Repurposing of histone deacetylase inhibitors: A promising strategy to combat pulmonary fibrosis promoted by TGF-β signalling in COVID-19 survivors

Persistent microbial infections and idiopathic pulmonary fibrosis - an insight into non-typeable Haemophilus influenza pathogenesis

Interstitial lung disease (ILD) is characterized by chronic inflammation and scarring of the lungs, of which idiopathic pulmonary fibrosis (IPF) is the most devastating pathologic form. Idiopathic pulmonary fibrosis pathogenesis leads to loss of lung function and eventual death in 50% of patients, making it the leading cause of ILD-associated mortality worldwide. Persistent and subclinical microbial infections are implicated in the acute exacerbation of chronic lung diseases. However, while epidemiological studies have highlighted pollutants, gastric aspirate, and microbial infections as major causes for the progression and exacerbation of IPF, the role of persistent microbial infections in the pathogenesis of IPF remains unclear. In this review, we have focused on the role of persistent microbial infections, including viral, bacterial, and fungal infections, and their mechanisms of action in the pathogenesis of IPF. In particular, the mechanisms and pathogenesis of the Gram-negative bacteria Non-typeable Haemophilus influenzae (NTHi) in ILDs are discussed, along with growing evidence of its role in IPF, given its unique ability to establish persistent intracellular infections by leveraging its non-capsulated nature to evade host defenses. While antibiotic treatments are presumably beneficial to target the extracellular, interstitial, and systemic burden of pathogens, their effects are significantly reduced in combating pathogens that reside in the intracellular compartments. The review also includes recent clinical trials, which center on combinatorial treatments involving antimicrobials and immunosuppressants, along with antifibrotic drugs that help mitigate disease progression in IPF patients. Finally, future directions focus on mRNA-based therapeutics, given their demonstrated effectiveness across a wide range of clinical applications and feasibility in targeting intracellular pathogens.

SAHA inhibits lung fibroblast activation by increasing p66Shc expression epigenetically

Objectives

To investigate the effects of suberoylanilide hydroxamic acid (SAHA) on lung fibroblast activation and to examine the role of p66Shc in this process.

Methods

An in vitro pulmonary fibrosis model was established using transforming growth factor-β (TGF-β)-induced MRC-5 lung fibroblasts. The proliferation and migration capacities of MRC-5 cells, along with the expression of fibrosis-related genes, were assessed following treatment with SAHA and/or silence of p66Shc.

Results

In TGF-β-induced MRC-5 lung fibroblasts, SAHA treatment significantly inhibited cell proliferation and migration, as well as the expression of fibrosis-related genes, including collagen I and α-smooth muscle actin (SMA). Western blot and immunofluorescence assays revealed that SAHA increased p66Shc expression in both whole cells and mitochondria. Additionally, mito-SOX assay confirmed that SAHA treatment led to a marked accumulation of mitochondrial reactive oxygen species (ROS). However, silencing of p66Shc significantly reversed the aforementioned effects of SAHA on MRC-5 cells. Furthermore, chromatin immunoprecipitation (ChIP) assays demonstrated that SAHA enhanced active histone markers, H3K9Ac and H3K4Me3, in the p66Shc gene region.

Conclusions

SAHA alleviates lung fibroblast activation and migration by increasing p66Shc expression and mitochondrial ROS generation through epigenetic modifications of histone 3.

SARS-CoV-2 NSP5 antagonizes MHC II expression by subverting histone deacetylase 2

SARS-CoV-2 interferes with antigen presentation by downregulating major histocompatibility complex (MHC) II on antigen-presenting cells, but the mechanism mediating this process is unelucidated. Herein, analysis of protein and gene expression in human antigen-presenting cells reveals that MHC II is downregulated by the SARS-CoV-2 main protease, NSP5. This suppression of MHC II expression occurs via decreased expression of the MHC II regulatory protein CIITA. CIITA downregulation is independent of the proteolytic activity of NSP5, and rather, NSP5 delivers HDAC2 to the transcription factor IRF3 at an IRF-binding site within the CIITA promoter. Here, HDAC2 deacetylates and inactivates the CIITA promoter. This loss of CIITA expression prevents further expression of MHC II, with this suppression alleviated by ectopic expression of CIITA or knockdown of HDAC2. These results identify a mechanism by which SARS-CoV-2 limits MHC II expression, thereby delaying or weakening the subsequent adaptive immune response.

