Adrenal crisis presenting as hypoglycemic coma

An 18-month-old male infant presented with hypoglycemic coma and clinical signs of bronchopneumonia. He was suspected of suffering from septic shock. The patient progressed to irreversible multiple organ failure before the diagnosis of adrenal crisis was established. Plasma levels of ACTH and cortisol remained undetectable. Renin and aldosterone were normal. An autopsy failed to demonstrate any adrenal gland cortical tissue. Immunohistochemical staining demonstrated the presence of all pituitary hormones except ACTH, establishing the diagnosis of isolated ACTH deficiency. Intensive care clinicians should consider adrenal crisis in non-diabetic children with hypoglycemia and rapid circulatory deterioration.

IL-1beta induction of NF-kappaB activation in human intestinal epithelial cells is independent of oxyradical signaling

IL-1beta stimulation of cultured epithelial cells induces the degradation of IkappaBalpha and the consequent nuclear translocation of NF-lambdaB, a critical proinflammatory transcription factor in the mucosal host immune response. The role of reactive oxygen intermediates, serine protease activity, and tyrosine kinase activity in the activation of NF-kappaB is weakly conserved across various cell lineages and has not been defined in human enterocytes, a major target of oxidant stress in sepsis, thermal injury, and hemorrhagic shock. We report here that in Caco-2BBe cells, a transformed human colon cancer cell line with features of small intestinal epithelial cells in culture, exposure to oxidant stress (hydrogen peroxide 1-10 mM) did not induce NF-kappaB activation. Similarly, scavenging of free radicals and oxidants by pyrrolidine dithiocarbamate and dimethyl sulfoxide did not block IL-1beta-induced IkappaBalpha degradation and NF-kappaB activation. Genistein, a nonspecific tyrosine kinase inhibitor, also had no effect on IL-1beta-mediated effects on NF-kappaB. Serine protease inhibition by tosyl-lysine-chloromethylketone and tosyl-phenylalanine-chloromethylketone inhibited IkappaBalpha degradation and NF-kappaB activation stimulated by IL-1beta. Our data highlight the strong divergence between epithelial and mononuclear cells in the signal transduction pathways relating IL-1beta stimulation and NF-kappaB nuclear translocation.

Implementation of a clinical pathway decreases length of stay and cost for bowel resection

OBJECTIVE

To examine the effect of a clinical pathway for small and large bowel resection on cost and length of hospital stay.

SUMMARY BACKGROUND DATA

Clinical pathways are designed to streamline patient care delivery and maximize efficiency while minimizing cost. Theoretically, they should be most effective in commonly performed procedures, in which volume and familiarity are high.

METHODS

A clinical pathway to assist in the management of patients undergoing bowel resection was developed by a multidisciplinary team and implemented. Data about length of stay and cost was collected for all patients undergoing bowel resection 1 year before and 1 year after pathway implementation. Three groups were compared: patients undergoing bowel resection in the year prior to pathway implementation (prepathway), patients in the year after pathway implementation but not included on the pathway (nonpathway), and patients included in the pathway (pathway).

RESULTS

The mean cost per hospital stay was $19,997.35 +/- 1244.61 for patients in the prepathway group, $20,835.28 +/- 2286.26 for those in the nonpathway group, and $13,908.53 +/- 1113.01 for those in the pathway group (p < 0.05 vs. other groups). Mean postoperative length of stay was 9.98 +/- 0.62 days (prepathway), 9.68 +/- 0.88 days for (nonpathway), and 7.71 +/- 0.37 days (pathway) (p < 0.05 vs. other groups).

CONCLUSIONS

Implementation of the pathway produced significant decreases in length of stay and cost in the pathway group as compared to the prepathway group. These results support the further development of clinical pathways for general surgical procedures.

The expression of genes in the ubiquitin-proteasome proteolytic pathway is increased in skeletal muscle from patients with cancer

BACKGROUND

The intracellular mechanisms of muscle cachexia in patients with cancer are not known. To assess the role of the ubiquitin-proteasome proteolytic pathway in cancer-induced muscle breakdown, we determined messenger RNA levels for ubiquitin and several 20S proteasome subunits in muscle from patients undergoing surgery for cancer

METHODS

A biopsy specimen was obtained from the rectus abdominis muscle in patients undergoing laparotomy for cancer (n = 6) or noncancer disease (n = 6). Tissue levels of mRNA for ubiquitin and the 20S proteasome subunits HC3, HC5, HC7, and HC9 were determined by dot blot analysis.

