The estrogen antagonist tamoxifen inhibits carrageenan induced inflammation in LEW/N female rats

Estrogenic endocrine disruptors: Molecular mechanisms of action

A comprehensive summary of more than 450 estrogenic chemicals including estrogenic endocrine disruptors is provided here to understand the complex and profound impact of estrogen action. First, estrogenic chemicals are categorized by structure as well as their applications, usage and effects. Second, estrogenic signaling is examined by the molecular mechanism based on the receptors, signaling pathways, crosstalk/bypassing and autocrine/paracrine/homeostatic networks involved in the signaling. Third, evaluation of estrogen action is discussed by focusing on the technologies and protocols of the assays for assessing estrogenicity. Understanding the molecular mechanisms of estrogen action is important to assess the action of endocrine disruptors and will be used for risk management based on pathway-based toxicity testing.

Tamoxifen alleviates irradiation-induced brain injury by attenuating microglial inflammatory response in vitro and in vivo

Irradiation-induced brain injury, leading to cognitive impairment several months to years after whole brain irradiation (WBI) therapy, is a common health problem in patients with primary or metastatic brain tumor and greatly impairs quality of life for tumor survivors. Recently, it has been demonstrated that a rapid and sustained increase in activated microglia following WBI led to a chronic inflammatory response and a corresponding decrease in hippocampal neurogenesis. Tamoxifen, serving as a radiosensitizer and a useful agent in combination therapy of glioma, has been found to exert anti-inflammatory response both in cultured microglial cells and in a spinal cord injury model. In the present study, we investigated whether tamoxifen alleviated inflammatory damage seen in the irradiated microglia in vitro and in the irradiated brain. Irradiating BV-2 cells (a murine microglial cell line) with various radiation doses (2-10 Gy) led to the increase in IL-1 beta and TNF-alpha expression determined by ELISA, and the conditioned culture medium of irradiated microglia with 10 Gy radiation dose initiated astroglial activation and decreased the number of neuronal cells in vitro. Incubation BV-2 cells with tamoxifen (1 microM) for 45 min significantly inhibited the radiation-induced microglial inflammatory response. In the irradiated brain, WBI induced the breakdown of the blood-brain barrier permeability at day 1 post irradiation and tissue edema formation at day 3 post-radiation. Furthermore, WBI led to microglial activation and reactive astrogliosis in the cerebral cortex and neuronal apoptosis in the CA1 hippocampus at day 3 post-radiation. Tamoxifen administration (i.p., 5 mg/kg) immediately post radiation reduced the irradiation-induced brain damage after WBI. Taken together, these data support that tamoxifen can decrease the irradiation-induced brain damage via attenuating the microglial inflammatory response.

Testosterone reduces cumulative burying in female Wistar rats with minimal participation of estradiol

Testosterone exerts anxiolytic effects, but the participation of its aromatase metabolic product estradiol is controversial. Therefore, we used the defensive burying paradigm in female Wistar rats to explore testosterone's (1.0 mg/rat, s.c.) interactions with picrotoxin (a noncompetitive gamma-aminobutyric acid-A receptor [GABA(A)] antagonist; 1.0 mg/kg, i.p.), formestane (an aromatase inhibitor; 3.0 mg/rat, s.c.), and tamoxifen (an estrogen receptor-beta antagonist; 1.0 mg/kg, s.c.). Serum levels of testosterone, estradiol, and progesterone were determined in the same rats. Burying latency and locomotion did not significantly change. Systemic testosterone administration enhanced serum testosterone and estradiol levels and reduced defensive burying. This reduction in total burying was blocked by pretreatment with picrotoxin and tamoxifen, but not formestane. We conclude that testosterone produced anxiolytic-like effects in female rats that were mediated by actions at the GABA(A) receptor, with participation of the estradiol receptor-beta, rather than estradiol aromatization.

