Effect of interleukin 1 beta on transducing mechanisms in 235-1 clonal pituitary cells. Part II: Modulation of calcium fluxes

Emerging Targets in Pituitary Adenomas: Role of the CXCL12/CXCR4-R7 System

Chemokines are chemotactic regulators of immune surveillance in physiological and pathological conditions such as inflammation, infection, and cancer. Several chemokines and cognate receptors are constitutively expressed in the central nervous system, not only in glial and endothelial cells but also in neurons, controlling neurogenesis, neurite outgrowth, and axonal guidance during development. In particular, the chemokine CXCL12 and its receptors, CXCR4 and CXCR7, form a functional network that controls plasticity in different brain areas, influencing neurotransmission, neuromodulation, and cell migration, and the dysregulation of this chemokinergic axis is involved in several neurodegenerative, neuroinflammatory, and malignant diseases. CXCR4 primarily mediates the transduction of proliferative signals, while CXCR7 seems to be mainly responsible for scavenging CXCL12. Importantly, the multiple intracellular signalling generated by CXCL12 interaction with its receptors influences hypothalamic modulation of neuroendocrine functions, although a direct modulation of pituitary functioning via autocrine/paracrine mechanisms was also reported. Both CXCL12 and CXCR4 are constitutively overexpressed in pituitary adenomas and their signalling induces cell survival and proliferation, as well as hormonal hypersecretion. In this review we focus on the physiological and pathological functions of immune-related cyto- and chemokines, mainly focusing on the CXCL12/CXCR4-7 axis, and their role in pituitary tumorigenesis. Accordingly, we discuss the potential targeting of CXCR4 as novel pharmacological approach for pituitary adenomas.

Beyond neurons: evidence that immune and glial cells contribute to pathological pain states

Chronic pain can occur after peripheral nerve injury, infection, or inflammation. Under such neuropathic pain conditions, sensory processing in the affected body region becomes grossly abnormal. Despite decades of research, currently available drugs largely fail to control such pain. This review explores the possibility that the reason for this failure lies in the fact that such drugs were designed to target neurons rather than immune or glial cells. It describes how immune cells are a natural and inextricable part of skin, peripheral nerves, dorsal root ganglia, and spinal cord. It then examines how immune and glial activation may participate in the etiology and symptomatology of diverse pathological pain states in both humans and laboratory animals. Of the variety of substances released by activated immune and glial cells, proinflammatory cytokines (tumor necrosis factor, interleukin-1, interleukin-6) appear to be of special importance in the creation of peripheral nerve and neuronal hyperexcitability. Although this review focuses on immune modulation of pain, the implications are pervasive. Indeed, all nerves and neurons regardless of modality or function are likely affected by immune and glial activation in the ways described for pain.

Interleukin-1 increases protein kinase A activity by a cAMP-independent mechanism in AtT-20 cells

A recent study from this laboratory has shown that the inflammatory mediator, interleukin-1 alpha (IL-1 alpha), stimulates protein kinase A (PKA) activity and adrenocorticotropic hormone (ACTH) secretion from AtT-20 cells without any detectable increase in intracellular cAMP accumulation. The present studies were conducted to determine if cAMP is involved in IL-1 alpha activation of PKA and if PKA is responsible for IL-1 alpha-induced ACTH release from AtT-20 cells. The data are consistent with a novel mechanism of PKA activation that does not involve cAMP. Inhibition of adenylate cyclase with 2'5'-dideoxyadenosine (2'5'-DDA) did not affect IL-1 alpha-induced increases in PKA activity and ACTH secretion. In contrast, CRF-stimulated PKA activity and ACTH secretion were inhibited by 2'5'-DDA. Additional evidence was obtained using the phosphodiesterase inhibitor, 3-isobutyl-1-methylxanthine (IBMX). IBMX did not alter IL-1 alpha-induced PKA activity or ACTH secretion, yet IBMX potentiated CRF-induced cAMP accumulation. Inhibition of PKA with the PKA inhibitor, H-8, blocked activation of PKA and ACTH secretion by both IL-1 alpha and CRF in AtT-20 cells. These observations demonstrate that 1) the mechanism of IL-1 alpha activation of PKA is independent of adenylate cyclase or cAMP and 2) PKA is used by IL-1 alpha to induce ACTH secretion from AtT-20 cells.

Interleukin-1 receptor antagonist inhibits calcium accumulation in in vivo chronic granuloma induced by potassium permanganate

Interleukin-1 (IL-1) is a monokine that exerts multiple biological activity, including immunity and inflammation. Moreover, IL-1 is involved in Ca2+ release causing hypercalcemia and bone resorption. Recently, a 22 kDa natural inhibitor to IL-1 called interleukin-1 receptor antagonist (IL-1ra) has been described in human fluids, which specifically binds IL-1 alpha or IL-1 beta receptors. In this study, we found that experimental granuloma induced by subcutaneous injections (0.2 ml) of potassium permanganate (KMnO4) 1:40 saturated crystal solution, after 7 days was strongly inhibited in size, weight and calcium content (measured as dry ash weight by incineration of granuloma tissue) compared with untreated controls, in mice treated intraperitoneally with IL-1ra (20 micrograms/bolus) given twice; the first at the same time of the induction of the granuloma and the second 24 hours later. In addition, leukotriene B4 and prostaglandin E2 were also inhibited in fresh granuloma of mice treated with IL-1ra. Taken together, these findings conclude for the first time, that the accumulation of calcium in chronic inflammatory states is strongly inhibited by IL-1ra, which decreases tissue calcergy and can potentially be useful for the treatment of calcium-related inflammatory diseases and malignancy-associated hypercalcemia.

Interleukin 1 beta inhibition of TRH-stimulated prolactin secretion and phosphoinositides metabolism

The effect of interleukin 1 beta on prolactin secretion and on phosphoinositide turnover in anterior pituitary cells was evaluated. Interleukin 1 beta significantly inhibited TRH-stimulated prolactin secretion assessed by the reverse hemolytic plaque assay. In particular, the cytokine reduced the percentage of plaque forming cells, the plaque mean area, the large plaques percentage. TRH-stimulated inositol phosphate production was also significantly inhibited by interleukin 1 beta. This study shows that interleukin 1 beta reduces TRH-induced prolactin secretion through a direct action on pituitary cell, and attenuates the TRH-stimulated phosphoinositide breakdown. This latter effect may suggest that the reduced lactotropes sensitivity to TRH action may be partially due to interleukin 1 beta inhibition of phosphatidylinositol breakdown.