Some characteristics of inflammation induced by muramyl dipeptide, endotoxin, and concanavalin A

Pre-diagnosis oophorectomy, estrogen therapy and mortality in a cohort of women diagnosed with breast cancer

Introduction

Pre-diagnosis oophorectomy and estrogen therapy could impact mortality due to breast cancer and cardiovascular disease (CVD) among breast cancer survivors. Elective bilateral oophorectomy at the time of hysterectomy for benign conditions is not uncommon among US women.

Methods

We examined the association between pre-diagnosis total abdominal hysterectomy with bilateral salpingo-oophorectomy (TAHBSO) and both overall and cause-specific mortality in the Collaborative Breast Cancer Studies cohort. Medical history and prior estrogen use were collected during standardized telephone interviews. Vital status, including date and cause of death, was obtained by linkage with the National Death Index. Multivariate hazard ratios (HR) and 95% confidence intervals (CI) for cause-specific mortality were calculated using Cox proportional hazards regression.

Results

Seventeen percent (N = 1,778) of breast cancer survivors (mean age at diagnosis = 63.5) reported pre-diagnosis TAHBSO. During follow-up (mean = 9.5 years), 2,856 deaths occurred, including 1,060 breast cancer deaths and 459 CVD deaths. Breast cancer deaths occurred a median of 5.1 years after diagnosis; CVD deaths occurred further from diagnosis (median = 9.7 years). Women who reported pre-diagnosis TAHBSO had a 16% decrease in all-cause mortality (HR = 0.84; 95% CI: 0.76, 0.92) compared to those with an intact uterus and ovaries. This overall decrease reflected a 27% lower breast cancer mortality among women who never used postmenopausal hormones (HR = 0.73; CI: 0.55, 0.96) and 43% lower CVD risk among women who reported using estrogen (HR = 0.57; CI: 0.39, 0.83) after TAHBSO.

Conclusions

Information on prior TAHBSO and estrogen use can inform risk of death from both breast cancer and cardiovascular disease among breast cancer survivors.

Quantified pH imaging with hyperpolarized (13) C-bicarbonate

PURPOSE

Because pH plays a crucial role in several diseases, it is desirable to measure pH in vivo noninvasively and in a spatially localized manner. Spatial maps of pH were quantified in vitro, with a focus on method-based errors, and applied in vivo.

METHODS

In vitro and in vivo (13) C mapping were performed for various flip angles for bicarbonate (BiC) and CO2 with spectral-spatial excitation and spiral readout in healthy Lewis rats in five slices. Acute subcutaneous sterile inflammation was induced with Concanavalin A in the right leg of Buffalo rats. pH and proton images were measured 2 h after induction.

RESULTS

After optimizing the signal to noise ratio of the hyperpolarized (13) C-bicarbonate, error estimation of the spectral-spatial excited spectrum reveals that the method covers the biologically relevant pH range of 6 to 8 with low pH error (< 0.2). Quantification of pH maps shows negligible impact of the residual bicarbonate signal. pH maps reflect the induction of acute metabolic alkalosis. Inflamed, infected regions exhibit lower pH.

CONCLUSION

Hyperpolarized (13) C-bicarbonate pH mapping was shown to be sensitive in the biologically relevant pH range. The mapping of pH was applied to healthy in vivo organs and interpreted within inflammation and acute metabolic alkalosis models.

Muramyl-dipeptide-induced mitochondrial proton leak in macrophages is associated with upregulation of uncoupling protein 2 and the production of reactive oxygen and reactive nitrogen species

The synthetic immunomodulator muramyl dipeptide (MDP) has been shown to induce, in vivo, mitochondrial proton leak. In the present work, we extended these findings to the cellular level and confirmed the effects of MDP in vitro on murine macrophages. The macrophage system was then used to analyse the mechanism of the MDP-induced mitochondrial proton leak. Our results demonstrate that the cellular levels of superoxide anion and nitric oxide were significantly elevated in response to MDP. Moreover, isolated mitochondria from cells treated with MDP presented a significant decrease in respiratory control ratio, an effect that was absent following treatment with a non-toxic analogue such as murabutide. Stimulation of cells with MDP, but not with murabutide, rapidly upregulates the expression of the mitochondrial protein uncoupling protein 2 (UCP2), and pretreatment with vitamin E attenuates upregulation of UCP2. These findings suggest that the MDP-induced reactive species upregulate UCP2 expression in order to counteract the effects of MDP on mitochondrial respiratory efficiency.

