The amplification of CNS damage in Alzheimer's disease due to SARS-CoV2 infection

Pre-existing Alzheimer's disease is a risk factor for severe/fatal COVID-19 and infection by SARS-CoV2 virus has been associated with an increased incidence of un-masked Alzheimer's disease. The molecular basis whereby SARS-CoV2 may amplify Alzheimer's disease is not well understood. This study analyzed the molecular changes in autopsy brain tissues from people with pre-existing dementia who died of COVID-19 (n = 5) which was compared to equivalent tissues of people who died of COVID-19 with no history of dementia (n = 8), Alzheimer's disease pre-COVID-19 (n = 10) and aged matched controls (n = 10) in a blinded fashion. Immunohistochemistry analyses for hyperphosphorylated tau protein, α-synuclein, and β-amyloid-42 confirmed the diagnoses of Alzheimer's disease (n = 4), and Lewy body dementia (n = 1) in the COVID-19 group. The brain tissues from patients who died of COVID-19 with no history of dementia showed a diffuse microangiopathy marked by endocytosis of spike subunit S1 and S2 in primarily CD31+ endothelia with strong co-localization with ACE2, Caspase-3, IL6, TNFα, and Complement component 6 that was not associated with SARS-CoV2 RNA. Microglial activation marked by increased TMEM119 and MCP1 protein expression closely paralleled the endocytosed spike protein. The COVID-19 tissues from people with no pre-existing dementia showed, compared to controls, 5-10× fold increases in expression of neuronal NOS and NMDAR2 as well as a marked decrease in the expression of proteins whose loss is associated with worsening Alzheimer's disease: MFSD2a, SHIP1, BCL6, BCL10, and BACH1. In COVID-19 tissues from people with dementia the widespread spike-induced microencephalitis with the concomitant microglial activation co-existed in the same areas where neurons had hyperphosphorylated tau protein suggesting that the already dysfunctional neurons were additionally stressed by the SARS-CoV2 induced microangiopathy. ACE2+ human brain endothelial cells treated with high dose (but not vaccine equivalent low dose) spike S1 protein demonstrated each of the molecular changes noted in the in vivo COVID-19 and COVID-19/Alzheimer's disease brain tissues. It is concluded that fatal COVID-19 induces a diffuse microencephalitis and microglial activation in the brain due to endocytosis of circulating viral spike protein that amplifies pre-existing dementia in at least two ways: 1) modulates the expression of proteins that may worsen Alzheimer's disease and 2) stresses the already dysfunctional neurons by causing an acute proinflammatory/hypercoagulable/hypoxic microenvironment in areas with abundant hyperphosphorylated tau protein and/or βA-42.

MicroRNA miR-155 Activity in Mouse Choline Acetyltransferase-Positive Neurons Is Critical for the Rate of Early and Late Paraplegia After Transient Aortic Cross-Clamping

Aortic aneurism open repair surgery can cause spinal cord (SC) injury with 5–15% of patients developing paraparesis or paraplegia. Using a mouse model of transient aortic cross-clamping (ACC), we have previously found that the expression of proinflammatory microRNA miR-155 increases in motoneurons (MNs) and endothelial cells (ECs) of ischemic SCs, and that global miR-155 deletion decreases the percentage of paraplegia by 37.4% at 48-h post-ACC. Here, we investigated the cell-specific contribution of miR-155 in choline acetyltransferase-positive (ChAT+) neurons (that include all MNs of the SC) and ECs to SC injury after ACC. Mice lacking miR-155 in ChAT+ neurons (MN-miR-155-KO mice) developed 24.6% less paraplegia than control mice at 48-h post-ACC. In contrast, mice lacking miR-155 in ECs (ECs-miR-155-KO mice) experienced the same percentage of paraplegia as control mice, despite presenting smaller central cord edema. Unexpectedly, mice overexpressing miR-155 in ChAT+ neurons were less likely than control mice to develop early paraplegia during the first day post-ACC, however they reached the same percentage of paraplegia at 48-h. In addition, all mice overexpressing miR-155 in ECs (ECs-miR-155-KI mice) were paraplegic at 48-h post-ACC. Altogether, our results suggest that miR-155 activity in ChAT+ neurons protects the SC against ischemic injury during the first day post-ACC before becoming deleterious during the second day, which indicates that early and late paraplegias arise from different molecular malfunctions. These results point to the need to develop specific protective therapeutics aimed at inhibiting both the early and late deleterious events after open repair surgery of aortic aneurisms.

The histologic and molecular correlates of liver disease in fatal COVID-19 including with alcohol use disorder

Hepatic disease is common in severe COVID-19. This study compared the histologic/molecular findings in the liver in fatal COVID-19 (n = 9) and age-matched normal controls (n = 9); three of the fatal COVID-19 livers had pre-existing alcohol use disorder (AUD). Controls showed a high resident population of sinusoidal macrophages that had variable ACE2 expression. Histologic findings in the cases included periportal/lobular inflammation. SARS-CoV2 RNA and nucleocapsid protein were detected in situ in 2/9 COVID-19 livers in low amounts. In 9/9 cases, there was ample in situ SARS-CoV-2 spike protein that co-localized with viral matrix and envelope proteins. The number of cells positive for spike/100× field was significantly greater in the AUD/COVID-19 cases (mean 5.9) versus the non-AUD/COVID-19 cases (mean 0.4, p < 0.001) which was corroborated by Western blots. ACE2+ cells were 10× greater in AUD/COVID-19 livers versus the other COVID-19/control liver samples (p < 0.001). Co-expression experiments showed that the spike protein localized to the ACE2 positive macrophages and, in the AUD cases, hepatic stellate cells that were activated as evidenced by IL6 and TNFα expression. Injection of the S1, but not S2, subunit of spike in mice induced hepatic lobular inflammation in activated macrophages. It is concluded that endocytosed viral spike protein can induce hepatitis in fatal COVID-19. This spike induced hepatitis is more robust in the livers with pre-existing AUD which may relate to why patients with alcohol abuse are at higher risk of severe liver disease with SARS-CoV2 infection.

