Anthea Tench Stammers

Expression of inflammatory cytokines following acute spinal cord injury in a rodent model

Many therapies that have been developed for acute spinal cord injury (SCI) either influence or are influenced by posttraumatic inflammation. Many such therapies have reportedly produced promising neurologic benefits in animal models of SCI, but demonstrating convincing efficacy in human clinical trials has remained elusive. This discrepancy may be related in part to differences in the inflammatory response to SCI between human patients and the widely studied rodent models. Our objectives were, therefore, to establish the time course of inflammatory cytokine release in the spinal cord of rats after a thoracic contusion, to determine whether the cytokine release was injury dependent, and to correlate these findings with those that we have recently reported for the cerebrospinal fluid (CSF) of human SCI patients. After rodent SCI, GRO (the rat equivalent of IL‐8), IL‐6, IL‐1α, IL‐1β, IL‐13, MCP‐1, MIP1α, RANTES, and TNFα were elevated within the spinal cord, whereas IL‐12p70 was decreased. In human SCI, IL‐6, IL‐8, and MCP‐1 were also elevated within the cerebrospinal fluid but at later times than those observed in the rodent spinal cord. IL‐6, IL‐8, and MCP‐1 were released in an injury‐dependent manner in both the rodent model of SCI and the human condition. In this regard, similar patterns of expression were observed for a number of inflammatory cytokines after SCI in rodent spinal cords and in human CSF. Such proteins may therefore have potential utility as biomarkers and surrogate outcome measures for evaluating biological response to therapeutic interventions.

Lack of neuroprotective effects of simvastatin and minocycline in a model of cervical spinal cord injury

Minocycline, a commonly prescribed tetracycline antibiotic, has shown promise as a potential therapeutic agent in animal models of numerous neurologic disorders such as amyotrophic lateral sclerosis, multiple sclerosis, Parkinsons disease, Huntingtons disease, stroke, and spinal cord injury (SCI). Simvastatin is one of many hydroxymethylglutaryl-coenzyme-A reductase inhibitors prescribed to lower cholesterol. These drugs are also known to reduce inflammation and oxidative stress, improve endothelial function, and modulate the immune system in stroke, traumatic brain injury, and SCI. As both drugs have translational potential, we evaluated their neuroprotective properties here in a clinically relevant model of contusive cervical spinal cord injury. Sprague-Dawley rats underwent a unilateral cervical contusion SCI at C5 and were randomized to receive: 1. Minocycline 90 mg/kg x 3 days, 2. Simvastatin 20 mg/kg x 7 days, 3. Simvastatin 20 mg/kg x 7 days then 5mg/kg x 35 days, or 4. Saline (Control). Behavioral recovery was assessed over 6 weeks using the horizontal ladder test, cylinder rearing test, modified Montoya staircase test and grooming test. Forepaw sensitivity was also assessed using the electronic von Frey Aesthesiometer. The corticospinal and rubrospinal tracts were traced and the spinal cords were harvested 7 weeks after injury. The extent of gray matter and white matter sparing and corticospinal and rubrospinal tract sprouting were evaluated in cross sections of the spinal cord. In the end, neither minocycline nor simvastatin treatment was associated with improved performance on the behavioral tests, as compared to saline controls. Performance on the horizontal ladder test, cylinder rearing test, and von Frey sensory test were similar among all groups. Animals treated for 42 days with simvastatin scored significantly higher in the grooming score compared to other groups, but retrieved significantly fewer pellets on the modified Montoya staircase test than control and minocycline treated animals. Histologically, there were no significant differences in white and gray matter sparing and in the extent of corticospinal and rubrospinal sprouting between the four groups. In conclusion, both minocycline and simvastatin failed to improve functional and histological recovery in our model of contusive cervical spinal cord injury.