Research progress of post-acute sequelae after SARS-CoV-2 infection

SARS-CoV-2 has spread rapidly worldwide and infected hundreds of millions of people worldwide. With the increasing number of COVID-19 patients discharged from hospitals, the emergence of its associated complications, sequelae, has become a new global health crisis secondary to acute infection. For the time being, such complications and sequelae are collectively called "Post-acute sequelae after SARS-CoV-2 infection (PASC)", also referred to as "long COVID" syndrome. Similar to the acute infection period of COVID-19, there is also heterogeneity in PASC. This article reviews the various long-term complications and sequelae observed in multiple organ systems caused by COVID-19, pathophysiological mechanisms, diagnosis, and treatment of PASC, aiming to raise awareness of PASC and optimize management strategies.

Review of Hyperpolarized Pulmonary Functional 129 Xe MR for Long-COVID

The respiratory consequences of acute COVID-19 infection and related symptoms tend to resolve 4 weeks post-infection. However, for some patients, new, recurrent, or persisting symptoms remain beyond the acute phase and persist for months, post-infection. The symptoms that remain have been referred to as long-COVID. A number of research sites employed 129 Xe magnetic resonance imaging (MRI) during the pandemic and evaluated patients post-infection, months after hospitalization or home-based care as a way to better understand the consequences of infection on 129 Xe MR gas-exchange and ventilation imaging. A systematic review and comprehensive search were employed using MEDLINE via PubMed (April 2023) using the National Library of Medicine's Medical Subject Headings and key words: post-COVID-19, MRI, 129 Xe, long-COVID, COVID pneumonia, and post-acute COVID-19 syndrome. Fifteen peer-reviewed manuscripts were identified including four editorials, a single letter to the editor, one review article, and nine original research manuscripts (2020-2023). MRI and MR spectroscopy results are summarized from these prospective, controlled studies, which involved small sample sizes ranging from 9 to 76 participants. Key findings included: 1) 129 Xe MRI gas-exchange and ventilation abnormalities, 3 months post-COVID-19 infection, and 2) a combination of MRI gas-exchange and ventilation abnormalities alongside persistent symptoms in patients hospitalized and not hospitalized for COVID-19, 1-year post-infection. The persistence of respiratory symptoms and 129 Xe MRI abnormalities in the context of normal or nearly normal pulmonary function test results and chest computed tomography (CT) was consistent. Longitudinal improvements were observed in long-term follow-up of long-COVID patients but mean 129 Xe gas-exchange, ventilation heterogeneity values and symptoms remained abnormal, 1-year post-infection. Pulmonary functional MRI using inhaled hyperpolarized 129 Xe gas has played a role in detecting gas-exchange and ventilation abnormalities providing complementary information that may help develop our understanding of the root causes of long-COVID. LEVEL OF EVIDENCE: 1 TECHNICAL EFFICACY: Stage 5.

Epigenetic perspectives associated with COVID-19 infection and related cytokine storm: an updated review

PURPOSE

The COVID-19 pandemic caused by the novel Severe Acute Respiratory Syndrome Corona Virus 2 (SARS-CoV-2) has put the world in a medical crisis for the past three years; nearly 6.3 million lives have been diminished due to the virus outbreak. This review aims to update the recent findings on COVID-19 infections from an epigenetic scenario and develop future perspectives of epi-drugs to treat the disease.

METHODS

Original research articles and review studies related to COVID-19 were searched and analyzed from the Google Scholar/PubMed/Medline databases mainly between 2019 and 2022 to brief the recent work.

