Effects Of Tumor Necrosis Factor-α Research Articles

Protective effect of tumor necrosis factor-alpha against subsequent endotoxemia in mice is mediated, in part, by interleukin-10.

Tumor necrosis factor (TNF)-alpha administration in large amounts can induce a state of shock similar to that observed in patients suffering from septic shock. Small doses of TNF-alpha induce only mild, transient hemodynamic alterations and can confer protection against subsequent inflammatory stimuli. The objective of this study was to determine whether this protective mechanism could be attributed to activity of the anti-inflammatory cytokine interleukin (IL)-10. Prospective, randomized, controlled study. Investigative intensive care unit at a medical university. Female BALB-c mice, 10-12 wks of age (approximately 20 g). All mice were subjected to intraperitoneal (ip) injection of lipopolysaccharide (LPS; Escherichia coli 0111:B4, 125 microg). Mice were randomly assigned to the following groups: TNF-alpha pretreated (100 microg ip 24 hrs before LPS); control (TNF vehicle alone 24 hrs before LPS); TNF/anti-IL-10 pretreated (TNF pretreatment as above and a neutralizing anti-IL-10 antibody); TNF/anti-IL-10 control (TNF pretreatment as above and an isotype-matched control antibody with no IL-10 activity); IL-10 (100 microg ip 1 hr before LPS); and IL-10 control (IL-10 vehicle 1 hr before LPS). Mice were observed for a 48-hr period after endotoxin administration. Mortality in each group was recorded. Separate groups of mice were pretreated with TNF (or vehicle) and killed at 0, 2, or 4 hrs after LPS injection for collection of serum and peritoneal lavage samples that were used to assay IL-10 concentrations. A small dose of TNF-alpha attenuated mortality in mice that were subsequently injected with a highly lethal dose of endotoxin and observed for 48 hrs. Peritoneal lavage fluid concentrations of IL-10 were consistently higher in TNF-pretreated mice after endotoxin administration. The TNF-alpha protective effect was reversed by administration of a neutralizing antibody directed against murine IL-10. These findings indicate that administration of a low dose of TNF-alpha can induce cross-tolerance to endotoxin by induction of endogenous anti-inflammatory mechanisms.

Nitric Oxide Mediates the Inhibitory Effect of Tumor Necrosis Factor-α on Prolactin Release

Tumor necrosis factor-α (TNF-α) is a pleiotropic cytokine that markedly affects neuroendocrine functions. This cytokine is expressed in the anterior pituitary where its receptors are also present. Nitric oxide (NO) is synthesized in gonadotropes and folliculo-stellate cells of the anterior pituitary. Since NO directly inhibits prolactin secretion, we investigated the involvement of NO in the inhibitory effect of TNF-α on prolactin release from anterior pituitary cells of female rats. The presence of L-NAME (1 mM), an inhibitor of NO synthase (NOS), in the incubation medium significantly blunted the inhibition of prolactin release produced by TNF-α (50 ng/ml). TNF-α increased nitrite release to the incubation medium. The activity of NOS as measured by [¹⁴C]citrulline production was significantly enhanced when anterior pituitary cells were incubated with TNF-α for 8 h or more. Also, TNF-α induced iNOS gene expression in anterior pituitary cells as assessed by reverse transcriptase-polymerase chain reaction. The current results indicate that NO is involved in the inhibitory effect of TNF-α on prolactin secretion and that TNF-α induces iNOS transcription and stimulates NO synthesis in anterior pituitary cells.

Effects of tumor necrosis factor-α, epidermal growth factor and transforming growth factor-α on interleukin-8 production by, and human rhinovirus replication in, bronchial epithelial cells

Previous studies have shown that the epidermal growth factor (EGF) and transforming growth factor-α (TGF-α), members of the EGF growth factor family, regulate processes involved in airway repair after injury. Our studies were conducted to determine whether EGF and TGF-α directly control processes involved in the pathogenesis of airway inflammation and/or modulate the inflammatory effects of TNF-α in the airway mucosa. We have found that these cell growth factors directly induced interleukin-8 (IL-8) production by an immortalized human bronchial epithelial cell line (BEAS-2B cells). Furthermore, EGF and TGF-α enhanced tumor necrosis factor-α (TNF-α) induced IL-8 production by BEAS-2B cells. On the other hand, EGF but not TGF-α increased viral replication by BEAS-2B cells exposed to HRV-14. Moreover, TNF-α increased viral replication in the presence of EGF but not TGF-α. In conclusion, this study demonstrates that both EGF and TGF-α play an active role in the pathogenesis of airway inflammation.