Effect of muramyl peptides on mitochondrial respiration

Muramyl peptides have been shown to exert several biological activities including potentiation of humoral and cell-mediated immunity and stimulation of natural resistance. The mode of action of muramyl peptides has not been elucidated fully and the immunological activities of some derivatives have been associated with toxic effects, including pyrogenicity and inflammatory reactions. Nevertheless, the impact of muramyl peptides on mitochondrial respiration has never been addressed. In this study, the in vitro effects of muramyl peptides on rat liver mitochondria were examined. Toxic muramyl peptides induced a significant decrease in respiratory control ratio versus non-toxic analogues. These results were confirmed by in vivo studies in mice and were extended to mitochondria isolated from spleens. Our data address, for the first time, the effect of muramyl peptides on mitochondrial bioenergetics. Further studies are required to reveal the mechanism of mitochondrial toxicity in relation to the damaging effects of toxic muramyl peptides.

Kinetics, dose response, tachyphylaxis and cross-tachyphylaxis of vascular leakage induced by endotoxin, zymosan-activated plasma and platelet-activating factor in the horse

Vascular leakage induced by intradermal injection of endotoxin, zymosan-activated plasma (ZAP) and platelet-activating factor (PAF) was measured in nine Thoroughbreds using 125-iodine human serum albumin (125I-HSA) as a marker in the blood. ZAP and PAF produced dose-dependent increases in vascular permeability with the maximum occurring within the first 15 min after injection. The vascular leakage induced by endotoxin was also dose-dependent, but the maximum occurred 2 h after intradermal injection. Intradermal sites previously injected with endotoxin were refractory to a second injection of endotoxin for up to 5 days. However, sites injected with endotoxin and re-injected with either ZAP or PAF remained responsive with increased vascular leakage compared to saline injected control sites re-injected with either ZAP or PAF. Diminished response to endotoxin challenge may contribute to the poor prognosis of endotoxaemia in the horse.

Immunopharmacological activities and clinical development of muramyl peptides with particular emphasis on murabutide

Certain immunopharmacological activities of muramyl peptides have been associated with inflammatory and undesirable side-effects typically observed following the administration of the prototype molecule muramyl dipeptide. This activity is now demonstrated not to be linked to a direct activation of inflammatory processes in endothelial cells. Neither MDP nor other structural derivatives were able to induce inflammatory cytokines release or E-selectin gene expression in cultured human umbilical vein endothelial cells. However, oral administration of muramyl peptides has been reported to induce certain biological effects, including the downregulation of anamnestic, antigen-specific IgE responses, which are not observed following parenteral administration. We elaborate on these findings and extend them to show the efficacy of a new muramyl peptide in suppressing polyclonally induced serum IgE levels in anti-IgD-treated mice. The comparative effects of muramyl peptides, selected for clinical development, on the induction of cytokines in human whole blood are then presented at the level of mRNA accumulation and protein secretion. Moreover, the cytokine profile induced in vitro and in vivo by the combination of the safe immunostimulant, Murabutide, with interferon-alpha is examined. This combination reveals a selective and beneficial synergistic activity and induces anti-inflammatory cytokines in the absence of synergistic toxicity. The potential and the implications for the use of a therapeutic combination of an immunostimulant with a cytokine are discussed.