Tamoxifen attenuates inflammatory-mediated damage and improves functional outcome after spinal cord injury in rats

Tamoxifen has been found to be neuroprotective in both transient and permanent experimental ischemic stroke. However, it remains unknown whether this agent shows a similar beneficial effect after spinal cord injury (SCI), and what are its underlying mechanisms. In this study, we investigated the efficacy of tamoxifen treatment in attenuating SCI-induced pathology. Blood-spinal cord barrier (BSCB) permeability, tissue edema formation, microglial activation, neuronal cell death and myelin loss were determined in rats subjected to spinal cord contusion. The results showed that tamoxifen, administered at 30 min post-injury, significantly decreased interleukin-1beta (IL-1beta) production induced by microglial activation, alleviated the amount of Evans blue leakage and edema formation. In addition, tamoxifen treatment clearly reduced the number of apoptotic neurons post-SCI. The myelin loss and the increase in production of myelin-associated axonal growth inhibitors were also found to be significantly attenuated at day 3 post-injury. Furthermore, rats treated with tamoxifen scored much higher on the locomotor rating scale after SCI than did vehicle-treated rats, suggesting improved functional outcome after SCI. Together, these results demonstrate that tamoxifen provides neuroprotective effects for treatment of SCI-related pathology and disability, and is therefore a potential neuroprotectant for human spinal cord injury therapy.

Social isolation and the inflammatory response: sex differences in the enduring effects of a prior stressor

Numerous epidemiological studies have demonstrated an association between persistent social isolation and “all-cause” morbidity and mortality. To date, no causal mechanism for these findings has been established. Whereas animal studies have often reported short-term effects of social isolation on biological systems, the long-term effects of this adverse psychological state have been understudied. This is the first animal study to examine the effects of long-term social isolation from weaning through young adulthood on an innate inflammatory response linked to numerous disease processes. Results presented here offer a plausible link between vulnerability to disease and social neglect. For socially isolated male and female Sprague-Dawley rats, a naturally gregarious species, formation of a granuloma in response to a subcutaneous injection of carrageenin (seaweed) was significantly delayed compared with the response of animals housed in single-sex groups of five. Significant sex differences, however, emerged when an acute prior stressor was superimposed on the experience of chronic social isolation. In this context, isolated females produced a more robust inflammatory response than isolated males. This sexual dimorphism at the nexus of chronic social isolation, acute stress, and inflammatory processes may account for the observation in humans that men with low levels of social integration are more vulnerable to disease and death than women.

Strain-dependent differences in schedule-induced polydipsia: an assessment in Lewis and Fischer rats

Strain-dependent differences have been used to highlight unknown genetic contributions to important behavioral and physiological end points. In this regard, the Fischer (F344) and Lewis (LEW) rat strains have often been studied because they exhibit a myriad of behavioral and physiological differences. Recently, schedule-induced polydipsia (SIP), a potential model of stress and drug abuse, has been reported to differ between the two strains (see [Pharmacol. Biochem. Behav. 67 (2002) 809]) with F344 rats displaying greater levels of consumption than LEW rats. Given the importance of SIP as a behavioral model of stress and of drug abuse, the present study further explored SIP in F344 and LEW strains by assessing the acquisition and steady-state performance of SIP (under a fixed-time 30 schedule of food delivery; FT30), its characteristic postprandial temporal licking pattern and its modulation by variations in the food delivery schedule (FT15, FT30 and FT60). F344 rats acquired SIP at a faster rate and drank at a higher asymptotic level than LEW rats. Both strains displayed the typical inverted U-shaped post-pellet pattern of drinking and changes in levels of consumption (and displacement of the initiation of post-pellet drinking) with changes in the FT value, supporting the position that the increased drinking seen in both groups was schedule induced. These strain differences in SIP are consistent with the fact that the F344 and LEW strains differ on other behavioral and physiological indices of stress and raise the issue of the use of this model in the assessment of differential drug intake between the two strains.

