Autoantibodies against the cardiovascular protective BPIFB4 in hospitalized patients with COVID-19

Background/Introduction

The bactericidal/permeability-increasing fold-containing family-B-member-4 (BPIFB4) serves as a biomarker of healthy aging [1,2] and displays prognostic relevance in vascular pathology [3–5]. We recently described a drop in plasma BPIFB4 level in patients with severe COVID-19 compared to low-grade disease patients [6].

Purpose

As COVID-19 is associated with autoimmune features, we developed the methods for determination of Anti-BPIFB4 IgG (autoAbs) and then characterized their neutralizing activity in COVID-19 patients.

Methods

A sandwich ELISA-based colorimetric assay followed by immunoblot analysis detected the presence of autoAbs against BPIFB4 in 60 hospitalized COVID-19 patients and in 30 healthy volunteers. Compared to the healthy controls, the optical density (OD) level of autoAbs in COVID-19 showed considerable variability distributing over a range between 0.13 and 0.85. We thus divided the patients into two groups, one with OD >0,29 and the other one with a OD >0,29, where 0,29 represents the OD mean value of autoAbs against BPIFB4 in physiological conditions.

Results

Since patients with higher OD are mainly those who spend in average a higher number of days in hospital, we stratified the patients according to the Length of Stay (LoS) in hospital (Figure 1), and found a trend towards a positive correlation between AutoAbs OD level and length of hospitalization within COVID-19 patients.

When present, autoAbs exclusively target the WT-BPIFB4 autoantigens and neglect the recognition of the Longevity-associated-variant-(LAV) of the BPIFB4 gene known for its therapeutic efficacy in cardiomyopathy, atherosclerosis (4), diabetes (6) and platelets' reactivity.

As expected, the pre-treatment of human PrP with the recombinant rhLAV-BPIFB4 reduces platelets' aggregation in response to ADP and collagen in COVID-19 patients in vitro.

On the other hand, at functional level, the well established LAV-BPIFB4-regulated M2 macrophage polarization (4,7), is neutralized in presence of anti-BPIFB4 autoAbs-enriched plasma.

Conclusion

We conclude that a significant proportion of hospitalized COVID-19 patients displays BPIFB4-AutoAbs which are positively correlated with the Length of Stay (LoS) in hospital. In future, it will be of utmost importance to clarify if the 4 missense SNPs which distinguish LAV-BPIFB4 gene from its WT-counterpart, are instrumental to prevent the self-tolerance brake-down and the potential development of specific antibodies against endogenous cardiovascular protectors.

Funding Acknowledgement

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Cariplo Foundation (n.2016-0874) to AAP and CV; Ministry of Health (RF-2016-02364864) to AAP and CV

P746Protective role of the longevity associated variant of BPIFB4 in chronic ischemia

Background

A rare Longevity Associated Variant (LAV) of the gene BPIFB4, whose protein product can be secreted, is recessively associated with extreme longevity, positively impacting the cardiovascular system and promoting therapeutic angiogenesis in an hindlimb ischemia model.

Aim

Aim of this work is to verify if LAV-BPIFB4 may temper the phenotype of chronic ischemia in humans, thus suggesting its therapeutic potential.

Methods and results

39 hearts explanted from patients affected by end-stage ischemic heart disease were studied. Of these, 7 were homozygous for BPIFB4-LAV. Homozygous and non-homozygous patients did not differ in sex, age and in the prevalence of comorbidities or risk factors. However, the time elapsed from myocardial infarction to transplantation was significantly longer for LAV homozygous with respect to LAV heterozygous patients (159±95 vs 58±27 months, p=0.045). Histologically, while BPIFB4 levels did not differ in accordance with the genotype, the fraction of Tunel+and 53BP1+apoptotic and senescent myocytes was significantly lower in homozygous patients (1.2±0.4% vs 23.8±21.7%, p=0.026 and 31.5±6.7% vs 44.4±6.1%, p=0.031, respectively). Significantly lower levels of lipoperoxides and higher levels of Parkin were observed in homozygous hearts too. Next, we directly tested the role of BPIFB4 on PDGFRb+ NG2+Tbx18+cardiac pericytes/mural cells (PM) cultured from normal atria (PMnorm, n=10) and from ischemic failing hearts (PMfail, n=7). BPIFB4 gene transcript was significantly more expressed in PMnorm than PMfail. Silencing BPIFB4 expression in PMnorm significantly increased the proportion of senescent gH2AX+Ki67-cells (3.6±2.9% vs 13.6±9.5%, p=0.049). Conversely, addition of recombinant LAV BPIFB4 protein to PMfail cultures significantly reduced the rate of senescent cells (21.1±9.4% vs 6.0±4.8%, p=0.03), an effect that was not observed with the administration of WT BPIFB4. PMfail cultures exposed to LAV BPIFB4 significantly reversed alterations observed with pathology, such as the accumulation of both lipofuscins and of very elongated and interconnected mitochondria in the cell cytoplasm, as well as elevated mitochondrial superoxide anion levels. Finally, a larger fraction of PMnorm cells showed, with respect to PMfail, the nuclear translocation of vitamin D receptor (74.6±6.1% vs 50.1±14.4, p=0.04), coupled with a significant upregulation of its, longevity associated, target gene Klotho. Importantly, LAV BPIFB4 significantly increased the fraction of PMfail with vitamin D receptor nuclear localization (55.8±17.6% vs 85.1±8.2%, p=0.005).

