Short analytical review

Tumor necrosis factor in the pathophysiology of infection and sepsis☆

AT-rich interactive domain 5A (ARID5A/Arid5a) is a known cofactor of transcription factors (TFs) that contributes to cell growth and differentiation. It has recently been recognized for its unique function in the stabilization of mRNA, which is associated with inflammatory autoimmune diseases. Studies have revolutionized our understanding of the post-transcriptional regulation of inflammatory genes by revealing the fundamental events underpinning novel functions and activities of Arid5a. We review current research on Arid5a, which has focused our attention towards the therapeutic potential of this factor in the putative treatment of inflammatory and autoimmune disorders, including experimental autoimmune encephalomyelitis and sepsis in mice.

Treatment of PBMCs with TNF-α decreased the levels of heat shock protein (HSP) 27, but had little effect on the level of HSP70. Parallel to the decrease of HSP27, TNF-α increased the level of HSP27 in the incubation medium of the cells. The decrease of HSP27 induced by TNF-α was suppressed by the pretreatment of PBMCs with the specific protein kinase C (PKC) inhibitor, GF109203X. Furthermore, phorbol myristate acetate (PMA), a PKC stimulant, but not dibutyryl cyclic AMP, a protein kinase A stimulant, decreased the levels of HSP27. To investigate the effect of TNF-α on the oligomerization state of HSP27 in PBMCs, we performed sucrose density gradient centrifugation with subsequent fractionation and immunoassay. Extract of vehicle-treated PBMCs contained mainly dissociated forms of HSP27. The amounts of dissociated forms of HSP27 in PBMCs was decreased by TNF-α, while the amounts of aggregated form of HSP27 was little changed. In intact PBMCs, HSP27 is constitutively phosphorylated at Ser78, but not at Ser15 or at Ser82. The amount of phosphorylated HSP27 at Ser78 was decreased by TNF-α. These results indicate that TNF-α reduces HSP27 in PBMCs through PKC activation. This decrease may be due to efflux of dissociated form of HSP27, phosphorylated HSP27 at Ser78, from the cells.

Tumor necrosis factor-α (TNF-α) is released from activated mast cells via an IgE-dependent mechanisms, and plays a crucial role in ocular allergic inflammation. This study examined the influence of three antiglaucoma drugs differing in their chemical structure and pharmacological profile (i.e. latanoprost, timolol, GLC756) on TNF-α release from activated rat mast cells. A rat basophilic leukemia mast cell line (RBL-2H3) was activated via IgE/anti-IgE. Rat mast cells were incubated with latanoprost, timolol, GLC756 or betamethasone (positive control) at concentrations of 0.1, 1, 10 and 30 μM. TNF-α concentration in supernatant was measured by ELISA 5 h post-activation. Compared to controls, the prostaglandin derivative latanoprost and the beta-blocker timolol in the concentration range 0.1–30 μM, had no significant effect on TNF-α release from rat mast cells measured 5 h after activation. By contrast, the dopaminergic drug GLC756 compared to controls in the concentration range 1–30 μM significantly inhibited TNF-α release from activated rat mast cells in a concentration-dependent manner. The positive control betamethasone inhibited TNF-α release almost completely at all concentrations tested. In conclusion, the results of this study suggest that latanoprost and timolol do not reduce inflammation triggered by activated mast cells. By contrast, the dopaminergic drug GLC756 inhibited TNF-α release from activated mast cells, suggesting an palliative potential of dopaminergic compounds on allergic conjunctivitis in topical glaucoma medication.

Clinical responses to some disease agents differ between sexes and this dimorphism has been attributed to the immunomodulating effects of steroid hormones. Our objective was to determine in steers the effect of testosterone on circulating concentrations of immune response mediators (tumor necrosis factor-α, TNF-α; serum amyloid-A, SAA; haptoglobin, HG; xanthine oxidase, XO; nitric oxide, NO) after two consecutive endotoxin challenges (LPS1 and LPS2, 5 days apart; 0.25 μg/kg BW). Sixteen crossbred steers (328 ± 6 kg) were assigned to control (CON, n = 8) or testosterone cypionate treatment (TES, n = 8; 100 mg/m² body surface; i.m. injection 12 and 2 days before LPS1). The response to LPS was calculated as area under the time × concentration curve (AUC) for the parameter measured. After LPS1, TNF-α AUC was greater in TES than CON (P < 0.05). Plasma HG and SAA concentrations increased (P < 0.01) after LPS1 and LPS2. In all steers SAA AUC was greater after LPS1 than LPS2 (P < 0.01) but the response was augmented over CON with testosterone treatment (P < 0.05). HG response to LPS1 within 24 h was not affected by testosterone. However, 5 days after LPS1 mean plasma HG concentration remained higher in TES than CON (P < 0.01). HG response to LPS2 was greater in TES than CON (P < 0.01). Plasma nitrate + nitrite concentration (NO production marker) and XO activity increased after each LPS challenge but responses were not affected by testosterone treatment. Results indicate that the presence of circulating testosterone increases the magnitude of the TNF-α response to LPS challenge as well as the subsequent increases in acute phase proteins (APP). Effects of testosterone on increases in TNF-α and APP may underlie a differential presentation of disease symptoms between sexes or between steers and bulls. The data also suggest a role for testosterone in the development of tolerance to repeated immune challenge through its effect on the increased magnitude and duration of HG response.

GLC756, a polyvalent anti-glaucoma drug showed in an endotoxin-induced-uveitis model (EIU) in rats a significant tumor necrosis factor-α (TNF-α) decrease in serum, indicating an additional anti-inflammatory potential of this compound. The receptors on which GLC756 binds (D1, D2, D4, α-1, α-2, 5-HT1A, 5-HT2C, 5-HT1D, 5-HT2 A, β-1, and β-2) were suggested to play a role. In order to identify a receptor type mediating the TNF-α lowering response, GLC756 was combined with various counteracting compounds (CP). For EIU, 8 week old Lewis rats were intravenously injected at 160 μg lipopolysaccharide (LPS) from Salmonella typhimurium. Before EIU-induction animals received either one of the CP's or GLC756 alone, or GLC756 in combination with one of the CP's. TNF-α was determined in serum 2 h post EIU-induction. Treatment with CP's alone indicated that agonistic effects on β-2 adrenoceptors and antagonistic effects on α-2, 5-HT1A and 5-HT1D receptors resulted in statistically significant decreased TNF-α levels in comparison to the LPS-control group. In combination with GLC756, the counteracting CP's domitor (α-2 adrenoceptor agonist) and ICI 118551 (β-2 adrenoceptor antagonist) inhibited completely the TNF-α decreasing effect of GLC756. Counteracting the 5-HT1A receptor with the 5-HT1A agonist 8-OH-DPAT could not prevent the TNF-α decreasing effect of GLC756. In conclusion, the antagonistic effect on α-2 adrenoceptors and the agonistic effect on β-2 adrenoceptors were identified as mechanism for the TNF-α decreasing effect of GLC756.