Effects of tumor necrosis factor-α on secretion of prostaglandins E 2 and F 2α in bovine endometrium throughout the estrous cycle

To determine the physiological significance of tumor necrosis factor-α (TNFα) in the regulation of endometrial prostaglandin (PG) release in cattle, we investigated the effects of TNFα on the secretion of PGE 2 and PGF 2α by bovine endometrium during the estrous cycle. Bovine uteri were classified into six stages (estrus: Day 0, early luteal I: Days 2 to 3, early luteal II: Days 5 to 6, mid-luteal: Days 8 to 12, late luteal: Days 15 to 17 and follicular: Days 19 to 21). After 1 h of pre-incubation, endometrial tissues (20 to 30 mg) were exposed to 0 or 0.6 nM TNFα for 4 h. The PGE 2 concentrations in the medium were higher in the luteal stages than in the follicular stage and in estrus. In contrast, PGF 2α concentrations were higher in the follicular stage and in estrus than in the luteal stages. The ratio of the basal concentrations of PGE 2 and PGF 2α (PGE 2/PGF 2α ratio) was higher in the luteal stages than in the follicular stage and in estrus. Although TNFα stimulated both PGE 2 and PGF 2α secretion during the entire period of the estrous cycle, the level of stimulation of TNFα on PGE 2 output by the bovine endometrium does not show the same cyclical changes as that shown on PGF 2α output. The stimulation of TNFα resulted in a decrease in the PGE 2/PGF 2α ratio only in the late luteal stage. Furthermore, TNFα stimulated PGE 2 secretion in stromal, but not epithelial cells. The overall results suggest that TNFα is a potent regulator of endometrial PGE 2 secretion as well as PGF 2α secretion during the entire period of estrous cycle, and that TNFα plays different roles in the regulation of secretory function of bovine endometrium at different phases of the estrous cycle.

Neutrophils delay gastric ulcer healing by inhibiting angiogenesis in rats: Involvement of antiangiogenic effect of tumor necrosis factor-α

Neutrophils delay gastric ulcer healing by inhibiting angiogenesis in rats: Involvement of antiangiogenic effect of tumor necrosis factor-α

Neutrophils delay gastric ulcer healing by inhibiting angiogenesis in rats: Involvement of antiangiogenic effect of tumor necrosis factor-α

Neutrophils delay gastric ulcer healing by inhibiting angiogenesis in rats: Involvement of antiangiogenic effect of tumor necrosis factor-α

Inhibitory effects of tumor necrosis factor-α on cationic lipid-mediated gene delivery to airway cells in vitro

Cationic liposomes have been used successfully for DNA delivery to airway cells in vitro and are being tested in human clinical trials for their efficacy in cystic fibrosis transmembrane conductance regulator (CFTR) gene delivery in cystic fibrosis patients. While cationic liposomes are effective for transfection of airway cells in culture, they have not been effectively used for gene delivery to human airway cells in vivo. Several barriers in cystic fibrosis lungs, including increased amounts of mucus, phagocytic cell activity and cytokine-rich milieu caused by inflammation, may cause inhibition of gene transfection. As presented in this paper, we examined the effects of inflammatory cytokines on cationic lipid-mediated transfection of model airway cells. The results of these experiments indicate that tumor necrosis factor (TNF)-α dramatically inhibits Lipofectin-mediated transfection efficiency of H441 cells. Addition of anti-TNF-α neutralizing antibody results in recovery of efficiency. Results of temporal studies are consistent with the concept that TNF-α reduces transfection efficiency by a mechanism(s) other than or in addition to gene expression. These results are corroborated by fluorescence microscopic experiments which demonstrate that endocytosis of lipoplex is altered in the presence of TNF-α.

