Tumor necrosis factor inhibits growth hormone-mediated gene expression in hepatocytes

Growth hormone (GH) stimulates STAT5 phosphorylation by JAK2, which activates IGF-I and serine protease inhibitor 2.1 (Spi 2.1) transcription, whereas STAT5 dephosphorylation by protein tyrosine phosphatases (PTPs) terminates this signal. We hypothesized that the inhibitory effects of TNF on GH signaling and gene transcription were responsible for hepatic GH resistance. CWSV-1 hepatocytes were treated with TNF, pervanadate (a PTP inhibitor), or both, before GH stimulation. Total and tyrosine-phosphorylated JAK2, STAT5, ERK1/2, SHP-1 and SHP-2, IGF-I, and Spi 2.1 mRNA levels were measured. GH stimulated STAT5 and ERK1/2 phosphorylation, IGF-I, and Spi 2.1 mRNA expression. TNF attenuated JAK2/STAT5 and ERK1/2 phosphorylation and IGF-I and Spi 2.1 mRNA expression following GH stimulation. SHP-1 and SHP-2 protein levels were unaltered by TNF or GH, and the GH-induced increase in SHP-1 PTP activity was not further increased by TNF. In TNF-treated cells, pervanadate restored STAT5 and ERK1/2 phosphorylation to control levels following GH stimulation but did not restore IGF-I or Spi 2.1 mRNA induction. Cells transfected with a Spi 2.1 promoter-luciferase vector demonstrate a 50-fold induction in luciferase activity following GH stimulation or cotransfection with a constitutively active STAT5 vector. TNF prevented the induction of Spi 2.1 promoter activity by GH and the STAT5 construct. We conclude that TNF does not inhibit GH activity by inducing SHP-1 or -2 expression and that correction of GH signaling defects in TNF-treated cells by pervanadate does not restore GH-induced gene expression. The inhibitory effects of TNF on GH-mediated gene transcription appear independent of STAT5 activity and previously identified abnormalities in JAK2/STAT5 signaling.

The Inhibitory Effects of Interleukin‐1 on Growth Hormone Action During Catabolic Illness

Growth hormone (GH) induces the expression of the anabolic genes responsible for growth, metabolism, and differentiation. Normally, GH stimulates the synthesis of circulating insulin-like growth factor-I (IGF-I) by liver, which upregulates protein synthesis in many tissues. The development of GH resistance during catabolic illness or inflammation contributes to loss of body protein, resulting in multiple complications that prolong recovery and cause death. In septic patients, increased levels of proinflammatory cytokines and GH resistance are commonly observed together. Numerous studies have provided evidence that the inhibitory effects of cytokines on skeletal muscle protein synthesis during sepsis and inflammation are mediated indirectly by changes in the GH/IGF-I system. Interleukin (IL)-1, a member of the family of proinflammatory cytokines, interacts with most cell types and is an important mediator of the inflammatory response. Infusion of a specific IL-1 receptor antagonist (IL-1Ra) ameliorates protein catabolism and GH resistance during systemic infection. This suggests that IL-1 is an important mediator of GH resistance during systemic infection or inflammation. Consequently, a better understanding of the interaction between GH, IL-1, and the regulation of protein metabolism is of great importance for the care of the patient.

Capsaicin-sensitive nerves regulate the metabolic response to abdominal sepsis

BACKGROUND

Both the systemic release of inflammatory mediators and activation of the neuroendocrine axis by sensory afferent nerves (SANs) have been implicated as initiators of the metabolic response to infection. In this study, we investigate the role of SANs as mediators of protein catabolism and the insulin-like growth factor (IGF) axis during abdominal sepsis using capsaicin (Cap) to selectively destroy nociceptive sensory axons.

METHODS

Four groups of male Sprague-Dawley rats were studied: Control, Control+Cap, Sepsis, and Sepsis+Cap. Rats were injected with Cap (75 mg/kg) on day 1 and (50 mg/kg) on day 2 to destroy SANs. Time-matched control and septic rats were pair-fed and injected with vehicle on the same schedule. Controls underwent sham laparotomy, while septic rats had a fecal-agar pellet inoculated with Escherichia coli and Bacteroides fragilis implanted in the peritoneal cavity. Blood and tissues were harvested 5 days after the induction of sepsis. Plasma IGF-I, IGFBP-1, and -3 were measured by radioimmunoassay and Western blot analysis. IGF-I, acid-labile subunit (ALS), IGFBP-1 and -3 mRNA levels were determined by Northern blot analysis.

