SARS-CoV-2, periodontal pathogens, and host factors: The trinity of oral post-acute sequelae of COVID-19.

COVID-19 as a pan-epidemic is waning but there it is imperative to understand virus interaction with oral tissues and oral inflammatory diseases. We review periodontal disease (PD), a common inflammatory oral disease, as a driver of COVID-19 and oral post-acute-sequelae conditions (PASC). Oral PASC identifies with PD, loss of teeth, dysgeusia, xerostomia, sialolitis-sialolith, and mucositis. We contend that PD-associated oral microbial dysbiosis involving higher burden of periodontopathic bacteria provide an optimal microenvironment for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. These pathogens interact with oral epithelial cells activate molecular or biochemical pathways that promote viral adherence, entry, and persistence in the oral cavity. A repertoire of diverse molecules identifies this relationship including lipids, carbohydrates and enzymes. The S protein of SARS-CoV-2 binds to the ACE2 receptor and is activated by protease activity of host furin or TRMPSS2 that cleave S protein subunits to promote viral entry. However, PD pathogens provide additional enzymatic assistance mimicking furin and augment SARS-CoV-2 adherence by inducing viral entry receptors ACE2/TRMPSS, which are poorly expressed on oral epithelial cells. We discuss the mechanisms involving periodontopathogens and host factors that facilitate SARS-CoV-2 infection and immune resistance resulting in incomplete clearance and risk for 'long-haul' oral health issues characterising PASC. Finally, we suggest potential diagnostic markers and treatment avenues to mitigate oral PASC.

MicroRNAs in shaping the resolution phase of inflammation.

Inflammation is a host defense mechanism orchestrated through imperative factors - acute inflammatory responses mediated by cellular and molecular events leading to activation of defensive immune subsets - to marginalize detrimental injury, pathogenic agents and infected cells. These potent inflammatory events, if uncontrolled, may cause tissue damage by perturbing homeostasis towards immune dysregulation. A parallel host mechanism operates to contain inflammatory pathways and facilitate tissue regeneration. Thus, resolution of inflammation is an effective moratorium on the pro-inflammatory pathway to avoid the tissue damage inside the host and leads to reestablishment of tissue homeostasis. Dysregulation of the resolution pathway can have a detrimental impact on tissue functionality and contribute to the diseased state. Multiple reports have suggested peculiar dynamics of miRNA expression during various pro- and anti-inflammatory events. The roles of miRNAs in the regulation of immune responses are well-established. However, understanding of miRNA regulation of the resolution phase of events in infection or wound healing models, which is sometimes misconstrued as anti-inflammatory signaling, remains limited. Due to the deterministic role of miRNAs in pro-inflammatory and anti-inflammatory pathways, in this review we have provided a broad perspective on the putative role of miRNAs in the resolution of inflammation and explored their imminent role in therapeutics.

Regulatory roles of MicroRNA in shaping T cell function, differentiation and polarization.

T lymphocytes are an integral component of adaptive immunity with pleotropic effector functions. Impairment of T cell activity is implicated in various immune pathologies including autoimmune diseases, AIDS, carcinogenesis, and periodontitis. Evidently, T cell differentiation and function are under robust regulation by various endogenous factors that orchestrate underlying molecular pathways. MicroRNAs (miRNA) are a class of noncoding, regulatory RNAs that post-transcriptionally control multiple mRNA targets by sequence-specific interaction. In this article, we will review the recent progress in our understanding of miRNA-gene networks that are uniquely required by specific T cell effector functions and provide miRNA-mediated mechanisms that govern the fate of T cells. A subset of miRNAs may act in a synergistic or antagonistic manner to exert functional suppression of genes and regulate pathways that control T cell activation and differentiation. Significance of T cell-specific miRNAs and their dysregulation in immune-mediated diseases is discussed. Exosome-mediated horizontal transfer of miRNAs from antigen presenting cells (APCs) to T cells and from one T cell to another T cell subset and their impact on recipient cell functions is summarized.

Non-coding RNA LINC01010 regulates macrophage polarization and innate immune functions by modulating NFκB signaling pathway.