RESULTS

The mRNA levels for ubiquitin and the 20S proteasome subunits were 2 to 4 times higher in muscle from patients with cancer than in muscle from control patients.

CONCLUSION

This is the first report of increased expression of genes in the ubiquitin-proteasome proteolytic pathway in muscle tissue from patients with cancer. Cancer-induced muscle catabolism may at least in part reflect ubiquitin-proteasome-dependent protein breakdown.

Stress response decreases the interleukin-1beta-induced production of complement component C3 in human intestinal epithelial cells

Interleukin-1beta (IL-1beta) increases the production of complement component C3 in enterocytes. Heat shock regulates the response to cytokines and other inflammatory mediators in various cell types. We tested the hypothesis that the heat-shock response regulates IL-1beta-induced C3 production in the enterocyte. Cultured Caco-2 cells, a human intestinal epithelial cell line, were treated with sodium arsenite (10-500 microM) for 1 h or subjected to hyperthermia (43 degrees C) for 1-4 h, and allowed to recover for 1 h. The cells were then treated with IL-1beta (0.5 ng/ml) for up to 24 h, whereafter C3 levels were measured by ELISA and C3 mRNA by Northern blot analysis. Heat-shock protein of 72 kDa (hsp72) was determined by Western blot analysis. Treatment of the cells with sodium arsenite or subjecting them to hyperthermia induced the expression of hsp72. The IL-1beta-induced expression of C3 mRNA and C3 production were down-regulated by hyperthermia and sodium arsenite in a dose-dependent fashion. The results suggest that the stress response induced by hyperthermia or sodium arsenite decreases IL-1beta-induced C3 production in human enterocytes.

Vaccination with pertussis toxin alters the antibody response to simultaneous respiratory syncytial virus challenge

Many bacterial toxins, including pertussis toxin (PT), exert potent adjuvant effects on antibody synthesis to coadministered antigens. In these studies, we examined whether locally or peripherally administered PT similarly altered the antibody isotype selection to replicating virus after intranasal (inl) challenge. Mice primed intramuscularly with PT and inl with respiratory syncytial virus (RSV) produced RSV-specific antibodies of the IgG2a isotype at a level similar to that of unprimed controls, with some increase in IgG1 production. Mice primed inl with both PT and RSV showed elevated RSV-specific IgG1, increased serum IgE levels, and increased interleukin (IL)-4 in lung supernatants. Splenocytes from these animals produced increased IL-4 when stimulated in vitro with RSV or PT antigens after infection. These results suggest that PT can influence the local production of IL-4 to alter the humoral and cellular immune responses to viral infection as well as to coadministered antigens.

Lactate is an unreliable indicator of tissue hypoxia in injury or sepsis

High blood lactate concentration (hyperlactacidaemia) in trauma or sepsis is thought to indicate tissue hypoxia and anaerobic glycolysis even when blood pressure, cardiac output, and urine output are within clinically acceptable ranges. However, mechanisms of lactate generation by well-oxygenated tissues have received little attention. Within cells, oxidative and glycolytic energy production can proceed in separate, independent compartments. In skeletal muscle and other tissues, aerobic glycolysis is linked to ATP provision for the Na+-K+ pump, the activity of which is stimulated by epinephrine. In injured patients, hypokalaemia may reflect increased Na+,K+-ATPase activity. We propose that increased blood lactate often reflects increased aerobic glycolysis in skeletal muscle secondary to epinephrine-stimulated Na+,K+-ATPase activity and not anaerobic glycolysis due to hypoperfusion. The hypothesis explains why hyperlactacidaemia often neither correlates with traditional indicators of perfusion nor diminishes with increased oxygen delivery. When other variables have returned to normal, continued attempts at resuscitation based on elevated blood lactate may lead to unnecessary use of blood transfusion and inotropic agents in an effort to increase oxygen delivery and lactate clearance.