RESULTS

Mortality was 40% in septic rats vs 0% in the sepsis+Cap group. Capsaicin had no effect on muscle mass, protein content, or the IGF system in control rats. However, sepsis-induced reductions in gastrocnemius mass (25%) and protein content (35%) were ameliorated by capsaicin. The sepsis-induced decrease in hepatic IGF-I mRNA and circulating IGF-I (26%), as well as the 4-fold increase in plasma IGFBP-1 and hepatic IGFBP-1 mRNA were prevented by capsaicin.

CONCLUSIONS

Capsaicin-sensitive nerves mediate mortality, the catabolism of skeletal muscle, and selected elements of the IGF system during abdominal sepsis. The results suggest an important role for nociceptive SANs and the neuroendocrine system in mediating the host response to abdominal infection.

Effectiveness of components of self-verbalization training for control of cold pressor pain

The increase of positive self-verbalizations (PSV), the decrease of negative self-verbalizations (NSV), their combination (PSV + NSV) and the use of an informational rationale that included a reconceptualization of pain were compared to a test-retest control group for ice water endurance. The Thought-Listing Questionnaire (TLQ) was used to assess participant thoughts. Sixty college women were pretested, given training, and posttested for ice water tolerance. Only the three self-talk treatments (PSV, NSV, PSV + NSV) produced greater pain tolerance. Analysis of TLQ data revealed a relationship between changes in thoughts and self-control of pain. Results suggest that, in contrast to some previous research, PSV and NSV were effective pain control techniques. Differences from other studies included using client-generated thoughts, examining client metacognitions, and promoting high compliance with training (tested by the TLQ). Client use of 'spontaneous' coping strategies was also discussed.

Effects of tumor necrosis factor-binding protein on hepatic protein synthesis during chronic sepsis

BACKGROUND

Cytokines are thought to play a role in the stimulation of protein synthesis in liver during inflammation and sepsis. We previously showed that administration of tumor necrosis factor-binding protein (TNFbp) prevents the sepsis-induced inhibition of protein synthesis in skeletal muscle. The purpose of the present set of experiments was to investigate the effect of TNFbp on hepatic protein synthesis and its ability to modulate the mechanisms responsible for increased hepatic protein synthesis during chronic (5-day) intraabdominal sepsis.

MATERIALS AND METHODS

We examined the effects of TNFbp on hepatic protein synthesis during sepsis in four groups of rats: control, control + TNFbp, septic, and septic + TNFbp. Saline (1.0 ml) or TNFbp (1 mg/kg, 1.0 ml) was injected daily starting 4 h prior to the induction of sepsis. The effect of sepsis and TNFbp administration on hepatic protein synthesis in vivo was examined 5 days later.

RESULTS

Sepsis increased the rate of protein synthesis by 35% relative to controls. Accelerated rates of protein synthesis were accompanied by increased total RNA content, eukaryotic initiation factor (eIF) 2alpha content, and phosphorylation of p70S6 kinase. Injection of TNFbp into septic rats for 5 days did not diminish the sepsis-induced stimulation of hepatic protein synthesis. Compared with controls, septic rats treated with TNFbp also showed elevated total RNA content, elF2alpha content, and phosphorylation of p70S6 kinase. No significant differences in any of the parameters measured were observed between untreated and TNFbp-treated septic rats. Treatment of control animals with TNFbp for 5 days was without effect on any of the parameters examined.

CONCLUSIONS

TNFbp did not prevent the sepsis-induced stimulation of hepatic protein metabolism or modulate the septic-induced changes in factors regulating protein synthesis. Global rates of protein synthesis in livers from septic rats are accelerated by increases in the abundance or activity of components of translational apparatus.

Chronic infusion of interleukin 1 induces hyperlactatemia and altered regulation of lactate metabolism in skeletal muscle

BACKGROUND

Hyperlactatemia is observed commonly in patients with severe inflammation syndrome or sepsis. Elevated plasma lactate concentrations may be caused by cytokine-mediated alterations in specific organ systems responsible for lactate homeostasis. The role of interleukin 1 (IL-1) in inducing hyperlactatemia and derangements in skeletal muscle and hepatic lactate metabolism was investigated by examining the consequences of infusing IL-1 continuously into normal rats.

METHODS

Male Sprague-Dawley rats were anesthetized, and catheters were placed in the jugular vein. Rats were allowed to recover for 48 hours and were infused subsequently with either saline (control) or human recombinant IL-1alpha (20 microg/kg/d) for 6 days. On day 6, plasma, liver, and muscle samples were extracted and assayed for lactate and pyruvate dehydrogenase (PDH) activity.

RESULTS

Plasma glucose concentrations were not different in the two groups. IL-1 infusion resulted in a twofold (p < .05) increase in the plasma lactate concentration compared with controls. IL-1 infusion also resulted in an elevated lactate content in skeletal muscle (p < .05) but not in liver. The proportion of PDH in the active form (PDHa) was reduced significantly (p < .05) in the skeletal muscle of animals infused with IL-1 compared with controls. In contrast to muscle, hepatic PDHa did not differ between the two groups. Total PDH complex activity was not affected in either liver or skeletal muscle.

