CD1d expression and NKT cells in a haploinsufficiency model of NF1 (121.20)

Neurofibromin 1 (NF1) is a tumor suppressor gene encoding a Ras GTPase that negatively regulates Ras signaling pathways. Mutations in NF1 are linked to neurofibromatosis type 1, juvenile myelomonocytic leukemia (JML) and Watson syndrome. CD1d-dependent natural killer T (NKT) cells play an important role in anti-tumor immunity. We have shown that CD1d-mediated antigen presentation is regulated by cell signaling pathways. To study whether a haploinsufficiency in NF1 would affect CD1d-mediated activation of NKT cells, we analyzed the NKT cell population as well as CD1d expression levels from NF1+/- mice. Our results suggest that NF1+/- mice have similar levels of NKT cells as WT littermates. However, but interestingly, CD1d expression on BMDCs from NF1+/- mice was found to be lower than those from WT littermates. There was also a slight but statistically significant decrease in the splenic B220+CD1dhi population from NF1+/- mice. On the other hand, NF1+/- mice survived better than WT littermates when challenged with a T-cell lymphoma in vivo. NKT cells from NF1+/- mice were found to be more responsive to CD1d-mediated antigen presentation in vitro, which may partly explain the increased antitumor activity observed in NF1+/- mice. In conclusion, our data suggest that NF1 plays a role in negatively regulating CD1d-mediated activation of NKT cells, and this is translated in enhanced antitumor activity in mice with a haploinsufficiency in NF1.

Relation between previous angiotensin-converting enzyme inhibitor use and in-hospital outcomes in acute coronary syndromes

Angiotensin-converting enzyme (ACE) inhibitor use in patients at high risk of coronary artery disease has been associated with a decrease in the risk of myocardial infarction (MI) and death. However, it is unclear whether chronic use of these agents modifies the course and outcome of an acute coronary syndrome (ACS). This study assessed the association between chronic use of ACE inhibitors and clinical outcomes in patients with ACS. From 1999 through 2008, 13,632 Canadian patients with ACS were identified in the Global Registry of Acute Coronary Events (GRACE), the expanded GRACE (GRACE(2)), and the Canadian Registry of Acute Coronary Events (CANRACE). Patients were stratified by previous use of an ACE inhibitor. Clinical characteristics, in-hospital treatment, and outcomes were compared between the 2 groups. Multivariable logistic regression analysis adjusting for GRACE risk score and other clinical factors was performed. Patients receiving an ACE inhibitor before the ACS had a higher prevalence of diabetes (40.6% vs 21.2%, p <0.001), previous MI (51.8% vs 23.3%, p <0.001), heart failure (18.0% vs 6.9%), and higher GRACE scores at presentation (133 vs 124, p <0.001). Multivariable analysis demonstrated no significant association between previous ACE inhibitor use and death (adjusted odds ratio [OR] 1.15, confidence interval [CI] 0.90 to 1.49, p = 0.27), in-hospital re-MI (adjusted OR 0.99, CI 0.78 to 1.25, p = 0.91), or the composite end point of death/re-MI (adjusted OR 1.01, CI 0.84 to 1.20, p = 0.94). In conclusion, previous use of an ACE inhibitor is not independently associated with improved in-hospital outcomes after an ACS.

Cathelicidin signaling via the Toll-like receptor protects against colitis in mice

BACKGROUND & AIMS

Cathelicidin (encoded by Camp) is an antimicrobial peptide in the innate immune system. We examined whether macrophages express cathelicidin in colons of mice with experimental colitis and patients with inflammatory bowel disease, and we investigated its signaling mechanisms.

METHODS

Quantitative, real-time, reverse-transcription polymerase chain reaction (PCR), bacterial 16S PCR, immunofluorescence, and small interfering RNA (siRNA) analyses were performed. Colitis was induced in mice using dextran sulfate sodium (DSS); levels of cathelicidin were measured in human primary monocytes.

