Funk, J. L., Lausier, J., Moser, A. H., Shigenaga, J. K., Huling, S., Nissenson, R. A., Strewler, G. J., Grunfeld, C., & Feingold, K. R. (1995). Endotoxin induces parathyroid hormone-related protein gene expression in splenic stromal and smooth muscle cells, not in splenic lymphocytes. Endocrinology, 136(8), 3412-21.
PTH-related protein (PTHrP), the peptide that is responsible for most cases of hypercalcemia of malignancy, is also produced under normal circumstances by a variety of tissues. Its role and regulation at these sites are not well understood. Recently, we have shown that PTHrP is induced in the spleen during the host response to endotoxin (LPS) and that tumor necrosis factor (TNF) is a major mediator of this effect. Given the large body of in vitro evidence suggesting that PTHrP can be produced by lymphocytes and act in an autocrine loop to alter their function, studies were undertaken to determine whether lymphocytes were the cells responsible for PTHrP production in the spleen. Both constitutive and LPS-induced PTHrP messenger RNA (mRNA) levels were the same in mice lacking mature T cells (nude mice) and in mice lacking natural killer (NK) cells (due to pretreatment with antibody against NK 1.1) compared to levels in normal mice, suggesting that neither mature T cells nor NK cells were the splenic source of PTHrP. Even scid mice that lack functioning T and B cells responded to TNF with the induction of splenic PTHrP mRNA levels comparable to those in control mice. Localization of PTHrP mRNA in subfractions of rat spleens after in vivo treatment with LPS confirmed the results of the murine studies; PTHrP mRNA was barely detectable in the lymphocyte-rich single cell fraction of the spleen. In contrast, the stromal fraction of the spleen was enriched with PTHrP mRNA both in the basal state and in response to LPS. A similar pattern of distribution was seen for interleukin-6; LPS only increased mRNA levels of this TNF-inducible cytokine in the splenic stroma. In addition, mRNA for the PTH/PTHrP receptor, which decreased in response to LPS, colocalized with PTHrP mRNA in the stromal fraction of the spleen. Immunohistochemical studies identified PTHrP in two populations of splenic cells: 1) smooth muscle cells located in the splenic capsule and trabeculae and 2) a subpopulation of stromal cells located in the red pulp of the spleen, primarily in a subcapsular distribution. Consistent with the localization of PTHrP mRNA, lymphocytes in the white pulp of the spleen did not stain for PTHrP.
Funk, J. L., Moser, A. H., Grunfeld, C., & Feingold, K. R. (1997). Parathyroid hormone-related protein is induced in the adult liver during endotoxemia and stimulates the hepatic acute phase response. Endocrinology, 138(7), 2665-73.
Previously, we reported that PTH-related protein (PTHrP) gene expression is induced in vital organs, including the liver, during endotoxemia. The liver plays a central role in the acute phase response (APR), a cytokine-mediated host defense against infection and inflammation that includes increased production of acute phase proteins and lipids by hepatocytes. Because PTHrP is thought to act locally at its site of production, in vivo studies were carried out to determine whether PTHrP could contribute to the induction of the hepatic APR. Hepatic PTHrP messenger RNA (mRNA) levels were induced acutely in rat liver in response to a near lethal dose of endotoxin. PTHrP protein, which was located by immunohistochemical staining in hepatocytes from both control and LPS-treated rats, was markedly induced in periportal hepatocytes in response to LPS treatment. Co-incident with this transient increase in PTHrP gene expression, PTH/PTHrP receptor mRNA levels were down-regulated. Administration of PTHrP(1-34), a PTH/PTHrP receptor agonist, to mice increased hepatic serum amyloid A (SAA) mRNA levels as well as circulating levels of SAA. In addition, PTHrP(1-34) increased serum triglyceride (TG) levels in rats and mice in a dose-dependent fashion. The hypertriglyceridemic effect of PTHrP(1-34) was accompanied by an increase in hepatic fatty acid synthesis. In contrast, PTHrP(7-34) amide, a receptor antagonist, had no effect on serum SAA or TG levels. These results, which provide evidence for the regulated expression of PTHrP in adult liver, suggest that PTHrP may be one additional member of the cytokine cascade produced locally in liver that can act to stimulate the hepatic acute phase response.