Innate immune response is regulated by tissue resident or infiltrating immune cells such as macrophages (Mφ) that play critical role in tissue development, homeostasis, and repair of damaged tissue. However, the epigenetic mechanisms that regulate Mφ plasticity and innate immune functions are not well understood. Long non-coding RNA (lncRNA) are among the most abundant class of transcriptome but their function in myeloid cell biology is less explored. In this study, we deciphered the regulatory role of previously uncharacterized lncRNAs in Mφ polarization and innate immune responses. Two lncRNAs showed notable changes in their levels during M1 and M2 Mφ differentiation. Our findings indicate that LINC01010 expression increased and AC007032 expression decreased significantly. LINC01010 exhibit myeloid cell-specificity, while AC007032.1 is ubiquitous and expressed in both myeloid and lymphoid (T cells, B cells and NK cells) cells. Expression of these lncRNAs is dysregulated in periodontal disease (PD), a microbial biofilm-induced immune disease, and responsive to lipopolysaccharide (LPS) from different oral and non-oral bacteria. Knockdown of LINC01010 but not AC007032.1 reduced the surface expression of Mφ differentiation markers CD206 and CD68, and M1Mφ polarization markers MHCII and CD32. Furthermore, LINC01010 RNAi attenuated bacterial phagocytosis, antigen processing and cytokine secretion suggesting its key function in innate immunity. Mechanistically, LINC01010 knockdown Mφ treated with Escherichia coli LPS exhibit significantly reduced expression of multiple nuclear factor kappa B pathway genes. Together, our data highlight functional role of a PD-associated lncRNA LINC01010 in shaping macrophage differentiation, polarization, and innate immune activation.

Macrophage-enriched novel functional long noncoding RNAs LRRC75A-AS1 and GAPLINC regulate polarization and innate immune responses.

INTRODUCTION: Macrophages (Mφs) are functionally dynamic immune cells that bridge innate and adaptive immune responses; however, the underlying epigenetic mechanisms that control Mφ plasticity and innate immune functions are not well elucidated. OBJECTIVE: To identify novel functions of macrophage-enriched lncRNAs in regulating polarization and innate immune responses. METHODS: Total RNA isolated from differentiating monocyte-derived M1 and M2 Mφs was profiled for lncRNAs expression using RNAseq. Impact of LRRC75A-AS1, GAPLINC and AL139099.5 knockdown was examined on macrophage differentiation, polarization markers, phagocytosis, and antigen processing by flow cytometry and florescence microscopy. Cytokine profiles were examined by multiplex bead array and cytoskeletal signaling pathway genes were quantified by PCR-based array. Gingival biopsies were collected from periodontally healthy and diseased subjects to examine lncRNAs, M1/M2 marker expression. RESULTS: Transcriptome profiling of M1 and M2 Mφs identified thousands of differentially expressed known and novel lncRNAs. We characterized three Mφ-enriched lncRNAs LRRC75A-AS1, GAPLINC and AL139099.5 in polarization and innate immunity. Knockdown of LRRC75A-AS1 and GAPLINC downregulated the Mφ differentiation markers and skewed Mφ polarization by decreasing M1 markers without a significant impact on M2 markers. LRRC75A-AS1 and GAPLINC knockdown also attenuated bacterial phagocytosis, antigen processing and inflammatory cytokine secretion in Mφs, supporting their functional role in potentiating innate immune functions. Mechanistically, LRRC75A-AS1 and GAPLINC knockdown impaired Mφ migration by downregulating the expression of multiple cytoskeletal signaling pathways suggesting their critical role in regulating Mφ migration. Finally, we showed that LRRC75A-AS1 and GAPLINC were upregulated in periodontitis and their expression correlates with higher M1 markers suggesting their role in macrophage polarization in vivo. CONCLUSION: Our results show that polarized Mφs acquire a unique lncRNA repertoire and identified many previously unknown lncRNA sequences. LRRC75A-AS1 and GAPLINC, which are induced in periodontitis, regulate Mφ polarization and innate immune functions supporting their critical role in inflammation.

Viruses of the oral cavity: Prevalence, pathobiology and association with oral diseases.

