Influence of the Ward colon tumor on the host response to endotoxin

Myeloid-derived suppressor cells in cancer cachexia syndrome: a new explanation for an old problem

Cachexia accompanies many chronic inflammatory diseases, including cancer. Lean tissue wasting is only one component of the cancer cachexia response, which also includes anemia, anorexia, a hepatic acute phase protein response, and increased susceptibility to secondary infections. The etiologies of cancer cachexia are multifactorial and include an overproduction of inflammatory mediators, including cytokines produced by inappropriate activation of innate immunity. However, anticytokine therapies have generally not been seriously considered for cancer cachexia, in large part because of the overlapping activities of several inflammatory cytokines and the inability to prospectively identify the contributions of individual mediators. In contrast, recent evidence has focused on an immature myeloid cell population that expands dramatically in the tumors and secondary lymphoid organs of animals with some actively growing tumors. These immature GR-1(+)CD11b(+) cells are metabolically active and secrete large quantities of inflammatory cytokines and chemokines with the potential to produce cachexia. Their expansion is temporally associated with the development of cachexia. Future studies are required to determine whether therapeutic efforts intended to block the expansion of these cells can prevent the lean tissue wasting that accompanies active tumor growth.

A proinflammatory tumor that activates protein degradation sensitizes rats to catabolic effects of endotoxin

Chronic or acute inflammation may participate in the etiology of cancer cachexia. To investigate the interaction between tumor and a secondary inflammatory stimulus on muscle wasting, rats with and without tumors (Yoshida ascites hepatoma) received low doses of endotoxin (LPS, 400 microg/kg sc) or saline. Nitrogen balance was measured 24 h before and after LPS/saline. Epitrochlearis muscle was used to measure in vitro protein metabolism, and gastrocnemius muscle was used for quantification of the mRNA for components of the ubiquitin proteolytic pathway. The YAH reduced muscle mass (P = 0.002), increased muscle protein degradation (P = 0.042), and elevated mRNA expression of components of the ubiquitin proteolytic pathway (P < 0.01) including ubiquitin, ubiquitin-conjugating enzyme E2(14k), and ubiquitin ligases muscle RING Finger 1 and atrogin-1. Although the selected low dose of LPS had no impact on protein metabolism in control rats, LPS in rats bearing YAH caused weight loss (P = 0.0007), lowered nitrogen balance (P = <0.0001), and increased muscle protein degradation (P = 0.0336). In conclusion, the presence of a tumor can potentiate whole body and muscle-specific catabolic losses of protein in response to a stimulus that is not catabolic in healthy animals. This effect might be dependent on the inflammatory nature of the tumor.

Influence of the ward colon tumor on the innate and endotoxin-induced inflammatory response of the rat

Cachexia, a depressed immune function, and an increased infection rate are recurring problems for cancer patients; the response of the host to an infection may also be increased. We have reported that the transplantable Ward colon tumor (WCT) enhanced the lethality of endotoxin (lipopolysaccharide [LPS]) to the host. The mechanism of this increased LPS lethality and the effect of the presence of the WCT on the host inflammatory response, however, have not been reported. The effect of a transplantable WCT on the innate and endotoxin-induced inflammatory response of rats was, therefore, investigated. The innate inflammatory response was investigated in two ways. First, the formation of a granuloma around a sterile string implanted subcutaneously for 6 days was determined. Second, the effect of tumor presence on the trafficking of leukocytes to a sponge implanted subcutaneously for 2 or 6 days was determined. The tumor decreased the foreign body granuloma formation around a sterile string. The presence of the WCT also significantly blunted the increase of lymphocytes that migrated to the sponge area at 6 days. There was no significant effect of the WCT, however, on the migration of neutrophils, monocytes, or eosinophils to the implanted sponge. The leukocyte distribution of the peripheral blood was not affected by the presence of the WCT or implantation of a sterile string or sponge. To determine the effect of the presence of the WCT on the response of the host to an infection, rats were given LPS (5 mg/kg, i.p.) and the alanine amino transferase (ALT) of plasma and inducible isoforms of nitric oxide synthase (NOS2) protein content of liver, spleen, and terminal ileum was determined. The LPS challenge resulted in an increase in plasma ALT concentrations and NOS2 protein content of liver and spleen, but not the terminal ileum of WCT rats. This elevation in WCT rats confirms that the enhanced LPS-related toxicity in WCT rats was related to an increased liver toxicity. The increased toxicity may be related to an increase in the nitric oxide synthesis of the liver. These results suggest that the WCT, and possibly other tumors, will reduce the ability of the host to respond to a foreign body. If this were an infection, the host would be more likely to succumb to the resulting inflammatory mediators. Further evaluations of the lymphocyte subsets and cytokines in the sponge exudate will be required to completely understand this response.