Differential regulation of JNK activation and MKP-1 expression by peroxovanadium complexes

Bisperoxovanadium complexes have been identified as insulinomimetic agents and protein tyrosine phosphatase inhibitors. The aim of the present study was to examine the effects of the most potent bisperoxovanadium complex, potassium bisperoxo (1,10-phenanthroline) oxovanadate (V) [bpV(phen)], on expression and activation of c-jun N-terminal protein kinases (JNK) and on expression of mitogen-activated protein kinase phosphatase-1 (MKP-1) in different cell lines. We compared the effects of bpV(phen) with the effects of tumor necrosis factor-α (TNF-α), a known regulator of JNK phosphorylation and inducer of MKP-1. Treatment with bpV(phen) causes significant and sustained down-regulation of MKP-1 expression both in PC12 and HeLa cells. In contrast, TNF-α induces MKP-1 expression in PC12 cells and does not alter MKP-1 expression in HeLa cells. Both bpV(phen) and TNF-α induce MKP-1 expression in OVCAR-3 cell line but with different dynamics: TNF-α causes transient and bpV(phen) sustained induction of MKP-1 expression. Temporal pattern of level of MKP-1 expression correlates with the regulation of JNK phosphorylation by bpV(phen) and TNF-α in PC12 cells. However, no detectable phospho-JNK signal is observed in either OVCAR-3 or HeLa cells treated with bpV(phen). In contrast, TNF-α causes strong and sustained JNK phosphorylation in OVCAR-3 cell line, and strong but transient JNK activation in HeLa cells. BpV(phen) and TNF-α does not alter JNK expression in any of the cell lines studied. We demonstrate that the effect of two stressors, bpV(phen) and TNF-α, on MKP-1 expression and JNK phosphorylation are strikingly different, depending on the cell type. These results suggest the possible role of MKP-1 in regulation of JNK phosphorylation in both PC12 and OVCAR-3 cell lines treated with bpV(phen).

Effects of tumour necrosis factor-α and inhibition of protein kinase C on glucose uptake in L6 myoblasts

Effects of tumour necrosis factor-α and inhibition of protein kinase C on glucose uptake in L6 myoblasts

Effects of tumor necrosis factor-α and interferon-γ on expressions of matrix metalloproteinase-2 and -9 in human bladder cancer cells

We have investigated the effects of tumor necrosis factor-α (TNF-α) and interferon (INF-γ), the potent Bacillus Calmette–Guerin (BCG)-induced cytokines on the production of MMP-2, MMP-9, TIMP-1, TIMP-2 and MT1-MMP in high grade human bladder cancer cell lines, T-24, J-82 and HT-1376 cell lines. MMP-2 expression and activity were decreased in T-24 cells treated with both cytokines in a dose dependent manner. However, J-82 cells treated with TNF-α and INF-γ revealed dose dependent increases of MMP-9 expression and activity with similar baseline expression and activity of MMP-2. HT-1376 cells after exposure to TNF-α only enhanced the expression and activity of MMP-9. These results indicate that TNF-α and INF-γ could regulate the production of MMP-2 or MMP-9 on bladder cancer cells and their patterns of regulation are cell specific. Furthermore, this diverse response of bladder cancer cells to TNF-α and INF-γ suggests that BCG immunotherapy may enhance the invasiveness of bladder cancer in certain conditions with induction of MMPs.

Effects of tumour necrosis factor-alpha and inhibition of protein kinase C on glucose uptake in L6 myoblasts.