Sepsis stimulates release of myofilaments in skeletal muscle by a calcium-dependent mechanism

Sepsis is associated with a pronounced catabolic response in skeletal muscle, mainly reflecting degradation of the myofibrillar proteins actin and myosin. Recent studies suggest that sepsis-induced muscle proteolysis may reflect ubiquitin-proteasome-dependent protein breakdown. An apparently conflicting observation is that the ubiquitin-proteasome pathway does not degrade intact myofibrils. Thus, it is possible that actin and myosin need to be released from the myofibrils before they can be ubiquitinated and degraded by the proteasome. We tested the hypothesis that sepsis results in disruption of Z-bands, increased expression of calpains, and calcium-dependent release of myofilaments in skeletal muscle. Sepsis induced in rats by cecal ligation and puncture resulted in increased gene expression of micro-calpain, m-calpain, and p94 and in Z-band disintegration in the extensor digitorum longus muscle. The release of myofilaments from myofibrillar proteins was increased in septic muscle. This response to sepsis was blocked by treating the rats with dantrolene, a substance that inhibits the release of calcium from intracellular stores to the cytoplasm. The present results provide evidence that sepsis is associated with Z-band disintegration and a calcium-dependent release of myofilaments in skeletal muscle. Release of myofilaments may be an initial and perhaps rate-limiting component of sepsis-induced muscle breakdown.

Activity and expression of the 20S proteasome are increased in skeletal muscle during sepsis

Recent studies suggest that sepsis stimulates ubiquitin-dependent protein breakdown in skeletal muscle. In this proteolytic pathway, ubiquitinated proteins are recognized, unfolded, and degraded by the multicatalytic 26S protease complex. The 20S proteasome is the catalytic core of the 26S protease complex. The role of the 20S proteasome in the regulation of sepsis-induced muscle proteolysis is not known. We tested the hypothesis that sepsis increases 20S proteasome activity and the expression of mRNA for various subunits of this complex. Proteolytic activity of isolated 20S proteasomes, assessed as activity against fluorogenic peptide substrates, was increased in extensor digitorum longus muscles from septic rats. The proteolytic activity was inhibited by specific proteasome blockers. Northern blot analysis revealed an approximately twofold increase in the relative abundance of mRNA for the 20S alpha-subunits RC3 and RC9 and the beta-subunit RC7. However, Western blot analysis did not show any difference in RC9 protein content between sham-operated and septic rats. The increased activity and expression of the 20S proteasome in muscles from septic rats lend further support for a role of the ubiquitin-proteasome-pathway in the regulation of sepsis-induced muscle proteolysis.

Flexner and the whole-time system: the second Flexner report and the whole-time system in American academic surgery

BACKGROUND

Reform in medical education started in the mid 19th century and continued through the early decades of the 20th century. Both Carnegie and Rockefeller foundation monies were applied to the process of attempting to improve medical education. The University of Cincinnati College of Medicine, associated with a municipal hospital and a municipally owned university, offered a model for improvements in medical education in other municipal hospitals. The attempt to institute the "whole-time" ("full-time" salaried, "University") system, and restructure the University of Cincinnati College of Medicine along radical lines hitherto unknown in much of the country and in particular to the city of Cincinnati, disturbed the relationship of the College of Medicine with the community and echoes to this day. The tensions between the "University-salaried" professors of clinical surgery and the practitioners attempting to practice at the institution have abated but remain unresolved.

CONCLUSION

The history of the establishment of the full-time chairs, including the Christian R. Holmes Chair of Surgery, led to a rethinking of the role that the full-time system might play in American medical education.

Stimulation of both aerobic glycolysis and Na(+)-K(+)-ATPase activity in skeletal muscle by epinephrine or amylin

Epinephrine and amylin stimulate glycogenolysis, glycolysis, and Na(+)-K(+)-ATPase activity in skeletal muscle. However, it is not known whether these hormones stimulate glycolytic ATP production that is specifically coupled to ATP consumption by the Na(+)-K(+) pump. These studies correlated glycolysis with Na(+)-K(+)-ATPase activity in resting rat extensor digitorum longus and soleus muscles incubated at 30 degrees C in well-oxygenated medium. Lactate production rose three- to fourfold, and the intracellular Na(+)-to-K(+) ratio (Na(+)/K(+)) fell with increasing concentrations of epinephrine or amylin. In muscles exposed to epinephrine at high concentrations (5 x 10(-7) and 5 x 10(-6) M), ouabain significantly inhibited glycolysis by approximately 70% in either muscle and inhibited glycogenolysis by approximately 40 and approximately 75% in extensor digitorum longus and soleus, respectively. In the absence of ouabain, but not in its presence, statistically significant inverse correlations were observed between lactate production and intracellular Na(+)/K(+) for each hormone. Epinephrine had no significant effect on oxygen consumption or ATP content in either muscle. These results suggest for the first time that stimulation of glycolysis and glycogenolysis in resting skeletal muscle by epinephrine or amylin is closely linked to stimulation of active Na(+)-K(+) transport.