RESULTS

Numerous in-depth studies of the mechanisms used by SARS-CoV-2 have been going on to minimize the consequences of the viral outburst. Angiotensin-Converting Enzyme 2 receptors and Transmembrane serine protease 2 facilitate viral entry to the host cells. Upon internalization, it uses the host machinery to replicate viral copies and alter the downstream regulation of the normal cells, causing infection-related morbidities and mortalities. In addition, several epigenetic regulations such as DNA methylation, acetylation, histone modifications, microRNA, and other factors (age, sex, etc.) are responsible for the regulations of viral entry, its immune evasion, and cytokine responses also play a major modulatory role in COVID-19 severity, which has been discussed in detail in this review.

CONCLUSION

Findings of epigenetic regulation of viral pathogenicity open a new window for epi-drugs as a possible therapeutical approach against COVID-19.

Synergistic Power of Piceatannol and/or Vitamin D in Bleomycin-Induced Pulmonary Fibrosis In Vivo: A Preliminary Study

Oxidative stress and epigenetic alterations, including the overexpression of all class I and II histone deacetylases (HDACs), particularly HDAC2 and HDAC4, have been identified as key molecular mechanisms driving pulmonary fibrosis. Treatment with piceatannol (PIC) or vitamin D (Vit D) has previously exhibited mitigating impacts in pulmonary fibrosis models. The present study investigated the effects of PIC, Vit D, or a combination (PIC-Vit D) on the expression of HDAC2, HDAC4, and transforming growth factor-beta (TGF-β) in the lungs; the phosphatidylinositide-3-kinase (PI3K)/AKT signaling pathway; and the antioxidant status of the lungs. The objective was to determine if the treatments had protective mechanisms against pulmonary fibrosis caused by bleomycin (BLM) in rats. Adult male albino rats were given a single intratracheal dosage of BLM (10 mg/kg) to induce pulmonary fibrosis. PIC (15 mg/kg/day, oral (p.o.)), Vit D (0.5 μg/kg/day, intraperitoneal (i.p.)), or PIC-Vit D (15 mg/kg/day, p.o. plus 0.5 μg/kg/day, i.p.) were given the day following BLM instillation and maintained for 14 days. The results showed that PIC, Vit D, and PIC-Vit D significantly improved the histopathological sections; downregulated the expression of HDAC2, HDAC4, and TGF-β in the lungs; inhibited the PI3K/AKT signaling pathway; decreased extracellular matrix (ECM) deposition including collagen type I and alpha smooth muscle actin (α-SMA); and increased the antioxidant capacity of the lungs by increasing the levels of glutathione (GSH) that had been reduced and decreasing the levels of malondialdehyde (MDA) compared with the BLM group at a p-value less than 0.05. The concomitant administration of PIC and Vit D had a synergistic impact that was greater than the impact of monotherapy with either PIC or Vit D. PIC, Vit D, and PIC-Vit D exhibited a notable protective effect through their antioxidant effects, modulation of the expression of HDAC2, HDAC4, and TGF-β in the lungs, and suppression of the PI3K/AKT signaling pathway.

Searching for Novel Candidate Small Molecules for Ameliorating Idiopathic Pulmonary Fibrosis: a Narrative Review