The human oral cavity contains a plethora of habitats and tissue environments, such as teeth, tongue, and gingiva, which are home to a rich microbial flora including bacteria, fungi, and viruses. Given the exposed nature of the mouth, oral tissues constantly encounter infectious agents, forming a complex ecological community. In the past, the discussion of microbiological aspects of oral disease has traditionally focused on bacteria and fungi, but viruses are attracting increasing attention as pathogens in oral inflammatory diseases. Therefore, understanding viral prevalence, pathogenicity, and preference regarding oral tissues is critical to understanding the holistic effects of viruses on oral infections. Recent investigations have demonstrated the abundance of certain viruses in oral inflammatory diseases, suggesting an association between viruses and disease. Human herpesviruses are the most extensively studied viruses in different oral inflammatory diseases. However, challenges in viral detection and the lack of reproducible in vitro and in vivo infection models have limited our progress in understanding viruses and their contribution to oral diseases. This review presents a summary of major mammalian viruses and associated diseases in the human oral cavity. The emergence of a recent pathogen SARS-CoV-2 and its tropism for salivary and periodontal tissues further highlights the relevance of the oral cavity in host-pathogen interaction. Understanding how these different viruses present clinically and influence oral health will advance our understanding of multifactorial oral diseases and their association with viruses.

Downregulation of miRNA-26 in chronic periodontitis interferes with innate immune responses and cell migration by targeting phospholipase C beta 1.

AIM: To evaluate the potential role of miR-26 family members in periodontal pathogenesis by assessing innate immune responses to periopathic bacteria and regulation of cytoskeletal organization. MATERIALS AND METHODS: Expression of miR-26a-5p and miR-26b-5p was quantified in gingival biopsies derived from healthy and periodontally diseased subjects before and after non-surgical (scaling and root planing) therapy by RT-qPCR. Global pathway analysis and luciferase assays were performed for target identification and validation. Cytokine expression was assessed in miR-26a-5p transfected human oral keratinocytes upon stimulation with either live Porphyromonas gingivalis (Pg), Aggregatibacter actinomycetemcomitans or Pg lipopolysaccharide (LPS). Wound closure assays were performed in cells transfected with miR-26a-5p, while the impact on cytoskeletal organization was assessed by F-actin staining. RESULTS: miR-26a-5p and miR-26b-5p were downregulated in diseased gingiva and restored 4-6 weeks post-therapy to levels comparable with healthy subjects. Target validation assays identified phospholipase C beta 1 as a bona fide novel target exhibiting antagonistic expression pattern in disease and post-therapy cohorts. miR-26a-5p transfected cells secreted higher levels of cytokine/chemokines upon stimulation with periopathogens and demonstrated impaired cell migration and cytoskeletal rearrangement. CONCLUSIONS: Downregulated miR-26a-5p levels in periodontal inflammation may interfere with key cellular functions that may have significant implications for host defence and wound healing.

Unveiling Novel Avenues in mTOR-Targeted Therapeutics: Advancements in Glioblastoma Treatment.

The mTOR signaling pathway plays a pivotal and intricate role in the pathogenesis of glioblastoma, driving tumorigenesis and proliferation. Mutations or deletions in the PTEN gene constitutively activate the mTOR pathway by expressing growth factors EGF and PDGF, which activate their respective receptor pathways (e.g., EGFR and PDGFR). The convergence of signaling pathways, such as the PI3K-AKT pathway, intensifies the effect of mTOR activity. The inhibition of mTOR has the potential to disrupt diverse oncogenic processes and improve patient outcomes. However, the complexity of the mTOR signaling, off-target effects, cytotoxicity, suboptimal pharmacokinetics, and drug resistance of the mTOR inhibitors pose ongoing challenges in effectively targeting glioblastoma. Identifying innovative treatment strategies to address these challenges is vital for advancing the field of glioblastoma therapeutics. This review discusses the potential targets of mTOR signaling and the strategies of target-specific mTOR inhibitor development, optimized drug delivery system, and the implementation of personalized treatment approaches to mitigate the complications of mTOR inhibitors. The exploration of precise mTOR-targeted therapies ultimately offers elevated therapeutic outcomes and the development of more effective strategies to combat the deadliest form of adult brain cancer and transform the landscape of glioblastoma therapy.

Covid-19 and oral diseases: Crosstalk, synergy or association?

