression analysis was performed utilizing variables which achieved univariable significance (P < 0.05) for the outcomes. RESULTS: Mean follow-up for those meeting inclusion was 432 days. Among all patients meeting inclusion, 46.7% of patients did not acquire a prosthetic limb and 44.1% were nonambulatory. Sociodemographic factors with significant multivariable association for the outcome of no prosthetic limb acquisition in follow-up were as follows: advancing age (adjusted odds ratio [aOR] 1.011/year (1.006-1.016), P < 0.001); female sex (aOR 1.43 (1.28-1.61), P < 0.001); top 20% area deprivation index representing highest deprivation (aOR 1.24 (1.09-1.41) P = 0.001); race (P = 0.002) insurance status (P = 0.028) with protective status for commercial insurance (39% rate of no prosthetic) and non-US insurance (33%) versus Medicare (51%), Medicaid (48%), Veterans Affairs insurance (49%), Self-pay (42%), and Medicare Advantage (51%). There were numerous comorbidities which also had association with lack of prosthetic limb acquisition. Sociodemographic variables which achieved multivariable significance (P < 0.05) for the outcome of nonambulatory status after major amputation were as follows: female sex (aOR 1.37 (1.23-1.54), P < 0.001); Medicare insurance (P = 0.016); advancing age (aOR 1.009/year (1.004-1.014), P < 0.001); congestive heart failure (aOR 1.15 (1.02-1.31), P = 0.028); and, not living at home in follow-up (aOR (3.53 (2.99-4.17) P < 0.001). Physical therapy at any point after surgery (aOR 0.742 (0.662-0.832), P < 0.001) and commercial insurance (aOR 0.839 (0.737-0.956), P = 0.008) were protective. There were numerous comorbidities which also had association with nonambulatory status in follow-up. CONCLUSIONS: Living within the most financially disadvantaged areas and race both have a significant independent association with lack of prosthetic limb acquisition following major amputation. Black, Native American, and Pacific Islander demographic patients experience lack of acquisition at a higher rate than White and Asian patients independent of comorbidities and socioeconomic covariables. Female patients obtain a prosthetic limb and ambulate less frequently than males after major amputation, largely due to a higher rate of above knee amputation. Comorbidities and not socioeconomic variables are the leading drivers of nonambulation.

Deletion of ferroportin in murine myeloid cells increases iron accumulation and stimulates osteoclastogenesis in vitro and in vivo.

Osteoporosis, osteopenia, and pathological bone fractures are frequent complications of iron-overload conditions such as hereditary hemochromatosis, thalassemia, and sickle cell disease. Moreover, animal models of iron overload have revealed increased bone resorption and decreased bone formation. Although systemic iron overload affects multiple organs and tissues, leading to significant changes on bone modeling and remodeling, the cell autonomous effects of excessive iron on bone cells remain unknown. Here, to elucidate the role of cellular iron homeostasis in osteoclasts, we generated two mouse strains in which solute carrier family 40 member 1 (Slc40a1), a gene encoding ferroportin (FPN), the sole iron exporter in mammalian cells, was specifically deleted in myeloid osteoclast precursors or mature cells. The FPN deletion mildly increased iron levels in both precursor and mature osteoclasts, and its loss in precursors, but not in mature cells, increased osteoclastogenesis and decreased bone mass in vivo Of note, these phenotypes were more pronounced in female than in male mice. In vitro studies revealed that the elevated intracellular iron promoted macrophage proliferation and amplified expression of nuclear factor of activated T cells 1 (Nfatc1) and PPARG coactivator 1ß (Pgc-1ß), two transcription factors critical for osteoclast differentiation. However, the iron excess did not affect osteoclast survival. While increased iron stimulated global mitochondrial metabolism in osteoclast precursors, it had little influence on mitochondrial mass and reactive oxygen species production. These results indicate that FPN-regulated intracellular iron levels are critical for mitochondrial metabolism, osteoclastogenesis, and skeletal homeostasis in mice.

Loss of C/EBPδ Exacerbates Radiation-Induced Cognitive Decline in Aged Mice due to Impaired Oxidative Stress Response.

Aging is characterized by increased inflammation and deterioration of the cellular stress responses such as the oxidant/antioxidant equilibrium, DNA damage repair fidelity, and telomeric attrition. All these factors contribute to the increased radiation sensitivity in the elderly as shown by epidemiological studies of the Japanese atomic bomb survivors. There is a global increase in the aging population, who may be at increased risk of exposure to ionizing radiation (IR) as part of cancer therapy or accidental exposure. Therefore, it is critical to delineate the factors that exacerbate age-related radiation sensitivity and neurocognitive decline. The transcription factor CCAAT enhancer binding protein delta (C/EBPδ) is implicated with regulatory roles in neuroinflammation, learning, and memory, however its role in IR-induced neurocognitive decline and aging is not known. The purpose of this study was to delineate the role of C/EBPδ in IR-induced neurocognitive decline in aged mice. We report that aged Cebpd-/- mice exposed to acute IR exposure display impairment in short-term memory and spatial memory that correlated with significant alterations in the morphology of neurons in the dentate gyrus (DG) and CA1 apical and basal regions. There were no significant changes in the expression of inflammatory markers. However, the expression of superoxide dismutase 2 (SOD2) and catalase (CAT) were altered post-IR in the hippocampus of aged Cebpd-/- mice. These results suggest that Cebpd may protect from IR-induced neurocognitive dysfunction by suppressing oxidative stress in aged mice.