Idiopathic pulmonary fibrosis (IPF) can be defined as a progressive chronic pulmonary disease showing scarring in the lung parenchyma, thereby resulting in increase in mortality and decrease in the quality of life. The pathophysiologic mechanism of fibrosis in IPF is still unclear. Repetitive microinjuries to alveolar epithelium with genetical predisposition and an abnormal restorative reaction accompanied by excessive deposition of collagens are involved in the pathogenesis. Although the two FDA-approved drugs, pirfenidone and nintedanib, are under use for retarding the decline in lung function of patients suffered from IPF, they are not able to improve the survival rate or quality of life. Therefore, a novel therapeutic agent acting on the major steps of the pathogenesis of disease and/or, at least, managing the clinical symptoms of IPF should be developed for the effective regulation of this incurable disease. In the present review, we tried to find a potential of managing the clinical symptoms of IPF by natural products derived from medicinal plants used for controlling the pulmonary inflammatory diseases in traditional Asian medicine. A multitude of natural products have been reported to exert an antifibrotic effect in vitro and in vivo through acting on the epithelial-mesenchymal transition pathway, transforming growth factor (TGF)-β-induced intracellular signaling, and the deposition of extracellular matrix. However, clinical antifibrotic efficacy of these natural products on IPF have not been elucidated yet. Thus, those effects should be proven by further examinations including the randomized clinical trials, in order to develop the ideal and optimal candidate for the therapeutics of IPF.

Molecular mechanisms of COVID-19-induced pulmonary fibrosis and epithelial-mesenchymal transition

As the outbreak of COVID-19 caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) first broke out in Hubei Province, China, at the end of 2019. It has brought great challenges and harms to global public health. SARS-CoV-2 mainly affects the lungs and is mainly manifested as pulmonary disease. However, one of the biggest crises arises from the emergence of COVID-19-induced fibrosis. At present, there are still many questions about how COVID-19 induced pulmonary fibrosis (PF) occurs and how to treat and regulate its long-term effects. In addition, as an important process of fibrosis, the effect of COVID-19 on epithelial-mesenchymal transition (EMT) may be an important factor driving PF. This review summarizes the main pathogenesis and treatment mechanisms of COVID-19 related to PF. Starting with the basic mechanisms of PF, such as EMT, transforming growth factor-β (TGF-β), fibroblasts and myofibroblasts, inflammation, macrophages, innate lymphoid cells, matrix metalloproteinases and tissue inhibitors of metalloproteinases, hedgehog pathway as well as Notch signaling. Further, we highlight the importance of COVID-19-induced EMT in the process of PF and provide an overview of the related molecular mechanisms, which will facilitate future research to propose new clinical therapeutic solutions for the treatment of COVID-19-induced PF.

Clinicopathological Outlines of Post-COVID-19 Pulmonary Fibrosis Compared with Idiopathic Pulmonary Fibrosis

This review brings together the current knowledge regarding the risk factors and the clinical, radiologic, and histological features of both post-COVID-19 pulmonary fibrosis (PCPF) and idiopathic pulmonary fibrosis (IPF), describing the similarities and the disparities between these two diseases, using numerous databases to identify relevant articles published in English through October 2022. This review would help clinicians, pathologists, and researchers make an accurate diagnosis, which can help identify the group of patients selected for anti-fibrotic therapies and future therapeutic perspectives.

Post-COVID Interstitial Lung Disease—The Tip of the Iceberg

The proportion of symptomatic patients with post-coronavirus 2019 (COVID-19) condition (long COVID) represents a significant burden on the individual as well as on the health care systems. A greater understanding of the natural evolution of symptoms over a longer period and the impacts of interventions will improve our understanding of the long-term impacts of the COVID-19 disease. This review will discuss the emerging evidence for the development of post-COVID interstitial lung disease focusing on the pathophysiological mechanisms, incidence, diagnosis, and impact of this potentially new and emerging respiratory disease.

Lung fibrosis: Post-COVID-19 complications and evidences

BACKGROUND

COVID 19, a lethal viral outbreak that devastated lives and the economy across the globe witnessed non-compensable respiratory illnesses in patients. As been evaluated in reports, patients receiving long-term treatment are more prone to acquire Pulmonary Fibrosis (PF). Repetitive damage and repair of alveolar tissues increase oxidative stress, inflammation and elevated production of fibrotic proteins ultimately disrupting normal lung physiology skewing the balance towards the fibrotic milieu.

