Citations

Gentamicin is a widely used ototoxic agent. In this study, we shed light on the mechanisms underlying gentamicin-induced hearing loss. More importantly, we demonstrate in vivo and in vitro the effectiveness of a strategy for preventing drug-induced hearing loss using l -carnitine (LCAR), a safe micronutrient that plays a key role in energy metabolism and detoxification [Rebouche, C. J. & Seim, H. (1998) Annu. Rev. Nutr. 18, 39-61]. We show that LCAR prevents changes in hearing threshold and cochlear damage in newborn guinea pigs exposed to gentamicin in utero . Mechanistically, gentamicin-induced apoptosis of auditory cells is mediated by the extracellular signal-regulated kinase (ERK) 1/2 mitogen-activated protein kinase (MAPK) pathway through up-regulation of the proapoptotic factor Harakiri ( Hrk ). Most important, small interfering RNA (siRNA) experiments demonstrate that Hrk up-regulation is crucial for gentamicin-induced apoptosis. LCAR, in contrast, prevents both gentamicin-induced Hrk up-regulation and apoptosis acting by means of c-Jun N-terminal kinase (JNK). Together, these results outline pathways for gentamicin-induced hearing loss and its prevention and assign a key role to Hrk in these processes. Thus, our data offer a conceptual framework for designing clinical trials using a safe micronutrient, LCAR, as a simple preventive strategy for iatrogenically induced ototoxicity.

AbstractPurpose: The B7 family molecules have been shown to regulate immune responses in both positive and negative fashions. Their roles in the progression of human cancers, however, are not well established. The aim of this study was to examine whether leukemic cells of acute myeloid leukemia express functional B7 family molecules and, if so, whether such expression has any clinical significance.Experimental Design: The expression of four B7 family molecules, B7.1, B7.2, B7-H1, and B7-H2, on leukemic cells from acute myeloid leukemia patients was analyzed by flow cytometry. The function of the expressed molecules was examined by the allogeneic mixed lymphocyte-leukemic cell reaction, and their relationship to the clinical data and survival was analyzed.Results: Although B7.1 and B7-H1 expressions were rare, the cells from a substantial number of acute myeloid leukemia cases expressed B7.2 and B7-H2 molecules [mean percentages of B7.2- and B7-H2-positive cells were 28.9% (n = 58) and 15.3% (n = 59), respectively]. Patients in whom >25% of leukemic cells expressed B7-H2 had significantly shorter survival, and this B7-H2 positivity had the strongest prognostic value when B7-H2 and other prognostic factors were analyzed together by multivariate analysis (P = 0.0108). Furthermore, B7.2 expression was associated with hyperleukocytosis (P = 0.026). Consistent with this finding, acute myeloid leukemia cells expressing B7.2 and B7-H2 induced allogeneic CD4+ T cells to proliferate and secrete interleukin-4 and interleukin-10 in vitro, effects that were partially blocked by antibodies against B7.2 and B7-H2.Conclusions: Our results indicate the expression of functional B7.2 and B7-H2 molecules, and these molecules may facilitate progression of acute myeloid leukemia.

Abstract A naturally occurring human antibody potentiates dendritic cell function on cross-linking B7-DC (PD-L2), supporting robust T-cell responses in vitro. Moreover, treatment of dendritic cells with B7-DC cross-linking antibody resulted in secretion of interleukin-12, suggesting a TH1 polarization of this response. Here we show an in vivo immunotherapeutic effect of this B7-DC cross-linking antibody using a poorly immunogenic B16 melanoma tumor model. Treatment of mice systemically with antibody at the time of tumor cell engraftment prevented tumor growth in a CD4 and CD8 T-cell-dependent manner. The protective effect of B7-DC cross-linking antibody treatment was independent of endogenous antibody responses. Tumor-specific CTL precursors could be isolated from lymph nodes draining the tumor site in animals treated with B7-DC cross-linking antibody, but not from those treated with isotype control antibodies. The elicited antitumor responses in vivo were specific and long-lasting. More strikingly, treatment of mice with B7-DC cross-linking antibody after the tumors were established in the lungs resulted in protection in a CD8-, perforin-, and granzyme B-dependent fashion. Depletion of natural killer cells did not block the effects of treatment with B7-DC cross-linking antibody. Together, these findings demonstrate that cross-linking B7-DC with the human IgM antibody sHIgM12 can induce a protective immune response against a weakly antigenic experimental tumor and therefore has potential as a novel immunotherapeutic approach for treating cancer.

Abstract A possible role for SV40, a macaque polyomavirus, in non-Hodgkin lymphoma (NHL) in humans was raised recently by the reported detection of SV40 DNA in tumor tissue. Animals with SV40-induced tumors frequently produce high-level antibodies against T antigen, the SV40 oncoprotein. In this study, we assessed whether SV40 T antibody measured in humans supported a relationship between SV40 and NHL. Subjects were sampled from a U.S. population-based case-control study of NHL, according to presence of antibodies against capsids of SV40 and BK, a related human polyomavirus (n = 85 cases, n = 95 controls). T antibody was measured by enzyme immunoassay. We also evaluated serum specimens from SV40-infected and SV40-uninfected macaques (n = 19 and n = 8, respectively), SV40-uninfected hamsters (n = 5), and hamsters with SV40-induced tumors (n = 10). Hamsters with SV40-induced tumors all produced robust SV40 T antibody [median absorbance, 0.99), whereas SV40-uninfected hamsters and macaques had much lower levels (median absorbance, 0.05 and 0.04, respectively). NHL cases, controls, and SV40-infected macaques resembled these latter two groups, generally showing only low-level T antibody (median absorbance, 0.03, 0.04, and 0.04, respectively). Overall, only five cases (6%) and five controls (5%) had T antibody responses classified as seropositive (odds ratio, 1.2; 95% confidence interval, 0.3-4.6). Interestingly, all 10 humans with T antibody responses also showed antibody responses to BK capsid. We found no association between the presence of T antibody and NHL, arguing against SV40 as a cause of NHL. Infrequent and low-level T antibody responses among humans could represent cross-reactivity to BK virus T antigen.

