Intracerebral injection of human immunodeficiency virus type 1 coat protein gp120 differentially affects the expression of nerve growth factor and nitric oxide synthase in the hippocampus of rat.

We have studied the neuropathological characteristics of the brain of rats receiving daily intracerebroventricular administration of freshly dissolved human immunodeficiency virus type 1 recombinant protein gp120 (100 ng per rat per day) given for up to 14 days. Histological examination of serial brain sections revealed no apparent gross damage to the cortex or hippocampus, nor did cell counting yield significant neuronal cell loss. However, the viral protein caused after 7 and 14 days of treatment DNA fragmentation in 10% of brain cortical neurons. Interestingly, reduced neuronal nitric oxide synthase (NOS) expression along with significant increases in nerve growth factor (NGF) were observed in the hippocampus, where gp120 did not cause neuronal damage. No changes in NGF and NOS expression were seen in the cortex, where cell death is likely to be of the apoptotic type. The present data demonstrate that gp120-induced cortical cell death is associated with the lack of increase of NGF in the cerebral cortex and suggest that the latter may be important for the expression of neuropathology in the rat brain. By contrast, enhanced levels of NGF may prevent or delay neuronal death in the hippocampus, where reduced NOS expression may be a reflection of a subcellular insult inflicted by the viral protein.

Longevity and the genetic determination of collagen glycoxidation kinetics in mammalian senescence.

A fundamental question in the basic biology of aging is whether there is a universal aging process. If indeed such a process exists, one would expect that it develops at a higher rate in short- versus long-lived species. We have quantitated pentosidine, a marker of glycoxidative stress in skin collagen from eight mammalian species as a function of age. A curvilinear increase was modeled for all species, and the rate of increase correlated inversely with maximum life-span. Dietary restriction, a potent intervention associated with increased life-span, markedly inhibited glycoxidation rate in the rodent. On the assumption that collagen turnover rate is primarily influenced by the crosslinking due to glycoxidation, these results suggest that there is a progressive age-related deterioration of the process that controls the collagen glycoxidation rate. Thus, the ability to withstand damage due to glycoxidation and the Maillard reaction may be under genetic control.

Role of the C2A domain of synaptotagmin in transmitter release as determined by specific antibody injection into the squid giant synapse preterminal.

Squid synaptotagmin (Syt) cDNA, including its open reading frame, was cloned and polyclonal antibodies were obtained in rabbits immunized with glutathione S-transferase (GST)-Syt-C2A. Binding assays indicated that the antibody, anti-Syt-C2A, recognized squid Syt and inhibited the Ca(2+)-dependent phospholipid binding to the C2A domain. This antibody, when injected into the preterminal at the squid giant synapse, blocked transmitter release in a manner similar to that previously reported for the presynaptic injection of members of the inositol high-polyphosphate series. The block was not accompanied by any change in the presynaptic action potential or the amplitude or voltage dependence of the presynaptic Ca2+ current. The postsynaptic potential was rather insensitive to repetitive presynaptic stimulation, indicating a direct effect of the antibody on the transmitter release system. Following block of transmitter release, confocal microscopical analysis of the preterminal junction injected with rhodamine-conjugated anti-Syt-C2A demonstrated fluorescent spots at the inner surface of the presynaptic plasmalemma next to the active zones. Structural analysis of the same preparations demonstrated an accumulation of synaptic vesicles corresponding in size and distribution to the fluorescent spots demonstrated confocally. Together with the finding that such antibody prevents Ca2+ binding to a specific receptor in the C2A domain, these results indicate that Ca2+ triggers transmitter release by activating the C2A domain of Syt. We conclude that the C2A domain is directly related to the fusion of synaptic vesicles that results in transmitter release.

Role of the C2B domain of synaptotagmin in vesicular release and recycling as determined by specific antibody injection into the squid giant synapse preterminal.

