Carlos Lavalle

Prolactin, immunoregulation, and autoimmune diseases

Cells of the immune system synthesize prolactin and express mRNA and receptors for that hormone. Interleukin 1, interleukin 6, gamma interferon, tumor necrosis factor, platelet activator factor, and substance P participate in the release of prolactin. This hormone is involved in the pathogenesis of adjuvant arthritis and restores immunocompetence in experimental models. In vitro studies suggest that lymphocytes are an important target tissue for circulating prolactin. Prolactin antibodies inhibit lymphocyte proliferation. Prolactin is comitogenic with concanavalin A and induces interleukin 2 receptors on the surface of lymphocytes. Prolactin stimulates ornithine decarboxylase and activates protein kinase C, which are pivotal enzymes in the differentiation, proliferation, and function of lymphocytes. Cyclosporine A interferes with prolactin binding to its receptors on lymphocytes. Hyperprolactinemia has been found in patients with systemic lupus erythematosus. Fibromyalgia, rheumatoid arthritis, and low back pain patients present a hyperprolactinemic response to thyrotropin-releasing hormone. Experimental autoimmune uveitis, as well as patients with uveitis whether or not associated with spondyloarthropathies, and patients with psoriatic arthritis may respond to bromocriptine treatment. Suppression of circulating prolactin by bromocriptine appears to improve the immunosuppressive effect of cyclosporine A with significantly less toxicity. Prolactin may also be a new marker of rejection in heart-transplant patients. This body of evidence may have an impact in the study of rheumatic disorders, especially connective tissue diseases. A role for prolactin in autoimmune diseases remains to be demonstrated.

Matrix metalloproteases from chondrocytes generate an antiangiogenic 16 kDa prolactin

The 16 kDa N-terminal fragment of prolactin (16K-prolactin) is a potent antiangiogenic factor. Here, we demonstrate that matrix metalloproteases (MMPs) produced and secreted by chondrocytes generate biologically functional 16K-prolactin from full-length prolactin. When incubated with human prolactin at neutral pH, chondrocyte extracts and conditioned medium, as well as chondrocytes in culture, cleaved the Ser155-Leu156 peptide bond in prolactin, yielding - upon reduction of intramolecular disulfide bonds - a 16 kDa N-terminal fragment. This 16K-prolactin inhibited basic fibroblast growth factor (FGF)-induced endothelial cell proliferation in vitro. The Ser155-Leu156 site is highly conserved, and both human and rat prolactin were cleaved at this site by chondrocytes from either species. Conversion of prolactin to 16K-prolactin by chondrocyte lysates was completely abolished by the MMP inhibitors EDTA, GM6001 or 1,10-phenanthroline. Purified MMP-1, MMP-2, MMP-3, MMP-8, MMP-9 and MMP-13 cleaved human prolactin at Gln157, one residue downstream from the chondrocyte protease cleavage site, with the following relative potency: MMP-8>MMP-13 >MMP-3>MMP-1=MMP-2>MMP-9. Finally, chondrocytes expressed prolactin mRNA (as revealed by RT-PCR) and they contained and released antiangiogenic N-terminal 16 kDa prolactin (detected by western blot and endothelial cell proliferation). These results suggest that several matrix metalloproteases in cartilage generate antiangiogenic 16K-prolactin from systemically derived or locally produced prolactin.

Cyclophosphamide pulse therapy in optic neuritis due to systemic lupus erythematosus: an open trial

OBJECTIVE To evaluate the efficacy of intravenous cyclophosphamide pulse therapy in patients with optic neuritis associated with systemic lupus erythematosus (SLE). PATIENTS AND METHODS Ten consecutive patients with optic neuritis due to SLE whose condition was refractory to corticosteroids and oral immunosuppressants were treated with intravenous cyclophosphamide (0.5 to 1.0 g/m2) monthly for 6 months. RESULTS All patients had bilateral eye involvement. One eye was legally blind, and 13 eyes could see only hand movements or count fingers. Six patients had evidence of the secondary antiphospholipid antibody syndrome. Complete recovery in visual acuity occurred in 10 eyes (50%), and a partial response occurred in six eyes (30%); four eyes (20%) had no response. Complete response in the field tests occurred in eight eyes (40%), with a partial response in nine eyes (45%); no improvement occurred in three eyes (15%). CONCLUSIONS Intravenous cyclophosphamide pulse therapy seems to be an effective treatment for optic neuritis refractory to corticosteroids, oral immunosuppressants, or both. A randomized controlled trial will be necessary to confirm our results.