Endovascular repair and open repair surgery of thoraco-abdominal aortic aneurysms cause drastically different types of spinal cord injury

Both endovascular repair (EVR) and open repair (OR) surgery of thoraco-abdominal aortic aneurysms cause spinal cord (SC) injury that can lead to paraparesis or paraplegia. It has been assumed that mechanisms responsible for SC damage after EVR are similar to those after OR. This pilot study compared the pathophysiology of SC injury after EVR versus OR using a newly developed EVR dog model. An increasing number of stents similar to those used in patients were inserted in the aorta of three dogs to ensure thoracic or thoracic plus lumbar coverage. The aorta of OR dogs was cross-clamped for 45 min. Behavior assessment demonstrated unique patterns of proprioceptive ataxia and evolving paraparesis in EVR versus irreversible paraplegia in OR. MRI showed posterior signal in lumbar SC after EVR versus central cord edema after OR. Histopathology showed white matter edema in L3-L5 localized to the dorsal column medial lemniscus area associated with loss of myelin basic protein but not neurons after EVR, versus massive neuronal loss in the gray matter in L3-L5 after OR. Metabolome analysis demonstrates a distinctive chemical fingerprint of cellular processes in both interventions. Our results call for the development of new therapeutics tailored to these distinct pathophysiologic findings.

Endothelial cell damage is the central part of COVID-19 and a mouse model induced by injection of the S1 subunit of the spike protein

Neurologic complications of symptomatic COVID-19 are common. Brain tissues from 13 autopsies of people who died of COVID-19 were examined. Cultured endothelial and neuronal cells were incubated with and wild type mice were injected IV with different spike subunits. In situ analyses were used to detect SARS-CoV-2 proteins and the host response. In 13/13 brains from fatal COVID-19, pseudovirions (spike, envelope, and membrane proteins without viral RNA) were present in the endothelia of microvessels ranging from 0 to 14 positive cells/200× field (mean 4.3). The pseudovirions strongly co-localized with caspase-3, ACE2, IL6, TNFα, and C5b-9. The surrounding neurons demonstrated increased NMDAR2 and neuronal NOS plus decreased MFSD2a and SHIP1 proteins. Tail vein injection of the full length S1 spike subunit in mice led to neurologic signs (increased thirst, stressed behavior) not evident in those injected with the S2 subunit. The S1 subunit localized to the endothelia of microvessels in the mice brain and showed co-localization with caspase-3, ACE2, IL6, TNFα, and C5b-9. The surrounding neurons showed increased neuronal NOS and decreased MFSD2a. It is concluded that ACE2+ endothelial damage is a central part of SARS-CoV2 pathology and may be induced by the spike protein alone. Thus, the diagnostic pathologist can use either hematoxylin and eosin stain or immunohistochemistry for caspase 3 and ACE2 to document the endothelial cell damage of COVID-19.

miR-155 expression in antitumor immunity: The higher the better?

MicroRNAs are small noncoding RNAs that modulate gene expression either directly, by impairing the stability and/or translation of transcripts that contain their specific target sequence, or indirectly through the targeting of transcripts that encode transcription factors, factors implicated in signal transduction pathways, or epigenetic regulators. Abnormal expression of micro-RNAs has been found in nearly all types of pathologies, including cancers. MiR-155 has been the first microRNA to be implicated in the regulation of the innate and adaptative immune responses, and its expression is either increased or decreased in a variety of liquid and solid malignancies. In this review, we examine the oncogenic and antitumor potentials of miR-155, with special emphasize on its dose-dependent effects. We describe the impact of miR-155 levels on antitumor activity of lymphocytes and myeloid cells. We discuss miR-155 dose-dependent effects in leukemias and analyze results showing that miR-155 intermediate levels tend to be detrimental, whereas high levels of miR-155 expression usually prove beneficial. We also examine the beneficial effects of high levels of miR-155 expression in solid tumors. We discuss the possible causal involvement of miR-155 in leukemias and dementia in individuals with Down's syndrome. We finally propose that increasing miR-155 levels in immune cells might increase the efficiency of newly developed cancer immunotherapies, due to miR-155 ability to target transcripts encoding immune checkpoints such as cytotoxic T lymphocyte antigen-4 or programmed death-ligand 1.

MiR-155 deletion reduces ischemia-induced paralysis in an aortic aneurysm repair mouse model: Utility of immunohistochemistry and histopathology in understanding etiology of spinal cord paralysis

Spinal cord paralysis is relatively common after surgical repair of thoraco-abdominal aortic aneurysm (TAAA) and its etiology is unknown. The present study was designed to examine the histopathology of the disease and investigate whether miR-155 ablation would reduce spinal cord ischemic damage and delayed hindlimb paralysis induced by aortic cross-clamping (ACC) in our mouse model. The loss of locomotor function in ACC-paralyzed mice correlated with the presence of extensive gray matter damage and central cord edema, with minimal white matter histopathology. qRTPCR and Western blotting showed that the spinal cords of wild-type ACC mice that escaped paralysis showed lower miR-155 expression and higher levels of transcripts encoding Mfsd2a, which is implicated in the maintenance of blood-brain barrier integrity. In situ based testing demonstrated that increased miR-155 detection in neurons was highly correlated with the gray matter damage and the loss of one of its targets, Mfsd2a, could serve as a good biomarker of the endothelial cell damage. In vitro, we demonstrated that miR-155 targeted Mfsd2a in endothelial cells and motoneurons and increased endothelial cell permeability. Finally, miR-155 ablation slowed the progression of central cord edema, and reduced the incidence of paralysis by 40%. In sum, the surgical pathology findings clearly indicated that the epicenter of the ischemic-induced paralysis was the gray matter and that endothelial cell damage correlated to Mfsd2a loss is a good biomarker of the disease. MiR-155 targeting therefore offers new therapeutic opportunity for edema caused by traumatic spinal cord injury and diagnostic pathologists, by using immunohistochemistry, can clarify if this mechanism also is important in other ischemic diseases of the CNS, including stroke.

