Ga Schuiling

A NEW ANIMAL-MODEL FOR HUMAN PREECLAMPSIA - ULTRA-LOW-DOSE ENDOTOXIN INFUSION IN PREGNANT RATS

OBJECTIVE An animal model for preeclampsia was developed by means of an ultra-low-dose endotoxin infusion protocol in conscious pregnant rats. STUDY DESIGN Rats received a permanent jugular vein cannula on day 0 of pregnancy, through which endotoxin (1.0 micrograms/kg body weight) (n = 10) or saline solution (n = 6) was infused during 1 hour on day 14 of pregnancy. Blood pressure, albuminuria, and platelet counts were measured, and histopathologic studies was performed in these rats. RESULTS A significant increase of blood pressure (p < 0.05) and of urinary albumin excretion (p < 0.05) was observed in endotoxin-treated pregnant animals, in contrast to control pregnant rats receiving saline solution. Platelet coagulopathy was found and glomerular fibrinogen deposits could be detected only in the endotoxin-treated pregnant rats. In addition, the activity of the glomerular antithrombotic enzyme adenosine diphosphatase was decreased in endotoxin-treated pregnant rats compared with saline solution-treated pregnant rats. CONCLUSION Because histopathologic and clinical events in this model mimic predominant features of human preeclampsia, this model may enable further study into the pathophysiologic mechanisms of this complication of pregnancy.

The immune response during the luteal phase of the ovarian cycle : a Th2-type response?

OBJECTIVE To test the hypothesis that during the luteal phase of the ovarian cycle, as compared with the follicular phase, the peripheral immune response is shifted toward a type-2 response. DESIGN Prospective study. SETTING Academic research setting. PATIENT(S) Women with regular menstrual cycles. INTERVENTION(S) Blood samples were collected between days 6 and 9 of the menstrual cycle and 6-9 days after the LH surge. MAIN OUTCOME MEASURE(S) Intracellular cytokine production of interferon (IFN)-gamma, interleukin (IL)-2, IL-4, and IL-10 after in vitro stimulation of lymphocytes as well as total white blood cell (WBC) count, differential WBC count, and plasma 17 beta-E(2) and P concentrations. RESULT(S) Mean plasma 17 beta-E(2) and P concentrations, WBC count, and mean granulocyte, monocyte, and lymphocyte counts were significantly increased in the luteal phase as compared with the follicular phase of the ovarian cycle. Production of type-1 cytokines (IFN-gamma and IL-2) and production of the type-2 cytokine IL-10 did not vary between the phases of the ovarian cycle. Production of the type-2 cytokine IL-4, however, was significantly increased in the luteal phase as compared with the follicular phase of the ovarian cycle. CONCLUSION(S) During the luteal phase of the ovarian cycle, the immune response is shifted toward a Th2-type response, as reflected by increased IL-4 production in this phase of the cycle. These results may suggest that increased levels of P and 17 beta-E(2) in the luteal phase of the ovarian cycle play a role in the deviation of the immune response toward a type-2 response.

Pre-eclampsia and the inflammatory response

Pre-eclampsia, a human disease of pregnancy, is the leading cause of maternal morbidity in the western world. Despite the ubiquity of the disease and the plethora of studies concerning its aetiology and pathogenesis no comprehensive theory concerning its aetiology and pathogenesis have been put forward until now and so far there are no adequate therapies other than bed rest and, if necessary, early delivery. We recently developed an animal model for preeclampsia [1,2], whereby activation of the inflammatory response by low dose endotoxin resulted in pregnant rats, and not in non-pregnant rats, in a pre-eclampsia-like syndrome. Analysis of the inflammatory reaction induced by low dose endotoxin in pregnant — and non-pregnant rats revealed that this reaction was much more persistent and intense in pregnant rats as compared with non-pregnant rats; this is in line with the vast literature showing that pregnant individuals are much more sensitive to endotoxin than nonpregnant individuals [3‐5]. Based on the animal model, we have thus put forward the hypothesis that also human preeclampsia results from activation of the inflammatory system [6,7]. Here, we raise and try to answer, from a biological point of view, various questions such as ‘‘why is pregnancy a pro-inflammatory condition?’’, ‘‘what triggers the inflammatory response leading to human pre-eclampsia?’’ and ‘‘why is pre-eclampsia so relatively common in humans?’’.