Conclusion

LAV BPIFB4 could attenuate the progression of ischemic heart disease to heart failure. Part of its protective effect may be due to its ability to reduce mitochondrial oxidative stress and to revert the senescent phenotype of cardiac derived cells.

Acknowledgement/Funding

CARIPLO foundation

A genome-wide scan for linkage to human exceptional longevity identifies a locus on chromosome 4

Substantial evidence supports the familial aggregation of exceptional longevity. The existence of rare families demonstrating clustering for this phenotype suggests that a genetic etiology may be an important component. Previous attempts at localizing loci predisposing for exceptional longevity have been limited to association studies of candidate gene polymorphisms. In this study, a genome-wide scan for such predisposing loci was conducted by using 308 individuals belonging to 137 sibships demonstrating exceptional longevity. By using nonparametric analysis, significant evidence for linkage was noted for chromosome 4 at D4S1564 with a MLS of 3.65 (P = 0.044). The analysis was corroborated by a parametric analysis (P = 0.052). These linkage results indicate the likelihood that there exists a gene, or genes, that exerts a substantial influence on the ability to achieve exceptional old age. Identification of the genes in humans that allow certain individuals to live to extreme old age should lead to insights on cellular pathways that are important to the aging process.

Exceptional familial clustering for extreme longevity in humans

Four families highly clustered for extreme longevity are described here, representing the first report of clustering for this phenotype. Families such as these may prove to be helpful in the further understanding of the genetic contribution to achieving exceptional longevity.

Gamma1- and gamma2-syntrophins, two novel dystrophin-binding proteins localized in neuronal cells

Dystrophin is the scaffold of a protein complex, disrupted in inherited muscular dystrophies. At the last 3' terminus of the gene, a protein domain is encoded, where syntrophins are tightly bound. These are a family of cytoplasmic peripheral membrane proteins. Three genes have been described encoding one acidic (alpha1) and two basic (beta1 and beta2) proteins of approximately 57-60 kDa. Here, we describe the characterization of two novel putative members of the syntrophin family, named gamma1- and gamma2-syntrophins. The human gamma1-syntrophin gene is composed of 19 exons and encodes a brain-specific protein of 517 amino acids. The human gamma2-syntrophin gene is composed of at least 17 exons, and its transcript is expressed in brain and, to a lesser degree, in other tissues. We mapped the gamma1-syntrophin gene to human chromosome 8q11 and the gamma2-syntrophin gene to chromosome 2p25. Yeast two-hybrid experiments and pull-down studies showed that both proteins can bind the C-terminal region of dystrophin and related proteins. We raised antibodies against these proteins and recognized expression in both rat and human central neurons, coincident with RNA in situ hybridization of adjacent sections. Our present findings suggest a differentiated role of a modified dystrophin-associated complex in the central nervous system.

The retinoblastoma-interacting zinc-finger protein RIZ is a downstream effector of estrogen action

Co-immunoprecipitation experiments in cell extract from cultured cells or target tissues indicated that estrogen receptor was complexed with the retinoblastoma binding protein RIZ in a ligand-dependent manner. Mapping of interaction sites indicated that in both proteins the same regions and motifs responsible for the interaction of transcriptional co-activator and nuclear receptors were involved. In cultured cells, estradiol induced a redistribution of RIZ protein within the nucleus and in the cytoplasm. A similar effect was produced in vivo, in prepuberal rat endometrium, by administration of a physiological dose of estradiol. Therefore, RIZ protein could be a specific effector of estrogen action downstream of the hormone-receptor interaction, presumably involved in proliferation control.