MiR-663, a MicroRNA Linked with Inflammation and Cancer That Is under the Influence of Resveratrol

Resveratrol (trans-3,5,4′-trihydroxystilbene, RSV) is a non-flavonoid dietary polyphenol with antioxidant, anti-inflammatory and anti-cancer properties that is primarily found in red berries. While RSV displays many beneficial effects in vitro, its actual effects in vivo or in animal models remain passionately debated. Recent publications suggest that RSV pleiotropic effects could arise from its capability to regulate the expression and activity of microRNAs, short regulators themselves capable of regulating up to several hundreds of target genes. In particular, RSV increases microRNA miR-663 expression in different human cell lines, suggesting that at least some of its multiple beneficial properties are through the modulation of expression of this microRNA. Indeed, the expression of microRNA miR-663 is reduced in certain cancers where miR-663 is considered to act as a tumor suppressor gene, as well as in other pathologies such as cardiovascular disorders. Target of miR-663 include genes involved in tumor initiation and/or progression as well as genes involved in pathologies associated with chronic inflammation. Here, we review the direct and indirect effects of RSV on the expression of miR-663 and its target transcripts, with emphasise on TGFβ1, and their expected health benefits, and argue that elucidating the molecular effects of different classes of natural compounds on the expression of microRNAs should help to identify new therapeutic targets and design new treatments.

microRNA 155 up regulation in the CNS is strongly correlated to Down's syndrome dementia

This study examined the molecular correlates of Down's dementia. qRTPCR for chromosome 21 microRNAs was correlated with in situ hybridization, immunohistochemistry for microRNA targets, mRNAs located on chromosome 21, and neurofibrillary tangles in human and the Ts65 dn mouse Down's model. qRTPCR for the microRNAs on the triplicated chromosome showed miR-155 dominance in brain tissues (14.3 fold increase, human and 24.2 fold increase, mouse model) that co-expressed with hyperphosphorylated tau protein. miR-155 was not elevated in Alzheimer's disease or neonates with Downs' syndrome. Chromosome 21 genes APP/BA-42, DYRK1a and BACH1 were not correlated to pathologic changes in Down's dementia. Validated CNS targets of miR-155 that were present in controls and Alzheimer's disease but lacking in Down's dementia brains included BACH1, CoREST1, bcl6, BIM, bcl10, cyclin D, and SAPK4. It is concluded that Down's dementia strongly correlated with overexpression of chromosome 21 microRNA 155 with concomitant reduction of multiple CNS-functional targets. This study highlights the need for anatomic pathologists to determine the specific and diverse pathways cells may take to form neurofibrillary tangles in the different dementias.

Exploring new ways of regulation by resveratrol involving miRNAs, with emphasis on inflammation

This review presents recent evidence implicating microRNAs (miRNAs) in the beneficial effects of resveratrol (trihydroxystilbene), a nonflavonoid plant polyphenol, with emphasis on its anti-inflammatory effects. Many diseases and pathologies have been linked, directly or indirectly, to inflammation. These include infections, injuries, atherosclerosis, diabetes mellitus, obesity, cancer, osteoarthritis, age-related macular degeneration, demyelination, and neurodegenerative diseases. Resveratrol can both decrease the secretion of proinflammatory cytokines (e.g., IL-6, IL-8, and TNF-α) and increase the production of anti-inflammatory cytokines; it also decreases the expression of adhesion proteins (e.g., ICAM-1) and leukocyte chemoattractants (e.g., MCP-1). Resveratrol's primary targets appear to be the transcription factors AP-1 and NF-κB, as well as the gene COX2. Although no mechanistic link between any particular miRNA and resveratrol has been identified, resveratrol effects depend at least in part upon the modification of the expression of a variety of miRNAs that can be anti-inflammatory (e.g., miR-663), proinflammatory (e.g., miR-155), tumor suppressing (e.g., miR-663), or oncogenic (e.g., miR-21).

Effects of dietary phytophenols on the expression of microRNAs involved in mammalian cell homeostasis

Besides synthesizing nutritive substances (proteins, fats and carbohydrates) for energy and growth, plants produce numerous non-energetic so-called secondary metabolites (mainly polyphenols) that allow them to protect themselves against infections and other types of hostile environments. Interestingly, these polyphenols often provide cells with valuable bioactive properties for the maintenance of their functions and homeostasis (signaling, gene regulation, protection against acquired or infectious diseases, etc.) both in humans and animals. Namely, from a nutritional point of view, and based on epidemiological data, it is now well accepted that the regular consumption of green vegetables, fruits and fibers has protective effects against the onset of cancer as well as of inflammatory, neurodegenerative, metabolic and cardiovascular diseases, and consequently increases the overall longevity. In particular, grapevine plants produce large amounts of a wide variety of polyphenols. The most prominent of those-resveratrol-has been shown to impair or delay cardiovascular alterations, cancer, inflammation, aging, etc. Until recently, the molecular bases of the pleiotropic effects of resveratrol remained largely unclear despite numerous studies on a variety of signaling pathways and the transcriptional networks that they control. However, it has been recently proposed that the protective properties of resveratrol may arise from its modulation of small non-coding regulatory RNAs, namely microRNAs. The aim of this review is to present up-to-date data on the control of microRNA expression by dietary phytophenols in different types of human cells, and their impact on cell differentiation, cancer development and the regulation of the inflammatory response.

Control of MicroRNA expression as a new way for resveratrol to deliver its beneficial effects

Grapes produce large amounts of polyphenols. Many of them accumulate in the skin, pulp, and seeds and are consequently found in wine. The health benefits of a moderate consumption of wine have been attributed at least in part to grape's polyphenols. Among them, resveratrol (3,5,4'-trihydroxystilbene) is a phytoalexin that stimulates plant cell defenses against infections and also plays protective roles in humans, where it delays cardiovascular alterations and exerts anticancer and anti-inflammatory effects. Despite numerous studies, the molecular mechanisms of resveratrol action are only partially understood. Given its pleiotropic effects, it was previously suggested that resveratrol protective properties may arise from its modulation of the expression of microRNAs. Therefore, this review will focus on the effects of resveratrol on microRNA populations in humans and human cell lines, especially emphasizing the microRNAs that have been implicated in resveratrol effects on inflammation, cancer, metabolism, and muscle differentiation.