Caps on malpractice awards: update

Tort reform for professional liability is in the best interests of not only all physicians, but for industry and the citizenry as a whole. The enormous sums of money donated by the Trial Lawyers Association, whose livelihood is at stake, makes initial passage of tort reform difficult and, once passed, brings it under constant attack. Even if a well-disposed legislature passes a professional liability law, state supreme courts are ever ready to invalidate such laws. Thus, once tort reform has been passed, the next battleground is the state supreme court. ACS chapters should be preparing their membership for educating the public as well as themselves as to the danger of a state supreme court comprised of members opposed to tort reform, and be prepared to help the election of those individuals who are more sympathetic to tort reform.

Prospective, randomized comparison of epidural versus parenteral opioid analgesia in thoracic trauma

OBJECTIVE

To evaluate systemic versus epidural opioid administration for analgesia in patients sustaining thoracic trauma.

SUMMARY BACKGROUND DATA

The authors have previously shown that epidural analgesia significantly reduces the pain associated with significant chest wall injury. Recent studies report that epidural analgesia is associated with a lower catecholamine and cytokine response in patients undergoing elective thoracotomy compared with patient-controlled analgesia (PCA). This study compares the effect of epidural analgesia and PCA on pain relief, pulmonary function, cathechol release, and immune response in patients sustaining significant thoracic trauma.

METHODS

Patients (ages 18 to 60 years) sustaining thoracic injury were prospectively randomized to receive epidural analgesia or PCA during an 18-month period. Levels of serum interleukin (IL)-1beta, IL-2, IL-6, IL-8, and tumor necrosis factor-alpha (TNF-alpha) were measured every 12 hours for 3 days by enzyme-linked immunosorbent assay. Urinary catecholamine levels were measured every 24 hours. Independent observers assessed pulmonary function using standard techniques and analgesia using a verbal rating score.

RESULTS

Twenty-four patients of the 34 enrolled completed the study. Age, injury severity score, thoracic abbreviated injury score, and length of hospital stay did not differ between the two groups. There was no significant difference in plasma levels of IL-1beta, IL-2, IL-6, or TNF-alpha or urinary catecholamines between the two groups at any time point. Epidural analgesia was associated with significantly reduced plasma levels of IL-8 at days 2 and 3, verbal rating score of pain on days 1 and 3, and maximal inspiratory force and tidal volume on day 3 versus PCA.

CONCLUSIONS

Epidural analgesia significantly reduced pain with chest wall excursion compared with PCA. The route of analgesia did not affect the catecholamine response. However, serum levels of IL-8, a proinflammatory chemoattractant that has been implicated in acute lung injury, were significantly reduced in patients receiving epidural analgesia on days 2 and 3. This may have important clinical implications because lower levels of IL-8 may reduce infectious or inflammatory complications in the trauma patient. Also, tidal volume and maximal inspiratory force were improved with epidural analgesia by day 3. These results demonstrate that epidural analgesia is superior to PCA in providing analgesia, improving pulmonary function, and modifying the immune response in patients with severe chest injury.

Complement component C3 production in IL-1beta-stimulated human intestinal epithelial cells is blocked by NF-kappaB inhibitors and by transfection with ser 32/36 mutant IkappaBalpha

BACKGROUND

Recent studies suggest that interleukin-1beta (IL-1beta) stimulates the production of the acute phase protein complement component C3 in human intestinal epithelial cells. The transcription factor NF-kappaB activates different genes involved in the response to cytokines. It is not known if IL-1beta-induced C3 production in the enterocyte is regulated by NF-kappaB.

MATERIALS AND METHODS

Cultured Caco-2 cells, a human intestinal epithelial cell line, were treated with one of the NF-kappaB inhibitors, tosyl-lys-chloromethylketone (TLCK), genistein, or pyrrolidine dithiocarbamate (PDTC), or with N-acetyl-leu-leu-norleucinal (LLnL), a proteasome inhibitor known to block the degradation of Ikappabeta, the cytosolic inhibitor of NF-kappaB. Following this treatment, the Caco-2 cells were stimulated with IL-1beta, and C3 levels in the culture medium were measured after 24 h by ELISA. C3 mRNA levels were determined after 4 h by Northern blot analysis. In other experiments, Caco-2 cells were transfected with a mutant IkappaBalpha in which serines 32 and 36 were substituted by alanine. This mutation prevents IkBalpha phosphorylation and subsequent NF-kappaB nuclear translocation. After transfection, the cells were stimulated with IL-1beta, and C3 levels in the culture medium were measured after 24 h. Cytosolic IkappaBalpha was determined by Western blot analysis.