Clinical and experimental studies have implicated high circulating levels of the cytokine tumour necrosis factor-alpha (TNF-alpha) in the pathogenesis of insulin resistance, not only in obesity and diabetes, but also in clinical conditions associated with cachexia and sepsis. TNF-alpha impairs insulin-mediated glucose uptake in adipocytes, but because of lipolytic effects the interpretation of clinical studies and the extent to which TNF-alpha affects muscle insulin sensitivity are unclear. In addition, protein kinase C (PKC) has recently been implicated in the mechanism of TNF-alpha-induced insulin resistance. The present study investigated the effects of TNF-alpha and a PKC inhibitor (RO-318220) on basal and insulin-stimulated 2-[(3)H]deoxyglucose uptake in cultured L6 myoblasts. Reverse transcriptase-PCR analysis confirmed that L6 myoblasts express TNF-alpha receptors I and II (p60 and p80). Dose-response curves for glucose uptake were fitted to a quadratic function to derive C(I-150) values (concentration of insulin required to increase glucose uptake by 50%). Incubation with TNF-alpha at 1 or 10 ng/ml for 24 h had no significant effect on basal glucose uptake, insulin sensitivity or maximal insulin responsiveness. C(I-150) values (means+/-S.E.M.) were as follows: basal, 91.2+/-13 nM; 1 ng/ml TNF-alpha, 102+/-12 nM; and basal, 70.8+/-13 nM; 10 ng/ml TNF-alpha, 43.7+/-40 nM. PKC inhibition markedly attenuated glucose uptake, but there was no difference in insulin sensitivity with RO-318220 alone compared with RO-318220+TNF-alpha. In conclusion, although increased TNF-alpha expression and plasma concentrations have been implicated in the pathogenesis of insulin resistance in various clinical states, there is no evidence that TNF-alpha impairs insulin-stimulated glucose uptake in a skeletal-muscle-derived cell line.

Regulation of cell cycle proteins by TNF-α and TGF-β in cells of oligodendroglial lineage

Proliferation and apoptosis are two dynamic, interrelated processes that are regulated by growth factors and cytokines. We investigated the effects of tumor necrosis factor-α (TNF-α) and transforming growth factor-β (TGF-β) on apoptosis and regulation of cell cycle proteins in OLG lineage cells. We found that: (1) both cytokines enhanced apoptosis in neonatal pre-OLGs but only TNFα-mediated apoptosis persisted in the presence of a mitogen, fibroblast growth factor (FGF); (2) cell cycle proteins such as p21 waf1/cip1, p27 kip1, cyclin D1 and PCNA were differentially regulated by TNF-α and TGF-β. We conclude that differential modulation of cell cycle proteins by TNF-α and TGF-β contributes to the diversity of their biological effects in OLG lineage cells.

Suppression of cytokine production and cell adhesion molecule expression in human monocytic cell line THP-1 by Tripterygium wilfordii polysaccharide moiety

Extracts of the vine-like plant Tripterygium wilfordii (TW) have been widely used in China as an immunosuppressant and anti-inflammatory drug for the treatments of rheumatoid arthritis, lupus erythematosus and other inflammatory disorders. In this study the molecular mechanisms of action of three TW extracts (ethanol, aqueous, polysaccharide) on the expression of inflammatory cytokines and adhesion molecules were investigated by RT-PCR and immunofluorescence binding techniques. The lipopolysaccharide (LPS)-mediated stimulatory effects of tumor necrosis factor-α (TNF-α) cytokine production and cell adhesion molecule (CD11c, CD18, CD14, CD54) expression in human monocytic THP-1 cells were modulated by treatments of the TW extracts or tacrolimus (FK506). The TW polysaccharide moiety exhibited more profound immunosuppressive properties than the aqueous and ethanol extracts. Biochemical characterization of the polysaccharide moiety revealed a major molecular weight of 22 kDa (viz. PSP22). The PSP22 was found to be a potential immunosuppressant that manifests the necessary immunomodulating properties.

Expression of GMP-140 (P-selectin) correlates with graft viability in cold-preserved rat livers.

Ischemia/reperfusion injury is an inflammatory process involving cytokine release, Kupffer cell activation, and sinusoidal endothelial cell activation. GMP-140 is synthesized by endothelial cells. We analyzed by Western blotting the expression of GMP-140 in a syngeneic rat liver transplantation model using grafts preserved for different periods of time. Compared with prereperfusion samples, expression did not change significantly in freshly harvested and 4-hr preserved livers. In grafts preserved for 24 hr (100% survival), GMP-140 levels increased dramatically at 1 hr, then returned to baseline at 24 hr after transplantation. Forty-eight hour preserved grafts (0% survival) showed a decreasing expression. To identify possible mediators, the effects of tumor necrosis factor-alpha and interleukin-1beta on GMP-140 expression in primary sinusoidal endothelial cells were analyzed. These cytokines increased both the percentage of stained cells as well as their mean staining fluorescence. The absence of increase in 48-hr grafts suggests that GMP-140 may distinguish viable from nonviable livers.