The coronavirus disease 2019 (Covid-19) is a viral infection caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) that clinically affects multiple organs of the human body. Cells in the oral cavity express viral entry receptor angiotensin-converting enzyme 2 that allows viral replication and may cause tissue inflammation and destruction. Recent studies have reported that Covid-19 patients present oral manifestations with multiple clinical aspects. In this review, we aim to summarise main signs and symptoms of Covid-19 in the oral cavity, its possible association with oral diseases, and the plausible underlying mechanisms of hyperinflammation reflecting crosstalk between Covid-19 and oral diseases. Ulcers, blisters, necrotising gingivitis, opportunistic coinfections, salivary gland alterations, white and erythematous plaques and gustatory dysfunction were the most reported clinical oral manifestations in patients with Covid-19. In general, the lesions appear concomitant with the loss of smell and taste. Multiple reports show evidences of necrotic/ulcerative gingiva, oral blisters and hypergrowth of opportunistic oral pathogens. SARS-CoV-2 exhibits tropism for endothelial cells and Covid-19-mediated endotheliitis can not only promote inflammation in oral tissues but can also facilitate virus spread. In addition, elevated levels of proinflammatory mediators in patients with Covid-19 and oral infectious disease can impair tissue homeostasis and cause delayed disease resolution. This suggests potential crosstalk of immune-mediated pathways underlying pathogenesis. Interestingly, few reports suggest recurrent herpetic lesions and higher bacterial growth in Covid-19 subjects, indicating SARS-CoV-2 and oral virus/bacteria interaction. Larger cohort studies comparing SARS-CoV-2 negative and positive subjects will reveal oral manifestation of the virus on oral health and its role in exacerbating oral infection.

CRISPR-Cas based targeting of host and viral genes as an antiviral strategy.

Viral infections in human are leading cause of mortality and morbidity across the globe. Several viruses (including HIV and Herpesvirus), have evolved ingenious strategies to evade host-immune system and persist life-long. Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR) and CRISPR-associated (Cas) is an ancient antiviral system recently discovered in bacteria that has shown tremendous potential as a precise, invariant genome editing tool. Using CRISPR-Cas based system to activate host defenses or genetic modification of viral genome can provide novel, exciting and successful antiviral mechanisms and treatment modalities. In this review, we will provide progress on the CRISPR-Cas based antiviral approaches that facilitate clearance of virus-infected cells and/or prohibit virus infection or replication. We will discuss on the possibilities of CRIPSR-Cas as prophylaxis and therapy in viral infections and review the challenges of this potent gene editing technology.

Pathobiology and treatment of viral keratitis.

Keratitis is one of the most prevalent ocular diseases manifested by partial or total loss of vision. Amongst infectious (viz., microbes including bacteria, fungi, amebae, and viruses) and non-infectious (viz., eye trauma, chemical exposure, and ultraviolet exposure, contact lens) risk factors, viral keratitis has been demonstrated as one of the leading causes of corneal opacity. While many viruses have been shown to cause keratitis (such as rhabdoviruses, coxsackieviruses, etc.), herpesviruses are the predominant etiologic agent of viral keratitis. This chapter will summarize current knowledge on the prevalence, diagnosis, and pathobiology of viral keratitis. Virus-mediated immunomodulation of host innate and adaptive immune components is critical for viral persistence, and dysfunctional immune responses may cause destruction of ocular tissues leading to keratitis. Immunosuppressed or immunocompromised individuals may display recurring disease with pronounced severity. Early diagnosis of viral keratitis is beneficial for disease management and response to treatment. Finally, we have discussed current and emerging therapies to treat viral keratitis.

Human and herpesvirus microRNAs in periodontal disease.

Periodontitis is a multi-etiologic infection characterized clinically by pathologic loss of the periodontal ligament and alveolar bone. Herpesviruses and specific bacterial species are major periodontal pathogens that cooperate synergistically in producing severe periodontitis. Cellular immunity against herpesviruses and humoral immunity against bacteria are key periodontal host defenses. Genetic, epigenetic, and environmental factors are modifiers of periodontal disease severity. MicroRNAs are a class of noncoding, gene expression-based, posttranscriptional regulatory RNAs of great importance for maintaining tissue homeostasis. Aberrant expression of microRNAs has been associated with several medical diseases. Periodontal tissue cells and herpesviruses elaborate several microRNAs that are of current research interest. This review attempts to conceptualize the role of periodontal microRNAs in the pathogenesis of periodontitis. The diagnostic potential of salivary microRNAs is also addressed. Employment of microRNA technology in periodontics represents an interesting new preventive and therapeutic possibility.

Immunomodulatory roles of human herpesvirus-encoded microRNA in host-virus interaction.