Effect of estradiol and progesterone on the low-dose endotoxin-induced glomerular inflammatory response of the female rat

PROBLEM: Is the endotoxin‐induced glomerular inflammatory response of the female rat under ovarian control?

Aspirin treatment of the low-dose-endotoxin-treated pregnant rat: pathophysiologic and immunohistologic aspects☆

In the present study, we evaluated the effect of low-dose aspirin (acetylsalicylic acid (ASA); 1.0 mg/kg daily) on blood pressure, albumin excretion, glomerular fibrinogen deposits, and glomerular (basement) membrane-bound adenosine diphosphatase (ecto-ADPase) activity, as well as on glomerular inflammation in pregnant rats infused with low-dose endotoxin (1.0 mg/kg). Rats (day 14 of pregnancy) were infused with endotoxin (ET rats) or saline (control rats) and received ASA in their drinking water. These rats were compared with non-ASA-treated rats. Blood pressure and albumin excretion were measured from day 15 to day 21, and glomerular fibrinogen and ecto-ADPase activity were measured at day 21. Glomerular inflammation was evaluated at various times after the start of the infusion. The results show that treatment with ASA had a significant beneficial effect on hypertension and inflammation induced by endotoxin in pregnant rats, whereas it reduced albumin excretion and glomerular fibrinogen deposits in some of the rats.

Pancreatic beta-cell function and islet-cell proliferation: Effect of hyperinsulinaemia

Pancreatic beta-cell function was studied in adult female rats, in which endogenous insulin demand was fully met by SC infusion of human insulin (4.8 IU/24 h) for 6 days, resulting in hyperinsulinaemia and severe hypoglycaemia. The amount of pancreatic endocrine tissue declined by 40%, (pro)insulin mRNA, as determined by in situ hybridisation by 95%, and the amount of stored insulin by 90%. Islet-cell proliferation as determined by 24 h of BrdU infusion declined by 60%. Basal glucose levels normalized within 2 days after the insulin treatment was ended, whereas about 1 week was needed to restore the amount of pancreatic insulin, glucose-induced insulin release, and glucose tolerance to normal values. The amount of endocrine tissue recovered within 48 h and mRNA abundance within 96 h after discontinuation of the insulin infusion, whereas at that time islet-cell proliferation still showed a sixfold increase, before returning to control levels after 1 week. These results show that after a period of suppression of beta-cell function, recovery of insulin synthetic capacity does not immediately result in normalization of insulin stores and insulin release. Under these conditions, episodes of hyperglycaemia may occur, which may act as a stimulus for islet-cell proliferation.

Endotoxin induced intraplacental thrombotic tendency and decreased vascular adpase in the pregnant rat

The mechanism underlying increased sensitivity for endotoxin in pregnancy, as reflected by intravascular thrombus formation in various organs i.e. the placenta, is unknown. We studied the influence of endotoxin infusion at day 14 upon the vascular antithrombotic ADPase present in the labyrinth of the rat placenta just before term (day 21). Pregnant Wistar rats were infused with either endotoxin (1 microgram/kg body weight) or saline through permanent vena jugularis catheters and their placenta and kidneys were examined at day 21 using light electron microscopy and enzyme cytochemistry at the ultrastructural level. Also, placenta perfusion ex vivo was done using platelets and ADP to test the thrombotic tendency of placental vessels in endotoxin treated and control rats. The results show in both maternal as well as the fetal vessels of the placental labyrinth vascular occlusions and decreased membrane ADPase activity exclusively in endotoxin treated and not in saline infused pregnant animals. Alternate placenta and kidney perfusion ex vivo resulted in intraplacental and intraglomerular platelet aggregation again exclusively in endotoxin-treated rats. It is concluded that vascular ADPase may be affected by endotoxin due to the pregnant condition, resulting in a functional defect in antithrombotic potention which may promote intravascular formation of microthrombi in situ.