AIM

In the present work, we have discussed several important pathways which are involved in post-COVID PF. Further, we have also highlighted the rationale for the use of antifibrotic agents for post-COVID PF to decrease the burden and improve pulmonary functions in COVID-19 patients.

CONCLUSION

Based on the available literature and recent incidences, it is crucial to monitor COVID-19 patients over a period of time to rule out the possibility of residual effects. There is a need for concrete evidence to deeply understand the mechanisms responsible for PF in COVID-19 patients.

Pathophysiology and mechanism of long COVID: a comprehensive review

BACKGROUND

After almost 2 years of fighting against SARS-CoV-2 pandemic, the number of patients enduring persistent symptoms long after acute infection is a matter of concern. This set of symptoms was referred to as "long COVID", and it was defined more recently as "Post COVID-19 condition" by the World health Organization (WHO). Although studies have revealed that long COVID can manifest whatever the severity of inaugural illness, the underlying pathophysiology is still enigmatic.

AIM

To conduct a comprehensive review to address the putative pathophysiology underlying the persisting symptoms of long COVID.

METHOD

We searched 11 bibliographic databases (Cochrane Library, JBI EBP Database, Medline, Embase, PsycInfo, CINHAL, Ovid Nursing Database, Journals@Ovid, SciLit, EuropePMC, and CoronaCentral). We selected studies that put forward hypotheses on the pathophysiology, as well as those that encompassed long COVID patients in their research investigation.

RESULTS

A total of 98 articles were included in the systematic review, 54 of which exclusively addressed hypotheses on pathophysiology, while 44 involved COVID patients. Studies that included patients displayed heterogeneity with respect to the severity of initial illness, timing of analysis, or presence of a control group. Although long COVID likely results from long-term organ damage due to acute-phase infection, specific mechanisms following the initial illness could contribute to the later symptoms possibly affecting many organs. As such, autonomic nervous system damage could account for many symptoms without clear evidence of organ damage. Immune dysregulation, auto-immunity, endothelial dysfunction, occult viral persistence, as well as coagulation activation are the main underlying pathophysiological mechanisms so far.

CONCLUSION

Evidence on why persistent symptoms occur is still limited, and available studies are heterogeneous. Apart from long-term organ damage, many hints suggest that specific mechanisms following acute illness could be involved in long COVID symptoms. KEY MESSAGESLong-COVID is a multisystem disease that develops regardless of the initial disease severity. Its clinical spectrum comprises a wide range of symptoms.The mechanisms underlying its pathophysiology are still unclear. Although organ damage from the acute infection phase likely accounts for symptoms, specific long-lasting inflammatory mechanisms have been proposed, as well.Existing studies involving Long-COVID patients are highly heterogeneous, as they include patients with various COVID-19 severity levels and different time frame analysis, as well.

Cytokine Patterns in COVID-19 Patients: Which Cytokines Predict Mortality and Which Protect Against?

(1) Background/Aim: People infected with SARS-CoV-2 may develop COVID-19 in a wide range of clinical severity. Pulmonary fibrosis is characterized by several grades of chronic inflammation and collagen deposition in the interalveolar space. SARS-CoV-2 infection has been demonstrated to cause lung fibrosis without a currently elucidated mechanism. Some studies emphasize the role of proinflammatory cytokines. This research studies the correlation of the released cytokines with mortality or lung injury in COVID-19 patients. (2) Methods: Electronic medical record data from 40 patients diagnosed with COVID-19 in the COVID-19 Department, Galilee Medical Center, Nahariya, Israel, were collected. Epidemiological, clinical, laboratory, and imaging variables were analyzed. The cytokine levels were measured upon admission and discharge. A correlation between cytokine levels and severity and mortality or lung involvement was undertaken. (3) Results: IFN-gamma and IL-10 are the most powerful risk factors for mortality in the COVID-19 patient groups in a multivariate analysis. However, in a univariate analysis, TGF-β, CXCL-10, IFN gamma, and IL-7 affected mortality in COVID-19 patients. MMP-7 was significantly correlated with a cytokine storm and a high 4-C (severity) score in COVID-19 patients. MMP-7, TGF-β, IL-10, IL-7, TNF-α, and IL-6 were correlated with high lung involvement in COVID-19 patients. Serum concentrations of IGF-1 were significantly increased upon discharge, but MMP-7 was decreased. (4) Conclusions: Proinflammatory cytokines predict clinical severity, lung fibrosis, and mortality in COVID-19 patients. High concentrations of TGF-β, CXCL-10, IL-10, IL-6, and TNF-α are correlated to severity and lung injury. However, certain cytokines have protective effects and higher levels of these cytokines increase survival levels and lower lung damage. High levels of INF-γ, IL-7, MMP-7, and IGF-1 have protection probabilities against lung injury and severity.