Resveratrol, MicroRNAs, Inflammation, and Cancer

MicroRNAs are short noncoding RNAs that regulate the expression of many target genes posttranscriptionally and are thus implicated in a wide array of cellular and developmental processes. The expression of miR-155 or miR-21 is upregulated during the course of the inflammatory response, but these microRNAs are also considered oncogenes due to their upregulation of expression in several types of tumors. Furthermore, it is now well established that inflammation is associated with the induction or the aggravation of nearly 25% of cancers. Therefore, the above microRNAs are thought to link inflammation and cancer. Recently, resveratrol (trans-3,4′,5-trihydroxystilbene), a natural polyphenol with antioxidant, anti-inflammatory, and anticancer properties, currently at the stage of preclinical studies for human cancer prevention, has been shown to induce the expression of miR-663, a tumor-suppressor and anti-inflammatory microRNA, while downregulating miR-155 and miR-21. In this paper we will discuss how the use of resveratrol in therapeutics may benefit from the preanalyses on the status of expression of miR-155 or miR-21 as well as of TGFβ1. In addition, we will discuss how resveratrol activity might possibly be enhanced by simultaneously manipulating the levels of its key target microRNAs, such as miR-663.

GAM/ZFp/ZNF512B is central to a gene sensor circuitry involving cell-cycle regulators, TGF{beta} effectors, Drosha and microRNAs with opposite oncogenic potentials

MicroRNAs (miRNAs) are small regulatory RNAs targeting multiple effectors of cell homeostasis and development, whose malfunctions are associated with major pathologies such as cancer. Herein we show that GAM/ZFp/ZNF512B works within an intricate gene regulatory network involving cell-cycle regulators, TGFβ effectors and oncogenic miRNAs of the miR-17-92 cluster. Thus, GAM impairs the transcriptional activation of the miR-17-92 promoter by c-Myc, downregulates miR-17-92 miRNAs differentially, and limits the activation of genes responsive to TGFβ canonical pathway. In contrast, TGFβ decreases GAM transcripts levels while differentially upregulating miR-17-92 miRNAs. In turn, miR-17, miR-20a and miR-92a-1 target GAM transcripts, thus establishing a feedback autoregulatory loop. GAM transcripts are also targeted by miRNAs of the let-7 family. GAM downregulates Drosha, the main effector of miRNA maturation in the nucleus, and interacts with it in a RNA-dependent manner. Finally, GAM modulates the levels of E2F1 and Ras, and increases apoptosis while reducing cell proliferation. We propose that GAM represents a new kind of vertebrate regulator aimed at balancing the opposite effects of regulators of cell homeostasis by increasing the robustness of gene circuitries controlling cell proliferation, differentiation and development.

Resveratrol decreases the levels of miR-155 by upregulating miR-663, a microRNA targeting JunB and JunD

An inflammatory component is present in the microenvironment of most neoplastic tissues, including those not causally related to an obvious inflammatory process. Several microRNAs, and especially miR-155, play an essential role in both the innate and adaptative immune response. Resveratrol (trans-3,4',5-trihydroxystilbene) is a natural antioxidant with anti-inflammatory properties that is currently at the stage of preclinical studies for human cancer prevention. Here, we establish that, in human THP-1 monocytic cells as well as in human blood monocytes, resveratrol upregulates miR-663, a microRNA potentially targeting multiple genes implicated in the immune response. In THP-1 cells, miR-663 decreases endogenous activator protein-1 (AP-1) activity and impairs its upregulation by lipopolysaccharides (LPS), at least in part by directly targeting JunB and JunD transcripts. We further establish that the downregulation of AP-1 activity by resveratrol is miR-663 dependent and that the effects of resveratrol on both AP-1 activity and JunB levels are dose dependent. Finally, we show that resveratrol impairs the upregulation of miR-155 by LPS in a miR-663-dependent manner. Given the role of miR-155 in the innate immune response and the fact that it is upregulated in many cancers, our results suggest that manipulating miR-663 levels may help to optimize the use of resveratrol as both an anti-inflammatory and anticancer agent against malignancies associated with high levels of miR-155.

Resveratrol decreases the levels of miR-155 by upregulating miR-663, a microRNA targeting JunB and JunD

An inflammatory component is present in the microenvironment of most neoplastic tissues, including those not causally related to an obvious inflammatory process. Several microRNAs, and especially miR-155, play an essential role in both the innate and adaptative immune response. Resveratrol (trans-3,4',5-trihydroxystilbene) is a natural antioxidant with anti-inflammatory properties that is currently at the stage of preclinical studies for human cancer prevention. Here, we establish that, in human THP-1 monocytic cells as well as in human blood monocytes, resveratrol upregulates miR-663, a microRNA potentially targeting multiple genes implicated in the immune response. In THP-1 cells, miR-663 decreases endogenous activator protein-1 (AP-1) activity and impairs its upregulation by lipopolysaccharides (LPS), at least in part by directly targeting JunB and JunD transcripts. We further establish that the downregulation of AP-1 activity by resveratrol is miR-663 dependent and that the effects of resveratrol on both AP-1 activity and JunB levels are dose dependent. Finally, we show that resveratrol impairs the upregulation of miR-155 by LPS in a miR-663-dependent manner. Given the role of miR-155 in the innate immune response and the fact that it is upregulated in many cancers, our results suggest that manipulating miR-663 levels may help to optimize the use of resveratrol as both an anti-inflammatory and anticancer agent against malignancies associated with high levels of miR-155.

miR-155: on the crosstalk between inflammation and cancer

MicroRNAs are short non-coding RNAs that posttranscriptionally modulate the expression of multiple target genes and are thus implicated in a wide array of cellular and developmental processes. miR-155 is processed from BIC, a non-coding transcript highly expressed in both activated B and T cells and in monocytes/macrophages. miR-155 levels change dynamically during both hematopoietic lineage differentiation and the course of the immune response. Different mouse models developed recently indicate that miR-155 plays a critical role during hematopoiesis and regulates lymphocyte homeostasis and tolerance. A moderate increase of miR-155 levels is observed in many types of malignancies of B cell or myeloid origin, and transgenic over-expression of miR-155 in mice results in cancer. While the high levels of miR-155 reached transiently during the course of the immune response remain unharmful for the organism, the reason why a moderate up-regulation of miR-155 can lead to cancer remains obscure. As prolonged exposure to inflammation can lead to cancer, the permanent up-regulation of miR-155 might be a link between the two. Therefore, designing miR-155 based therapies will require a better understanding of the molecular basis of its action as well as of how miR-155 levels are regulated in a cell-specific manner.

