Endotoxemia and acute-phase proteins in major abdominal surgery

Effects of infection and inflammation on lipid and lipoprotein metabolism: mechanisms and consequences to the host

Infection and inflammation induce the acute-phase response (APR), leading to multiple alterations in lipid and lipoprotein metabolism. Plasma triglyceride levels increase from increased VLDL secretion as a result of adipose tissue lipolysis, increased de novo hepatic fatty acid synthesis, and suppression of fatty acid oxidation. With more severe infection, VLDL clearance decreases secondary to decreased lipoprotein lipase and apolipoprotein E in VLDL. In rodents, hypercholesterolemia occurs attributable to increased hepatic cholesterol synthesis and decreased LDL clearance, conversion of cholesterol to bile acids, and secretion of cholesterol into the bile. Marked alterations in proteins important in HDL metabolism lead to decreased reverse cholesterol transport and increased cholesterol delivery to immune cells. Oxidation of LDL and VLDL increases, whereas HDL becomes a proinflammatory molecule. Lipoproteins become enriched in ceramide, glucosylceramide, and sphingomyelin, enhancing uptake by macrophages. Thus, many of the changes in lipoproteins are proatherogenic. The molecular mechanisms underlying the decrease in many of the proteins during the APR involve coordinated decreases in several nuclear hormone receptors, including peroxisome proliferator-activated receptor, liver X receptor, farnesoid X receptor, and retinoid X receptor. APR-induced alterations initially protect the host from the harmful effects of bacteria, viruses, and parasites. However, if prolonged, these changes in the structure and function of lipoproteins will contribute to atherogenesis.

Catecholamines potentiate LPS-induced expression of MMP-1 and MMP-9 in human monocytes and in the human monocytic cell line U937: possible implications for peri-operative plaque instability

Plaque destabilization leading to myocardial infarction is observed after surgery even if the intervention is of noncardiovascular nature. Mediators of peri- or postoperative stress responsible for such events could include catecholamines and lipopolysaccharide (LPS). Monocytes may be involved in destabilization of atherosclerotic plaques by production of matrix metalloproteinases (MMP). We examined whether catecholamines could affect the expression of MMPs in human monocytes/macrophages and whether catecholamines could modulate LPS-stimulated expression of particular MMPs in these cells. Epinephrine and norepinephrine up-regulated MMP-1 and potentiated LPS-induced expression of MMP-1 in peripheral blood monocytes and monocyte-derived macrophages. We further characterized this effect employing the monocytic cell line U937 and showed that catecholamines potentiate LPS-induced effects on MMP-1 and MMP-9 antigen and activity. mRNA levels of the respective MMPs also increased. These effects did not result from higher mRNA stability but rather from increased transcription possibly induced by enhanced DNA binding of AP-1 and were mediated by either beta1- or beta 2-receptors. If this mechanism is also effective in vivo, our findings might, at least in part, help to explain the observation that cardiac events are important causes of morbidity and mortality after noncardiac surgery and support the findings that peri-operative beta-blockade has been shown to reduce postoperative mortality from cardiac events.

Methodological studies on plasma endotoxin level and endotoxin inactivation capacity

To establish stable methods for detecting plasma endotoxin level and endotoxin inactivation capacity in a normal population and general surgical patients and evaluate their perioperative changes. 50 healthy people and 50 patients receiving gastrointestinal operation were enrolled, their plasma endotoxin levels and plasma endotoxin inactivation capacity were assayed. Our results showed that plasma endotoxin levels were 0.044 +/- 0.009 EU/ml in the normal population and 0.044 +/- 0.023 EU/ml in the preoperative patients. Endotoxin level peaked 3 h after the operation (0.223 +/- 0.041 EU/ml), and then decreased rapidly on the first day after the operation (0.134 +/- 0.164 EU/ml). Endotoxin inactivation capacity also had the same time course as endotoxin level. Systemic inflammatory response syndrome and infection induced another elevation in the time course. It is concluded that establishing the endotoxin standard curve by using pyrogenic free water is better than by using plasma. Plasma endotoxin inactivation capacity can be used as an indirect indicator of postoperative immune depression. Plasma endotoxin level and endotoxin inactivation capacity peaked shortly after operation, indicating surgical stress is closely related with the changes.

