Background: Altered Cl -homeostasis and GABAergic function are associated with nociceptive input hypersensitivity. This study investigated the role of two major intracellular Cl -regulatory proteins, Na + -K + -Cl -cotransporter 1 (NKCC1) and K + -Cl -cotransporter 2 (KCC2), in neuropathic pain following spinal cord injury (SCI).

Mice (C57BL/6), treated with progesterone and infected intravaginally with the mouse pneumonitis strain of Chlamydia trachomatis (MoPn), acquired genital tract disease that ascended from the endocervix to the uterine horns, oviducts, and ovaries in a temporal fashion before the occurrence of spontaneous microbiological resolution by about 28 days after infection. Surprisingly, dissemination of MoPn in small numbers to draining lymph nodes, the peritoneal cavity, spleen, liver, kidneys, and lungs occurred in normal mice during the early stages of disease (7 to 14 days) in a portion of infected animals but resolved from these tissues, by microbiological criteria, prior to resolution of genital tract involvement. In contrast, gamma interferon knockout (IFN-␥ KO) mice exhibited dissemination of infection to a greater extent and for longer periods in a variety of tissues, and a portion of infected IFN-␥ KO mice failed to microbiologically resolve their genital tract disease. By comparison, C57BL/6 SCID mice uniformly failed to resolve their genital tract disease and exhibited high levels of dissemination to all tissues tested for extended (50-day) periods of times. Interestingly, although IFN-␥ KO mice failed to completely clear organisms from their genital tracts, they exhibited an attenuated infection indistinguishable from that of heterozygous littermates when challenged 112 days after primary infection. These data support a role for IFN-␥ in containing dissemination of MoPn from the genital tract to extragenital sites and in the microbiological resolution of infection. Data also indicate that IFN-␥ is not required for modulating reinfections, which normally follow a shorter and less dramatic course.

SUMMARYIncreased stimulation of Th2 cytokines may contribute to the development of persistent ocular chlamydial infection, resulting in the blinding pathological changes of trachoma. Proliferation and cytokine production profiles of PBMC in response to stimulation with antigens of Chlamydia trachomatis were compared in 30 patients with severe conjunctival scarring due to trachoma and in 30 age-, sex-and location-matched controls. Interferon-gamma (IFN-°) and IL-4 were detected at the single-cell level by ELISPOT assay. Transcription of the genes encoding IFN-°, IL-4 and IL-10 was detected in mRNA isolated from parallel cultures of PBMC using reverse transcriptase-polymerase chain reaction (RT-PCR). Incubation with the chlamydial heat shock protein (hsp)60 resulted in increased numbers of IL-4-producing cells in PBMC isolated from patients with scarring disease and increased secretion of IFN-°from PBMC of control subjects. Incubation with the chlamydial major outer membrane protein (MOMP) increased the number of IFN-°-producing cells in the control group only. Messenger RNA encoding IL-4 was only detected in PBMC of patients with scarring disease after in vitro stimulation with chlamydial antigens, but IFN-°mRNA and IL-10 mRNA were also more frequently detected in this group. Thirty-eight subjects were HLA-DRB1 and -DQB1 typed. Associations were observed between certain HLA class II alleles and cellular immune responses to chlamydial antigens. No HLA associations were found with clinical status, and overall we found no evidence of strong associations and the type of immune response. These data are consistent with a role for Th2 cells and cytokines in the pathogenesis of trachomatous scarring.

Neuropathic pain is a common problem following spinal cord injury (SCI). Effective analgesic therapy has been hampered by the lack of knowledge about the mechanisms underlying post-SCI neuropathic pain. Current evidence suggests GABAergic spinal nociceptive processing is a critical functional node in this complex phenotype, representing a potential target for therapeutic intervention. Normal GABA neurotransmission is dependent on precise regulation of the level of intracellular chloride, which is determined by the coordinated activities of two cation/chloride cotransporters (CCCs) in the SLC12 family: the inwardly directed Na(+)-K(+)-Cl(-) cotransporter isoform 1 (NKCC1) and outwardly directed K(+)-Cl(-) cotransporter isoform 2 (KCC2). Inhibition of NKCC1 with its potent antagonist bumetanide reduces pain behavior in rats following SCI. Moreover, the injured spinal cord tissues exhibit a significant transient upregulation of NKCC1 protein and a concurrent downregulation of KCC2 protein. Thus, imbalanced function of NKCC1 and KCC2 may contribute to the induction and maintenance of the chronic neuropathic pain following SCI.

It was previously reported that female mice resolve a primary Chlamydia trachomatis urogenital infection independent of inducible nitric oxide synthase (iNOS). We now report that although iNOS-deficient (NOS2 ؊/؊ ) mice resolve culture-apparent infection in a fashion similar to that of normal control (NOS2 ؉/؉ ) mice, they sustain significantly increased rates of disease, as assessed by hydrosalpinx formation. PCR amplification of ompA followed by Southern blot detection of amplicands revealed the presence of chlamydial DNA in the lower genital tracts of both NOS2؊/؊ and NOS2 ؉/؉ mice at >120 days postinfection and in upper genital tract tissues at >120 days postinfection. However, only NOS2 ؊/؊ mice shed low numbers of viable chlamydiae from the lower genital tract after immunosuppressive treatment at 120 days postinfection. When cultured primary murine lung fibroblasts were activated in the presence of gamma interferon (IFN-␥), inhibition of chlamydial growth occurred in both NOS2؉/؉ and NOS2 ؊/؊ cells, but the inhibition was reversible after removal of the cytokine in the NOS2 ؊/؊ primary cell culture only. The iNOS-independent inhibition was microbistatic but was independent of 2,3-indoleamine dioxygenase activity. We conclude that chlamydial DNA and antigens persist in mice subsequent to culture-apparent resolution. In addition, IFN-␥ induces in vivo inhibition of chlamydial growth through microbistatic mechanisms in the absence of iNOS activity, but in the presence of iNOS activity, IFN-␥ is microbicidal and effects eradication.