CONCLUSIONS

IL-1 infusion results in hyperlactatemia, increased skeletal muscle lactate, and a reduced PDHa in skeletal muscle. We conclude that IL-1 is a potential mediator of the derangements in lactate metabolism in skeletal muscle but not in liver.

TNF-binding protein ameliorates inhibition of skeletal muscle protein synthesis during sepsis

We examined the effects of TNF-binding protein (TNFBP) on regulatory mechanisms of muscle protein synthesis during sepsis in four groups of rats: Control; Control+TNFBP; Septic; and Septic+TNFBP. Saline (1. 0 ml) or TNFBP (1 mg/kg, 1.0 ml) was injected daily starting 4 h before the induction of sepsis. The effect of TNFBP on gastrocnemius weight, protein content, and the rate of protein synthesis was examined 5 days later. Sepsis reduced the rate of protein synthesis by 35% relative to controls by depressing translational efficiency. Decreases in protein synthesis were accompanied by similar reductions in protein content and muscle weight. Treatment of septic animals with TNFBP for 5 days prevented the sepsis-induced inhibition of protein synthesis and restored translational efficiency to control values. TNFBP treatment of Control rats for 5 days was without effect on muscle protein content or protein synthesis. We also assessed potential mechanisms regulating translational efficiency. The phosphorylation state of p70(S6) kinase was not altered by sepsis. Sepsis reduced the gastrocnemius content of eukaryotic initiation factor 2Bepsilon (eIF2Bepsilon), but not eIF2alpha. The decrease in eIF2Bepsilon content was prevented by treatment of septic rats with TNFBP. TNFBP ameliorates the sepsis-induced changes in protein metabolism in gastrocnemius, indicating a role for TNF in the septic process. The data suggest that TNF may impair muscle protein synthesis by reducing expression of specific initiation factors during sepsis.

Brain injury-induced enhanced limbic epileptogenesis: anatomical and physiological parallels to an animal model of temporal lobe epilepsy

Traumatic brain injury (TBI) is a leading cause of symptomatic epilepsy in young adults. This study examined physiological and anatomical epileptogenic consequences of a prior incident of TBI in rats. Rats were subjected to a fluid percussion brain injury one week prior to experimentation, and in vitro electrophysiological recording studies were conducted using combined hippocampal-entorhinal cortical slices (HEC slices). Results were compared to sham operated controls and rats in which a condition of chronic temporal lobe epilepsy was induced by a 2 h bout of pilocarpine-induced status epilepticus 2 months prior to recording (PILO). In field potential recording, PILO HEC slices evidenced a greater degree of disinhibition in Ca1 than did TBI or control slices. TBI slices showed greater disinhibition in the dentate gyrus than did PILO or control rats. In in vitro kindling experiments, 86% of TBI HEC slices generated self-sustaining epileptic activity within 9 stimulus trains. This type of activity was never triggered in control slices. HEC slices prepared from PILO animals generated self-sustaining epileptic activity with fewer stimulus trains than did TBI slices. In anatomical studies, both TBI and PILO hippocampi evidenced significant loss of neurons within the hilar region. TBI induces a series of changes within the limbic system of rats, which are qualitatively similar in many aspects but quantitatively less severe than changes seen in rats with chronic temporal lobe epilepsy. These physiological and anatomical TBI-associated alterations in the limbic system may contribute to the development of epilepsy following head trauma.

Which prepared-childbirth coping strategies are effective?

To investigate coping strategies taught in childbirth education classes, a study was conducted to nulliparous women immersing their hands in ice water. Length of tolerance and self-reported pain served as measures of the techniques' effectiveness. Results in Experiment 1 showed structured breathing to be more effective than normal breathing. Effleurage was less helpful than no effleurage. Practice under stress was better than either imaginal practice or no practice. In Experiment 2 a combination of structured breathing and attention focal points was much better than normal breathing. While coaching was better than no coaching, the combination of structured breathing, attention focal points, and coaching produced the strongest treatment.

Is the Vando Scale a valid measure of perceptual reactance?

A test of the validity of the Vando Scale of perceptual reactance was made by correlating Vando Scale scores with objective pain tolerance, subjective discomfort, distortion in estimation of duration of discomfort, and assertiveness. 84 college women participated in an ice water-tolerance task. Higher scores associated with less subjective discomfort, greater time distortion and reduced submissiveness. Objective tolerance was not correlated with scale scores. It was concluded that the Vando Scale has relatively low construct validity and may be very sensitive to the demand characteristics of the research situation.