RESULTS

Expression of cathelicidin increased in the inflamed colonic mucosa of mice with DSS-induced colitis compared with controls. Cathelicidin expression localized to mucosal macrophages in inflamed colon tissues of patients and mice. Exposure of human primary monocytes to Escherichia coli DNA induced expression of Camp messenger RNA, which required signaling by extracellular signal-regulated kinase (ERK); expression was reduced by siRNAs against Toll-like receptor (TLR)9 and MyD88. Intracolonic administration of bacterial DNA to wild-type mice induced expression of cathelicidin in colons of control mice and mice with DSS-induced colitis. Colon expression of cathelicidin was significantly reduced in TLR9(-/-) mice with DSS-induced colitis. Compared with wild-type mice, Camp(-/-) mice developed a more severe form of DSS-induced colitis, particularly after intracolonic administration of E coli DNA. Expression of cathelicidin from bone marrow-derived immune cells regulated DSS induction of colitis in transplantation studies in mice.

CONCLUSIONS

Cathelicidin protects against induction of colitis in mice. Increased expression of cathelicidin in monocytes and experimental models of colitis involves activation of TLR9-ERK signaling by bacterial DNA. This pathway might be involved in the pathogenesis of ulcerative colitis.

Cathelicidin is involved in the intracellular killing of mycobacteria in macrophages

Macrophages have been shown to kill Mycobacterium tuberculosis through the action of the antimicrobial peptide cathelicidin (CAMP), whose expression was shown to be induced by 1,25-dihydroxyvitamin D3 (1,25D3). Here, we investigated in detail the antimycobacterial effect of murine and human cathelicidin against Mycobacterium smegmatis and M. bovis BCG infections. We have synthesized novel LL-37 peptide variants that exhibited potent in vitro bactericidal activity against M. smegmatis, M. bovis BCG and M. tuberculosis H37Rv, as compared with parental peptide. We show that the exogenous addition of LL-37 or endogenous overexpression of cathelicidin in macrophages significantly reduced the intracellular survival of mycobacteria relative to control cells. An upregulation of cathelicidin mRNA expression was observed that correlated with known M. smegmatis killing phases in J774 macrophages. Moreover, RNAi-based Camp knock-down macrophages and Camp(-/-) bone marrow derived mouse macrophages were significantly impaired in their ability to kill mycobacteria. M. smegmatis killing in Camp(-/-) macrophages was less extensive than in Camp(+/+) cells following activation with FSL-1, an inducer of cathelicidin expression. Finally we show that LL-37 and 1,25D3 treatment results in increase in colocalization of BCG-containing phagosomes with lysosomes. Altogether, these data demonstrate that cathelicidin plays an important role in controlling intracellular survival of mycobacteria.

Temporal changes in the management and outcome of Canadian diabetic patients hospitalized for non-ST-elevation acute coronary syndromes

BACKGROUND

There are limited data on the contemporary management and outcomes of non-ST-elevation acute coronary syndrome (NSTE-ACS) patients with diabetes in the "real world." We sought to evaluate (1) the temporal changes in the medical and invasive management and (2) in-hospital outcome of NSTE-ACS patients with and without diabetes.

METHODS

We included Canadian patients hospitalized for NSTE-ACS enrolled in 4 consecutive, prospective, multicenter registries: Canadian ACS-I (n = 3259; 1999-2001), ACS-II (n = 1,956; 2002-2003), Global Registry of Acute Coronary Events (GRACE/GRACE2 [n = 7,561; 2004-2007]) and Canadian Registry of Acute Coronary Events (n = 1,326; 2008). Participants were stratified by the presence or absence of preexisting diabetes on admission. Temporal changes in patient management and outcomes were evaluated across the 4 registries. Multivariable analyses were performed to determine the independent prognostic significance of diabetes.

RESULTS

Of the 14,102 NSTE-ACS patients, 4,046 (28.7%) had previously diagnosed diabetes. Patients with diabetes were older; were more likely to have prior cardiac history including myocardial infarction, revascularization, and heart failure; and had worse Killip class and higher GRACE risk score (all P < .001). Over time, there were significant increases in the use of in-hospital coronary angiography and revascularization. However, diabetic patients were less likely to undergo coronary angiography (52.5% vs 57%, P < .001) or revascularization (28.4% vs 33.4%, P < .001). The underuse of invasive procedures in diabetic patients was seen in all registries and was persistent over time. Overall, compared with the group without diabetes, diabetic patients had higher unadjusted rates of in-hospital mortality (3.0% vs 1.6%, P < .001). In multivariable analysis adjusting for components of the GRACE risk score, diabetes remained an independent predictor of in-hospital death (adjusted odds ratio 1.66, 95% CI 1.30-2.11, P < .001).