Human herpesviruses (HHV) are large, double stranded, DNA viruses with high seroprevalence across the globe. Clinical manifestation of primary HHV infection resolve shortly, however, this period is prolonged in immunocompromised patients or individuals with suppressed immunity. Examining molecular mechanisms of HHV-encoded virulence factors can provide finer details of HHV-host interaction. A unique genetic feature of most members of HHV is that they encode multiple microRNAs (miR). In this review, I will provide mechanistic insights into the immunomodulatory functions of herpesvirus-encoded viral miR (v-miR) that favor viral persistence and spread by ingenious immune evasion schemes. Similar to host miR, v-miR can simultaneously regulate expression of multiple transcripts including host- and virus-derived. V-miRs, by virtue of their direct interaction with various transcripts, can regulate expression of critical components of host innate and adaptive immune system. V-miRs are also exported through exosomal route and gain entry into various cells even at distant sites, thereby allowing HHV to manipulate cellular and tissue immunity. Targeting v-miR may serve as a novel and promising therapeutic candidate to mitigate HHV-mediated clinical manifestations.

Dysregulation of human miRNAs and increased prevalence of HHV miRNAs in obese periodontitis subjects.

AIM: To evaluate human and herpesvirus-encoded microRNA (miRNA) expression in healthy and diseased gingiva of obese and non-obese subjects and compare the impact of localized and systemic inflammation on human miRNA profiles. MATERIAL AND METHODS: Healthy and inflamed gingival biopsies were collected from obese and non-obese subjects. Human and herpesvirus miRNA expression was quantified using quantitative PCR. Predicted targets of dysregulated miRNAs were identified using bioinformatics analysis, validated by dual luciferase assays and their expression assessed in healthy and diseased tissues. RESULTS: Our results show differential expression of miRNAs in both diseased groups compared to healthy counterparts. MMP-16 is identified as a novel target of miRNAs altered in disease. Expression analysis of genes predicted as target of differentially expressed miRNAs show significant changes in disease compared with healthy tissues. Finally, quantitation of four herpesvirus-derived viral miRNAs show that the expression and prevalence of herpesvirus miRNAs in diseased gingiva of obese subjects. CONCLUSION: Our findings show that miRNA (both cellular and virus) expression is differentially responsive to local and systemic inflammation. Some of these miRNAs can modulate key cellular genes with direct consequences on inflammatory pathways suggesting their impact on oral tissue transcriptome and functions.

Herpesviruses and SARS-CoV-2: Viral Association with Oral Inflammatory Diseases.

The oral cavity is a niche for diverse microbes, including viruses. Members of the Herpesviridae family, comprised of dsDNA viruses, as well as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), an ssRNA virus, are among the most prevalent viruses infecting the oral cavity, and they exhibit clinical manifestations unique to oral tissues. Viral infection of oral mucosal epithelia triggers an immune response that results in prolonged inflammation. The clinical and systemic disease manifestations of HHV have been researched extensively, and several recent studies have illuminated the relationship between HHV and oral inflammatory diseases. Burgeoning evidence suggests the oral manifestation of SARS-CoV-2 infection includes xerostomia, dysgeusia, periodontal disease, mucositis, and opportunistic viral and bacterial infections, collectively described as oral post-acute sequelae of COVID-19 (PASC). These diverse sequelae could be a result of intensified immune responses initially due to the copious production of proinflammatory cytokines: the so-called "cytokine storm syndrome", facilitating widespread oral and non-oral tissue damage. This review explores the interplay between HHV, SARS-CoV-2, and oral inflammatory diseases such as periodontitis, endodontic disease, and peri-implantitis. Additionally, the review discusses proper diagnostic techniques for identifying viral infection and how viral diagnostics can lead to improved overall patient health.

Viral MicroRNAs in Herpes Simplex Virus 1 Pathobiology.

