Glucose Increases STAT3 Activation, Promoting Sustained XRCC1 Expression and Increasing DNA Repair.

Dysregulation of DNA repair is a hallmark of cancer, though few cancer-specific mechanisms that drive the overexpression of DNA repair proteins are known. We previously identified STAT3 as a novel transcriptional regulator of X-ray cross-complementing group 1 (XRCC1), an essential scaffold protein in base excision repair in triple-negative breast cancers. We also identified an inducible response to IL-6 and epidermal growth factor stimulation in the non-tumorigenic embryonic kidney cell line HEK293T. As IL-6 and EGF signaling are growth and inflammatory-inducible responses, we examined if glucose challenge can increase STAT3 activation, promoting adaptive changes in XRCC1 expression in different cell types. Acute high glucose exposure promoted XRCC1 expression through STAT3 activation, increasing the repair of methyl methanesulfonate-induced DNA damage in HEK293T cells and the osteosarcoma cell line U2OS. Sustained exposure to high glucose promoted the overexpression of XRCC1, which can be reversed upon glucose restriction and down-regulation of STAT3 activation. Thus, we have identified a novel link between XRCC1 expression and STAT3 activation following exogenous exposures, which could play a critical role in dictating a cancer cell's response to DNA-damaging agents.

Inhibition of Necroptosis to Prevent Long-term Cardiac Damage During Pneumococcal Pneumonia and Invasive Disease.

BACKGROUND: Streptococcus pneumoniae infection can result in bacteremia with devastating consequences including heart damage. Necroptosis is a proinflammatory form of cell death instigated by pore-forming toxins such as S. pneumoniae pneumolysin. Necroptosis-inhibiting drugs may lessen organ damage during invasive pneumococcal disease (IPD). METHODS: In vitro experiments were carried out with human and mouse cardiomyocytes. Long-term cardiac damage was assessed using high-resolution echocardiography in ampicillin-rescued mice 3 months after challenge with S. pneumoniae. Ponatinib, a necroptosis-inhibiting and Food and Drug Administration-approved drug for lymphocytic leukemia treatment, was administered intraperitoneally alongside ampicillin to test its therapeutic efficacy. Histology of heart sections included hematoxylin-eosin staining for overt damage, immunofluorescence for necroptosis, and Sirius red/fast green staining for collagen deposition. RESULTS: Cardiomyocyte death and heart damage was due to pneumolysin-mediated necroptosis. IPD leads to long-term cardiac damage, as evidenced by de novo collagen deposition in mouse hearts and a decrease in fractional shortening. Adjunct necroptosis inhibition reduced the number of S. pneumoniae foci observed in hearts of acutely infected mice and serum levels of troponin I. Ponatinib reduced collagen deposition and protected heart function in convalescence. CONCLUSIONS: Acute and long-term cardiac damage incurred during IPD is due in part to cardiomyocyte necroptosis. Necroptosis inhibitors may be a viable adjunct therapy.

Subacute treatment of carprofen facilitate splenocardiac resolution deficit in cardiac injury.

Inflammation-limiting nonsteroidal pain relievers magnify myocardial infarction (MI) incidences and increase re-admission events in heart failure (HF) patients. However, the molecular and cellular mechanism of this provocative adverse effect is unclear. Our goal was to determine whether carprofen (CAP) impedes splenic leukocyte-directed acute inflammation-resolving response in cardiac injury. After subacute CAP treatment, mice were subjected to permanent coronary ligation maintaining MI- and naïve-controls. Spleen and left ventricle (LV) leukocytes were quantitated using flow cytometry pre- and 24 h post-MI. The inflammation resolution mediators were quantified using mass spectrometry while splenocardiac apoptosis and leukocyte phagocytosis were measured by immunofluorescence and ImageStream, respectively. Subacute CAP treatment promoted strain and cardiac dysfunction before MI and coronary occlusion showed signs of acute HF in CAP and MI-controls. Subacute CAP-injected mice had pre-activated splenic neutrophils, an over activated "don't eat me" signal (CD47) with reduced total Mϕs (F4/80+ ) and reparative Mϕs (F4/80/Ly6Clo /CD206) compared with control in LV and spleen. Post-MI, CAP pre-activated neutrophils (Ly6G+ ) were intensified and reduced reparative neutrophils (Ly6G+ /CD206+ ) and Mϕs (F4/80/Ly6Clo ) in LV was indicative of non-resolving inflammation compared with MI-control. Subacute CAP treatment deferred neutrophil phagocytosis functions in the spleen and LV and was more evident post-MI compared with MI-control. CAP pre-activated splenic neutrophils that tailored the Mϕ phagocytosis thereby increased splenocardiac leukocyte death. CAP over amplified COX-1 and COX-2 compared with MI-control and failed to limit prostaglandins and thromboxane in post-MI setting. Further, CAP reduced cardiac-protective epoxyeicosatrienoic acids and over amplified pyrogenic inflammatory cytokines and reduced reparative cytokines, thereby non-resolving inflammation.