CONCLUSIONS

Over the last decade, NSTE-ACS patients with diabetes continue to be treated more conservatively, despite evidence that they would derive similar or even greater benefits from aggressive treatment. This underutilization of evidence-based therapies among diabetic patients with NSTE-ACS in the "real world" may partly explain their worse outcome.

An innate bactericidal oleic acid effective against skin infection of methicillin-resistant Staphylococcus aureus: a therapy concordant with evolutionary medicine

Free fatty acids (FFAs) are known to have bacteriocidal activity and are important components of the innate immune system. Many FFAs are naturally present in human and animal skin, breast milk, and in the bloodstream. Here, the therapeutic potential of FFAs against methicillin-resistant Staphylococcus aureus (MRSA) is demonstrated in cultures and in mice. Among a series of FFAs, only oleic acid (OA) (C18:1, cis-9) can effectively eliminate Staphylococcus aureus (S. aureus) through cell wall disruption. Lauric acid (LA, C12:0) and palmitic acid (PA, C16:0) do not have this ability. OA can inhibit growth of a number of Gram-positive bacteria, including hospital and community-associated MRSA at a dose that did not show any toxicity to human sebocytes. The bacteriocidal activities of FFAs were also demonstrated in vivo through injection of OA into mouse skin lesions previously infected with a strain of MRSA. In conclusion, our results suggest a promising therapeutic approach against MRSA through boosting the bacteriocidal activities of native FFAs, which may have been co-evolved during the interactions between microbes and their hosts.

Effect on bleeding, time to revascularization, and one-year clinical outcomes of the radial approach during primary percutaneous coronary intervention in patients with ST-segment elevation myocardial infarction

The radial approach during percutaneous coronary intervention (PCI) has been reported to reduce the incidence of bleeding complications. However, the radial approach still accounts for <10% of procedures worldwide and only 1% in the United States. Our objective was to compare the effect of radial versus femoral vascular access on the time to reperfusion, incidence of bleeding complications, and overall clinical outcomes in the setting of primary PCI. We prospectively collected data on all patients undergoing primary PCI at the Montreal Heart Institute from April 1, 2007 to March 30, 2008. The time to revascularization and major bleeding were prespecified as a co-primary end point, and major adverse cardiac events, including death, myocardial infarction, and target vessel revascularization within 12 months, were considered a secondary end point. A total of 489 patients were included in the present longitudinal cohort study, 234 in the femoral group and 254 in the radial group. In the propensity-adjusted model, the use of the femoral approach was a strong independent predictor of bleeding (odds ratio 4.22, 95% confidence interval 3.17 to 10.60). No significant difference between the radial and femoral groups was observed relative to the time to revascularization (21.4 +/- 11.8 minutes vs 22.8 +/- 10.3 minutes, respectively; p = 0.68). Moreover, the radial approach was associated with a decreased risk of major adverse cardiac events (odds ratio 0.31, 95% confidence interval 0.10 to 0.94). In conclusion, primary PCI using the radial approach was associated with a fourfold reduction in major bleeding, without compromising the time to revascularization. Moreover, the radial approach was associated with a significant reduction in major adverse cardiac events at 12 months.

The antimicrobial peptide LL-37 modulates the inflammatory and host defense response of human neutrophils

The human cathelicidin antimicrobial peptide acts as an effector molecule of the innate immune system with direct antimicrobial and immunomodulatory effects. The aim of this study was to test whether the cathelicidin LL-37 modulates the response of neutrophils to microbial stimulation. Human neutrophils were exposed to LPS, Staphylococcus aureus and Pseudomonas aeruginosa subsequent to incubation with LL-37 and cytokine release was measured by ELISA. The incubation with LL-37 significantly decreased the release of proinflammatory cytokines from stimulated human neutrophils. ROS production of neutrophils was determined by a luminometric and a flow cytometry method. The peptide induced the production of ROS and the engulfment of bacteria into neutrophils. Peritoneal mouse neutrophils isolated from CRAMP-deficient and WT animals were treated with LPS and TNF-alpha in the supernatant was measured by ELISA. Antimicrobial activity of neutrophils was detected by incubating neutrophils isolated from CRAMP-knockout and WT mice with bacteria. Neutrophils from CRAMP-deficient mice released significantly more TNF-alpha after bacterial stimulation and showed decreased antimicrobial activity as compared to cells from WT animals. In conclusion, LL-37 modulates the response of neutrophils to bacterial activation. Cathelicidin controls the release of inflammatory mediators while increasing antimicrobial activity of neutrophils.

