The Histone Methyltransferase SETDB2 Modulates Tissue Inhibitors of Metalloproteinase-Matrix Metalloproteinase Activity During Abdominal Aortic Aneurysm Development.

OBJECTIVE: To determine macrophage-specific alterations in epigenetic enzyme function contributing to the development of abdominal aortic aneurysms (AAAs). BACKGROUND: AAA is a life-threatening disease, characterized by pathologic vascular remodeling driven by an imbalance of matrix metalloproteinases and tissue inhibitors of metalloproteinases (TIMPs). Identifying mechanisms regulating macrophage-mediated extracellular matrix degradation is of critical importance to developing novel therapies. METHODS: The role of SET Domain Bifurcated Histone Lysine Methyltransferase 2 (SETDB2) in AAA formation was examined in human aortic tissue samples by single-cell RNA sequencing and in a myeloid-specific SETDB2 deficient murine model induced by challenging mice with a combination of a high-fat diet and angiotensin II. RESULTS: Single-cell RNA sequencing of human AAA tissues identified SETDB2 was upregulated in aortic monocyte/macrophages and murine AAA models compared with controls. Mechanistically, interferon-ß regulates SETDB2 expression through Janus kinase/signal transducer and activator of transcription signaling, which trimethylates histone 3 lysine 9 on the TIMP1-3 gene promoters thereby suppressing TIMP1-3 transcription and leading to unregulated matrix metalloproteinase activity. Macrophage-specific knockout of SETDB2 ( Setdb2f/fLyz2Cre+ ) protected mice from AAA formation with suppression of vascular inflammation, macrophage infiltration, and elastin fragmentation. Genetic depletion of SETDB2 prevented AAA development due to the removal of the repressive histone 3 lysine 9 trimethylation mark on the TIMP1-3 gene promoter resulting in increased TIMP expression, decreased protease activity, and preserved aortic architecture. Lastly, inhibition of the Janus kinase/signal transducer and activator of the transcription pathway with an FDA-approved inhibitor, Tofacitinib, limited SETDB2 expression in aortic macrophages. CONCLUSIONS: These findings identify SETDB2 as a critical regulator of macrophage-mediated protease activity in AAAs and identify SETDB2 as a mechanistic target for the management of AAAs.

Mycobacterial Infections With Ruxolitinib: A Retrospective Pharmacovigilance Review.

BACKGROUND: Ruxolitinib is a selective Janus kinase inhibitor (JAKI) 1/2 approved for the treatment of myelofibrosis (MF) and polycythemia vera (PV). These patients may be at risk for developing opportunistic infections. We assessed the number of patients that developed typical (Mycobacterium tuberculosis [MTB]) and atypical mycobacterial infections (AMI) while on treatment with ruxolitinib by utilizing the United States Food and Drug Administration (FDA) adverse events reporting system (FAERS). MATERIALS AND METHODS: This is a retrospective study utilizing FAERS, a pharmacovigilance database. We queried FAERS for cases of MTB and AMI secondary to ruxolitinib between January 1, 2011 and December 31, 2018. Disproportionality signal analysis was done by calculating the reporting odds ratio (ROR). ROR was considered significant when the lower limit of 95% confidence interval (CI) was > 1. RESULTS: There were 91 reported cases of MTB associated with ruxolitinib compared with 4575 cases from all other drugs. The ROR was significant at 9.2 (95% CI, 7.5-11.4). There were 23 reports of AMI with ruxolitinib compared with 1287 reported with all other drugs. The ROR was significant at 8.3 (95% CI, 5.5-12.6). Twelve (13.2%) patients with MTB and 8 (34.8%) with AMI died. CONCLUSION: Patients on ruxolitinib are at increased risk of developing MTB and AMI. Clinicians should be aware of this risk and consider screening patients for latent MTB prior to initiating ruxolitinib.

Kinase inhibitors: a new approach to rheumatoid arthritis treatment.

PURPOSE OF REVIEW: Due to the cost and parenteral mode of administration of biologics, efforts to develop oral small molecule inhibitors to protein kinases involved in cellular signaling that impact inflammatory cytokine production have been ongoing. This article will review the recent publications on these efforts. RECENT FINDINGS: On preclinical work, p38 mitogen-activated kinases were considered attractive targets to suppress cytokine production. Three different molecules (SCIO_469, Pamapimod, VX-702) that target the p38alpha isoform have been evaluated in phase 2 trials. Unfortunately, clinical efficacy was not observed, and dose-related toxicity was seen. The future of this approach is unclear. Targeting more upstream protein tyrosine kinases such as spleen tyrosine kinase (SyK) and the JAK family of kinases has been associated with greater success in clinical trials, with efficacy demonstrated. Adverse events occurred in a dose-dependent fashion with the SyK inhibitor, such as diarrhea and hypertension. Neutropenia, elevated liver-function tests, serum creatinine elevations and lipid elevations have occurred with JAK-kinase inhibition. Dose modifications have been made based on the phase 2 trial results; phase 3 clinical trials are ongoing. SUMMARY: Inhibiting downstream proteins involved in cellular signaling, such as p38, has not been successful to date. Inhibitors of more upstream protein-tyrosine kinases involved in cellular signaling appear to be viable molecular candidates for rheumatoid arthritis. If the results seen in phase 2 studies are confirmed in larger phase 3 studies, we may soon have new, oral DMARD therapies available.