MicroRNAs, the immune system and rheumatic disease

MicroRNAs (miRNAs) are short noncoding RNA molecules that modulate the expression of multiple target genes at the post-transcriptional level and are implicated in a wide array of cellular and developmental processes. In hematopoietic cells, miRNA levels are dynamically regulated during lineage differentiation and also during the course of the immune response. Mouse models have provided good evidence for miRNAs being key players in the establishment of hematopoietic lineages. Furthermore, miRNA-dependent alterations in gene expression in hematopoietic cells are critical for mounting an appropriate immune response to a wide range of pathogens, spontaneously emerging tumors, and autoimmune cells. Deregulation of hematopoietic-specific miRNA expression results in defects in both central and peripheral tolerance, hematopoietic malignancies, and sometimes both. Abnormal expression of miRNAs-which is implicated in inflammation-has also been found in patients with rheumatoid arthritis. These findings identify miRNAs as critical targets for immunomodulatory drug development.

Expression and function of micro-RNAs in immune cells during normal or disease state

Micro-RNAs (miRNAs) are 19-24 nucleotide long non-coding RNAs that posttranscriptionally modulate gene expression. They are found in almost all species: viruses, plants, nematodes, fly, fish, mouse, human, and are implicated in a wide array of cellular and developmental processes. Microarray-based miRNA profiling brought to the discovery of miRNAs specific to different hematopoietic lineages. Furthermore, the functional assays performed in tissue cultures to discover miRNAs involved in immune responses in combination with the reports of miRNA-transgenic or miRNA -knockout mouse models has helped elucidating the miRNA roles in the development and function of immune system. Abnormal patterns of hematopoietic-specific miRNAs have been found in different types of cancer and miRNA based gene therapy is being considered as a potential technology of choice in immunological disorders and cancer. The purpose of this review is to discuss recent findings related with the expression and function of miRNAs in hematopoietic lineages.

miRNAs and their potential for use against cancer and other diseases

miRNAs are 19-24 nucleotide long noncoding RNAs found in almost all genetically dissected species, including viruses, plants, nematodes, flies, fish, mice and humans. Rapid advances have been made in understanding their physiological functions, while abnormal patterns of miRNA expression have been found in many disease states, most notably human cancer. It is now clear that miRNAs represent a class of genes with a great potential for use in diagnosis, prognosis and therapy. In this review we will focus on the discoveries that elucidate their crucial role in mammalian diseases, particularly in cancer, and propose that miRNA-based gene therapy might become the potential technology of choice in a wide range of human diseases including cancer.

Modulation of miR-155 and miR-125b levels following lipopolysaccharide/TNF-alpha stimulation and their possible roles in regulating the response to endotoxin shock

We report here that miR-155 and miR-125b play a role in innate immune response. LPS stimulation of mouse Raw 264.7 macrophages resulted in the up-regulation of miR-155 and down-regulation of miR-125b levels. The same changes also occurred when C57BL/6 mice were i.p. injected with LPS. Furthermore, the levels of miR-155 and miR-125b in Raw 264.7 cells displayed oscillatory changes in response to TNF-alpha. These changes were impaired by pretreating the cells with the proteasome inhibitor MG-132, suggesting that these two microRNAs (miRNAs) may be at least transiently under the direct control of NF-kappaB transcriptional activity. We show that miR-155 most probably directly targets transcript coding for several proteins involved in LPS signaling such as the Fas-associated death domain protein (FADD), IkappaB kinase epsilon (IKKepsilon), and the receptor (TNFR superfamily)-interacting serine-threonine kinase 1 (Ripk1) while enhancing TNF-alpha translation. In contrast, miR-125b targets the 3'-untranslated region of TNF-alpha transcripts; therefore, its down-regulation in response to LPS may be required for proper TNF-alpha production. Finally, Emu-miR-155 transgenic mice produced higher levels of TNF-alpha when exposed to LPS and were hypersensitive to LPS/d-galactosamine-induced septic shock. Altogether, our data suggest that the LPS/TNF-alpha-dependent regulation of miR-155 and miR-125b may be implicated in the response to endotoxin shock, thus offering new targets for drug design.

Function of RARgamma and RARalpha2 at the initiation of retinoid signaling is essential for avian embryo survival and for distinct events in cardiac morphogenesis

Avian embryogenesis requires retinoid receptor activation by the vitamin A active form, retinoic acid (RA), during neurulation. We conducted loss-of-function analysis in quail embryos by nutritional deprivation of RA and by blocking generation of retinoid receptors. Here we identify a distinct role for RARalpha2 in cardiac inflow tract morphogenesis and for RARgamma in cardiac left/right orientation and looping morphogenesis. Blocking normal embryos with antisense oligonucleotides to RARalpha2 or RXRalpha diminishes GATA-4 transcripts, while blocking RARgamma or RXRalpha diminishes nodal and Pitx2 transcripts; the expression of these genes in the heart forming region resembles that of the vitamin A-deficient embryo. Blocking the function of RARgamma, RARalpha2, and RXRalpha recapitulates the complete vitamin A-deficient phenotype. RARgamma is the most potent mediator of the retinoid signal at this time of development. Our studies provide strong evidence that critical RA-requiring developmental events in the early avian embryo are regulated by means of distinct retinoid receptor signaling pathways.