Pregnancy enhances the sensitivity of glomerular ecto-adenosine triphosphate-diphosphohydrolase to products of activated polymorphonuclear leukocytes

To test the hypothesis that pregnancy enhances the sensitivity of glomerular ecto-adenosine triphosphate-diphosphohydrolase to products of activated polymorphonuclear leukocytes, cryostat-cut kidney sections of pregnant and cycling rats were exposed to activated polymorphonuclear leukocytes and subsequently stained for ecto-adenosine triphosphate-diphosphohydrolase activity. The results show that the levels of ecto-adenosine triphosphate-diphosphohydrolase activity of pregnant rats showed a significantly greater decrease after incubation with activated polymorphonuclear leukocytes than did those of cycling rats.

GLUCOSE AND INSULIN RESPONSES DURING MIXED MEALS OR INFUSION OF GLUCOSE IN PREGNANT AND LACTATING RATS

We studied the glucose tolerance in freely moving rats throughout pregnancy and lactation and during the first week after weaning. Dioestrous virgin rats served as controls. Basal glucose and insulin levels were determined after a 2-hr fasting period. Subsequently, the changes of the insulin and the glucose levels were determined during ingestion of a mixed ad lib meal or a 2 g mixed test meal, or during infusion of glucose (7.4 mg/min for 20 min) into the vena cava. Basal glucose levels were high during early pregnancy, low during late pregnancy, and in the normal range throughout lactation and after weaning. Basal insulin levels were decreased at the end of lactation. The results of the ad lib meal and test meal experiments were essentially the same. Glucose tolerance during meals was somewhat decreased early in pregnancy. The corresponding insulin responses greatly increased during the last week of pregnancy. Glucose tolerance during IV infusion of glucose was normal during pregnancy, but increased during lactation. Insulin responses to the infusion were increased during pregnancy and decreased during lactation. We concluded that glucose tolerance is hardly affected by pregnancy and even increases in the course of lactation. This is effected by an increased responsiveness of the B-cells to glucose during late pregnancy and by an increased turnover of glucose during lactation. We discuss to what extent the actions of progesterone, placental lactogen and prolactin may explain these adaptions of maternal metabolism.

Superoxide–Mediated Glomerulopathy in the Endotoxin–Treated Pregnant Rat

In the present study the role of superoxide in the glomerular damage in the low–dose endotoxin–infused pregnant rats was investigated. On day 14 of pregnancy, 12 rats were infused for 1 h with 1.0 μg/kg bw endotoxin via a permanent jugular vein cannula. Of these rats, 6 were treated with SOD both prior to endotoxin infusion (7,000 U/kg) and 30 min (7,000 U/kg) and 4 h (14,000 U/kg) after the start of the infusion (SOD rats). The other 6 rats received no SOD treatment (endotoxin rats). Control pregnant rats were infused for 1 h with saline (saline rats; n = 6). Urinary albumin was measured on days 15 and 19 of pregnancy. On day 21, rats were sacrificed and kidney specimens were snap–frozen. Cryostat kidney sections were stained for fibrinogen, ecto–ATP diphosphohydrolase (e–ATPase) activity, polymorphonuclear cells, monocytes and various adhesion molecules on the endothelium and the leukocytes. SOD treatment appeared to significantly prevent the increased urinary albumin excretion and the decrease of glomerular e–ATPase activity which were observed in endotoxin–treated rats. This effect of SOD treatment after endotoxin infusion was associated with a significant inhibition of glomerular monocyte influx and a significant inhibition of adhesion molecule expression (glomerular ICAM–1 and VCAM–1 and leukocyte LFA–1 and VLA–4).The present data suggest that in the endotoxin–infused pregnant rat, production of superoxide in the first few hours after the infusion plays a role in the induction of glomerular damage, leading to albuminuria and diminished e–ATPase expression during the following days.