Identification of a DNA binding protein cooperating with estrogen receptor as RIZ (retinoblastoma interacting zinc finger protein)

Double-stranded DNA fragments were selected from a random pool by repeated cycles of estrogen receptor-specific immunoprecipitation in the presence of a nuclear extract and PCR amplification (cyclic amplification and selection of target, CAST, for multiple elements). Fragments were cloned and sequence analysis indicated the 5-nucleotide word TTGGC was the most recurrent sequence unrelated to the known estrogen responsive element. Screening a HeLa cell expression library with a probe designed with multiple repeats of this sequence resulted in the identification of a 1700-aa protein showing a complete homology with the product of the human retinoblastoma-interacting zinc-finger gene RIZ. In transfection experiments, RIZ protein was able to bestow estrogen inducibility to a promoter containing an incomplete estrogen responsive element and a TTGGC motif. RIZ protein present in MCF-7 cell nuclear extract retarded the TTGGC-containing probe in an EMSA. Estrogen receptor was co-immunoprecipitated from MCF-7 cell extract by antibodies to RIZ protein and vice versa, thus indicating an existing interaction between these two proteins.

Lack of sodium channel mutation in an Italian family with paramyotonia congenita

OBJECTIVE

To conduct the genotype-phenotype correlation in a family in which several individuals share clinical and electrophysiologic features of paramyotonia congenita (PC).

BACKGROUND

PC, hyperkalemic periodic paralysis (HyperPP), and potassium-aggravated myotonias form the group of hereditary sodium channelopathies. Each of these disorders is associated with different point mutations in SCN4A, the gene encoding the alpha-subunit of the adult human skeletal muscle sodium channel. However, in HyperPP families, evidence of a causative gene different from SCN4A has been found.

METHODS

We conducted direct clinical examination, electrophysiologic (EMG/electroneurographic) and cardiologic studies, as well as laboratory screening in several affected and nonaffected members of the family. We performed the genotype-phenotype correlation by microsatellite linkage and cDNA-mutation analyses of the SCN4A gene.

RESULTS

Affected members in this family showed clinical and electrophysiologic features typical of PC. The disease phenotype segregated with the chromosomal region that includes the SCN4A gene. Analysis of the entire cDNA sequence of the SCN4A gene in the index case disclosed a G3826A transition, which results in the Val1276Ile substitution. However, PCR-single-stranded confirmation polymorphism and direct sequencing analysis of the segment coding for Val-1276 on genomic DNA confirmed the G3826A transition in the index case but was negative in 11 affected members of the family; however, neither mutations nor aberrant splicings causative of the PC phenotype in this family were found on SCN4A.

CONCLUSION

The existence of a second gene different from SCN4A that can give rise to a clinical PC phenotype can be speculated upon.

Identification and characterization of a novel member of the dystrobrevin gene family

A new member of the dystrobrevin gene family was identified using a bioinformatics approach. Sequence analysis indicates that this gene, named DTN-B, is highly homologous to the rabbit A0, the previously described dystrobrevin (DTN), Torpedo 87 kDa and to the C-terminus of dystrophin. The coiled-coil domain, shown to be the site of interaction between dystrobrevins and dystrophin, is highly conserved. Immunostaining studies indicate that DTN-B and DTN expression is absent in affected muscle fibers from DMD patients and carriers.

A novel human serine-threonine phosphatase related to the Drosophila retinal degeneration C (rdgC) gene is selectively expressed in sensory neurons of neural crest origin

Through our transcriptional mapping effort in the Xp22 region, we have isolated by exon trapping a new transcript highly homologous to the Drosophila retinal degeneration C (rdgC) gene. rdgC encodes a serine/threonine phosphatase protein and is required in Drosophila to prevent light-induced retinal degeneration. This human gene is the first mammalian member of the serine-threonine phosphatase with EF hand motif gene family, and was thus named PPEF (Protein Phosphatase with EF calcium-binding domain). The expression pattern of the mouse Ppef gene was studied by RNA in situ hybridization on embryonic tissue sections. While rdgC is expressed in the visual system of the fly, as well as in the mushroom bodies of the central brain, we found that Ppef is highly expressed in sensory neurons of the dorsal root ganglia (DRG) and neural crest-derived cranial ganglia. The selective pattern of expression makes PPEF an important marker for sensory neuron differentiation and suggests a role for serine-threonine phosphatases in mammalian development.