Tumor necrosis factor-α augments contraction and cytosolic Ca 2+ sensitivity through phospholipase A 2 in bovine tracheal smooth muscle

To elucidate the effects of tumor necrosis factor-α (TNF-α) on tracheal smooth muscle contraction, we simultaneously measured isometric tension and intracellular Ca 2+ ([Ca 2+] i) in fura 2-loaded muscle strips. Smooth muscle force generation was evaluated in a high potassium (K +; 20.0–80.0 mM) solution and with acetylcholine (3 nM–10 μM ). TNF-α (1–100 ng/ml) did not directly contract muscle strips. The contractile response to acetylcholine was enhanced after application of 10 ng/ml of TNF-α for 30 min but not the response of [Ca 2+] i. The contractile response and the response of [Ca 2+] i to a high K + solution were not altered after application of TNF-α. The [Ca 2+] i–tension curve indicated that TNF-α enhanced the responsiveness of tracheal smooth muscle through the acetylcholine-mediated Ca 2+ sensitivity of intracellular contractile elements. The augmentation of the acetylcholine concentration–response curves for muscle tension in the presence of TNF-α (10 ng/ml) was inhibited in part after application of manoalide, a phospholipase A 2 inhibitor. We conclude that a low concentration of TNF-α enhances smooth muscle responsiveness to acetylcholine by agonist-mediated Ca 2+ sensitivity facilitated by phospholipase A 2.

Estrogens modulate the inhibitory effect of tumor necrosis factor-alpha on anterior pituitary cell proliferation and prolactin release.

Considering that tumor necrosis factor-alpha (TNF-alpha) is involved in normal tissue homeostasis and that its receptors are expressed in the anterior pituitary, we examined the effect of this cytokine on pituitary cell growth. Because anterior pituitary function depends on hormonal environment, we also investigated the influence of gonadal steroids in the effects of TNF-alpha on cell proliferation and the release of PRL from anterior pituitary cells. In addition, the release of TNF-alpha and its action on the release of PRL from anterior pituitary cells of rats at different stages of the estrous cycle was evaluated. In minimum essential medium D-valine, a medium that restricts fibroblastic proliferation, TNF-alpha (10 and 50 ng/mL) reduced 3H-Thymidine incorporation, DNA content, and active cell number. TNF-alpha failed to affect proliferation of cells from ovariectomized (OVX) rats. However, it significantly inhibited growth of cells from OVX rats cultured with 17beta-estradiol (E2) (10(-9) M) and from chronically estrogenized rats. TNF-alpha decreased the release of PRL from cells of intact rats, especially in proestrous, OVX rats cultured with E2 and chronically estrogenized rats. The release of anterior pituitary TNF-alpha was higher in proestrous rats. These results indicate that TNF-alpha plays an inhibitory role in anterior pituitary cell growth and the release of PRL in an estrogen-dependent manner.

Tumour necrosis factor-α exerts dual effects on human adipose leptin synthesis and release

The acute and chronic effects of tumour necrosis factor-α (TNF-α) on leptin production by human preadipocytes, differentiated preadipocytes, and mature adipocytes have been examined by competitive RT-PCR of leptin mRNA and by western blotting. In preadipocytes, secreted leptin was detectable after 5-day incubation in differentiation medium and this increased 4-fold by day 20. TNF-α blocked leptin synthesis during differentiation. In differentiated preadipocytes and mature adipocytes, TNF-α treatment resulted in time-dependent decreases in mRNA for leptin and glycerol-3-phosphate dehydrogenase (G3PD). In contrast, TNF-α (4–8-h treatment) resulted in a 4-fold increase in leptin release. This effect was lost at 24 h and leptin accumulation in culture medium was decreased 24–48 h after TNF-α addition. We conclude that TNF-α stimulates the release of preformed leptin from human mature adipocytes and existing differentiated preadipocytes, which may contribute to obesity/infection-linked hyperleptinemia, and that TNF-α inhibits leptin synthesis via inhibition of preadipocyte differentiation and induction of adipocyte dedifferentiation.

