Histone deacetylase 3 regulates microglial function through histone deacetylation.

As the primary innate immune cells of the brain, microglia respond to damage and disease through pro-inflammatory release of cytokines and neuroinflammatory molecules. Histone acetylation is an activating transcriptional mark that regulates inflammatory gene expression. Inhibition of histone deacetylase 3 (Hdac3) has been utilized in pre-clinical models of depression, stroke, and spinal cord injury to improve recovery following injury, but the molecular mechanisms underlying Hdac3's regulation of inflammatory gene expression in microglia is not well understood. To address this lack of knowledge, we examined how pharmacological inhibition of Hdac3 in an immortalized microglial cell line (BV2) impacted histone acetylation and gene expression of pro- and anti-inflammatory genes in response to immune challenge with lipopolysaccharide (LPS). Flow cytometry and cleavage under tags & release using nuclease (CUT & RUN) revealed that Hdac3 inhibition increases global and promoter-specific histone acetylation, resulting in the release of gene repression at baseline and enhanced responses to LPS. Hdac3 inhibition enhanced neuroprotective functions of microglia in response to LPS through reduced nitric oxide release and increased phagocytosis. The findings suggest Hdac3 serves as a regulator of microglial inflammation, and that inhibition of Hdac3 facilitates the microglial response to inflammation and its subsequent clearing of debris or damaged cells. Together, this work provides new mechanistic insights into therapeutic applications of Hdac3 inhibition which mediate reduced neuroinflammatory insults through microglial response.

Progression to Anti-TNF Treatment in Very Early Onset Inflammatory Bowel Disease Patients.

OBJECTIVES: Limited data are currently available regarding anti-tumor necrosis factor (TNF) use and outcomes in very early onset inflammatory bowel disease (VEOIBD) patients. We aimed to assess the long-term outcomes and time to progression to anti-TNF treatment in VEOIBD patients. METHODS: We retrospectively reviewed IBD patients diagnosed under 6 years of age, between January 2005 and December 2019, from the British-Columbia (BC) Pediatric IBD database. Demographic data, disease characteristics, disease location and severity were documented. Data on anti-TNF treatment at initiation and during follow up including type of biologic, dosing, and response were collected. Kaplan-Meier curves were used to assess the number of years to progression to anti-TNF treatment and the parameters influencing commencement. RESULTS: Eighty-nine patients with VEOIBD were diagnosed during the study period. Median age at diagnosis was 3.8 years [interquartile range (IQR) 2.6-5.1], 45.3% had Crohn disease (CD) and 62.8% were males. Median duration of follow up was 6.39 years (IQR 3.71-10.55). Anti-TNF treatment was started on 39.5% of patients and 7.0% underwent surgery. Rapid progression to biologic treatment was associated with Perianal fistulizing disease or stricturing disease in CD patients ( P = 0.026, P = 0.033, respectively), and disease severity ( P = 0.017) in ulcerative colitis(UC) patients. The median dose of infliximab at 1 year was 10 mg/kg (IQR 7.5-11) and a median dose interval of 4.5 weeks (IQR 4-6). Clinical remission was reported in 61.8% of patients on their first biologic agent. CONCLUSIONS: The response rate was higher than previously reported and might be due to higher infliximab dosing with shorter infusion intervals than standard dosing.

High body mass index is not associated with increased treatment failure in infliximab treated pediatric patients with inflammatory bowel disease.

BACKGROUND AND AIM: While weight gain during infliximab therapy in inflammatory bowel disease (IBD) is common, there has been limited research evaluating its impact on infliximab efficacy. METHODS: Primary aims of this study were to determine the frequency of excess weight gain (body mass index [BMI] > 25 kg/m2) in children with IBD on maintenance infliximab and evaluate the impact on infliximab dosing, serum trough levels, and treatment failure. Secondary aims were to determine differences in weight gain, treatment characteristics, and clinical/biochemical variables between patients with therapeutic and subtherapeutic maintenance therapy trough levels. We performed a retrospective study of 253 pediatric IBD (75.1% Crohn's disease, 23.3% ulcerative colitis, 1.6% IBD-unclassified) patients on infliximab followed at BC Children's Hospital between January 2013 and January 2018. RESULTS: Median age at infliximab initiation was 13.9 years, median length of follow up was 56.9 months, and 55.7% were males; 10.3% of the cohort demonstrated excess weight gain (7.5% overweight, 2.8% obese). Average mg/kg dosing was not statistically different between groups (normal, overweight, and obese: 6.7, 6.4, and 6.7 mg/kg, respectively, P = 0.52). Median BMI of patients with therapeutic and subtherapeutic trough levels was similar at 19.9 kg/m2 (interquartile range [IQR], 17.3-23.8) and 19.7 kg/m2 (IQR, 17.4-21.9), respectively. BMI had no effect on secondary loss of response to infliximab, with no significant difference between normal and high BMI subgroups (13.4 vs. 16.7%, P = 0.9). CONCLUSIONS: In a subgroup of pediatric IBD patients on maintenance infliximab, excess weight gain was not associated with higher weight-based dosing, lower serum trough levels, or increased risk of treatment failure.