Organ sites of lipopolysaccharide-induced nitric oxide production in the anesthetized rat

The objective of this research was to determine the amount and timing of nitric oxide (NO, nitrogen monoxide) gas produced by the lungs, intestinal mucosa, and organ surfaces facing the peritoneal cavity after iv injection of a bacterial toxin, lipopolysaccharide (LPS). Some of the deleterious effects of LPS on organ function have been attributed to NO or strong oxidants formed locally from NO. Medical-grade air was used as an inspiratory air source (50 strokes/min x 3 ml/stroke) or was pumped through the ileal lumen or peritoneal cavity (20 strokes/min x 3 ml/stroke). The air was collected at intervals of 15-30 min for 3 h after LPS and analyzed for authentic NO gas by chemiluminescence. LPS (5 mg/kg) or saline was injected iv. Sodium nitroprusside (SNP) was injected to determine the appearance of its NO released into the perfused compartments. Blood pressure, plasma nitrate plus nitrite (NO(x)), and total plasma leukocytes were measured as other manifestations of LPS effects. NO began to increase in the pulmonary expired air 90 min after LPS and continued to increase for the remainder of the experiment. The final pulmonary post-LPS [NO] was about 20-fold greater than the [NO] before LPS. LPS had no effect on intraluminal or intraperitoneal [NO]. The saline injection had no effect on [NO] in any compartment. SNP injection increased NO entry into all three air-perfused compartments. Thus, NO from an exogenous tissue source was not prevented from being detected. Blood pressure was decreased by LPS only during the pulmonary perfusion. There were no significant effects of LPS on leukocytes or plasma NO(x). LPS decreased blood pressure and leukocytes and increased plasma NO(x) when air perfusion was not done. It was concluded that different organs can produce LPS-induced NO at markedly different rates and times. However, some aspect of the experimental technique of air perfusion could alter the effects of LPS.

Growth inhibition of subcutaneously transplanted hepatomas without cachexia by alteration of the dietary arginine-methionine balance

Previous studies have shown that alteration of the dietary arginine-methionine balance by use of synthetic L-amino acids inhibits tumor growth of a subcutaneously transplanted Morris hepatoma at the expense of maintaining body weight. However, L-methionine is susceptible to degradation and, therefore, may contribute to a deficiency state. The present studies were performed to determine whether growth of subcutaneous hepatoma transplants is inhibited, and body growth maintained, when rats are fed diets containing L-methionine in replacement of N-acetyl-L-methionine (NALM) for 28 days. Tumor-free and tumor-bearing rats fed a control diet, with amino acids replacing protein, had gains in body weight: 31.3 +/- 1.0 and 19.1 +/- 0.5 g (12% and 7%), respectively. Rats fed six experimental diets, with varying L-arginine-NALM balances, had body weight gains ranging from 18.4 +/- 0.3 to 26.7 +/- 0.9 g (7-10%). Tumor weight of control rats was 10.65 +/- 0.24% of body weight. Diets supplemented with L-arginine in combination with normal and deficient NALM decreased tumor weights by 35% and 38%, respectively, It is concluded that dietary replacement of L-methionine with NALM and supplementation with L-arginine inhibits growth of a subcutaneously transplanted Morris hepatoma in the absence of cachexia.