Evaluation of left ventricular ejection fraction in non-ST-segment elevation acute coronary syndromes and its relationship to treatment

BACKGROUND

In-hospital assessment of left ventricular ejection fraction (LVEF) in non-ST-segment elevation acute coronary syndrome (NSTE-ACS) is emphasized in current practice guidelines. There are limited data regarding the evaluation of LVEF and clinical characteristics and in-hospital management in the "real world."

METHODS

Registries including the Canadian Acute Coronary Syndrome (ACS) I and II, Global Registry of Acute Coronary Events (main GRACE/expanded GRACE(2)), and Canadian Registry of Acute Coronary Events (CANRACE) enrolled 13,703 NSTE-ACS patients across Canada between 1999 and 2008. Patients were stratified by in-hospital LVEF measurement, and LVEF was categorized as normal, mildly, or moderately to severely impaired. We compared clinical characteristics, cardiac procedures, and clinical outcomes across these groups. Multivariable logistic regression identified factors independently associated with the assessment of LVEF.

RESULTS

Overall, 8,116 patients (59.2%) had LVEF measurement, and of the 7,667 patients with available LVEF data, 4,470 (58.3%) had normal, 1,916 (25%) mildly impaired, and 1,281 (16.7%) moderately to severely impaired LVEF. Patients with LVEF assessment more frequently (all P < .001) underwent cardiac catheterization, percutaneous coronary intervention or coronary bypass surgery, and had higher (both P < .001) rates of myocardial (re) infarction and heart failure. In-hospital reinfarction, higher Killip class, abnormal biomarker, hospital stay >10 days, and on-site cardiac catheterization facility were independently associated with LVEF assessment. Despite increasing LVEF assessment over time (P for trend < .001), 31.2% of patients in the most recent registry (2008) had no in-hospital LVEF assessment.

CONCLUSIONS

In-hospital LVEF assessment is not performed in many NSTE-ACS patients. The LVEF assessment, associated with increased use of evidence-based therapies and invasive cardiac procedures, was obtained more frequently in patients with myocardial (re) infarction, heart failure on presentation, and prolonged hospital stay.

CC chemokine ligand 3 overcomes the bacteriocidal and phagocytic defect of macrophages and hastens recovery from experimental otitis media in TNF-/- mice

Innate immune mechanisms are crucial in defense against bacterial illnesses in humans, as evidenced by abnormal antibacterial responses due to defects in TLR signaling, seen in children with MyD88 or IL-1R-associated kinase 4 deficiency. Otitis media (OM) is the most common disease of childhood, and the role of innate immune molecules in this disorder remains unclear. In a murine model of OM, we show that, in the absence of TNF, a key effector of innate immunity, this disease is prolonged after middle ear infection with nontypeable Haemophilus influenzae (NTHi). In the absence of TNF, mice fail to upregulate both TLRs and downstream genes and proteins, such as CCL3, resulting in defects in both inflammatory cell recruitment and macrophage function. Peritoneal macrophages of mice lacking TNF have a diminished ability to phagocytose and kill NTHi, and this defect is partially corrected in vitro by exogenous rTNF. Addition of rCCL3 alone or in combination with rTNF restores phagocytosis and killing by TNF-deficient macrophages to that of unstimulated wild-type macrophages. In vivo administration of rCCL3 to animals deficient in TNF fully restores the ability to control OM due to NTHi, whereas a CCL3-blocking Ab impaired the ability of wild-type mice to recover from OM. Thus, CCL3 is a potent downstream effector of TNF-mediated inflammation in vitro and in vivo. Manipulation of CCL3 and/or TNF may prove to be effective therapeutic approaches in OM or other conditions associated with defective TNF generation.