Apolipoprotein M Attenuates Anthracycline Cardiotoxicity and Lysosomal Injury

Apolipoprotein M (ApoM) binds sphingosine-1-phosphate (S1P) and is inversely associated with mortality in human heart failure (HF). Here, we show that anthracyclines such as doxorubicin (Dox) reduce circulating ApoM in mice and humans, that ApoM is inversely associated with mortality in patients with anthracycline-induced heart failure, and ApoM heterozygosity in mice increases Dox-induced mortality. In the setting of Dox stress, our studies suggest ApoM can help sustain myocardial autophagic flux in a post-transcriptional manner, attenuate Dox cardiotoxicity, and prevent lysosomal injury.

Abstract 521: Apolipoprotein M Links High-density Lipoprotein to Myocardial Autophagy

Background: Apolipoprotein M (APOM) is a lipoprotein that binds sphingosine-1-phosphate (S1P) and high-density lipoprotein (HDL). APOM/S1P attenuate myocardial ischemia/reperfusion injury by reducing infarct size. We recently published that reduced APOM plasma protein levels are associated with mortality across the spectrum of human heart failure. With the goal of uncovering mechanisms by which APOM impacts heart failure mortality, we modeled doxorubicin cardiotoxicity in hepatocyte specific APOM overexpression (APOM TG ) and littermate controls.

Results: Doxorubicin treatment acutely reduces APOM plasma protein levels in control mice. APOM TG mice exhibit ~3-5 fold increased APOM and ~2.5 fold increased S1P. In acute and chronic doxorubicin cardiotoxicity models, APOM TG mice were protected from mortality and reductions in left-ventricular mass and ejection fraction observed in littermate controls. In murine models of acute leukemia, doxorubicin effectively killed leukemic cells in control and APOM TG mice. In the myocardium, APOM TG mice and controls had similar levels of γ-H2AX foci after doxorubicin treatment, indicating similar levels of DNA damage, and electron microscopy indicated similar mitochondrial morphology. However, APOM TG mice exhibited enhanced autophagic flux, and APOM prevented doxorubicin-induced reductions in autophagic flux observed in littermate control mice (Figure). Mechanistically, treatment of neonatal rat cardiomyocytes with S1P mimetics attenuated doxorubicin-induced loss of lysosomal pH, suggesting that APOM may enhance lysosomal function via S1P. In the murine myocardium, doxorubicin reduced the nuclear protein content of transcription factor EB (TFEB), a master regulator of autophagy and lysosomal biogenesis, in control mice but not APOM TG mice. Furthermore, adeno-associated virus mediated knockdown of TFEB completely reversed the beneficial effects of APOM on the myocardium, leading to cardiomyopathy and mortality in APOM TG mice.

Conclusions: Our studies identify APOM and S1P as regulators of TFEB in the myocardium, hence providing a mechanistic link between HDL and the autophagy-lysosome pathway in the murine heart. The role of APOM in myocardial autophagy may explain our observed clinical associations between reduced APOM and mortality.

Regulation of colonic epithelial repair in mice by Toll-like receptors and hyaluronic acid

BACKGROUND & AIMS

The protective component of the host response to dextran sodium sulfate (DSS)-induced colitis in the mouse is mediated through the activation of Toll-like receptor (TLR) 4, the induction of cyclooxygenase (COX)-2, and prostaglandin E(2) production. TLR4 ligands include bacterial lipopolysaccharide and hyaluronic acid, a component of the extracellular matrix. Our hypothesis is that hyaluronic acid, through TLRs, plays a protective role in the host response to DSS-induced colitis.

METHODS

DSS (2.5%) was administered for 7 days in wild-type and MyD88(-/-) mice. The mice also received intraperitoneal hyaluronic acid. The expression of hyaluronic acid, COX-2, and macrophage inflammatory protein (MIP)-2 was evaluated by immunohistochemistry.

