In vitro TNF-alpha production and in vivo alteration of TNF-alpha RNA in mouse peritoneal macrophages after treatment with different bacterial derived agents

The subdiaphragmatic vagus nerves mediate activation of locus coeruleus neurons by peripherally administered microbial substances

Our earlier studies demonstrated that representative microbial substances--lipopolysaccharide, peptidoglycan, and poly-inosine: poly-cytosine (poly(I):(C))--increased the spontaneous discharge rates and sensory-evoked responses of isolated locus coeruleus (LC) neurons in a dose- and time-related manner after i.p. injection into rats. We then turned our attention to the mechanism by which microbial substances administered into the peritoneal cavity affect the LC neurons. The involvement of the subdiaphragmatic vagus nerves was examined in this regard since several brain responses to peripherally administered lipopolysaccharide have been found to depend upon the integrity of these nerves. The experiments reported here show that lipopolysaccharide, peptidoglycan, and poly(I):(C) all failed to excite LC neurons after i.p. injection into rats that had previously been subjected to complete transection of the subdiaphragmatic vagus nerves. Furthermore, selective transection of the subdiaphragmatic vagus nerve trunks indicated that the dorsal trunk, and not the ventral trunk, was necessary to excite LC neurons in response to i.p. lipopolysaccharide. The inability of LC neurons to respond to i.p. lipopolysaccharide in vagotomized rats is unlikely to be attributed to a desensitization of the neurons to lipopolysaccharide since i.c.v. injection of lipopolysaccharide excited LC neurons in vagotomized rats as it did in vagus-intact rats. These findings suggest that a variety of microbial substances excited LC neurons after administration into the peritoneal cavity in a manner involving the subdiaphragmatic vagus nerves.

The effects of endogenous interleukin-1 bioactivity on locus coeruleus neurons in response to bacterial and viral substances

In a previous study, we found that microinjection of the cytokine interleukin-1 (IL-1) into the locus coeruleus (LC) increased the electrophysiological activity of LC neurons. To determine if endogenous IL-1 similarly affects the LC, brain IL-1 was induced with lipopolysaccharide (LPS), a substance derived from Gram-negative bacteria. LPS microinjected directly into the LC increased the activity of LC neurons in anesthetized rats, and this effect was blocked by microinfusion of the IL-1 receptor antagonist (IL-1RA) protein into the LC indicating the involvement of IL-1 receptors. Similarly, intraperitoneal (i.p.) LPS injection increased the activity of LC neurons in a dose- and time-related manner that was sensitive to IL-1RA. The change in the activity of LC neurons caused by a single i.p. injection of LPS was surprisingly long-lasting, and evolved over a period of at least 3 weeks. Other microbial substances-namely, peptidoglycan from Gram-positive bacteria and poly-inosine/poly-cytosine (poly(I)/(C)), which resembles RNA viruses-were used to determine the generality of the findings with LPS. Both i.p. peptidoglycan and poly(I)/(C) increased LC activity but with lesser efficacy than LPS. IL-1RA reversed the increase in the activity of LC neurons caused by i.p. peptidoglycan treatment; however, that caused by i.p. Poly(I)/(C) was not diminished by IL-1RA. Thus, the increased activity of LC neurons caused by LPS and peptidoglycan requires IL-1 receptor binding, suggesting the involvement of endogenously-produced IL-1. In contrast, poly(I)/(C) increased the activity of LC neurons but this did not critically involve IL-1 receptors in the LC.

Interleukin-12 has a role in mediating resistance of murine strains to Tyzzer's disease

Clostridium piliforme induces enterohepatic disease in many domestic and laboratory animal species. Susceptibility to infection is known to vary with the immune status and strain of the host, but little is known about specific immune mechanisms that regulate this disease. To evaluate host control of C. piliforme infection, we examined the role of interleukin-12 (IL-12) both in the control of and in the response to murine C. piliforme infection. For this study, 3-week-old C. piliforme-resistant C57BL/6 or -susceptible DBA/2 mice were infected intravenously with either the toxic H1 or the nontoxic M1 C. piliforme isolate. Serum and liver samples were collected prior to C. piliforme inoculation (day 0) and at days 1, 3, 7, 14, and 28 postinoculation. Evaluation of hepatic IL-12 p40 mRNA expression by reverse transcription-PCR and of total-IL-12 protein levels in serum by enzyme-linked immunosorbent assay revealed that C. piliforme induced elevations in both hepatic p40 mRNA and serum total-IL-12 levels at all times postinoculation. Elevations were similar with both toxic and nontoxic C. piliforme isolates. Levels of total IL-12 in serum were significantly (P < 0.05) higher in C57BL/6 mice than in DBA/2 mice. Additional experiments were performed in which polyclonal antibody treatment was used to neutralize IL-12 in mice of both strains prior to intravenous inoculation with toxic C. piliforme H1. IL-12 neutralization increased the severity of Tyzzer's disease at day 3 postinoculation in both mouse strains, but the degree of increase was greater in C57BL/6 mice than in DBA/2 mice.

Anti-tumor effectiveness of electrochemotherapy with bleomycin is increased by TNF-alpha on SA-1 tumors in mice

With the aim to increase anti-tumor effectiveness of electrochemotherapy, adjuvant immunotherapy with tumor necrosis factor-alpha (TNF-alpha) was tested on tumors in mice. Increased anti-tumor effectiveness on SA-1 tumors was observed after combining TNF-alpha, injected either intratumorally or peritumorally, with electrochemotherapy using suboptimal dose of bleomycin (BLM). The increased anti-tumor effectiveness was neither the result of potentiated anti-tumor effectiveness of TNF-alpha due to exposure of tumors to electric pulses, nor due to interaction with BLM. Therefore, the effect of adjuvant TNF-alpha treatment might be immunomodulatory, augmenting the anti-tumor activity of electrochemotherapy, and possibly adding a systemic component to the localized electrochemotherapy treatment.