Synaptotagmin (Syt) is an inositol high-polyphosphate series [IHPS inositol 1,3,4,5-tetrakisphosphate (IP4), inositol 1,3,4,5,6-pentakisphosphate, and inositol 1,2,3,4,5,6-hexakisphosphate] binding synaptic vesicle protein. A polyclonal antibody against the C2B domain (anti-Syt-C2B), an IHPS binding site, was produced. The specificity of this antibody to the C2B domain was determined by comparing its ability to inhibit IP4 binding to the C2B domain with that to inhibit the Ca2+/phospholipid binding to the C2A domain. Injection of the anti-Syt-C2B IgG into the squid giant presynapse did not block synaptic release. Coinjection of IP4 and anti-Syt-C2B IgG failed to block transmitter release, while IP4 itself was a powerful synpatic release blocker. Repetitive stimulation to presynaptic fiber injected with anti-Syt-C2B IgG demonstrated a rapid decline of the postsynaptic response amplitude probably due to its block of synaptic vesicle recycling. Electron microscopy of the anti-Syt-C2B-injected presynapse showed a 90% reduction of the numbers of synaptic vesicles. These results, taken together, indicate that the Syt molecule is central, in synaptic vesicle fusion by Ca2+ and its regulation by IHPS, as well as in the recycling of synaptic vesicles.

Suppression of lung metastasis of B16 mouse melanoma by N-acetylglucosaminyltransferase III gene transfection.

The beta 1-6 structure of N-linked oligosaccharides, formed by beta-1,6-N-acetylglucosaminyltransferase (GnT-V), is associated with metastatic potential. We established a highly metastatic subclone, B16-hm, from low metastatic B16-F1 murine melanoma cells. The gene encoding beta-1,4-N-acetylglucosaminyltransferase (GnT-III) was introduced into the B16-hm cells, and three clones that stably expressed high GnT-III activity were obtained. In these transfectants, the affinity to leukoagglutinating phytohemagglutinin was reduced, whereas the binding to erythroagglutinating phytohemagglutinin was increased, indicating that the level of beta 1-6 structure was decreased due to competition for substrate between intrinsic GnT-V and ectopically expressed GnT-III. Lung metastasis after intravenous injection of the transfectants into syngeneic and nude mice was significantly suppressed, suggesting that the decrease in beta 1-6 structure suppressed metastasis via a mechanism independent of the murine system. These transfectants also displayed decreased invasiveness into Matrigel and inhibited cell attachment to collagen and laminin. Cell growth was not affected. Our results demonstrate a causative role for beta 1-6 branches in invasion and cell attachment in the extravasation stage of metastasis.

Anti-C5 monoclonal antibody therapy prevents collagen-induced arthritis and ameliorates established disease.

Activated components of the complement system are potent mediators of inflammation that may play an important role in numerous disease states. For example, they have been implicated in the pathogenesis of inflammatory joint diseases including rheumatoid arthritis (RA). To target complement activation in immune-mediated joint inflammation, we have utilized monoclonal antibodies (mAbs) that inhibit the complement cascade at C5, blocking the generation of the major chemotactic and proinflammatory factors C5a and C5b-9. In this study, we demonstrate the efficacy of a mAb specific for murine C5 in the treatment of collagen-induced arthritis, an animal model for RA. We show that systemic administration of the anti-C5 mAb effectively inhibits terminal complement activation in vivo and prevents the onset of arthritis in immunized animals. Most important, anti-C5 mAb treatment is also highly effective in ameliorating established disease. These results demonstrate a critical role for activated terminal complement components not only in the induction but also in the progression of collagen-induced arthritis and suggest that C5 may be an attractive therapeutic target in RA.

Intratumoral injection of an adenovirus expressing interleukin 2 induces regression and immunity in a murine breast cancer model.

Rodent tumor cells engineered to secrete cytokines such as interleukin 2 (IL-2) or IL-4 are rejected by syngeneic recipients due to an enhanced antitumor host immune response. An adenovirus vector (AdCAIL-2) containing the human IL-2 gene has been constructed and shown to direct secretion of high levels of human IL-2 in infected tumor cells. AdCAIL-2 induces regression of tumors in a transgenic mouse model of mammary adenocarcinoma following intratumoral injection. Elimination of existing tumors in this way results in immunity against a second challenge with tumor cells. These findings suggest that adenovirus vectors expressing cytokines may form the basis for highly effective immunotherapies of human cancers.

