Interleukin-1beta administered intracerebroventricularly stimulates the release of noradrenaline in the hypothalamic paraventricular nucleus via prostaglandin in the rat

Sympathetic innervation, norepinephrine content, and norepinephrine turnover in orthotopic and spontaneous models of breast cancer

Activation of the sympathetic nervous system (SNS) drives breast cancer progression in preclinical breast cancer models, but it has yet to be established if neoplastic and stromal cells residing in the tumor are directly targeted by locally released norepinephrine (NE). In murine orthotopic and spontaneous mammary tumors, tyrosine hydroxylase (TH)+ sympathetic nerves were limited to the periphery of the tumor. No TH+ staining was detected deeper within these tumors, even in regions with a high density of blood vessels. NE concentration was much lower in tumors compared to the more densely innervated spleen, reflecting the relative paucity of tumor TH+ innervation. Tumor and spleen NE concentration decreased with increased tissue mass. In mice treated with the neurotoxin 6-hydroxydopamine (6-OHDA) to selectively destroy sympathetic nerves, tumor NE concentration was reduced approximately 50%, suggesting that the majority of tumor NE is derived from local sympathetic nerves. To evaluate NE utilization, NE turnover in orthotopic 4T1 mammary tumors was compared to spleen under baseline and stress conditions. In non-stressed mice, NE turnover was equivalent between tumor and spleen. In mice exposed to a stressor, tumor NE turnover was increased compared to spleen NE turnover, and compared to non-stressed tumor NE turnover. Together, these results demonstrate that NE in mammary tumors is derived from local sympathetic nerves that synthesize and metabolize NE. However, differences between spleen and tumor NE turnover with stressor exposure suggest that sympathetic NE release is regulated differently within the tumor microenvironment compared to the spleen. Local mammary tumor sympathetic innervation, despite its limited distribution, is responsive to stressor exposure and therefore can contribute to stress-induced tumor progression.

Systemic Interleukin-1β stimulates the simultaneous release of norepinephrine in the paraventricular nucleus and the median eminence

Interleukin-1beta (IL-1beta), a cytokine with pronounced central effects such as fever, anorexia, analgesia, etc., is also known to activate the hypothalamo-pituitary-adrenal (HPA) axis. Corticotropin releasing hormone (CRH) neurons located in the hypothalamus are important for HPA activation. The cell bodies of CRH neurons are located in the paraventricular nucleus (PVN) and their terminals are present in the median eminence (ME). Although the catecholamines, norepinephrine (NE) and dopamine (DA) are believed to be crucial factors in the stimulation of CRH neurons, it is not clear if they affect the cell bodies or terminals of these neurons to cause HPA activation. This study was done to determine if IL-1beta affects NE and DA release at the level of CRH cell bodies or their terminals. Adult male Sprague-Dawley rats were implanted with two push-pull cannulae, one in the PVN and another in the ME, and were subjected to push-pull perfusion. They were treated either with 0, 1 or 5 microg of IL-1beta. Perfusates were collected for 2 h after treatment and analyzed for NE concentrations using HPLC-EC. NE levels in the control and low dose groups did not change significantly during the entire period of observation both in the PVN and ME. In contrast, treatment with 5 microg of IL-1beta produced a marked increase in NE release in the PVN at 20 and 40 min post-treatment. NE release in the ME increased from 10 to 140 min post-treatment. There were no significant changes in the release of DA from both these areas. These results indicate that IL-1beta increases NE levels both in the PVN and in the ME and this could be a possible mechanism by which it stimulates the HPA axis.

The acute and sensitization effects of tumor necrosis factor-α: implications for immunotherapy as well as psychiatric and neurological conditions

In addition to their role as signaling molecules of the immune system, cytokines may participate in central neurotransmission. Variations of the central and/or peripheral levels of the proinflammatory cytokines, tumor necrosis factor-α (TNF-α) and interleukin-β (IL-1β), impact on neuroendocrine processes as well as central neurotransmitter activity. To a considerable extent, these effects are reminiscent of those elicited by psychogenic stressors. The current review describes recent findings consistent with a role for these cytokines in the neurochemical and behavioral manifestations of clinical depression, as well as the cellular death associated with cerebral ischemia. Moreover, the increasing use of cytokines in the immunotherapeutic treatment of various autoimmune diseases (e.g. rheumatoid arthritis) and cancers prompted us to consider the potential role of central processes in subserving the mood-related side-effects elicited by these treatments. Finally, a single administration of TNF-α has been shown to elicit a time-dependent sensitization effect, wherein the behavioral and neurochemical responses elicited by later cytokine treatment are greatly enhanced. Thus, particular attention was devoted to the possibility that elevated levels of TNF-α, through either exogenous (e.g. immunotherapy) or endogenous (e.g. brain damage or stressors) means may sensitize neurotransmitter or second messenger pathways important for the pathology. Given the time-dependent nature of cytokine sensitization effects, the schedule of cytokine administration during immunotherapy, or the timing of cytokine up-regulation in response to traumatic or stressful events may favor the development of sensitized central processes, which may influence clinical outcome.