Retinoid receptors and vitamin A deficiency: differential patterns of transcription during early avian development and the rapid induction of RARs by retinoic acid

The functional links of specific retinoid receptors to early developmental events in the avian embryo are not known. Before such studies are undertaken, knowledge is required of the spatiotemporal expression patterns of the receptor genes and their regulation by endogenous retinoic acid levels during the early stages of development. Here, we report the expression patterns of mRNAs for RARalpha, RARalpha2, RARbeta2, RARgamma, RARgamma2, RXRalpha, and RARgamma from neurulation to HH10 in the normal and vitamin A-deficient (VAD) quail embryo. The transcripts for all retinoid receptors are detectable at HH5, except for RXRgamma, which is detected at the beginning of HH6. At the 4/5 somite stage of HH8, when retinoid signaling is initiated in the avian embryo, mRNAs of all receptors are present, with very strong and ubiquitous expression patterns for RARalpha, RARalpha2, RARgamma, RARgamma2, and RXRalpha, a persistent expression of RARgamma in the neural tissues, a strong expression of RARbeta2 in lateral plate mesoderm and somites, and an anterior expression of RXRgamma. All retinoid receptors are expressed in the heart primordia. In the VAD quail embryo, the general pattern of retinoid receptor transcript localization is similar to that of the normal, except that the expression of RARalpha2 and RARbeta2 is severely diminished. Administration of retinol or retinoic acid to VAD embryos at or before the 4/5 somite stage rescues the expression of RARalpha2 and RARbeta2 within approximately 45 min and restores normal development. RARbeta2 expression requires the expression of RARalpha2. After neurulation, the expression of all retinoid receptors in the VAD quail embryo becomes independent of vitamin A status and is similar to that of the normal. The mRNA levels and sites of expression of the key enzyme for retinoic acid biosynthesis, Raldh-2, are not affected by vitamin A status; the expression pattern is restricted and does not correspond to that of retinoid receptors at all sites. The general patterns and intensity of retinoid receptor gene expression during early quail development are comparable to those of the mammalian and thus validate the application of results from retinoid-regulated avian development studies to those of the mammalian.

Quantitative assessment of retinoid signaling pathways in the developing eye and retina of the chicken embryo

Retinoid signaling has been implicated as an important regulator of retinal development and differentiation. We have used state of the art high-pressure liquid chromatography to identify and quantitate biologically active retinoids, immunohistochemistry to localize the retinoic acid synthetic enzyme retinaldehyde dehydrogenase 2 (RALDH2), and nucleic acid assays to quantitate and localize retinoid receptor gene transcripts in the developing eye and retina of the chicken. Our results demonstrate spatial distinctions in retinoid synthesis and signaling that may be related to laminar differentiation in the developing retina. Retinoic acids (RAs) and their precursor retinols (ROHs) are the predominant retinoids in the developing eye. All-trans-RA and all-trans-3,4-didehydro-RA are present in the neuroepithelium in approximately equal amounts from early stages of neurogenesis until shortly before hatching. The retinoid X receptor (RXR) ligand 9-cis-RA is undetectable at all stages; if present, it cannot exceed a small percentage of the total RA content. RAs are not detected in the pigment epithelium. All-trans-ROH is present in the neuroepithelium and pigment epithelium, whereas all-trans-3,4-didehydro-ROH is detected only in the pigment epithelium and/or the choroid and sclera. RALDH2 immunoreactivity is intense in the choroid, low or absent in the pigment epithelium, and moderate in the neuroepithelium, where it is highest in the outer layers. Transcripts of all five chicken retinoid receptor genes are present in the neural retina and eye throughout development. During the period of neurogenesis, at least three of the receptors (RAR gamma, RXR gamma, RXRalpha), exhibit dynamic patterns of differential localization within the depths of the neural retina.

Retinoid signaling is required for chondrocyte maturation and endochondral bone formation during limb skeletogenesis

Retinoids have long been known to influence skeletogenesis but the specific roles played by these effectors and their nuclear receptors remain unclear. Thus, it is not known whether endogenous retinoids are present in developing skeletal elements, whether expression of the retinoic acid receptor (RAR) genes alpha, beta, and gamma changes during chondrocyte maturation, or how interference with retinoid signaling affects skeletogenesis. We found that immature chondrocytes present in stage 27 (Day 5.5) chick embryo humerus exhibited low and diffuse expression of RARalpha and gamma, while RARbeta expression was strong in perichondrium. Emergence of hypertrophic chondrocytes in Day 8-10 embryo limbs was accompanied by a marked and selective up-regulation of RARgamma gene expression. The RARgamma-rich type X collagen-expressing hypertrophic chondrocytes lay below metaphyseal prehypertrophic chondrocytes expressing Indian hedgehog (Ihh) and were followed by mineralizing chondrocytes undergoing endochondral ossification. Bioassays revealed that cartilaginous elements in Day 5.5, 8.5, and 10 chick embryo limbs all contained endogenous retinoids; strikingly, the perichondrial tissues surrounding the cartilages contained very large amounts of retinoids. Implantation of beads filled with retinoid antagonist Ro 41-5253 or AGN 193109 near the humeral anlagens in stage 21 (Day 3.5) or stage 27 chick embryos severely affected humerus development. In comparison to their normal counterparts, antagonist-treated humeri in Day 8.5-10 chick embryos were significantly shorter and abnormally bent; their diaphyseal chondrocytes had remained prehypertrophic Ihh-expressing cells, did not express RARgamma, and were not undergoing endochondral ossification. Interestingly, formation of an intramembranous bony collar around the diaphysis was not affected by antagonist treatment. Using chondrocyte cultures, we found that the antagonists effectively interfered with the ability of all-trans-retinoic acid to induce terminal cell maturation. The results provide clear evidence that retinoid-dependent and RAR-mediated mechanisms are required for completion of the chondrocyte maturation process and endochondral ossification in the developing limb. These mechanisms may be positively influenced by cooperative interactions between the chondrocytes and their retinoid-rich perichondrial tissues.

Initial retinoid requirement for early avian development coincides with retinoid receptor coexpression in the precardiac fields and induction of normal cardiovascular development

Vitamin A requirement for early embryonic development is clearly evident in the gross cardiovascular and central nervous system abnormalities and an early death of the vitamin A-deficient quail embryo. This retinoid knockout model system was used to examine the biological activity of various natural retinoids in early cardiovascular development. We demonstrate that all-trans-, 9-cis-, 4-oxo-, and didehydroretinoic acids, and didehydroretinol and all-trans-retinol induce and maintain normal cardiovascular development as well as induce expression of the retinoic acid receptor beta2 in the vitamin A-deficient quail embryo. The expression of RARbeta2 is at the same level and at the same sites where it is expressed in the normal embryo. Retinoids provided to the vitamin A-deficient embryo up to the 5-somite stage of development, but not later, completely rescue embryonic development, suggesting the 5-somite stage as a critical retinoid-sensitive time point during early avian embryogenesis. Retinoid receptors RARalpha, RARgamma, and RXRalpha are expressed in both the precardiac endoderm and mesoderm in the normal and the vitamin A-deficient quail embryo, while the expression of RXRgamma is restricted to precardiac endoderm. Vitamin A deficiency downregulates the expression of RARalpha and RARbeta. Our studies provide strong evidence for a narrow retinoid-requiring developmental window during early embryogenesis, in which the presence of bioactive retinoids and their receptors is essential for a subsequent normal embryonic development.

