Chao Han Lai

Prosthetic valve endocarditis caused by Streptobacillus moniliformis: a case of rat bite fever.

ABSTRACT We report a case of rat bite fever caused by Streptobacillus moniliformis in Taiwan. It manifested as prosthetic valve endocarditis, which was cured by cardiac valve replacement and antimicrobial therapy. The DNA sequence of the 16S rRNA gene of S. moniliformis was detected in valve specimens by PCR and nucleotide sequencing.

Bilateral Persistent Sciatic Arteries Complicated with Acute Left Lower Limb Ischemia

Persistent sciatic artery (PSA) is a rare congenital malformation. In the early embryonic stage, the sciatic artery is the major blood supply for the lower limb bulb and is later replaced by the iliofemoral artery as the limb develops. Its failure to regress, sometimes associated with femoral arterial hypoplasia, and therefore becoming the dominant inflow to the lower extremity is called PSA. This anomaly is often associated with a higher rate of aneurysm formation or thromboembolic complications causing lower extremity ischemia. Here, we describe a 79-year-old male patient who presented with acute left lower extremity ischemia. He was treated initially with conventional embolectomy through inguinal and popliteal incisions. The bilateral PSA with thrombosed aneurysms was not identified at first on computed tomographic angiography. It was later diagnosed intraoperatively due to the discontinuity of the superficial femoral artery and popliteal artery found with embolectomy catheter, and was managed successfully with ePTFE graft bypass. Careful interpretation of the imaging study may be helpful in preoperative diagnosis.

Recombinant human thrombomodulin suppresses experimental abdominal aortic aneurysms induced by calcium chloride in mice

Objective: To investigate whether recombinant thrombomodulin containing all the extracellular domains (rTMD123) has therapeutic potential against aneurysm development. Summary Background Data: The pathogenesis of abdominal aortic aneurysm (AAA) is characterized by chronic inflammation and proteolytic degradation of extracellular matrix. Thrombomodulin, a transmembrane glycoprotein, exerts anti-inflammatory activities such as inhibition of cytokine production and sequestration of proinflammatory high-mobility group box 1 (HMGB1) to prevent it from engaging the receptor for advanced glycation end product (RAGE) that may sustain inflammation and tissue damage. Methods: The in vivo effects of treatment and posttreatment with rTMD123 on aortic dilatation were measured using the CaCl2-induced AAA model in mice. Results: Characterization of the CaCl2-induced model revealed that HMGB1 and RAGE, both localized mainly to macrophages, were persistently upregulated during a 28-day period of AAA development. In vitro, rTMD123-HMGB1 interaction prevented HMGB1 binding to macrophages, thereby prohibiting activation of HMGB1-RAGE signaling in macrophages. In vivo, short-term treatment with rTMD123 upon AAA induction suppressed the levels of proinflammatory cytokines, HMGB1, and RAGE in the aortic tissue; reduced the infiltrating macrophage number; and finally attenuated matrix metalloproteinase production, extracellular matrix destruction, and AAA formation without disturbing vascular calcification. Consistently, posttreatment with rTMD123 seven days after AAA induction alleviated vascular inflammation and retarded AAA progression. Conclusions: These data suggest that rTMD123 confers protection against AAA development. The mechanism of action may be associated with reduction of proinflammatory mediators, blockade of macrophage recruitment, and suppression of HMGB1-RAGE signaling involved in aneurysm formation and downstream macrophage activation.

Surgical Consideration of In Situ Prosthetic Replacement for Primary Infected Abdominal Aortic Aneurysms

OBJECTIVES To review our surgical experience of primary infected abdominal aortic aneurysms, with the aim of assessing the safety and durability of in situ prosthetic replacement. DESIGN Retrospective study in a university hospital. MATERIALS AND METHODS Thirty-four patients who underwent surgery for primary infected abdominal aortic aneurysms over the past 18 years were reviewed. Operative details and outcomes were recorded for analysis. RESULTS There were six suprarenal and 28 infrarenal infections. Salmonellae (18 patients) were the most common pathogens. Thirty patients underwent in situ prosthetic replacement, two underwent extra-anatomic bypass and two underwent endovascular repair. The surgical mortality for overall patients was 18%, and for patients reconstructed in situ, 17%. Among the 30 patients reconstructed in situ, four patients who underwent concomitant gastrointestinal procedures (e.g., repair of the duodenal defect) died. By contrast, 25 of 26 patients without gastrointestinal involvement survived surgery. After a median follow-up period of 58 months, two discharged patients who underwent in situ reconstruction died of late graft infection. CONCLUSIONS Our experience suggests that in situ prosthetic replacement can be performed safely with durable outcomes in the majority of patients with infected abdominal aortic aneurysms. Nevertheless, we advise caution when considering this technique with concomitant gastrointestinal procedures.