Experimental neurogenic cystitis

Recent advances in basic and clinical research indicate that interstitial cystitis (IC) is a form of neurogenic inflammation, thereby opening new avenues for research into this painful disease. With this in mind, we have recently developed a rat model of neurogenic inflammation of the bladder produced by a central nervous system viral disease. As in IC, the inflammation in this model develops without direct injury or trauma to the bladder, is non-infectious, and is limited to the bladder. Our most recent studies aimed at further testing the similarity of this animal model to IC by assessing the urine content in histamine with the occurrence of mast cell degranulation in the bladder wall. We further verified for a sex difference in the occurrence of the disease. Our results showed increased levels of urine histamine and mast cell activation during the early stages of the disease. We additionally observed that females had a greater degree of plasma extravasation, while males had a greater cellular infiltration together with worse behavioral signs. Gonadectomy prevented the bladder inflammation altogether in both males and females. These findings further validate our model of neurogenic cystitis to study the neurogenic component of IC.

Neuroendocrine regulation of immunity

A reciprocal regulation exists between the central nervous and immune systems through which the CNS signals the immune system via hormonal and neuronal pathways and the immune system signals the CNS through cytokines. The primary hormonal pathway by which the CNS regulates the immune system is the hypothalamic-pituitary-adrenal axis, through the hormones of the neuroendocrine stress response. The sympathetic nervous system regulates the function of the immune system primarily via adrenergic neurotransmitters released through neuronal routes. Neuroendocrine regulation of immune function is essential for survival during stress or infection and to modulate immune responses in inflammatory disease. Glucocorticoids are the main effector end point of this neuroendocrine system and, through the glucocorticoid receptor, have multiple effects on immune cells and molecules. This review focuses on the regulation of the immune response via the neuroendocrine system. Particular details are presented on the effects of interruptions of this regulatory loop at multiple levels in predisposition and expression of immune diseases and on mechanisms of glucocorticoid effects on immune cells and molecules.

Maternal behavior in F344/N and LEW/N rats. Effects on carrageenan-induced inflammatory reactivity and body weight

Inbred Fischer (F344/N) and Lewis (LEW/N) rats differ on a myriad of behavioral and physiological endpoints, such as inflammatory, startle and drug responsivity. These differences point to underlying genetic differences between the strains. However, genetic models of hypertension have shown the importance of the maternal environment in the development of high blood pressure, suggesting that maternal influences might also play a role in adult phenotypes of the LEW/N and F344/N strains. This was tested in the present series of experiments in which the effects of crossfostering on carrageenan-induced inflammation and on body weight were examined in the two strains. Following the demonstration that the two strains differed in maternal behavior (Experiment 1), which was independent of the pup being reared (Experiment 2), crossfostered and in-fostered pups from the LEW/N and F344/N strains were injected with carrageenan (at 60 days of age) and subsequently assessed for the accumulation of exudate in response to the injection. Body weights were also monitored from birth through 60 days of age. Although crossfostering affected body weight of the two strains, specifically, reducing weights in LEW/N pups reared by F344/N dams and increasing weights of F344/N pups reared by LEW/N dams, crossfostering did not affect inflammatory reactivity to carrageenan. Specifically, LEW/N pups had a greater level of exudate than F344/N pups, independent of the conditions under which they were reared, suggesting that differences in the inflammatory response between these two strains are under a high degree of genetic control. These results were discussed in terms of genetic factors mediating the early form of immune reactivity induced by carrageenan.