Simplexvirus humanalpha1 (Herpes simplex virus type 1 [HSV-1]) infects millions of people globally, manifesting as vesiculo-ulcerative lesions of the oral or genital mucosa. After primary infection, the virus establishes latency in the peripheral neurons and reactivates sporadically in response to various environmental and genetic factors. A unique feature of herpesviruses is their ability to encode tiny noncoding RNAs called microRNA (miRNAs). Simplexvirus humanalpha1 encodes eighteen miRNA precursors that generate twentyseven different mature miRNA sequences. Unique Simplexvirus humanalpha1 miRNAs repertoire is expressed in lytic and latent stages and exhibits expressional disparity in various cell types and model systems, suggesting their key pathological functions. This review will focus on elucidating the mechanisms underlying the regulation of host-virus interaction by HSV-1 encoded viral miRNAs. Numerous studies have demonstrated sequence- specific targeting of both viral and host transcripts by Simplexvirus humanalpha1 miRNAs. While these noncoding RNAs predominantly target viral genes involved in viral life cycle switch, they regulate host genes involved in antiviral immunity, thereby facilitating viral evasion and lifelong viral persistence inside the host. Expression of Simplexvirus humanalpha1 miRNAs has been associated with disease progression and resolution. Systemic circulation and stability of viral miRNAs compared to viral mRNAs can be harnessed to utilize their potential as diagnostic and prognostic markers. Moreover, functional inhibition of these enigmatic molecules may allow us to devise strategies that have therapeutic significance to contain Simplexvirus humanalpha1 infection.

Global Profiling of Differentiating Macrophages Identifies Novel Functional Long Non-coding RNAs Regulating Polarization and Innate Immune Responses.

Macrophages (Mφ) are functionally dynamic immune cells that bridge innate and adaptive immune responses. However, the underlying epigenetic mechanisms that control the macrophage plasticity and innate immune functions are not well-elucidated. Here we performed transcriptome profiling of differentiating M1Mφ and M2Mφ and identified thousands of previously known and novel lncRNAs. We characterized three Mφ-enriched lncRNAs (LRRC75A-As1, GAPLINC and AL139099.5) with novel functions in Mφ differentiation, polarization and innate immunity. Knockdown of LRRC75A-As1, and GAPLINC downregulated Mφ differentiation markers CDw93 and CD68, and skewed macrophage polarization by decreasing M1 markers but had no significant impact on M2 markers. LRRC75A-As1, and GAPLINC RNAi in Mφ attenuated bacterial phagocytosis, antigen processing and inflammatory cytokine secretion supporting their functional role in potentiating innate immune functions. Mechanistically, lncRNA knockdown perturbed the expression of multiple cytoskeleton signaling thereby impairing Mφ migration suggesting their critical role in regulating macrophage polarity and motility. Together, our results show that Mφ acquire a unique repertoire of lncRNAs to shape differentiation, polarization and innate immune functions.

LncRNA MALAT1/microRNA-30b axis regulate macrophage polarization and function.

Introduction: Macrophages (Mφ) can polarize towards the proinflammatory M1 or proresolving M2 phenotype to control diverse biological processes such as inflammation, and tissue regeneration. Noncoding RNAs play critical roles in numerous biological pathways; however, their functional interaction in the regulation of Mφ polarization and immune responses remain unclear. Objectives: To examine relationship between lncRNA (MALAT1) and microRNA (miR-30b) in shaping macrophage polarization and immune functions. Methods: Expression of MALAT1 and miR-30b was examined in differentiating M1/M2 Mφ, human and murine inflamed gingival biopsies by RT-qPCR. MALAT1 and miR-30b direct interaction was examined by dual luciferase assays. Impact of MALAT1 knockdown and miR-30b overexpression was examined on macrophage polarization markers, bacterial phagocytosis, antigen uptake/processing and cytokine profiles. Results: MALAT1 expression displays a time-dependent induction during Mφ differentiation and, upon challenge with TLR4 agonist ( E. coli LPS). Knockdown of MALAT1 enhanced the expression of M2Mφ markers without affecting the M1Mφ markers, suggesting that MALAT1 favors the M1 phenotype by suppressing M2 polarization. MALAT1 knockdown Mφ exhibit reduced antigen uptake and processing, bacterial phagocytosis, and bactericidal activity, strongly supporting its critical role in regulating innate immune functions. Consistent with this, MALAT1 knockdown showed impaired cytokine secretion upon challenge with LPS. Importantly, MALAT1 exhibit an antagonistic expression pattern with all five members of the miR-30 family during M2Mφ differentiation. Dual-luciferase assays validated a novel sequence on MALAT1 that interacts with miR-30b, a microRNA that promotes the M2 phenotype. Phagocytosis and antigen processing assays unequivocally demonstrated that MALAT1 and miR-30b are functionally antagonistic. In human subjects with periodontal disease and murine model of ligature-induced periodontitis, we observed higher levels of MALAT1, and downregulation of miR-30b that correlates with higher M1Mφ markers expression in gingival tissues suggesting a pro-inflammatory function of MALAT1. Conclusion: MALAT1/miR-30b antagonistic interaction shapes Mφ polarization in vitro and in inflamed gingival biopsies.

