RESUMO
BACKGROUND & AIMS: Early life adversity is considered a risk factor for the development of gastrointestinal diseases, including inflammatory bowel disease. We hypothesized that early life colonic inflammation causes susceptibility to aggravated overexpression of interleukin (IL)1ß. METHODS: We developed a 2-hit rat model in which neonatal inflammation (NI) and adult inflammation (AI) were induced by trinitrobenzene sulfonic acid. RESULTS: Aggravated immune responses were observed in NI + AI rats, including a sustained up-regulation of IL1ß and other cytokines. In parallel with exacerbated loss of inhibitor of kappa B alpha expression, NI + AI rats showed hyperacetylation of histone H4K12 and increased V-Rel Avian Reticuloendotheliosis Viral Oncogene Homolog A binding on the IL1B promoter, accompanied by high levels of norepinephrine/epinephrine. Propranolol, a ß-blocker, markedly ameliorated the inflammatory response and IL1ß overexpression by mitigating against epigenetic modifications. Adrenalectomy abrogated NI-induced disease susceptibility whereas yohimbine sensitized the epithelium for exacerbated immune response. The macrophages of NI rats produced more IL1ß than controls after exposure to lipopolysaccharide (LPS), suggesting hypersensitization; incubation with LPS plus Foradil (Sigma, St. Louis, MO), a ß2-agonist, induced a greater IL1ß expression than LPS alone. Epinephrine and Foradil also exacerbated LPS-induced IL1ß activation in human THP-1-derived macrophages, by increasing acetylated H4K12, and these increases were abrogated by propranolol. CONCLUSIONS: NI sensitizes the colon epithelium for exacerbated IL1ß activation by increasing stress hormones that induce histone hyperacetylation, allowing greater access of nuclear factor-κB to the IL1B promoter and rendering the host susceptible to aggravated immune responses. Our findings suggest that ß blockers have a therapeutic potential for inflammatory bowel disease susceptibility and establish a novel paradigm whereby NI induces epigenetic susceptibility to inflammatory bowel disease.
RESUMO
Glucocorticoids (GC) are a frontline therapy for numerous acute and chronic diseases because of their demonstrated efficacy at reducing systemic inflammation. An unintended side effect of GC therapy is the stimulation of skeletal muscle atrophy. Pathophysiological mechanisms responsible for GC-induced skeletal muscle atrophy have been extensively investigated, and the ability to treat patients with GC without unintended muscle atrophy has yet to be realized. We have reported that a single, standard-of-care dose of Methylprednisolone increases in vivo expression of NF-κB-inducing kinase (NIK), an important upstream regulatory kinase controlling NF-κB activation, along with other key muscle catabolic regulators such as Atrogin-1 and MuRF1 that induce skeletal muscle proteolysis. Here, we provide experimental evidence that overexpressing NIK by intramuscular injection of recombinant human NIK via adenoviral vector in mouse tibialis anterior muscle induces a 30% decrease in the average fiber cross-sectional area that is associated with increases in mRNA expression of skeletal muscle atrophy biomarkers MuRF1, Atrogin-1, myostatin and Gadd45. A single injection of GC induced NIK mRNA and protein within 2 h, with the increased NIK localized to nuclear and sarcolemmal locations within muscle fibers. Daily GC injections induced skeletal muscle fore limb weakness as early as 3 days with similar atrophy of muscle fibers as observed with NIK overexpression. NIK overexpression in primary human skeletal muscle myotubes increased skeletal muscle atrophy biomarkers, while NIK knockdown significantly attenuated GC-induced increases in NIK and Atrogin-1. These results suggest that NIK may be a novel, previously unrecognized mediator of GC-induced skeletal muscle atrophy.