Liposome encapsulated clodronate mediated elimination of pathogenic macrophages and microglia: A promising pharmacological regime to defuse cytokine storm in COVID-19

The emergence of new SARS-CoV-2 variants continues to pose an enormous public health concern. The SARS-CoV-2 infection disrupted host immune response accounting for cytokine storm has been linked to multiorgan failure and mortality in a significant portion of positive cases. Abruptly activated macrophages have been identified as the key pathogenic determinant of cytokine storm in COVID-19. Besides, reactive microglia have been known to discharge a surplus amount of proinflammatory factors leading to neuropathogenic events in the brains of SARS-CoV-2 infected individuals. Considering the fact, depletion of activated macrophages and microglia could be proposed to eradicate the life-threatening cytokine storm in COVID-19. Clodronate, a non-nitrogenous bisphosphonate drug has been identified as a potent macrophage and microglial depleting agent. While recent advancement in the field of liposome encapsulation technology offers the most promising biological tool for drug delivery, liposome encapsulated clodronate has been reported to effectively target and induce prominent phagocytic cell death in activated macrophages and microglia compared to free clodronate molecules. Thus, in this review article, we emphasize that depletion of activated macrophages and microglial cells by administration of liposome encapsulated clodronate can be a potential therapeutic strategy to diminish the pathogenic cytokine storm and alleviate multiorgan failure in COVID-19. Moreover, recently developed COVID-19 vaccines appear to render the chronic activation of macrophages accounting for immunological dysregulation in some cases. Therefore, the use of liposome encapsulated clodronate can also be extended to the clinical management of unforeseen immunogenic reactions resulting from activated macrophages associated adverse effects of COVID-19 vaccines.

The Mortality Risk and Pulmonary Fibrosis Investigated by Time-Resolved Fluorescence Spectroscopy from Plasma in COVID-19 Patients

A method of rapidly pointing out the risk of developing persistent pulmonary fibrosis from a sample of blood is extraordinarily needed for diagnosis, prediction of death, and post-infection prognosis assessment. Collagen scar formation has been found to play an important role in the lung remodeling following SARS-CoV-2 infection. For this reason, the concentration of collagen degradation products in plasma may reflect the process of lung remodeling and determine the extent of fibrosis. According to our previously published results of an in vitro study, an increase in the concentration of type III collagen degradation products in plasma resulted in a decrease in the fluorescence lifetime of plasma at a wavelength of 450 nm. The aim of this study was to use time-resolved fluorescence spectroscopy to assess pulmonary fibrosis, and to find out if the lifetime of plasma fluorescence is shortened in patients with COVID-19. The presented study is thus far the only one to explore the fluorescence lifetime of plasma in patients with COVID-19 and pulmonary fibrosis. The time-resolved spectrometer Life Spec II with the sub-nanosecond pulsed 360 nm EPLED® diode was used in order to measure the fluorescence lifetime of plasma. The survival analysis showed that COVID-19 mortality was associated with a decreased mean fluorescence lifetime of plasma. The AUC of mean fluorescence lifetime in predicting death was 0.853 (95% CI 0.735−0.972, p < 0.001) with a cut-off value of 7 ns, and with 62% sensitivity and 100% specificity. We observed a significant decrease in the mean fluorescence lifetime in COVID-19 non-survivors (p < 0.001), in bacterial pneumonia patients without COVID-19 (p < 0.001), and in patients diagnosed with idiopathic pulmonary fibrosis (p < 0.001), relative to healthy subjects. Furthermore, these results suggest that the development of pulmonary fibrosis may be a real and serious problem in former COVID-19 patients in the future. A reduction in the mean fluorescence lifetime of plasma was observed in many patients 6 months after discharge. On the basis of these data, it can be concluded that a decrease in the mean fluorescence lifetime of plasma at 450 nm may be a risk factor for mortality, and probably also for pulmonary fibrosis in hospitalized COVID-19 patients.