LncRNA MALAT1/microRNA-30b axis regulates macrophage polarization and function.

Macrophages (Mφ) are long-lived myeloid cells that can polarize towards the proinflammatory M1 or proresolving M2 phenotype to control diverse biological processes such as inflammation, tissue damage, and regeneration. Noncoding RNA are a class of nonprotein-coding transcriptome with numerous interdependent biological roles; however, their functional interaction in the regulation of Mφ polarization and immune responses remain unclear. Here, we show antagonistic relationship between lncRNA (MALAT1) and microRNA (miR-30b) in shaping macrophage polarization and immune functions. MALAT1 expression displays a time-dependent induction during Mφ differentiation and, upon challenge with TLR4 agonist (E. coli LPS). MALAT1 knockdown promoted the expression of M2Mφ markers without affecting M1Mφ markers, suggesting that MALAT1 favors the M1 phenotype by suppressing M2 differentiation. Compared to the control, MALAT1 knockdown resulted in reduced antigen uptake and processing, bacterial phagocytosis, and bactericidal activity, strongly supporting its critical role in regulating innate immune functions in Mφ. Consistent with this, MALAT1 knockdown showed impaired cytokine secretion upon challenge with LPS. Importantly, MALAT1 exhibit an antagonistic expression pattern with all five members of the miR-30 family during M2 Mφ differentiation. Dual-luciferase assays validated a novel sequence on MALAT1 that interacts with miR-30b, a microRNA that promotes the M2 phenotype. Phagocytosis and antigen processing assays unequivocally demonstrated that MALAT1 and miR-30b are functionally antagonistic. Concurrent MALAT1 knockdown and miR-30b overexpression exhibited the most significant attenuation in both assays. In human subjects with periodontal disease and murine model of ligature-induced periodontitis, we observed higher levels of MALAT1, M1Mφ markers and downregulation of miR-30b expression in gingival tissues suggesting a pro-inflammatory function of MALAT1 in vivo. Overall, we unraveled the role of MALAT1 in Mφ polarization and delineated the underlying mechanism of its regulation by involving MALAT-1-driven miR-30b sequestration.

Dynamic Changes in Macrophage Polarization during the Resolution Phase of Periodontal Disease.

Periodontal inflammation is largely governed by infiltration of myeloid cells, in particular macrophages. Polarization of Mφ within the gingival tissues is a well-controlled axis and has considerable consequences for how Mφ participate in inflammatory and resolution (tissue repair) phases. We hypothesize that periodontal therapy may instigate a pro-resolution environment favoring M2 Mφ polarization and contribute towards resolution of inflammation post-therapy. We aimed to evaluate the markers of macrophage polarization before and after periodontal therapy. Gingival biopsies were excised from human subjects with generalized severe periodontitis, undergoing routine non-surgical therapy. A second set of biopsies were excised after 4-6 weeks to assess the impact of therapeutic resolution at the molecular level. As controls, gingival biopsies were excised from periodontally healthy subjects, undergoing crown lengthening. Total RNA was isolated from gingival biopsies to evaluate pro- and anti-inflammatory markers associated with macrophage polarization by RT-qPCR. Mean periodontal probing depths, CAL and BOP reduced significantly after therapy and corroborated with the reduced levels of periopathic bacterial transcripts after therapy. Compared to heathy and treated biopsies, higher load of Aa and Pg transcripts were observed in disease. Lower expression of M1Mφ markers (TNF-α, STAT1) were observed after therapy as compared to diseased samples. Conversely, M2Mφ markers (STAT6, IL-10) were highly expressed in post-therapy as opposed to pre-therapy, which correlated with clinical improvement. These findings corroborated with murine ligature-induced periodontitis and resolution model, comparing the respective murine Mφ polarization markers (M1 Mφ: cox2 , iNOS2 and M2 Mφ: tgm2 and arg1 ). Our findings suggest that imbalance in M1 and M2 polarized macrophages by assessment of their markers can provide relevant clinical information on the successful response of periodontal therapy and can be used to target non-responders with exaggerated immune responses.