RESULTS

TLCK, genistein, and LLnL each inhibited IL-1beta-induced C3 production in a dose-dependent fashion. These responses were associated with decreased C3 mRNA levels. In contrast, PDTC did not influence C3 production or C3 mRNA in the Caco-2 cells. Transfection of the Caco-2 cells with the Ser 32/36 mutant IkBalpha resulted in maintained IkappaBalpha levels and decreased IL-beta-induced C3 production.

CONCLUSIONS

IL-1beta-stimulated C3 production in the enterocyte may be regulated by NF-kappaB.

Sepsis is associated with increased ubiquitinconjugating enzyme E214k mRNA in skeletal muscle

Previous studies provided evidence that sepsis is associated with increased ubiquitin-proteasome-dependent protein breakdown in skeletal muscle. The 14-kDa ubiquitin-conjugating enzyme (E214k) has been proposed to be a key regulator of the ubiquitin proteolytic pathway. We tested the hypothesis that E214k message and protein levels are increased in skeletal muscle during sepsis. Sepsis was induced in rats by cecal ligation and puncture (CLP). Control rats were sham operated. E214k mRNA and protein levels were quantitated after Northern and Western blot analysis, respectively, 16 h after CLP or sham operation. Sepsis resulted in a 70% increase in the 1. 2-kb E214k transcript in the fast-twitch extensor digitorum longus muscle, whereas no changes were seen in the slow-twitch soleus muscle. E214k protein levels were not influenced by sepsis in any of the muscles studied. Although the changes in the expression of the E214k 1.2-kb transcript paralleled the differential effect of sepsis on protein breakdown in fast- and slow-twitch muscle, the potential role of E214k in the regulation of sepsis-induced muscle proteolysis needs to be interpreted with caution, because the results demonstrated that increased message levels were not associated with increased E214k protein levels.

Counter-regulatory hormones and mechanisms in amino acid metabolism with special reference to the catabolic response in skeletal muscle

There is evidence that both counter-regulatory hormones, in particular glucocorticoids, and cytokines influence amino acid and protein metabolism in skeletal muscle, and that these two groups of regulators interact in the development of muscle catabolism. Glucocorticoids stimulate muscle proteolysis during sepsis and also in other catabolic conditions. In addition, glucocorticoids regulate muscle glutamine metabolism, resulting in increased glutamine release and reduced glutamine concentrations in skeletal muscle. Glucocorticoids inhibit the glutamine transporter in skeletal muscle and stimulate glutamine synthetase activity. Proinflammatory cytokines, in particular tumor necrosis factor and interleukin-1, inhibit muscle amino acid transport by system A, and these cytokine effects are probably indirect. Most of the catabolic effects of tumor necrosis factor in skeletal muscle, including stimulated protein degradation and inhibited amino acid uptake, are mediated by glucocorticoids.

Nuclear factor-kappaB is activated in intestinal mucosa during endotoxemia

BACKGROUND

The transcription factor nuclear factor-kappaB (NF-kappaB) regulates a large number of genes involved in the inflammatory response to critical illness. The intestinal mucosa plays an active role in the inflammatory and metabolic response to sepsis and endotoxemia, but it is not known if NF-kappaB is activated in the mucosa during these conditions.

OBJECTIVE

To test the hypothesis that endotoxemia in mice activates NF-kappaB in intestinal mucosa.

METHODS

Mice were injected subcutaneously with lipopolysaccharide, 12.5 mg/kg, or a corresponding volume of saline. At various intervals following injection, jejunal mucosa was harvested and nuclear and cytoplasmic fractions were prepared. The nuclear fractions were analyzed by electrophoretic mobility shift assay for NF-kappaB activation and by Western blot analysis for the NF-kappaB subunits p50 and p65. Cytoplasmic fractions were analyzed by Western blotting for the NF-kappaB inhibitory proteins IkappaB-alpha and IkappaB-beta.

