Raymond E. Eid

Cellular-specific role of toll-like receptor 4 in hepatic ischemia-reperfusion injury in mice.

Ischemia‐reperfusion (I/R) injury is a process whereby an initial hypoxic insult and subsequent return of blood flow leads to the propagation of innate immune responses and organ injury. The necessity of the pattern recognition receptor, Toll‐like receptor (TLR)4, for this innate immune response has been previously shown. However, TLR4 is present on various cell types of the liver, both immune and nonimmune cells. Therefore, we sought to determine the role of TLR4 in individual cell populations, specifically, parenchymal hepatocytes (HCs), myeloid cells, including Kupffer cells, and dendritic cells (DCs) subsequent to hepatic I/R. When HC‐specific (Alb‐TLR4−/−) and myeloid‐cell–specific (Lyz‐TLR4−/−) TLR4 knockout (KO) mice were subjected to warm hepatic ischemia, there was significant protection in these mice, compared to wild type (WT). However, the protection afforded in these two strains was significantly less than global TLR4 KO (TLR4−/−) mice. DC‐specific TLR4−/− (CD11c‐TLR4−/−) mice had significantly increased hepatocellular damage, compared to WT mice. Circulating levels of high‐mobility group box 1 (HMGB1) were significantly reduced in Alb‐TLR4−/− mice, compared to WT, Lyz‐TLR4−/−, CD11c‐TLR4−/− mice and equivalent to global TLR4−/− mice, suggesting that TLR4‐mediated HMGB1 release from HCs may be a source of HMGB1 after I/R. HCs exposed to hypoxia responded by rapidly phosphorylating the mitogen‐activated protein kinases, c‐Jun‐N‐terminal kinase (JNK) and p38, in a TLR4‐dependent manner; inhibition of JNK decreased release of HMGB1 after both hypoxia in vitro and I/R in vivo. Conclusion: These results provide insight into the individual cellular response of TLR4. The parenchymal HC is an active participant in sterile inflammatory response after I/R through TLR4‐mediated activation of proinflammatory signaling and release of danger signals, such as HMGB1. (HEPATOLOGY 2013)

Dendritic Cells and Damage-Associated Molecular Patterns: Endogenous Danger Signals Linking Innate and Adaptive Immunity

Dendritic cells (DCs) are potent antigen-presenting cells critical in regulating the adaptive immune response. The role of DCs is dichotomous; they may both present antigens and the appropriate stimulatory molecules to initiate an adaptive immune response, or they may induce tolerance and release anti-inflammatory signals. The activation of immature DCs, required for the expression of the necessary costimulatory T cell molecules, is dependent on pattern recognition receptors. In addition to the pathogen-derived ligands of pattern recognition receptors, several damage-associated molecular patterns (DAMPs) have recently been shown to interact with DCs and dramatically affect their ultimate function. The complex interplay of DAMPs on DCs is clinically important, with implications for transplantation, tumor immunity, autoimmunity, chronic inflammation and other conditions of sterile inflammation such as ischemia reperfusion injury. In this review, we will focus on the role of DAMPs in DC function.

Delayed open conversions after endovascular abdominal aortic aneurysm repair

OBJECTIVE Secondary interventions after endovascular aneurysm repair (EVAR) remain a concern. Most are simple catheter-based procedures, but in some instances, open conversions (OCs) are required and carry a worse outcome. We reviewed our experience to characterize these OCs. METHODS A retrospective review was conducted of all patients who underwent an OC after a previous EVAR for an aneurysm-related indication from 2001 to 2010. Clinical outcomes are reported. RESULTS Data were reviewed for 44 patients (77% men) with a mean age of 74 years (range, 55-90 years). The average time from EVAR to the first OC was 45 months (range, 2-190 months). In six patients (14%), the initial EVAR was at another institution. The endografts used were Ancure in 16, Excluder in 13, AneuRx in eight, Zenith in three, Lifepath in one, Renu in one, and undetermined in two. Twenty-two patients had previously undergone a total of 32 endovascular reinterventions before their index OC. Indications for OC were aneurysm expansion in 28 (64%), rupture in 12 (27%), and infection in four (9%). The endograft was preserved in situ in 10 patients (23%). Explantation was partial in 18 (41%) or complete in 16 (36%). Endograft preservation was used for type II endoleak in all but one patient by selective ligation of the culprit arteries (lumbar in four, inferior mesenteric artery in five, and middle sacral in one). Proximal neck banding was performed in one type Ia endoleak. Overall morbidity was 55%, and mortality was 18%. No deaths occurred in a subgroup of patients who underwent endograft preservation with selective ligation of culprit vessels for type II endoleak. Intraoperative complications included bowel injury in two, bleeding in two, splenectomy in one, and ureteral injury in one. At a mean follow-up of 20 months, two patients underwent additional procedures after the index OC: one after endograft preservation and one after partial explantation. None of the patients who underwent elective OC with endograft preservation required subsequent endograft explantation. CONCLUSIONS Most OCs after EVAR are associated with significant morbidity and mortality, except when electively treating an isolated type II endoleak with ligation of branches and preservation of the endograft.

Contemporary outcomes of intact and ruptured visceral artery aneurysms

OBJECTIVE The treatment outcomes of ruptured visceral artery aneurysms (rVAAs) have been sparsely characterized, with no clear comparison between different treatment modalities. The purpose of this paper was to review the perioperative and long-term outcomes of open and endovascular interventions for intact visceral artery aneurysms (iVAAs) and rVAAs. METHODS This was a retrospective review of all treated VAAs at one institution from 2003 to 2013. Patient demographics, aneurysm characteristics, management, and subsequent outcomes (technical success, mortality, reintervention) and complications were recorded. RESULTS The study identified 261 patients; 181 patients were repaired (77 ruptured, 104 intact). Pseudoaneurysms were more common in rVAAs (81.8% vs 35.3% for iVAAs; P < .001). The rVAAs were smaller than the iVAAs (20.7 mm vs 27.5 mm; P = .018), and their most common presentation was abdominal pain; 29.7% were hemodynamically unstable. Endovascular intervention was the initial treatment modality for 67.4% (75.3% for rVAAs, 61.5% for iVAAs). The perioperative complication rate was higher for rVAAs (13.7% vs 1% for iVAAs; P = .003), as was mortality at 30 days (13% vs 0% for iVAAs; P = .001), 1 year (32.5% for rVAAs vs 4.1% for iVAAs; P < .001), and 3 years (36.4% for rVAAs vs 8.3% for iVAAs; P < .001). Lower 30-day mortality was noted with endovascular repair for rVAAs (7.4% vs 28.6% open; P = .025). Predictors of mortality for rVAAs included age (odds ratio, 1.04; P = .002), whereas endovascular repair was protective (odds ratio, 0.43; P = .037). Mean follow-up was 26.2 months, and Kaplan-Meier estimates of survival were higher for iVAAs at 3 years (88% vs 62% for rVAAs; P = .045). The 30-day reintervention rate was higher for rVAAs (7.7% vs 19.5% for iVAAs; P = .019) but was similar between open and endovascular repair (8.2% vs 15%; P = NS). CONCLUSIONS rVAAs have significant mortality. Open and endovascular interventions are equally durable for elective repair of VAAs, but endovascular interventions for rVAAs result in lower morbidity and mortality. Aggressive treatment of pseudoaneurysms is electively recommended at diagnosis regardless of size.