Suppressor deletion therapy: selective elimination of T suppressor cells in vivo using a hematoporphyrin conjugated monoclonal antibody permits animals to reject syngeneic tumor cells

SummaryA MAb (B16G) which recognizes a constant epitope on TsC and their soluble factors in DBA/2 mice has been described previously. In this study, we show that when this MAb is covalently linked to the photoactivable molecule Hp, and injected i.v. into P815 tumor-bearing mice which were subsequently exposed to light, tumors undergo permanent regression in 10%–40% of these mice (depending on the individual experiment). All control animals died within an average of 22–24 days after tumor cell injection. It is suggested that tumor regression is attributable to immune mechanisms facilitated by the elimination of a population of TsC. When splenocytes of B16G-Hptreated mice were assayed in vitro for the generation of CTL active against P815 tumor cells, it was found that 24 h after treatment, a significant increase in killer cell activity was noted but that this effect was gone by 48h. We also show that B16G-Hp conjugates are capable in vitro of specifically killing cells of a TsC hybridoma, A10 (which has been shown previously to secrete a T suppressor factor reactive with P815 cell surface antigens). This conjugate had no cytotoxic effect on P815 cells under conditions in which A10 cells were killed.

Lack of robust neurologic benefits with simvastatin or atorvastatin treatment after acute thoracic spinal cord contusion injury

Although much progress has been made in the clinical care of patients with acute spinal cord injuries, there are no reliably effective treatments, which minimize secondary damage and improve neurologic outcome. The time and expense needed to establish de novo pharmacologic or biologic therapies for acute SCI has encouraged the development of neuroprotective treatments based on drugs that are already in clinical use and, therefore, have the advantage of a well-characterized safety and pharmacokinetic profile in humans. Statins are the most commonly prescribed class of lipid-lowering drugs, and recently, it has been recognized that statins also have powerful immunomodulatory and anti-inflammatory effects. This paper describes a series of experiments that were performed to evaluate the comparative neuroprotective effects of simvastatin and atorvastatin. We observed a promising signal of neurologic benefit with simvastatin in our first experiment, but in repeated attempts to replicate that effect in three subsequent experiments, we failed to reveal any behavioral or histologic improvements. We would conclude that simvastatin given orally or subcutaneously at doses previously reported by other investigators to be effective in different neurologic conditions does not confer a significant neurologic benefit in a thoracic contusion injury model (OSU Impactor) when administered with a 1-h delay in intervention. We contend that further preclinical investigation of atorvastatin and simvastatin is warranted before considering their translation into human SCI.

Delayed treatment of spinal cord injury with erythropoietin or darbepoetin--a lack of neuroprotective efficacy in a contusion model of cord injury.

A number of drugs commonly used for a variety of clinical indications have been found recently to have substantial neuroprotective properties, raising the potential for rapid translation into human clinical trials of spinal cord injury (SCI). In this study we compared the neuroprotective efficacy of erythropoietin and a derivative of it, darbepoetin, in an acute model of thoracic SCI. Sprague-Dawley rats were randomized to receive erythropoietin (5000 IU/kg), darbepoetin (10 mug/kg), or saline, as a single intravenous injection 1 h after a thoracic contusion SCI. The animals were evaluated for behavioral recovery over 6 weeks, which included BBB locomotor testing, horizontal ladder testing, video-analysis of gait, and hindlimb monofilament sensory testing. At 6 week post-injury, the spinal cords were evaluated histologically to measure white and grey matter sparing at and around the epicenter of injury. We found that neither erythropoietin nor darbepoetin led to improved behavioral recovery over saline controls, with no significant differences observed in BBB scores, BBB subscores, footfall errors on horizontal ladder testing, width of hindlimb base of support, or threshold for paw withdrawal on sensory testing. Furthermore, no differences were observed in grey or white matter sparing between the three experimental groups. Using doses of erythropoietin and darbepoetin that other investigators have reported to be beneficial in SCI and stroke models, we were unable to demonstrate a neuroprotective effect when administered 1 h after injury. Further preclinical investigation is necessary to refine the treatment strategy of using erythropoietin or darbepoetin in acute spinal cord injury.

Magnesium in a polyethylene glycol formulation provides neuroprotection after unilateral cervical spinal cord injury.