Increase of skeletal muscle relaxation speed by direct injection of parvalbumin cDNA.

Parvalbumin (PV) is a high affinity Ca(2+)-binding protein found at high concentration in fast-contracting/relaxing skeletal muscle fibers of vertebrates. It has been proposed that PV acts in the process of muscle relaxation by facilitating Ca2+ transport from the myofibrils to the sarcoplasmic reticulum. However, on the basis of metal-binding kinetics of PV in vitro, this hypothesis has been challenged. To investigate the function of PV in skeletal muscle fibers, direct gene transfer was applied in normal and regenerating rat soleus muscles which do not synthesize detectable amounts of PV. Two weeks after in vivo transfection with PV cDNA, considerable levels of PV mRNA and protein were detected in normal muscle, and even higher amounts were detected in regenerating muscle. Twitch half-relaxation time was significantly shortened in a dose-dependent way in transfected muscles, while contraction time remained unaltered. The observed shortening of half-relaxation time is due to PV and its ability to bind Ca2+, because a mutant protein lacking Ca(2+)-binding capacity did not promote any change in physiology. These results directly demonstrate the physiological function of PV as a relaxing factor in mammalian skeletal muscle.

Administration of interleukin 12 in combination with type II collagen induces severe arthritis in DBA/1 mice.

The induction of arthritis in DBA/1 mice usually requires immunization with the antigen type II collagen emulsified with Mycobacterium tuberculosis in oil. Here we describe that interleukin 12 (IL-12) can replace mycobacteria and cause severe arthritis of DBA/1 mice when administered in combination with type II collagen. Immunization of DBA/1 mice with type II collagen emulsified in oil alone resulted in a weak immune response, and only a few animals (10-30%) developed arthritis. Administration of IL-12 for 5 days simultaneously with each immunization strongly enhanced the anti-type II collagen immune response. Collagen-specific interferon gamma (IFN-gamma) synthesis by ex vivo activated spleen cells was enhanced 3- to 10-fold. IFN-gamma was almost completely produced by CD4+ T cells. Furthermore, the production of collagen-specific IgG2a and IgG2b antibodies was upregulated 10- to 100-fold. As a consequence, the incidence of arthritis in the group of mice immunized with collagen plus IL-12 was very high (80-100%). The developing arthritis was severe, involving approximately 50% of all limbs with strongly increased footpad thickness in most cases. Furthermore, histological examination revealed massive, mainly polymorphonuclear cell infiltration, synovial hyperplasia, cartilage and bone destruction, as well as new bone formation. In many cases, this resulted in the complete loss of joint structure. Neutralization of IFN-gamma in vivo prevented the development of arthritis in collagen-immunized and IL-12-treated mice. In conclusion, our data show that in vivo administered IL-12 can profoundly upregulate a T helper I-type autoimmune response, resulting in severe joint disease in DBA/1 mice.

L-arginine may mediate the therapeutic effects of low protein diets.

We have previously shown beneficial effects of dietary protein restriction on transforming growth factor beta (TGF-beta) expression and glomerular matrix accumulation in experimental glomerulonephritis. We hypothesized that these effects result from restriction of dietary L-arginine intake. Arginine is a precursor for three pathways, the products of which are involved in tissue injury and repair: nitric oxide, an effector molecule in inflammatory and immunological tissue injury; polyamines, which are required for DNA synthesis and cell growth; and proline, which is required for collagen production. Rats were fed six isocaloric diets differing in L-arginine and/or total protein content, starting immediately after induction of glomerulonephritis by injection of an antibody reactive to glomerular mesangial cells. Mesangial cell lysis and monocyte/macrophage infiltration did not differ with diet. However, restriction of dietary L-arginine intake, even when total protein intake was normal, resulted in decreased proteinuria, decreased expression of TGF-beta 1 mRNA and TGF-beta 1 protein, and decreased production and deposition of matrix components. L-Arginine, but not D-arginine, supplementation to low protein diets reversed these effects. These results implicate arginine as a key component in the beneficial effects of low protein diet.