Studies on the accumulation of serum proteins in zymosan-induced inflammation in mouse peritoneum

Inflammatory responses were induced in mice by intraperitoneal (i.p.) injection of zymosan. This resulted in a rapid accumulation of protein in the peritoneum that was dependent on the time of the injection and concentration of zymosan used. Though other stimuli, e.g., phorbol myristate acetate, lipopolysaccharide, carrageenan and latex beads, caused the accumulation of proteins, the maximum response was obtained only with zymosan. Injection of free fatty acids were unable to induce protein accumulation in peritoneum. Factors which decreased leukotriene production in mouse peritoneum, i.e., dietary n-3 fatty acids essential fatty acid deficient diets, did not affect protein accumulation. Direct injection of leukotrienes also failed to induce protein accumulation. Analyses revealed that the proteins were similar to serum proteins, indicating that zymosan causes the leakage of serum proteins into peritoneum.

Kinetics of endotoxin-induced inflammation in ovine mammary gland

The inflammatory response to stimulation with endotoxin of lactating and nonlactating mammary glands of sheep was examined. Similar numbers of neutrophils and mononuclear cells were recovered from nonlactating glands sampled every 2 h for 8 h and in glands sampled once at 8 h. Thus the inflammatory response was initiated by 2 h and repeated sampling did not modify the time course of the response. In contrast, in lactating ewes, fewer cells were recovered from glands sampled every 2 h than from glands sampled once at 8 h. Fewer neutrophils were also recovered when glands were serially sampled from 4 h to 8 h. Thus, removal of milk and inflammatory exudate modified the time course of the leukocyte influx into lactating glands. Significant accumulation of neutrophils occurred by 2 h in dose-response experiments in nonlactating glands. Peak accumulation of neutrophils occurred between 2 and 6 h, and a marked decline occurred after 8 h. In lactating glands, a slower onset and longer duration of neutrophil accumulation occurred. Twenty- to 30-fold more neutrophils were recovered by 8 h in lactating than nonlactating glands. This difference was not due to a lower threshold of sensitivity to endotoxin. Infusion of milk into nonlactating glands did not modify the intensity or time course of the inflammatory response to endotoxin. Thus, the physiological state of resident cells within the lactating gland, rather than the interaction of inflammatory exudate with milk, can account for the different reaction pattern in lactating glands. Inflammation in the nonlactating gland closely resembles inflammatory responses in skin and provides a convenient model for investigating the initiation and regulation of inflammatory processes.

Two patterns of early neutrophil accumulation in acute inflammatory lesions

A model of acute inflammation in the skin of sheep was developed using [111In]oxine-labeled neutrophils to quantify the accumulation of neutrophils in inflammatory lesions. Peak accumulation occurred during the first hour in lesions induced by zymosan-activated sheep plasma (ZAP, 100%) and during the second hour in lesions induced by endotoxin (10(-11) moles) and casein (2 x 10(-8) moles). The accumulation of neutrophils after the final stimulus diminished when lesions were restimulated every 2 h on two or more occasions. Thus desensitization of inflammatory lesions previously observed in rabbit skin is not restricted to that species. The early accumulation of neutrophils in primary and restimulated lesions was measured in lesions from 10 min to 2 h old. In primary lesions, ZAP induced significant neutrophil accumulation by 10 min, whereas 30 to 45 min elapsed before significant neutrophil accumulation occurred in lesions induced with endotoxin and casein. The initial responses in restimulated lesions were not diminished, but there was a failure of neutrophil accumulation to continue for as long as occurred in primary lesions. This finding indicates that regulation of the neutrophil influx into dermal inflammatory lesions may occur at a point after occupancy of the putative tissue receptors in the pathway which leads to accumulation of neutrophils at the injection site. The results indicate that there are at least two patterns of neutrophil accumulation in primary inflammatory lesions. The delayed pattern of neutrophil accumulation induced by casein and endotoxin resembles the enhanced binding of neutrophils to stimulated endothelial cultures in vitro, whereas the basis for the immediate response induced by ZAP remains conjectural. It is proposed that the primary action of chemotactic agents may be to provoke changes in the adhesive properties of endothelium and resident connective tissue cells thus permitting the migration of neutrophils into inflammatory lesions.