Background— The objective of this study was to address the feasibility and the biological activity of orally administered human brain natriuretic peptide (hBNP). Proprietary technology has been developed in which short, amphiphilic oligomers are covalently attached to peptides. The conjugated peptides are intended to have an improved pharmacokinetic profile and to enable oral administration. We hypothesized that novel oral conjugated hBNP (CONJ-hBNP) increases plasma hBNP, activates cGMP, and reduces mean arterial pressure (MAP). Methods and Results— This randomized crossover-designed study tested the biological activity of oral CONJ-hBNP compared with oral native hBNP in normal conscious dogs. Measurements of MAP, plasma hBNP, and cGMP were made at baseline (BL) and repeated at 10, 30, 60, 120, 180, and 240 minutes after oral administration. Plasma hBNP was not detectable in dogs at BL. Plasma hBNP was detected after native hBNP and CONJ-HBNP administration. However, plasma hBNP concentration was significantly higher after CONJ-hBNP than after native hBNP administration ( P =0.0374 between groups). Plasma cGMP increased after CONJ-hBNP for 60 minutes (from 10.8±3 to 36.8±26 pmol/mL; P <0.05), whereas it did not change after native hBNP ( P =0.001 between groups). MAP decreased at 10 minutes and remained decreased for 60 minutes after CONJ-hBNP (from 113±8 to 101±12 mm Hg after 10 minutes to 97.5±10 mm Hg after 30 minutes to 99±13 mm Hg after 60 minutes) while remaining unchanged after native hBNP ( P =0.0387 between groups). Conclusions— This study reports for the first time that novel conjugated oral BNP activates cGMP and significantly reduces MAP, thus implying an efficacious coupling of CONJ-hBNP to the natriuretic receptor-A. These data advance a new concept of orally administered chronic BNP therapy for cardiovascular diseases.

Patients with Alzheimer's disease (AD) have abnormally low positron emission tomography (PET) measurements of the cerebral metabolic rate for glucose (CMRgl) in regions of the precuneus and the posterior cingulate, parietotemporal, and frontal cortex. Apolipoprotein E (APOE) ε4 gene dose (i.e., the number of ε4 alleles in a person's APOE genotype) is associated with a higher risk of AD and a younger age at dementia onset. We previously found that cognitively normal late-middle-aged APOE ε4 carriers have abnormally low CMRgl in the same brain regions as patients with probable Alzheimer's dementia. In a PET study of 160 cognitively normal subjects 47–68 years of age, including 36 ε4 homozygotes, 46 heterozygotes, and 78 ε4 noncarriers who were individually matched for their gender, age, and educational level, we now find that ε4 gene dose is correlated with lower CMRgl in each of these brain regions. This study raises the possibility of using PET as a quantitative presymptomatic endophenotype to help evaluate the individual and aggregate effects of putative genetic and nongenetic modifiers of AD risk.

Background— B-type natriuretic peptide (BNP) activation observed in cardiac diseases is a predictor of poor outcome; however, in organic mitral regurgitation (MR), BNP determinants and prognostic value are unknown. Methods and Results— We prospectively enrolled 124 patients with chronic organic MR (aged 63±15 years, 60% males) in whom we measured BNP level and simultaneously quantified MR degree, left ventricular (LV) remodeling, and left atrial (LA) volumes and analyzed long-term outcome. Baseline BNP level (54±67 pg/mL, median 31 pg/mL) was associated univariately with multiple clinical and echocardiographic characteristics, but in multivariate analysis, independent determinants of BNP, beyond age and sex (both P ≤0.01), were LV end-systolic volume index, LA volume, atrial fibrillation, and symptoms (all P <0.02). Conversely, MR degree was not independently associated with BNP. During follow-up, patients with high versus low BNP (≥31 versus <31 pg/mL) displayed lower survival rates (at 5 years, 72±10% versus 95±5%, P =0.03) and higher rates of the combined end point of death and heart failure (at 5 years, 42±10% versus 16±7%, P =0.03). In multivariate analysis, with adjustment for age, sex, functional class, MR severity, and ejection fraction, BNP was independently predictive of mortality (hazard ratio per 10 pg/mL, 1.23 [95% CI 1.07 to 1.48], P =0.004) and of death or heart failure (hazard ratio per 10 pg/mL, 1.09 [95% CI 1.001 to 1.19], P =0.04). Conclusions— BNP activation in organic MR reflects primarily ventricular and atrial consequences rather than degree of MR. Higher BNP level in patients with organic MR independently predicts adverse events under conservative management. Therefore, BNP activation in organic MR is an emerging biomarker of severity of MR consequences and of poor clinical outcome, and its assessment should be considered in the clinical evaluation and risk stratification of patients with MR.