Study Design. Experimental animal study. Objective. To investigate the neuroprotective efficacy of this magnesium in polyethylene glycol (PEG) formulation in a contusive model of cervical spinal cord injury (SCI). Summary of Background Data. Intravenously administered magnesium has been extensively investigated as a neuroprotective agent in animal models of SCI, stroke, and traumatic brain injuries, and has been evaluated in large scale clinical trials for the latter 2 indications. We have developed a novel formulation of magnesium chloride (MgCl2) within PEG, and have previously demonstrated the neuroprotective benefit of this formulation in animal models of thoracic SCI. Methods. Twenty-two Sprague Dawley rats underwent a unilateral cervical hemicontusion at C4–C5 and were randomized 2 hours later to either the MgCl2 in PEG formulation, or normal saline. Each treatment was administered in 5 intravenous infusions spaced 6 hours apart. Behavioral recovery was assessed over 6 weeks, after which the cord was analyzed to measure the extent of gray matter and white matter sparing through the injury site. Results. In the horizontal ladder test, the percentage of forelimb errors made by the animals treated with MgCl2 in PEG formulation was significantly lower than the saline-treated controls. Histologic analysis also revealed a significantly higher cumulative white matter sparing through the injury site in the MgCl2 in PEG group. Conclusion. MgCl2 in a PEG formulation reduced secondary damage and improved behavioral recovery when administered 2 hours after a unilateral cervical hemicontusion injury. These findings are consistent with the neurologic benefit observed when administering this magnesium formulation in contusive and compressive models of thoracic SCI. Demonstrating the robustness of this neuroprotective effect in multiple injury models (and in the cervical injury model in particular) is important when considering the applicability of such a therapy for human SCIs.

Preliminary characterization of a soluble immunosuppressive molecule from DBA/2 spleen cells using monoclonal antibody immunoadsorbence☆

In a previous publication a monoclonal antibody (B16G) which appeared to recognize T suppressor cells and a T-suppressor factor (TsF) in the spleens of DBA/2 mice was described. B16G appears to be directed to a public specificity of DBA/2 TsF and therefore has been shown to inhibit a variety of immunological reactions. The present study involves preliminary characterization of the material with which B16G reacts. It was found that the B16G-reactive protein (putative TsF) could be absorbed and eluted specifically from a B16G immunoadsorbent column. Material eluting from the B16G column reacted with B16G in an ELISA and appeared to run as two or more bands of 40-45 kDa in sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The eluted material was biologically active (i.e., suppressive) in the standard assay (mixed leukocyte reaction of DBA/2 splenocytes with B10.BR targets), and its suppressive activity was abrogated by the addition of B16G to the mixed leukocyte reaction cultures. Sephadex G-150 chromatography of the B16G-reactive material showed that under these conditions, its native molecular mass was between 80-90 kDa, indicating that it might occur as a dimer under natural conditions.

Preadministration of a T-suppressor factor enhances tumor immunity in DBA/2 mice

SummaryPreviously we have described the isolation and characterization of a T-suppressor factor (TsF) from a T cell hybridoma (A10F), which has a degree of specificity for the DBA/2 mastocytoma P815. Administration of A10F intravenously at the time of tumor cell injection resulted in an accelerated rate of tumor growth, decreased cytotoxic T lymphocyte antitumor activity, and reduced survival time. In the work reported here, we have shown that administration of affinity-enriched A10F 7–14 days prior to tumor cell injection causes what appear to be reverse effects, in that an enhanced resistance to the P815 tumor is observed in vivo, an effect which we can correlate with the demonstration of antitumor cytotoxic T lymphocyte activity in vitro. These effects are dose-dependent since only doses of TsF at 20 μg or greater are effective. A similar effect was found when A10F was administered to DBA/2 mice 10 days prior to challenge with two unrelated tumors (L1210 and M-1). However, when another TsF (Fd11F) with apparent specificity for a nominal antigen was tested in this system, it had no effect on tumor growth.

Immune Regulation in Neoplasia

During the past decade, there has developed a consensus that neoplastically transformed cells (with a few notable exceptions) do not produce tumor-specific antigens (TSA), but rather may produce tumor markers better defined as tumor-associated antigens (TAA). TAA are those gene products expressed by the transformed cell constitutively which do not comprise part of the normal repertoire of its untransformed counterpart, either quantitatively or qualitatively. TAA can be the products of derepressed fetal genes such as carcinoembryonic antigen of α-fetoprotein, or of genes which are normally expressed at considerably lower levels in normal cells such as differentiation antigens, oncogene products, or cell surface receptor molecules. TAA as such must then be defined as part of the normal cell’s genetic makeup and expression potential. Thus, the question as to whether or not malignant cells would be expected to be immunogenic is a legitimate one, which deserves considerable thought. We are not here discussing those tumor cells lines which express tumor-specific transplantation antigens (TSTA) or virally encoded antigens, since these clearly form a group of tumor types with well-recognized neoantigens and thus immunogenic potential. Rather, we will discuss here the majority of neoplasms, both murine and human, which do not express these types of antigens.