Tamoxifen inhibits the release of arachidonic acid stimulated by thapsigargin in estrogen receptor-negative A549 cells

In pre-labelled A549 cells the tumour promoter thapsigargin (50 nM) stimulates the release of [5,6,8,9,11,12,14,15-3H(N)]-arachidonic acid (3H-AA) by ca. 300% above basal levels. A549 cells are estrogen receptor negative (ER-), yet this stimulation by thapsigargin is inhibited in a dose-dependent manner by a 3 h pre-treatment with the anti-estrogen tamoxifen (1-20 microM). Moreover, the presence of excess (100 microM) estradiol does not reverse this effect of tamoxifen. Thapsigargin stimulated 3H-AA release is not inhibited over the same concentration range by 4 hydroxy-tamoxifen nor by the steroidal anti-estrogen ICI 164384. However, the steroidal anti-estrogen ICI 182780 inhibits thapsigargin stimulated 3H-AA release in a similar manner to tamoxifen and this effect is also not reversed by the presence of excess estradiol. Stimulation of 3H-AA release by EGF (10 nM), IL-1beta (1 ng ml-1) and bradykinin (100 nM) was unaffected by these concentrations of tamoxifen. Ionomycin (10 microM) stimulates 3H-AA release by ca. 700% and A23187 (10 microM) by ca. 300% above basal levels. Pre-treatment with tamoxifen (1-20 microM) inhibits 3H-AA release stimulated by both these agents and again the presence of excess estradiol does not reverse this effect. Unlike the effects of glucocorticoids on 3H-AA release in A549 cells the effects of tamoxifen are not reversed by neutralizing anti-bodies to lipocortin 1. Arachidonic acid release is central to cell proliferation in A549 cells and we propose that this action of tamoxifen could explain the anti-proliferative effect seen in these cells and could have important implications for control of cell proliferation of ER- cells in general.

Anti-inflammatory activity of cationic lipids

1. The effect of liposome phospholipid composition has been assumed to be relatively unimportant because of the presumed inert nature of phospholipids. 2. We have previously shown that cationic liposome formulations used for gene therapy inhibit, through their cationic component, the synthesis by activated macrophages of the pro-inflammatory mediators nitric oxide (NO) and tumour necrosis factor-alpha (TNF-alpha). 3. In this study, we have evaluated the ability of different cationic lipids to reduce footpad inflammation induced by carrageenan and by sheep red blood cell challenge. 4. Parenteral (i.p. or s.c) or local injection of the positively charged lipids dimethyldioctadecylammomium bromide (DDAB), dioleyoltrimethylammonium propane (DOTAP), dimyristoyltrimethylammonium propane (DMTAP) or dimethylaminoethanecarbamoyl cholesterol (DC-Chol) significantly reduced the inflammation observed in both models in a dose-dependent manner (maximum inhibition: 70-95%). 5. Cationic lipids associated with dioleyol- or dipalmitoyl-phosphatidylethanolamine retained their anti-inflammatory activity while cationic lipids associated with dipalmitoylphosphatidylcholine (DPPC) or dimyristoylphosphatidylglycerol (DMPG) showed no anti-inflammatory activity, indicating that the release of cationic lipids into the macrophage cytoplasm is a necessary step for anti-inflammatory activity. The anti-inflammatory activity of cationic lipids was abrogated by the addition of dipalmitoylphosphatidylethanolamine-poly(ethylene)glycol-2000 (DPPE-PEG2000) which blocks the interaction of cationic lipids with macrophages. 6. Because of the significant role of protein kinase C (PKC) in the inflammatory process we have determined whether the cationic lipids used in this study inhibit PKC activity. The cationic lipids significantly inhibited the activity of PKC but not the activity of a non-related protein kinase, PKA. The synthesis of interleukin-6 (IL-6), which is not dependent on PKC activity for its induction in macrophages, was not modified in vitro or in situ by cationic lipids. The synthesis of NO and TNF-alpha in macrophages, both of which are PKC-dependent, was downregulated by cationic lipids. 7. These results demonstrate that cationic lipids can be considered as novel anti-inflammatory agents. The downregulation of pro-inflammatory mediators through interaction of cationic lipids with the PKC pathway may explain this anti-inflammatory activity. Furthermore, since cationic lipids have intrinsic anti-inflammatory activity, cationic liposomes should be used with caution to deliver nucleic acids for gene therapy in vivo.