Pathophysiology of Pulmonary Fibrosis in the Context of COVID-19 and Implications for Treatment: A Narrative Review

Pulmonary fibrosis (PF) is a feared outcome of many pulmonary diseases which results in a reduction in lung compliance and capacity. The development of PF is relatively rare, but it can occur secondary to viral pneumonia, especially COVID-19 infection. While COVID-19 infection and its complications are still under investigation, we can look at a similar outbreak in the past to gain better insight as to the expected long-term outcomes of COVID-19 patient lung function. In the current article, we review the literature relative to PF via PubMed. We also performed a literature search for COVID-related pathological changes in the lungs. Finally, the paper was reviewed and summarized based on the studies’ integrity, relative, or power calculations. This article provides a narrative review that endeavors to elucidate the current understanding of the pathophysiological mechanisms underlying PF and therapeutic strategies. We also discussed the potential for preventing progression to the fibrotic state within the context of the COVID-19 pandemic. With the massive scale of the COVID-19 pandemic, we expect there should more instances of PF due to COVID-19 infection. Patients who survive severe COVID-19 infection may suffer from a high incidence of PF.

COVID-19 and H1N1-09: A Systematic Review of Two Pandemics with a Focus on the Lung at Autopsy

BACKGROUND

The purpose of this manuscript is to provide a comparative overview of the two global pandemics: the first on June 11th 2009 due to influenza A H1N1 (H1N1-09); the second and current pandemic caused by coronavirus 2019 (COVID-19) on March 11th 2020, focusing on how autopsy can contribute to the definition of cellular pathology, to clinical pathology and, more generally, to public health.

METHODS

A systematic literature search selection was conducted on PubMed database on June 5, 2021, with this search strategy: (COVID-19) AND (H1N1 influenza) showing 101 results. The following inclusion criteria were selected: English language; published in a scholarly peer-reviewed journal; full-length articles were further elected. To further refine the research was to focus on the type of manuscript: review, systematic review, and meta-analysis. A critical appraisal of the collected studies was conducted, analyzing titles and abstracts, excluding the following topics: treatment, public health measures and perception of the general population or healthcare personnel about their quality of life. According to these procedures, 54 eligible studies were included in the present review.

RESULTS

Histopathological findings play a key role in understanding the pathophysiological mechanisms of diseases and, thus possible therapeutic approaches. The evidence on the thrombo-inflammatory mechanism underlying COVID-19 is growing to a much greater magnitude than the diffuse alveolar damage in common with H1N1-09; our study appears to be in line with these results. The prevailing scientific thinking to explain the morbidity and mortality of COVID-19 patients is that it elicits an exuberant immune reaction characterized by dysregulated cytokine production, known as a "cytokine storm".

CONCLUSIONS

The histological and immunohistochemical pattern demonstrated similarities and differences between the infectious manifestations of the two pathogens, which justify empirical therapeutic approaches, in the first phase of the COVID-19 pandemic. Therefore, the previous pandemic should have taught us to promote a culture of clinical and forensic autopsies in order to provide timely evidence from integration among autopsy and clinical data for early adopting adequate therapies.