RHBDL2 Is a Critical Membrane Protease for Anoikis Resistance in Human Malignant Epithelial Cells

Anoikis resistance allows metastatic tumor cells to survive in a homeless environment. Activation of epithelial growth factor receptor (EGFR) signaling is one of the key mechanisms for metastatic tumor cells to resist anoikis, yet the regulation mechanisms of homeless-triggered EGFR activation in metastatic tumor cells remain unclear. Rhomboid-like-2 (RHBDL2), an evolutionally conserved intramembrane serine protease, can cleave the EGF ligand and thus trigger EGFR activation. Herein, we demonstrated that RHBDL2 overexpression in human epithelial cells resulted in promotion of cell proliferation, reduction of cell adhesion, and suppression of anoikis. During long-term suspension cultures, increased RHBDL2 was only detected in aggressive tumor cell lines. Treatment with the rhomboid protease inhibitor or RHBDL2 shRNA increased cleaved caspase 3, a marker of apoptosis. Finally, inhibition of EGFR activation increased the cleaved caspase 3 and attenuated the detachment-induced focal adhesion kinase phosphorylation. Taken together, these findings provide evidence for the first time that RHBDL2 is a critical molecule in anoikis resistance of malignant epithelial cells, possibly through the EGFR-mediated signaling. Our study demonstrates RHBDL2 as a new therapeutic target for cancer metastasis.

Toll-Like Receptor 4 Is Essential in the Development of Abdominal Aortic Aneurysm.

Toll-like receptor (TLR) family plays a key role in innate immunity and various inflammatory responses. TLR4, one of the well-characterized pattern-recognition receptors, can be activated by endogenous damage-associated molecular pattern molecules such as high mobility group box 1 (HMGB1) to sustain sterile inflammation. Evidence suggested that blockade of TLR4 signaling may confer protection against abdominal aortic aneurysm (AAA). Herein we aimed to obtain further insight into the mechanism by which TLR4 might promote aneurysm formation. Characterization of the CaCl2-induced AAA model in mice revealed that upregulation of TLR4 expression, localized predominantly to vascular smooth muscle cells (VSMCs), was followed by a late decline during a 28-day period of AAA development. In vitro, TLR4 expression was increased in VSMCs treated with HMGB1. Knockdown of TLR4 by siRNA attenuated HMGB1-enhanced production of proinflammatory cytokines, specifically interleukin-6 and monocyte chemoattractant protein-1 (MCP-1), and matrix-degrading matrix metalloproteinase (MMP)-2 from VSMCs. In vivo, two different strains of TLR4-deficient (C57BL/10ScNJ and C3H/HeJ) mice were resistant to CaCl2-induced AAA formation compared to their respective controls (C57BL/10ScSnJ and C3H/HeN). Knockout of TLR4 reduced interleukin-6 and MCP-1 levels and HMGB1 expression, attenuated macrophage accumulation, and eventually suppressed MMP production, elastin destruction and VSMC loss. Finally, human AAA exhibited higher TLR4 expression that was localized to VSMCs. These data suggest that TLR4 signaling contributes to AAA formation by promoting a proinflammatory status of VSMCs and by inducing proteinase release from VSMCs during aneurysm initiation and development.

Membrane-Bound Thrombomodulin Regulates Macrophage Inflammation in Abdominal Aortic Aneurysm