RESULTS

DSS induced a marked increase in hyaluronic acid in the lamina propria of wild-type but not MyD88(-/-) mice. Treatment with DSS also induced the MyD88-dependent expression of hyaluronic acid synthases 2 and 3, enzymes involved in hyaluronic acid synthesis, in lamina propria macrophages. Exogenous hyaluronic acid induced the expression of tumor necrosis factor alpha, MIP-2, and COX-2 in the colon in a MyD88-dependent manner. In wild-type but not MyD88(-/-), TLR4(-/-), COX-2(-/-) mice, hyaluronic acid was protective against DSS-induced colitis. In wild-type mice, hyaluronic acid was therapeutic in established DSS-induced colitis.

CONCLUSIONS

Endogenous hyaluronic acid expression is markedly increased in DSS-induced colitis and preserves the epithelium through TLR activation and COX-2 expression. Furthermore, exogenous hyaluronic acid, through the activation of TLRs and the production of prostaglandin E(2) through COX-2, has protective effects in DSS-induced colitis.

Amebic infection in the human colon induces cyclooxygenase-2

We sought to determine if infection of the colon with Entamoeba histolytica induces the expression of cyclooxygenase-2 and, if it does, to determine the contribution of prostaglandins produced through cyclooxygenase-2 to the host response to amebic infection. Human fetal intestinal xenografts were implanted subcutaneously in mice with severe combined immunodeficiency and allowed to grow; the xenografts were then infected with E. histolytica trophozoites. Infection with E. histolytica resulted in the expression of cyclooxygenase-2 in epithelial cells and lamina propria macrophages. Infection with E. histolytica increased prostaglandin E(2) (PGE2) levels 10-fold in the xenografts and resulted in neutrophil infiltration, as manifested by an 18-fold increase in myeloperoxidase activity. Amebic infection also induced an 18-fold increase in interleukin 8 (IL-8) production and a >100-fold increase in epithelial permeability. Treatment of the host mouse with indomethacin, an inhibitor of cyclooxygenase-1 and cyclooxygenase-2, or with NS-398, a selective inhibitor of cyclooxygenase-2, resulted in (i) decreased PGE(2) levels, (ii) a decrease in neutrophil infiltration, (iii) a decrease in IL-8 production, and (iv) a decrease in the enhanced epithelial permeability seen with amebic infection. These results indicate that amebic infection in the colon induces the expression of cyclooxygenase-2 in epithelial cells and macrophages. Moreover, prostaglandins produced through cyclooxygenase-2 participate in the mediation of the neutrophil response to infection and enhance epithelial permeability.

Lipopolysaccharide is radioprotective in the mouse intestine through a prostaglandin-mediated mechanism

BACKGROUND & AIMS

The bone marrow and the intestine are the major sites of radiation-induced injury. The cellular response to radiation injury in the intestine or bone marrow can be modulated by agents given before irradiation. Lipopolysaccharide is known to be radioprotective in the bone marrow, but its effect on the intestine is not known. We sought to determine if lipopolysaccharide is radioprotective in the intestine and, if so, to determine the mechanism of its radioprotective effects.

METHODS

Mice were treated with parenteral lipopolysaccharide or vehicle and then irradiated (14 Gy total body irradiation in a cesium irradiator). The number of surviving intestinal crypts was assessed 3.5 days after irradiation using a clonogenic assay.

RESULTS

Parenteral administration of lipopolysaccharide 2-24 hours before irradiation resulted in a 2-fold increase in the number of surviving crypts 3.5 days after irradiation. The radioprotective effects of lipopolysaccharide could be eliminated by coadministration of a selective inhibitor of cyclooxygenase 2. Lipopolysaccharide was radioprotective in wild-type mice but not in mice with a disrupted cyclooxygenase 2. Parenteral administration of lipopolysaccharide resulted in increased production of prostaglandins in the intestine and in the induction of cyclooxygenase 2 expression in subepithelial fibroblasts and in villous, but not crypt, epithelial cells.