Funk, J. L., & Timmermann, B. N. (2006). Translational investigation of turmeric for arthritis treatment: a review of lessons learned. NATURAL PRODUCT COMMUNICATIONS, 1(11), 1061-1066.
Funk, J. L., Cordaro, L. A., Wei, H., Benjamin, J. B., & Yocum, D. E. (1998). Synovium as a source of increased amino-terminal parathyroid hormone-related protein expression in rheumatoid arthritis. A possible role for locally produced parathyroid hormone-related protein in the pathogenesis of rheumatoid arthritis. The Journal of clinical investigation, 101(7), 1362-71.
Proinflammatory cytokines, including tumor necrosis factor (TNF) and interleukin 1 (IL-1), mediate the joint destruction that characterizes rheumatoid arthritis (RA). Previous studies have shown that parathyroid hormone-related protein (PTHrP) is a member of the cascade of proinflammatory cytokines induced in parenchymal organs during lethal endotoxemia. To test the hypothesis that NH2-terminal PTHrP, a potent bone resorbing agent, could also be a member of the synovial cascade of tissue-destructive cytokines whose expression is induced in RA, PTHrP expression was examined in synovium and synoviocytes obtained from patients with RA and osteoarthritis (OA). PTHrP production, as determined by measurement of immunoreactive PTHrP(1-86) in tissue explant supernatants, was increased 10-fold in RA versus OA synovial tissue. Synovial lining cells and fibroblast-like cells within the pannus expressed both PTHrP and the PTH/PTHrP receptor, findings that were confirmed by in vitro studies of cultured synoviocytes. TNF-alpha and IL-1beta stimulated PTHrP expression in synoviocytes, while dexamethasone and interferon-gamma, agents with some therapeutic efficacy in the treatment of RA, inhibited PTHrP release. Treatment of synoviocytes with PTHrP(1-34) stimulated IL-6 secretion. These results suggest that proinflammatory cytokine-stimulated production of NH2-terminal PTHrP by synovial tissue directly invading cartilage and bone in RA may mediate joint destruction through direct effects on cartilage or bone, or, indirectly, via the induction of mediators of bone resorption in the tumor-like synovium.
Funk, J. L., & Wei, H. (1998). Regulation of parathyroid hormone-related protein expression in MCF-7 breast carcinoma cells by estrogen and antiestrogens. Biochemical and biophysical research communications, 251(3), 849-54.
Expression of parathyroid hormone-related protein (PTHrP) in breast carcinoma is a frequent cause of the paraneoplastic syndrome of hypercalcemia. In response to treatment with estrogen or tamoxifen, some breast cancer patients also develop a transient hypercalcemia. Therefore, the effect of 17beta-estradiol (E2), tamoxifen, or its more potent metabolite, 4-hydroxytamoxifen (OH-tamoxifen), on PTHrP expression in an estrogen receptor (ER)-positive breast carcinoma cell line (MCF-7) was evaluated. E2 increased PTHrP mRNA levels in MCF-7 cells and stimulated PTHrP(1-86) release in a dose-dependent fashion (10(-10)-10(-6) M). Tamoxifen and OH-tamoxifen also stimulated PTHrP release in a concentration-dependent fashion that paralleled their relative ER binding affinities (10(-6) or 10(-8)-10(-6) M, respectively). Combined treatment with the partial estrogen agonist, OH-tamoxifen, and E2 decreased E2-stimulated PTHrP secretion in MCF-7 cells to the levels seen with OH-tamoxifen treatment alone. These results suggest that transient estrogen- or tamoxifen-induced hypercalcemia in patients with breast carcinoma may be a PTHrP-mediated effect that is a marker of ER positivity.