Identification by shotgun sequencing, genomic organization, and functional analysis of a fourth arylsulfatase gene (ARSF) from the Xp22.3 region

We recently reported the isolation of two new members of the sulfatase gene family, arylsulfatase D (ARSD) and E (ARSE), located approximately 50 kb from each other in the Xp22.3 region. Mutation analysis indicated ARSE as the gene responsible for X-linked recessive chondrodysplasia punctata. Expression of the ARSE gene in COS cells resulted in a heat-labile arylsulfatase activity that was inhibited by warfarin. At the same time, we detected the presence of a 1.2-kb fragment located at approximately 60 kb from ARSD and ARSE with significant homology to these two genes, suggesting the existence of another sulfatase gene, arylsulfatase F (ARSF), in Xp22.3. We have used a combined approach of long-range genomic sequencing and screening of cDNA libraries to isolate the ARSF gene. Expression of the ARSF cDNA in COS cells resulted in a heat-labile arylsulfatase activity that is not inhibited by warfarin, supporting our hypothesis that only ARSE is specifically inhibited by warfarin and is most likely involved in warfarin embryopathy. Genomic analysis revealed that ARSF has an intron/exon organization highly similar to those of ARSD and ARSE, which is also shared by another Xp22.3 sulfatase gene, ARSC (arylsulfatase C, also known as steroid sulfatase), with the splice sites occurring at the same position in all four genes. The data obtained from sequence analysis and presented in this paper indicate that the ARSC, ARSD, ARSE, and ARSF genes are more similar to each other than to other members of the sulfatase gene family, supporting our hypothesis that they represent a subfamily of related proteins created through duplication events that occurred in an ancestral pseudoautosomal region.

Autosomal recessive limb-girdle muscular dystrophy, LGMD2F, is caused by a mutation in the delta-sarcoglycan gene

Limb-girdle muscular dystrophies (LGMD) are a heterogeneous group of inherited neuromuscular disorders characterized by proximal muscular weakness of the pelvic and shoulder girdles and a variable progression with symptoms, ranging from very severe to mild. One autosomal dominant (LGMD1A, at chromosome 5q22.3-31.3) (ref. 3) and five autosomal recessive (AR) loci responsible for this phenotype have been identified: LGMD2A at 15q (ref. 4); LGMD2B at 2p (ref. 5), LGMD2C at 13q (ref. 6), LGMD2D at 17q (ref. 7) and LGMD2E at 4q (refs 8,9). In the muscle membrane, dystrophin associates with several proteins and glycoproteins organized in two main subcomplexes: the dystroglycan (DG) and sarcoglycan (SG) complexes. The genes for LGMD2C, LGMD2D and LGMD2E code for proteins of the SG complex. We recently mapped a sixth AR form of LGMD, LGMD2F, to chromosome 5q33-34 in two Brazilian families. In the same chromosomal interval we also mapped the delta SG gene, encoding a novel 35-kD component of the sarcoglycan (SG) complex. We now show that a homozygous mutation in the delta SG gene (a single nucleotide deletion that alters its reading frame) is the cause of LGMD2F.

Identification of a novel sarcoglycan gene at 5q33 encoding a sarcolemmal 35 kDa glycoprotein

Mutations in any of the genes encoding the alpha, beta or gamma-sarcoglycan components of dystrophin-associated glycoproteins result in both sporadic and familial cases of either limb-girdle muscular dystrophy or severe childhood autosomal recessive muscular dystrophy. The collective name 'sarcoglycanopathies' has been proposed for these forms. We report the identification of a fourth member of the human sarcoglycan family. We named this novel cDNA delta-sarcoglycan. Its mRNA expression is abundant in striated and smooth muscles, with a main 8 kb transcript, encoding a predicted basic transmembrane glycoprotein of 290 amino acids. Antibodies specifically raised against this protein recognized a single band at 35 kDa on western blots of human and mouse muscle. Immunohistochemical staining revealed a unique sarcolemmal localization. FISH, radiation hybrid and YAC mapping concordantly linked the delta-sarcoglycan gene to 5q33, close to D5S487 and D5S1439. The gene spans at least 100 kb and is composed of eight exons. The identification of a novel sarcoglycan component modifies the current model of the dystrophin-glycoprotein complex.

A novel p53 mutant in human breast cancer revealed by multiple SSCP analysis

DNA from tumor tissue and peripheral blood lymphocytes of primary breast cancer patients was screened for the presence of p53 mutations. In DNA from one tumor we found that the histidine codon 193 (CAT) was somatically converted to arginine (CGT). This amino acid residue is highly conserved in many species, thus suggesting that such mutation plays an important role in the loss of wt-p53 function.