Molecular heterogeneity of prolactin in the plasma of patients with systemic lupus erythematosus

OBJECTIVE Systemic lupus erythematosus (SLE) has been associated with high levels of prolactin in the circulation of some patients. Although prolactin stimulates immune responses, the relationship between hyperprolactinemia and the pathophysiology of SLE remains controversial. This study was undertaken to investigate whether circulating bioactive prolactin isoforms are associated with the activity of SLE. METHODS The molecular heterogeneity of prolactin was studied in the plasma of patients with active and inactive SLE and in healthy volunteers by radioimmunoassay (RIA), enzyme-linked immunosorbent assay (ELISA), Nb2-cell bioassay, and immunoprecipitation-Western blots. The specificity of the bioassay determinations was assessed by neutralization of growth-promoting effects with antiserum to human prolactin. RESULTS Significantly higher prolactin levels were detected by bioassay and by ELISA than by RIA in both subsets of SLE patients and in normal individuals. Plasma prolactin levels in the SLE patients were significantly greater than those in the normal controls when measured by ELISA, but not by RIA or bioassay. The bioassay:ELISA and bioassay:RIA ratios were similar between SLE patients and controls, suggesting that prolactin biopotency was not altered with the disease, and none of the 3 assays detected a difference in prolactin levels between patients with active SLE and those with inactive SLE. However, the prolactin detected in plasma was associated with immunoreactive proteins of 130 kd and 23 kd, and the concentration of the 130-kd prolactin-like species was 10-fold higher in inactive SLE versus active SLE patients. CONCLUSION Discrepancies among assays substantiate the molecular heterogeneity of circulating prolactin. The prolactin isotype that is found in association with inactive SLE could be of potential use as a marker for the inactive form of the disease and as an index for the efficacy of treatment.

Myocardial Infarction in Patients with Systemic Lupus Erythematosus with Normal Findings from Coronary Arteriography and Without Coronary Vasculitis Case Reports

The authors present the cases of two young patients, a man and a woman, who presented with myocardial infarction, in the absence of ischemic heart disease or stenosis of the coronary arteries. The woman was known to have systemic lupus erythematosus (SLE) for the past 3 years (the immunoglobulin M [IgM] anticardiolipins antibodies were positive), without a history of coronary risk factors. Suddenly she presented with acute chest pain on rest that lasted 4 hours and culminated in anterior wall myocardial infarction. She was admitted to the coronary care unit, where no thrombolysis was given. She did not have echocardiographic evidence of Libman-Sacks endocarditis, but myocardial infarction was evident at the electrocardiogram (ECG) . The young man had SLE (the IgM anticardi olipins were absent, but he was positive for lupus anticoagulant antibodies), he was hyperlipidemic, was a moderate smoker and moderately obese, and had no history of ischemic heart disease. He suddenly presented with an acute myocardial infarction docu mented by ECG, enzymes, and gammagraphy. In both patients, coronary angiography findings were normal and myocardial biopsy did not show evidence of arteritis. The relevance of these cases is the rare association of ischemic heart disease in SLE, with normal coronary arteries and without evidence of arteritis or verrucous endocarditis.

Antigen association of total HEp-2 cell extract in the screening of autoimmune diseases by western blot.

Sera from patients with autoimmune diseases and healthy individuals were comparatively analyzed by Western blot, using total extract from HEp‐2 cells as antigen. Bands between 14 and 20 kDa were present in 99% of patients with autoimmune diseases and symptomatic seronegative patients, in contrast to only 4% of healthy controls. No bands were detected in the remaining 96% of healthy controls. We propose these antigens as pathologically important for the diagnostic screening of patients with suspected autoimmune disease.