Homozygous NLRP1 gain-of-function mutation in siblings with a syndromic form of recurrent respiratory papillomatosis.

Juvenile-onset recurrent respiratory papillomatosis (JRRP) is a rare and debilitating childhood disease that presents with recurrent growth of papillomas in the upper airway. Two common human papillomaviruses (HPVs), HPV-6 and -11, are implicated in most cases, but it is still not understood why only a small proportion of children develop JRRP following exposure to these common viruses. We report 2 siblings with a syndromic form of JRRP associated with mild dermatologic abnormalities. Whole-exome sequencing of the patients revealed a private homozygous mutation in NLRP1, encoding Nucleotide-Binding Domain Leucine-Rich Repeat Family Pyrin Domain-Containing 1. We find the NLRP1 mutant allele to be gain of function (GOF) for inflammasome activation, as demonstrated by the induction of inflammasome complex oligomerization and IL-1ß secretion in an overexpression system. Moreover, patient-derived keratinocytes secrete elevated levels of IL-1ß at baseline. Finally, both patients displayed elevated levels of inflammasome-induced cytokines in the serum. Six NLRP1 GOF mutations have previously been described to underlie 3 allelic Mendelian diseases with differing phenotypes and modes of inheritance. Our results demonstrate that an autosomal recessive, syndromic form of JRRP can be associated with an NLRP1 GOF mutation.

HDL redox activity is increased in HIV-infected men in association with macrophage activation and non-calcified coronary atherosclerotic plaque.

BACKGROUND: HIV is associated with atherosclerosis and low high-density lipoprotein (HDL). With inflammation, HDL becomes dysfunctional. We previously showed that proinflammatory HDL has high HDL redox activity (HRA). In this study, we compare HRA in HIV-infected versus non-HIV-infected subjects and relate HRA to indices of macrophage activation and cardiovascular disease risk. METHODS: 102 HIV-infected subjects and 41 matched non-HIV controls without clinical cardiovascular disease underwent coronary CT angiography (CTA) and testing for immune/inflammatory biomarkers. The effect of purified HDL from each study subject on the oxidation rate of dihydrorhodamine-123 (DOR) was normalized to the DOR of pooled HDL from healthy subjects. The normalized ratio DOR subject/DOR pooled was used as a measure of HRA, with higher HRA suggesting dysfunctional HDL. RESULTS: HRA was higher in HIV-infected versus non-HIV subjects (1.4 ±0.01 versus 1.3 ±0.01, P=0.03). In multivariate modelling for HRA among all subjects, HIV status remained positively related to HRA (P=0.02), even after controlling for traditional cardiovascular risk factors, comorbid conditions and immune activation. Among HIV-infected subjects, HRA correlated inversely with HDL (rho=-0.32, P=0.002) and log adiponectin (r=-0.28, P=0.006), and correlated positively with log sCD163 (r=0.24, P=0.02) - a monocyte/macrophage activation marker - and with the percentage of non-calcified coronary atherosclerotic plaque (r=0.29, P=0.03). sCD163 remained significantly associated with HRA in multivariate modelling among HIV-infected subjects (P=0.03). CONCLUSIONS: These data demonstrate increased HRA among HIV-infected subjects versus matched non-HIV subjects with comparable HDL levels. In HIV-infected subjects, HRA relates to macrophage activation and to non-calcified coronary atherosclerotic plaque, which may be rupture-prone. Further studies are needed in HIV-infected patients to elucidate the interplay between immune activation, HDL function and CVD risk. CLINICAL TRIAL REGISTRATION NUMBER: NCT 00455793.

High-density lipoprotein mediates anti-inflammatory reprogramming of macrophages via the transcriptional regulator ATF3.

High-density lipoprotein (HDL) mediates reverse cholesterol transport and is known to be protective against atherosclerosis. In addition, HDL has potent anti-inflammatory properties that may be critical for protection against other inflammatory diseases. The molecular mechanisms of how HDL can modulate inflammation, particularly in immune cells such as macrophages, remain poorly understood. Here we identify the transcriptional regulator ATF3, as an HDL-inducible target gene in macrophages that downregulates the expression of Toll-like receptor (TLR)-induced proinflammatory cytokines. The protective effects of HDL against TLR-induced inflammation were fully dependent on ATF3 in vitro and in vivo. Our findings may explain the broad anti-inflammatory and metabolic actions of HDL and provide the basis for predicting the success of new HDL-based therapies.

Endogenous ß-glucocerebrosidase activity in Abca12⁻/⁻epidermis elevates ceramide levels after topical lipid application but does not restore barrier function.

ABCA12 mutations disrupt the skin barrier and cause harlequin ichthyosis. We previously showed Abca12(-/-) skin has increased glucosylceramide (GlcCer) and correspondingly lower amounts of ceramide (Cer). To examine why loss of ABCA12 leads to accumulation of GlcCer, de novo sphingolipid synthesis was assayed using [(14)C]serine labeling in ex vivo skin cultures. A defect was found in ß-glucocerebrosidase (GCase) processing of newly synthesized GlcCer species. This was not due to a decline in GCase function. Abca12(-/-) epidermis had 5-fold more GCase protein (n = 4, P < 0.01), and a 5-fold increase in GCase activity (n = 3, P < 0.05). As with Abca12(+/+) epidermis, immunostaining in null skin showed a typical interstitial distribution of the GCase protein in the Abca12(-/-) stratum corneum. Hence, we tested whether the block in GlcCer conversion could be circumvented by topically providing GlcCer. This approach restored up to 15% of the lost Cer products of GCase activity in the Abca12(-/-) epidermis. However, this level of barrier ceramide replacement did not significantly reduce trans-epidermal water loss function. Our results indicate loss of ABCA12 function results in a failure of precursor GlcCer substrate to productively interact with an intact GCase enzyme, and they support a model of ABCA12 function that is critical for transporting GlcCer into lamellar bodies.