Simultaneous onset of acute inflammatory response, sepsis-like symptoms and intestinal mucosal injury after cancer chemotherapy

Chemotherapy is 1 method for the treatment of cancer, but serious side effects can sometimes limit the dosage given. Mild fever and diarrhea are common side effects of cancer chemotherapy. Gastrointestinal injury induced by chemotherapeutic agents may result in bacterial/endotoxin translocation from the gut into the systemic circulation. An experimental study was therefore conducted to clarify the effect of systemic chemotherapeutic agents on gastrointestinal barrier function. Male Wistar rats were divided into a 5-fluorouracil (5-FU) group (100 mg/kg/day for 4 days; n = 27) and a control group (n = 5). All rats were fasted and central venous catheterization was performed for total parenteral nutrition and blood sampling. Intestinal tissue was also sampled for pathological examination. Plasma levels of interleukin-6 (IL-6) and tumor necrosis factor alpha (TNFalpha) were determined by ELISA, bacterial translocation was quantified by lymph node culture and plasma endotoxin content of portal blood was measured by the Limulus-amebocyte-lysate test. In the 5-FU group on day 4, a proportion of rats exhibited severe watery diarrhea (73.9%) and occasional vomiting (86.2%). The levels of plasma TNFalpha and IL-6 were seen to increase, peaking at day 6 (IL-6, 350.0 +/- 67.8 pg/ml; TNFalpha, 26.1 +/- 3.2 pg/ml). The pathological findings also changed on day 4. On day 6, 90% of the rats in the 5-FU group showed dramatic sepsis-like manifestations, whereas the control group did not. Within the 5-FU group, only at day 6 was bacterial translocation in the rat mesenteric lymph nodes or significantly elevated levels of endotoxin evident. These results suggest that bacterial/endotoxin translocation might cause sepsis-like manifestations after systemic chemotherapy.

Influence of modest endotoxemia on postoperative antithrombin deficiency and circulating secretory immunoglobulin a levels

OBJECTIVE

To evaluate the influence of modest endotoxemia on postoperative antithrombin deficiency and cholestasis.

SUMMARY BACKGROUND DATA

It has not been determined whether endotoxin translocation in small amounts is a physiological phenomenon or whether it is a potential health hazard.

METHODS

Blood endotoxin, antithrombin III (ATIII), secretory immunoglobulin A (sIgA), which was selected as a marker of cholestasis, C-reactive protein (CRP), and alpha-1-antitrypsin (AAT) concentrations were measured from the 20 patients undergoing curative gastrectomy for gastric cancer preoperatively and postoperatively. Portal and systemic blood samples were taken for the analysis of endotoxin and interleukin-6 (IL-6) concentrations during surgery in these patients.

RESULTS

Although plasma endotoxin levels showed a significant increase during surgery, we did not find a correlation with ATIII, sIgA, CRP, and IL-6 levels. Systemic blood endotoxin levels during surgery correlated with a postoperative rise of serum AAT levels. Plasma ATIII levels transiently decreased on the first and third postoperative day, and sIgA levels were shown to increase on the seventh postoperative day. There was a weak relationship between the extent of postoperative endotoxemia and a reduction in ATIII concentrations.

CONCLUSIONS

The influence of modest endotoxemia on postoperative antithrombin deficiency and cholestasis was limited, and increased translocational endotoxemia during abdominal surgery may be a physiological phenomenon to trigger off an acute-phase protein response.

A single intravenous dose of endotoxin rapidly alters serum lipoproteins and lipid transfer proteins in normal volunteers

Endotoxemia is associated with rapid and marked declines in serum levels of LDL and HDL by unknown mechanisms. Six normal volunteers received a single, small intravenous (iv) dose of endotoxin (Escherichia coli 0113, 2 ng/kg) or saline in a random order, cross-over design. After endotoxin treatment, volunteers had mild, transient flu-like symptoms and markedly increased serum levels of tumor necrosis factor and its soluble receptors, interleukin-6, cortisol, serum amyloid A, and C-reactive protein. Triglyceride (TG), VLDL-TG, and nonesterified fatty acid increased (peak at 3-4 h), then TG declined (nadir at 9 h), and then cholesterol, LDL cholesterol, apolipoprotein B (apoB), and phospholipid declined (nadirs at 12-24 h). HDL cholesterol and apoA-I levels were not affected, but half of the decrease in phospholipid was HDL phospholipid. Lipopolysaccharide binding protein (LBP) rose 3-fold (peak at 12 h), with smaller and later decreases in the activities of phospholipid transfer protein and cholesteryl ester transfer protein. In conclusion, a decline in LDL was rapidly induced in normal volunteers with a single iv dose of endotoxin. The selective loss of phospholipid from HDL may have been mediated by LBP and, after more intense or prolonged inflammation, could result in increased HDL clearance and reduced HDL levels.