Objective—Thrombomodulin (TM), a glycoprotein constitutively expressed in the endothelium, is well known for its anticoagulant and anti-inflammatory properties. Paradoxically, we recently found that monocytic membrane-bound TM (ie, endogenous TM expression in monocytes) triggers lipopolysaccharide- and gram-negative bacteria–induced inflammatory responses. However, the significance of membrane-bound TM in chronic sterile vascular inflammation and the development of abdominal aortic aneurysm (AAA) remains undetermined. Approach and Results—Implicating a potential role for membrane-bound TM in AAA, we found that TM signals were predominantly localized to macrophages and vascular smooth muscle cells in human aneurysm specimens. Characterization of the CaCl2-induced AAA in mice revealed that during aneurysm development, TM expression was mainly localized in infiltrating macrophages and vascular smooth muscle cells. To investigate the function of membrane-bound TM in vivo, transgenic mice with myeloid- (LysMcre/TMflox/flox) and vascular smooth muscle cell–specific (SM22-cretg/TMflox/flox) TM ablation and their respective wild-type controls (TMflox/flox and SM22-cretg/TM+/+) were generated. In the mouse CaCl2-induced AAA model, deficiency of myeloid TM, but not vascular smooth muscle cell TM, inhibited macrophage accumulation, attenuated proinflammatory cytokine and matrix metalloproteinase-9 production, and finally mitigated elastin destruction and aortic dilatation. In vitro TM-deficient monocytes/macrophages, versus TM wild-type counterparts, exhibited attenuation of proinflammatory mediator expression, adhesion to endothelial cells, and generation of reactive oxygen species. Consistently, myeloid TM–deficient hyperlipidemic mice (ApoE−/−/LysMcre/TMflox/flox) were resistant to AAA formation induced by angiotensin II infusion, along with reduced macrophage infiltration, suppressed matrix metalloproteinase activities, and diminished oxidative stress. Conclusions—Membrane-bound TM in macrophages plays an essential role in the development of AAA by enhancing proinflammatory mediator elaboration, macrophage recruitment, and oxidative stress.

Secondary Aortocolic Fistula: Case Report and Review of the Literature

A secondary aortoenteric fistula (SAEF) is relatively rare after abdominal aortoiliac reconstructive surgery. Most SAEFs are associated with a graft prosthesis, and rectum involvement is rarely reported. We report a rectal SAEF after aortoiliac aneurysmorrhaphy, i.e., oversewing the artery without a graft. A 62-year-old man had an appendicitis-related infected right common iliac artery aneurysm and sterile left aortoiliac arterial aneurysm. Six weeks after an appendectomy with a right iliac aneurysmectomy, left aortoiliac reduction aneurysmorrhaphy, and femorofemoral bypass grafting, he developed repeated bloody stool. Abdominal computed tomography and colonoscopy findings strongly indicated communication between the native aortic or iliac arteries and the rectal lumen. Emergency surgery-left infected aortoiliac artery excision, oversewing the aortic stump, right axillofemoral bypass, and sigmoid protectomy with an end-colostomy-was performed. Unfortunately, the aortic stump developed a pseudoaneurysm 6 weeks after the second laparotomy. During the third emergency laparotomy, more of the stump was amputated and wrapped in the omentum. At 45-month follow-up, the patient was well and without infection recurrence or leg ischemia. This case is a reminder that even patients without a graft prosthesis are at risk for SAEF after any aortoiliac surgery. We also comprehensively reviewed the English literature from 1960 to 2008 on prosthesis-free SAEF patients.

Resuscitation for an octogenarian with ruptured abdominal aortic aneurysm using endovascular balloon

Ruptured abdominal aortic aneurysm is a true emergency for emergency physicians and surgeons. Achieving effective proximal control may ameliorate further hemodynamic deterioration and buy time for patients awaiting further repair. An 82-year-old man was referred to our hospital with shock resulting from a ruptured abdominal aortic aneurysm. At the moment of impending cardiac arrest, aortic occlusion was achieved with a transfemoral endovascular balloon, without fluoroscopic guidance. The octogenarian then underwent a prosthetic graft reconstruction and recovered well. In this report, the safeguards and pitfalls of aortic occlusion using an endovascular balloon are discussed. This procedure is not only effective in vascular control but also valuable in resuscitation.

Correction of Tetralogy of Fallot with Absent Pulmonary Valve Syndrome in a Young Infant Using a Bicuspid Equine Pericardial Tube

Absent pulmonary valve syndrome (APVS) is an uncommon variant of tetralogy of Fallot (TOF), which manifests morphologically as vestigial pulmonary valve cusps at the right ventricle-pulmonary trunk junction. The aneurysmally dilated pulmonary arteries may compress the tracheobronchial tree and cause severe respiratory distress in the neonatal or infant stage. Early surgical correction in these patients is necessary despite the high operative mortality rate. A 1-day-old male neonate suffered from progressive shortness of breath after birth. Echocardiography confirmed the diagnosis of TOF with APVS. The marked dilatation of pulmonary arteries resulted in airway compression in addition to heart failure. Total surgical correction was performed at 40 days of age, using a homemade bicuspid equine pericardial tube for right ventricular outflow reconstruction. The short-term follow-up echocardiogram demonstrated good motility of the pericardial leaflet. However, patients receiving this type of valved conduit require meticulous long-term follow-up.