Both retinoic acid receptors alpha (RARalpha) and gamma (RARgamma) are able to initiate mouse upper-lip skin glandular metaplasia

Embryonic mouse upper-lip skin explants treated with 16.7 microM all-trans retinoic acid (tRA) give rise to a glandular metaplasia of hair vibrissa follicles; however, at this concentration, tRA can activate not only the three retinoic acid receptors (RARalpha, beta, and gamma), but also the retinoid X receptors (RXRalpha, beta, and gamma) as a consequence of its isomerization to 9-cis retinoic acid. We therefore studied the respective roles of the RXR and RAR by treating RARalpha(-/-), beta(-/-), and gamma(-/-) skin explants with tRA and wild-type explants with synthetic retinoids specific for RXR or for each of the RAR. The null mutation of the RARalpha, RARbeta, and RARgamma genes did not prevent tRA-induced hair glandular metaplasia, but RARgamma inactivation dramatically reduced its ratio. As demonstrated by treating explants with a RAR- or a RXR-specific panagonist (CD367 and Ro25-7386, respectively), RAR are primarily responsible for this metaplasia. The use of two retinoids (Ro40-6055, 8 x 10(-3) microM, or CD437, 7.7 x 10(-2) microM) that are believed to act, respectively, as a RARalpha- or a RARgamma-specific agonist showed that both these receptors can initiate a metaplasia. In contrast, BMS453, a RARbeta-specific agonist, was unable to give rise to any metaplasia. Nevertheless, the highest degrees and ratios of metaplasia were only obtained after treatment with the CD367 RAR panagonist, or with either Ro40-6055 or CD437 at a concentration sufficient to allow the activation of the three RAR, suggesting that RARbeta activation is required for a metaplasia of all vibrissae.

Isolation and characterization of genomic clones of human sequences presumably coding for hair cysteine-rich proteins

The major biochemical components of the mammalian hair are the intermediate filaments or keratins and the keratin associated proteins. Keratin associated proteins are classified into two groups (high-cysteine and high glycine-tyrosine-rich polypeptides) according to the content of these amino acids. Cysteine-rich group contains high sulphur (16-24% cysteine) and ultra-high sulphur (> 30% cysteine) proteins. We report here the identification of a human sequence presumably coding for a new ultra-high sulphur protein (hUHSp21) and the isolation and characterization of four genomic clones containing six related sequences. We also discuss the possibility that all the genes encoding keratin associated proteins are evolutionary related. These human clones should provide useful molecular tools for studies of hair differentiation and understanding of the molecular basis of human trichothiodystrophy.

Characterization of cDNAs encoding two chick retinoic acid receptor alpha isoforms and distribution of retinoic acid receptor alpha, beta and gamma transcripts during chick skin development

The amino acid sequence of the retinoic acid receptors alpha, beta and gamma (RAR alpha, beta and gamma) can be divided into six functional domains (A-F), different isoforms arising from the presence of different A domains by differential splicing. In order to address the respective roles of the different RARs during skin morphogenesis in birds, cDNAs encoding two chick RAR alpha isoforms (alpha1 and alpha2) have been isolated. While the A1 and B-F domains of the RAR alpha are highly conserved across species, the chick A2 domain contains 50% specific amino acids. The three RAR alpha, beta and gamma genes display specific patterns of expression during chick skin morphogenesis. As in mouse, RAR alpha and gamma transcripts are present in both the dermis and epidermis during the first stages of skin appendage formation. Furthermore, Northern blot analysis suggests that different RAR alpha and gamma isoforms could be successively required during feather formation. The RAR gamma gene, continuously expressed in the epidermal cells in both chick and mouse, is thus likely to play a similar role in skin development in these two species. However, RAR alpha transcripts, only transiently detected during mouse skin development, still accumulate in epidermis during the later stages of chick skin differentiation. Furthermore, RAR beta transcripts, never detected during normal development in mouse skin, are actually present at the early stages of chick skin morphogenesis. Thus, our results suggest that the role of the three RAR in skin development has not been strictly conserved in the different classes of vertebrates.

Retinoic acid-mediated increase in TrkA expression is sufficient to elicit NGF-dependent survival of sympathetic neurons

Sympathetic neurons depend on the classical neurotrophin NGF for survival by the time they innervate their targets, but the mechanisms controlling the onset of NGF responsiveness in developing neuroblasts have not been defined. Immature chick sympathetic neurons are unresponsive to NGF, but express low mRNA levels of the high-affinity NGF receptor trkA. Treatment with retinoic acid (RA) leads to increased levels of both trkA mRNA and protein, a response mediated through retinoic acid receptor alpha (RAR alpha). Ectopic expression of trkA in these cells results in the ability to survive with NGF, suggesting that RA-induced trkA expression is sufficient to elicit NGF-dependent survival. Our data establish a mechanism controlling NGF responsiveness and implicate a function for RA at defined late stages of neuron development.

Isolation and characterization of a cDNA encoding a chicken actin-like protein

We report the isolation and characterization of a chicken cDNA which putatively encodes an actin-like protein (chACTL). This 394-amino-acid (aa) polypeptide shares sequence homology (81, 70 and 67% identical aa, respectively) with three actin-related proteins (ARP) described for Drosophila melanogaster (ARP14D), Caenorhabditis elegans (ACTL) and Saccharomyces cerevisiae (ACT2). At least six chACTL transcripts were detected in different tissues during chick embryogenesis. Sequence analysis suggests that at least three groups of ARP have been evolutionarily conserved.