Low albumin level in the emergency department: a potential independent predictor of delayed mortality in blunt trauma

Albumin is an abundant plasma protein with multiple physiologic functions, and low serum albumin levels have been associated with increased mortality in hospitalized patients. In a retrospective matched-pair study, we investigated whether emergency department (ED) albumin levels predict delayed mortality for patients initially stabilized after blunt trauma. Fifty-one hospital non-survivors who died more than 24 h after admission to a trauma center ED were matched by Injury Severity Score, type and location of injury, age, and gender with 51 survivors. All patients had serum albumin levels determined upon arrival in the ED. The non-survivors had a significantly lower admission albumin of 3.1 g/dL compared to 3.5 g/dL for survivors. Patients with albumin levels < 3.4 g/dL were 2.5 times more likely to die compared to patients with normal albumin levels. These preliminary results indicate that initial hypoalbuminemia in blunt trauma patients is an independent predictor of delayed mortality, suggesting that these patients require continued clinical vigilance and an aggressive search for evolving complications.

Nicotine inhibits cardiac apoptosis induced by lipopolysaccharide in rats

OBJECTIVES

Apoptosis develops in several heart diseases, but the therapeutic options are limited. It was hypothesized that nicotine, which inhibits apoptosis in several cells, inhibits cardiac apoptosis induced by lipopolysaccharide (LPS).

BACKGROUND

Over-the-counter nicotine produces sustained levels (10 to 25 ng/ml) that may be antiapoptotic. Low levels of LPS induce apoptosis by activating tissue renin-angiotensin to stimulate angiotensin II, type 1 (AT(1)) receptors in cardiac myocytes.

METHODS

Adult Sprague Dawley rats were pretreated with nicotine (6 mg/kg/day) or saline for seven to ten days (miniosmotic pumps). The LPS (1 mg/kg) was injected intravenously. Toll-like receptor 4 (TLR4) and angiotensinogen messenger ribonucleic acid (mRNA) were measured in the heart after 0, 4, 8, 16, and 24 h. Cardiac apoptosis was measured by terminal deoxy-nucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL) staining after 24 h. In vitro effects of LPS (10 ng/ml, 24 h) were studied in cardiac myocytes isolated from rats pretreated with nicotine for 7 to 10 days, or after pre-exposing myocytes to nicotine (15 ng/ml) for 1, 4, 16, or 24 h.

RESULTS

Neither nicotine nor LPS affected systolic blood pressure. The LPS increased cardiac apoptosis after 24 h in saline-treated, but not nicotine-treated rats, despite similar increases in cardiac TLR4 and angiotensinogen mRNA over 8 to 16 h. The LPS-induced apoptosis was blocked by pre-exposing myocytes to nicotine for 4 to 24 h (partial inhibition after 1 h). Nicotine did not inhibit apoptosis induced by angiotensin II (100 nM, 24 h).

CONCLUSIONS

Therapeutic levels of nicotine inhibit LPS-induced cardiac apoptosis. This occurs after LPS increases TLR4 and angiotensinogen mRNA, but proximal to AT(1) receptor activation. Nicotine may be a novel inhibitor of cardiac apoptosis in conditions associated with circulating LPS (e.g., decompensated heart failure, acute and chronic infections).

Endotoxin removal by direct hemoperfusion with an adsorbent column using polymyxin B-immobilized fiber ameliorates systemic circulatory disturbance in patients with septic shock

Direct hemoperfusion (DHP) with an adsorbent column using polymyxin B-immobilized fiber (PMX-F) has been shown to improve the state of shock in patients with septic shock. However, no evidence has been presented for a direct link between endotoxin removal by DHP with PMX-F and improvement in septic shock. We retrospectively analyzed clinical profiles of 24 patients with septic shock (16 patients, gram-negative; 8 patients, non-gram-negative septic shock) who underwent DHP with PMX-F. Patients with gram-negative septic shock were characterized by hyperdynamic circulation. DHP with PMX-F reduced blood endotoxin concentrations and ameliorated shock, with an improvement in hyperdynamic circulation in patients with gram-negative septic shock. Mean arterial pressure also was elevated after therapy in patients with non-gram-negative septic shock, but systemic hemodynamics were unaffected. Regardless of the causative microorganism, patients with endotoxemia (blood endotoxin level > 10 pg/mL) showed hyperdynamic shock, and DHP with PMX-F reduced blood endotoxin levels and ameliorated hyperdynamic circulation, whereas patients without endotoxemia showed features of shock without hyperdynamic circulation, and DHP with PMX-F ameliorated shock without affecting cardiac performance. In patients with gram-negative septic shock, blood endotoxin concentration correlated positively with cardiac output and negatively with systemic vascular resistance before DHP therapy. Reduction in blood endotoxin concentration by DHP therapy positively correlated with the reduction in cardiac output. Our findings indicate that the improvement in hyperdynamic circulation was related directly to endotoxin removal by the PMX-F column, and endotoxin has an important role in the development of hyperdynamic circulation in patients with gram-negative septic shock.

Inflammatory responses after surgery

The inflammatory response after major surgery is of great importance for patients, physicians and perioperative medicine in general. This article, although not intended to be comprehensive, provides an overview of present knowledge about inflammatory mechanisms, predictive parameters and therapeutic approaches.