RESULTS

Electrophoretic mobility shift assay showed that NF-kappaB was activated in jejunal mucosa 1 hour after injection of lipopolysaccharide and persisted for at least 4 hours. The NF-kappaB subunits p50 and p65 were present in nuclear fractions of mucosa from endotoxemic mice at the corresponding time points. Cytoplasmic levels of the inhibitory proteins IkappaB-alpha and IkappaB-beta decreased during endotoxemia, and the proteins were nearly absent 60 minutes after injection of lipopolysaccharide.

CONCLUSIONS

The results suggest that IkappaB is degraded and NF-kappaB is activated in intestinal mucosa during endotoxemia. The findings support the concept that the intestinal mucosa is an important component of the inflammatory response to sepsis and endotoxemia.

Sepsis in mice stimulates muscle proteolysis in the absence of IL-6

We tested the role of interleukin-6 (IL-6) in sepsis-induced muscle proteolysis by determining ubiquitin mRNA levels and protein breakdown rates in incubated extensor digitorum longus muscles from septic and sham-operated IL-6 knockout and wild-type mice. In addition, the effect of treatment of mice with human recombinant IL-6 on muscle protein breakdown rates was determined. Finally, protein breakdown rates were measured in myotubes treated for up to 48 h with different concentrations of IL-6. Sepsis in wild-type mice resulted in an approximately ninefold increase in plasma IL-6 levels, whereas IL-6 was not detectable in plasma of sham-operated or septic IL-6 knockout mice. Total and myofibrillar muscle protein breakdown rates were increased by approximately 30% and threefold, respectively, in septic IL-6 wild-type mice with an almost identical response noted in septic IL-6 knockout mice. Ubiquitin mRNA levels determined by dot blot analysis were increased during sepsis in muscles from both IL-6 knockout and wild-type mice, although the increase was less pronounced in IL-6 knockout than in wild-type mice. Treatment of normal mice or of cultured L6 myotubes with IL-6 did not influence protein breakdown rates. The present results suggest that IL-6 does not regulate muscle proteolysis during sepsis.

Endotoxemia in mice stimulates production of complement C3 and serum amyloid A in mucosa of small intestine

We examined the effect of endotoxemia in mice on protein and mRNA levels for the acute phase proteins complement C3 and serum amyloid A (SAA) in jejunal mucosa. Endotoxemia was induced in mice by the subcutaneous injection of 250 microg lipopolysaccharide per mouse. Control mice were injected with saline. C3 and SAA were measured by ELISA. Messenger RNA levels were determined by Northern blot analysis or competitive PCR. Immunohistochemistry was performed to determine in which cell type(s) C3 and SAA were present. Mucosal C3 and SAA protein and mRNA levels were increased in endotoxemic mice. Immunohistochemistry showed that C3 was present in both enterocytes and cells of the lamina propria, whereas SAA was seen mainly in lamina propria cells. Results suggest that endotoxemia stimulates production of C3 and SAA in small intestinal mucosa. The response may be regulated at the transcriptional level and probably reflects increased synthesis of the acute phase proteins in both enterocytes and cells of the lamina propria.

Mucosal production of complement C3 and serum amyloid A is differentially regulated in different parts of the gastrointestinal tract during endotoxemia in mice

The effect of endotoxemia and sepsis on mucosal production of the acute-phase proteins complement component C3 and serum amyloid A (SAA) was studied in mice. In addition, the role of the proinflammatory cytokines tumor necrosis factor-alpha, interleukin (IL)(-1)beta, and IL-6 on mucosal C3 and SAA production was examined. Endotoxemia was induced by the subcutaneous injection of 250 microg/mouse of lipopolysaccharide. Control mice were injected with corresponding volumes of sterile saline solution. Sepsis was induced by cecal ligation and puncture, and sham-operated mice served as controls. Endotoxemia resulted in increased mucosal C3 levels in all parts of the gastrointestinal tract examined, from the stomach to the colon, with the most pronounced effects noticed in the proximal gastrointestinal tract. The influence of endotoxemia on mucosal SAA production was more differentiated with increased levels noted in the jejunum and ileum, and no changes seen in gastric and colonic mucosa. Sepsis resulted in similar changes in mucosal C3 and SAA levels as seen in endotoxemic mice, except that SAA levels were increased in colonic mucosa of septic mice. Among the cytokines, IL(-1)beta resulted in the most pronounced changes in mucosal acute-phase proteins. The increase in C3 and SAA levels in the mucosa of the small intestine during endotoxemia was partially blocked by IL(-1) receptor antagonist. The results suggest that endotoxemia is associated with increased mucosal C3 production in different parts of the gastrointestinal tract and increased SAA production in the mucosa of the small intestine. Mucosal acute-phase protein synthesis may, at least in part, be regulated by IL(-1)beta.