Characterization of cDNAs encoding the chick retinoic acid receptor gamma 2 and preferential distribution of retinoic acid receptor gamma transcripts during chick skin development

Retinoic acid receptors alpha, beta and gamma (RAR alpha, beta and gamma) are ligand-inductible transcriptional activators which belong to the steroid/thyroid hormone receptor superfamily. At least two major isoforms (1 and 2) of each RAR arise by differential use of two promoters and alternative splicing. In mouse, the three RAR genes are expressed in stage- and tissue-specific patterns during embryonic development. In order to understand the role of the different RARs in chick, RAR gamma 2 cDNAs were isolated from an 8.5-day (stage 35 of Hamburger and Hamilton) chick embryo skin library. The deduced chick RAR gamma 2 amino acid sequence displays uncommon features such as 21 specific amino acid replacements, 12 of them being clustered in the amino-terminal region (domains A2 and B), and a truncated acidic carboxy-terminal region (F domain). However, the pattern of RAR gamma expression in chick embryo resembles that reported in mouse, particularly in skin where RAR gamma expression occurs in both the dermal and epidermal layers at the beginning of feather formation, and is subsequently restricted to the differentiating epidermal cells. Northern blot analysis suggests that different RAR gamma isoforms could be successively required during chick development.

c-erbA alpha/T3R and RARs control commitment of hematopoietic self-renewing progenitor cells to apoptosis or differentiation and are antagonized by the v-erbA oncogene

In AEV-transformed erythroleukemic cells the v-erbA gene product is likely to antagonize the function of triiodothyronine (T3) and retinoic acid (RA) receptors and thereby to block cell differentiation. We have thus investigated the effects of T3 and RA on normal early erythrocytic progenitor cells. Here we show: (1) that either RA or T3 play an essential role during the early commitment to erythrocytic differentiation, (2) that both T3 and RA induce death by apoptosis and a strong inhibition of self-renewal in progenitor cells grown in the absence of differentiation-inducing agents and (3) that the v-erbA oncogene renders erythrocytic progenitor cells insensitive to apoptosis and to self-renewal inhibition induced by RA or T3. The behaviour of a non-transforming mutant of v-erbA suggests that this v-erbA-induced protection is related to its transforming potential.

Isolation of two morphologically distinct cell lines from rat arterial smooth muscle expressing high tumorigenic potentials

Smooth muscle cell proliferation is an important feature of atherogenesis. Some works have hypothesized that a transformation of smooth muscle cells could arise during this pathological process. The present paper describes two spontaneously transformed cell lines of arterial smooth muscle cells (SMC) established from aortic media of adult rat. The cell lines have been designated V6 and V8; some of their morphologic, growth, and metabolic characteristics are described and compared to their parent cells. The two cell lines appeared distinct by their morphology and by their degree of transformation. V6 cells appeared as elongated spindle-shaped cells whereas V8 cells were spread cells with a cobblestone pattern. Karyotypes of both cell lines showed a high polyploidy level. V6 and V8 cell lines were immortalized and showed growth characteristics of transformed cells: low requirement of serum to grow, ability to form colonies in soft agar and tumorigenicity in nude mice; V8 cells presented a higher malignancy than V6 cells. Both V6 and V8 cells exhibited characteristics of cultured arterial SMC: ultrastructure, alpha actin expression at the protein and mRNA level, prostacyclin production. The remarkably different morphologies of the V6 and V8 lines and their transformed phenotype suggest that these cell lines could be useful models to study SMC differentiation and proliferation with respect to atherosclerotic or hypertensive vascular diseases.

Cloning and characterization of the highly polymorphic Ser2 gene of Bombyx mori

Three alleles of the sericin (Ser) 2-encoding gene (Ser2), called L, C and mC, were isolated from a Bombyx mori genomic library, and two related ones, called mCL and Cv, were also characterized in B. mori European strains. The Ser2 gene gives rise to two middle silk gland mRNAs by differential splicing. The size of a short mRNA (3.1 kb) is constant, but the length of a longer one ranges from 5 to 6.4 kb depending on the Ser2 allele. These length variations probably result from unequal recombinations in a region which contains about 30 well conserved 45-bp repeats coding for a Ser-like peptide. Furthermore, the L allele (and probably the mCL one) contains a 4.4-kb retrotransposon, resembling the copia-like ones of Drosophila.

Developmental switches of sericin mRNA splicing in individual cells of Bombyx mori silkgland

Four mRNA of 10.5, 9.0, 4.0, and 2.8 kb are made from the sericin Ser1 gene by alternative maturation of a unique mRNA precursor. By means of RNA blots and in situ hybridization, we investigated variations in the distribution of these mRNA during the last larval instar in different territories of the middle silkgland. Taken together, the results from these two techniques show that 150 out of the 266 cells of this region of the organ express the Ser1 gene, but accumulate distinct mature mRNA species. Of these 150 cells 42 are specialized in a processing pathway resulting in the production of the 2.8-kb Ser1 mRNA throughout the larval instar. The 108 others perform successively three distinct splicing pathways leading to a development-dependent accumulation of, respectively, the 4.0-, the 10.5-, and the 9.0-kb mRNA. This suggests the occurrence of two switches in the splicing capacities of these cells during the fifth instar. The middle silkgland cells also express another sericin gene (Ser2) which encodes two mRNA of 5.4 and 3.1 kb, also arising by differential splicing. At the beginning of development, all the middle silkgland cells express this gene but, as development proceeds, expression becomes restricted to only the anterior cells. The biological consequence of this topological and temporal regulation of the mode of expression of these two genes is the sequential secretion and layering of the different sericins around the silk thread.

A single gene produces multiple sericin messenger RNAs in the silk gland of Bombyx mori

The sericins are a family of major cocoon proteins specifically synthesized in the middle silk gland of the silkworm Bombyx mori. The 5' part of one sericin gene had been cloned and described by Okamoto et al. (1982, J. Biol. Chem. 257, 15192-15199). Using a differential screening procedure of Bombyx genomic libraries, we obtained the 3' part of this gene. We demonstrate that it consists of a single gene extending over 24 kb, present in two allelic forms in hybrid strains. This gene encodes for four mRNAs which result from a unique transcript by an alternative splicing mechanism. This explains, at least partially, the diversity of the sericins found in the cocoon.