CONCLUSIONS

Lipopolysaccharide is radioprotective in the mouse intestine through a prostaglandin-dependent pathway.

Cyclooxygenase 2 is induced in colonic epithelial cells in inflammatory bowel disease

BACKGROUND & AIMS

Prostaglandins are synthesized by cyclooxygenases (COX)-1 and -2. The expression and cellular localization of COX-1 and COX-2 in normal human colon and inflammatory bowel disease (IBD) surgical resections were studied.

METHODS

COX-1 and COX-2 protein expression and cellular localization were assessed by Western blotting and immunohistochemistry.

RESULTS

COX-1 protein was expressed at equal levels in normal, Crohn's disease, and ulcerative colitis colonic epithelial cells. COX-2 protein was not detected in normal epithelial cells but was detected in Crohn's disease and ulcerative colitis epithelial cells. Immunohistochemistry of normal, Crohn's colitis, and ulcerative colitis tissue showed equivalent COX-1 expression in epithelial cells in the lower half of the colonic crypts. COX-2 expression was absent from normal colon, whereas in Crohn's colitis and ulcerative colitis, COX-2 was observed in apical epithelial cells and in lamina propria mononuclear cells. In Crohn's ileitis, COX-2 was present in the villus epithelial cells. In ulcerative colitis, colonic epithelial cells expressing COX-2 also expressed inducible nitric oxide synthase.

CONCLUSIONS

COX-1 was localized in the crypt epithelium of the normal ileum and colon, and its expression was unchanged in IBD. COX-2 was undetectable in normal ileum or colon, but it was induced in apical epithelial cells of inflamed foci in IBD.

Efficacy and tolerability of a new antipsychotic compound (risperidone): results of a pilot study

Risperidone is a new benzisoxazole derivative displaying a very potent serotonin antagonism and a potent dopamine antagonism in pharmacological studies. These properties suggest the hypothesis that risperidone may exert antipsychotic effects and be superior to classic neuroleptics in its beneficial effects on negative and affective symptoms and its low extrapyramidal side-effect propensity. In an open pilot study 13 patients suffering from acute schizophrenic psychosis were treated with risperidone within an individually adapted dose range from 1 to 10 mg per day. A good antipsychotic efficacy could be demonstrated in 6 of the 8 patients who completed the trial. Risperidone was very well tolerated. The substance possesses a low EPS-inducing profile. Future research has to test the suggested advantage of risperidone over other neuroleptic drugs and its performance in the treatment of chronic schizophrenic patients.

A controlled study of the efficacy and safety of mianserin and maprotiline in outpatients with major depression

Efficacy and tolerability of mianserin (60-90 mg/day) or maprotiline (100-150 mg/day) were tested in a 4-week double-blind control group study on 317 depressive outpatients. The patients had to fulfill the criteria of a major depression according to DSM-III. The study was performed by psychiatrists after special rater training. Standardized rating procedures were applied to evaluate depressive symptoms and unwanted effects at three measurement points. A significant improvement was found in both groups, without any statistical differences between mianserin and maprotiline. According to the Clinical Global Impressions (CGI) 65% of the patients in both groups were judged as responders. A good tolerability of both drugs were demonstrated. With respect to anticholinergic side-effects there was a certain advantage in favor to mianserin.

Doubleblind evaluation of the antimanic properties of carbamazepine as a comedication to haloperidol

1. Today carbamazepine is the most important alternative to neuroleptic drugs for the treatment of manic psychoses. Often carbamazepine is administered as a comedication to a neuroleptic. 2. A doubleblind study with 20 patients suffering from manic or schizomanic psychoses was performed to determine whether carbamazepine and haloperidol in comedication are more effective than haloperidol alone. 3. Under the tested conditions (24 mg haloperidol p.d.) only the smaller amount of additional medication with levomepromazine in the experimental group gave evidence for the antimanic effect of carbamazepine in combination with haloperidol. 4. Especially the patients with pure manic psychoses seem to benefit from carbamazepine as an adjunct to haloperidol.