Treatment of burned rats with insulin-like growth factor I inhibits the catabolic response in skeletal muscle

Thermal injury is associated with a pronounced catabolic response in skeletal muscle, reflecting inhibited protein synthesis and increased protein breakdown, in particular myofibrillar protein breakdown. Administration of insulin-like growth factor I (IGF-I) has a nitrogen-sparing effect after burn injury, but the influence of this treatment on protein turnover rates in skeletal muscle is not known. In the present study, we examined the effect of IGF-I on muscle protein synthesis and breakdown rates following burn injury in rats. After a 30% total body surface area burn injury or sham procedure, rats were treated with a continuous infusion of IGF-I (3. 5 or 7 mg . kg-1 . 24 h-1) for 24 h. Protein synthesis and breakdown rates were determined in incubated extensor digitorum longus muscles. Burn injury resulted in increased total and myofibrillar protein breakdown rates and reduced protein synthesis in muscle. The increase in protein breakdown rates was blocked by both doses of IGF-I and the burn-induced inhibition of muscle protein synthesis was partially reversed by the higher dose of the hormone. IGF-I did not influence muscle protein turnover rates in nonburned rats. The results suggest that the catabolic response to burn injury in skeletal muscle can be inhibited by IGF-I.

Proteasome blockers inhibit protein breakdown in skeletal muscle after burn injury in rats

1. Burn injury stimulates ubiquitin-dependent protein breakdown in skeletal muscle. The 20S proteasome is the proteolytic core of the 26S proteasome that degrades ubiquitin conjugates. We examined the effects of the proteasome inhibitors N-acetyl-L-leucinyl-L-leucinal-L-norleucinal (LLnL), lactacystin and beta-lactone on protein breakdown in muscles from burned rats. 2. A full-thickness burn of 30% total body surface area was inflicted on the back of rats. Control rats underwent a sham procedure. After 24 h, extensor digitorum longus muscles were incubated in the absence or presence of 20S proteasome blocker and protein turnover rates and ubiquitin mRNA levels were determined. 3. LLnL resulted in a dose- and time-dependent inhibition of total protein breakdown in incubated muscles from burned rats. Lactacystin and beta-lactone blocked both total and myofibrillar muscle protein breakdown. In addition to inhibiting protein breakdown, LLnL increased ubiquitin mRNA levels, possibly reflecting inhibited proteasome-associated RNase activity. 4. Inhibited muscle protein breakdown caused by LLnL, lactacystin and beta-lactone supports the concept that the ubiquitin-proteasome pathway plays a central role in burn-induced muscle proteolysis. Because the proteasome has multiple important functions in the cell, in addition to regulating general protein breakdown, further studies are needed to test the role of proteasome blockers in the treatment or prevention of muscle catabolism.

Interleukin-6 production in human intestinal epithelial cells increases in association with the heat shock response

BACKGROUND

In recent studies, IL-1beta stimulated the production of IL-6 in human enterocytes. The heat shock response influences the production of inflammatory mediators in certain cell types. We tested the hypothesis that heat shock regulates IL-1beta-induced IL-6 production in human intestinal epithelial cells.

MATERIALS AND METHODS

Cultured Caco-2 cells, a human intestinal epithelial cell line, were exposed to thermal heat shock at 43 degreesC for 1 h and recovered at 37 degreesC for 1 h. Cells were harvested for analysis of heat shock protein-70 (HSP-70) production by Western blotting. In other experiments, IL-1beta (0.5 ng/ml) was added following heat shock and recovery. IL-6 protein was measured in culture medium after 24 h by enzyme-linked immunosorbent assay and IL-6 messenger RNA (mRNA) levels were measured after 4 h by competitive reverse transcriptase polymerase chain reaction.

RESULTS

Heat shock resulted in the production of HSP-70 and potentiated IL-1beta-induced IL-6 production. The response to heat shock was associated with increased IL-6 mRNA levels.

CONCLUSIONS

The results suggest that IL-1beta-induced IL-6 production in human enterocytes is increased in association with the heat shock response. The biological role of heat shock-potentiated IL-6 production in the enterocyte remains to be determined.