Growth-stimulating effects of tumor necrosis factor-α on simian virus 40-transformed human keratinocytes is linked to phosphorylation of retinoblastoma protein

In this report, we show that tumor necrosis factor-α (TNF-α) has a strong growth-stimulating effect on simian virus 40 (SV40)-transformed keratinocytes, while it exerts a potent growth-inhibitory effect on normal human keratinocytes. Addition of TNF-α to SV40-transformed keratinocytes stimulated cell growth by 216, 246, or 248% at 25, 50, or 250 ng/ml after 4 days culture compared with untreated cells, while addition to normal human keratinocytes reduced growth to 65, 38, and 32% at the same concentrations, respectively. Cell cycle analysis by flow cytometry showed that treatment of SV40-transformed keratinocytes with 250 ng/ml TNF-α for 48 h increased the S-phase cells from 19.8±0.3 to 49.7±2.4%. The percentage of G1/G0 phase cells decreased from 62.6±1.6 to 32.4±3.3%. We also demonstrated by immunofluorescent staining that SV40 large T antigen was enhanced by TNF-α incubation. Additionally, we examined the hyper and hypo-phosphorylated state of retinoblastoma protein (pRB), the cell cycle regulatory protein. TNF-α induced hyperphosphorylated pRB in SV40-transformed keratinocytes. On the other hand, TNF-α suppressed it in normal keratinocytes. We hypothesize that the enhancement of SV40 large T antigen and hyperphosphorylated pRB is involved in the mechanism of growth stimulation of SV40-transformed keratinocytes by TNF-α.

TNF-alpha enhances cardiac myocyte NO production through MAP kinase-mediated NF-kappaB activation.

We have previously reported that interleukin-1beta (IL-1beta) alone induced nitric oxide (NO) production by neonatal rat cardiac myocytes (CM). The effects of tumor necrosis factor-alpha (TNF-alpha) on inducible NO synthase (iNOS) were not characterized. Unlike IL-1beta, TNF-alpha alone failed to enhance NO production in CM. However, the addition of TNF-alpha to IL-1beta significantly enhanced iNOS mRNA expression, iNOS protein synthesis, and NO production (NO(-)(2)). TNF-alpha enhancement of IL-1beta-induced NO(-)(2) production was blocked by PD-98059, a selective mitogen-activated protein (MAP) kinase kinase inhibitor, but not calphostin C (Cal C), a protein kinase C inhibitor. TNF-alpha-enhanced MAP kinase activity was associated with an increase in IL-1beta-stimulated NF-kappaB activity. PD-98059, but not Cal C, inhibited both TNF-alpha-enhanced MAP kinase and NF-kappaB activities. Thus TNF-alpha enhancement of IL-1beta-induced NO production is associated with MAP kinase-mediated activation of NF-kappaB.

Influence of Tumor Necrosis Factor-α and Silibin on the Cytotoxic Action of α-Amanitin in Rat Hepatocyte Culture

Tumor necrosis factor-α is assumed to play a role in toxic liver damage. We examined whether exogenous tumor necrosis factor-α must be present for α-amanitin cytotoxicity in rat hepatocyte culture. α-Amanitin at a concentration of 0.1 μM, which is close to that found in intoxicated patients, inhibits RNA and protein synthesis within 12 h but cytotoxicity only occurs after a latency period and is pronounced at 36 h after the start of treatment. Tumor necrosis factor-α is not indispensable for the development of cytotoxicity but aggravates it and leads to a time shift towards earlier times. Lipid peroxidation is low with α-amanitin alone even at 36 h but markedly increased by cotreatment with tumor necrosis factor-α. The antioxidant silibin prevents the effect of tumor necrosis factor-α, indicating an involvement of reactive oxygen species. α-Amanitin alone does not increase but dose-dependently inhibits the expression of the antioxidant enzyme manganous superoxide dismutase and decreases the inducing effect of TNF-α on the expression of this enzyme. The gene expression of endogenous tumor necrosis factor-α in the hepatocytes is not increased but rather inhibited by α-amanitin treatment. The results suggest that α-amanitin causes delayed cytotoxicity following rapid inhibition of RNA and protein synthesis and that tumor necrosis factor-α shortens the latency period and aggravates the cytotoxicity by a mechanism which may involve reactive oxygen species.