Post-COVID Syndrome: The Research Progress in the Treatment of Pulmonary sequelae after COVID-19 Infection

Post-COVID syndrome or long COVID is defined as the persistence of symptoms after confirmed SARS-CoV-2 infection, the pathogen responsible for coronavirus disease. The content herein presented reviews the reported long-term consequences and aftereffects of COVID-19 infection and the potential strategies to adopt for their management. Recent studies have shown that severe forms of COVID-19 can progress into acute respiratory distress syndrome (ARDS), a predisposing factor of pulmonary fibrosis that can irreversibly compromise respiratory function. Considering that the most serious complications are observed in the airways, the inhalation delivery of drugs directly to the lungs should be preferred, since it allows to lower the dose and systemic side effects. Although further studies are needed to optimize these techniques, recent studies have also shown the importance of in vitro models to recreate the SARS-CoV-2 infection and study its sequelae. The information reported suggests the necessity to develop new inhalation therapies in order to improve the quality of life of patients who suffer from this condition.

HDAC inhibition as neuroprotection in COVID-19 infection

The SARS-CoV-2 virus is responsible of COVID-19 affecting millions of humans around the world. COVID-19 shows diverse clinical symptoms (fever, cough, fatigue, diarrhea, body aches, headaches, anosmia and hyposmia). Approximately 30% of the patients with COVID-19 showed neurological symptoms, these going from mild to severe manifestations including headache, dizziness, impaired consciousness, encephalopathy, anosmia, hypogeusia, hyposmia, psychology and psychiatry among others. The neurotropism of SARS-CoV-2 virus explains its neuroinvasion provoking neurological damage as acute demyelination, neuroinflammation etc. At molecular level, the COVID-19 patients had higher levels of cytokines and chemokines known as cytokines storms which disrupt the blood brain barrier allowing the entrance of monocytes and lymphocytes causing neuroinflammation, neurodegeneration and demyelination. In addition, ischemic, hemorrhagic strokes, seizures and encephalopathy have been observed due to the proinflammatory cytokines. In this sense, to avoid or decrease neurological damage due to SARS-CoV-2 infection, an early neuroprotective management should be adopted. Several approaches can be used; one of them includes the use of HDAC inhibitors (HDACi) due to their neuroprotective effects. Also, the HDACi down regulates the pro-inflammatory cytokines (IL-6 and TNF- decreasing the neurotoxicity. HDACi can also avoid and prevent the entrance of the virus into the Central nervous System (CNS) as well as decrease the virus replication by downregulating the virus receptors. Here we review the mechanisms that could explain how the SARS-CoV-2 virus could reach the CNS, induce the neurological damage and symptoms, as well as the possibility to use HDACi as neuroprotective therapy.

The Interaction Between Pulmonary Fibrosis and COVID-19 and the Application of Related Anti-Fibrotic Drugs

COVID-19 is a highly contagious respiratory disease, which mainly affects the lungs. Critically ill patients are easily complicated by cytokine storms, acute respiratory distress syndrome (ARDS), and respiratory failure, which seriously threaten their lives. Pulmonary fibrosis (PF) is a common interstitial lung disease, and its pathogenesis may involve the participation of a variety of immune cells and inflammatory factors. Current studies have shown that patients with COVID-19 may be complicated by pulmonary fibrosis, and patients with pulmonary fibrosis may also be at higher risk of contracting COVID-19 than healthy people. Pulmonary fibrosis is an important risk factor leading to the aggravation of COVID-19 disease. COVID-19 complicated by cytokine storm and ARDS mechanism pathways are similar to the pathogenesis of pulmonary fibrosis. The potential interaction between pulmonary fibrosis and COVID-19 can cause acute exacerbation of the patient's condition, but the potential mechanism between the two has not been fully elucidated. Most of the drug treatment programs for COVID-19-related pulmonary fibrosis are currently formulated about the relevant guidelines for idiopathic pulmonary fibrosis (IPF), and there is no clear drug treatment program recommendation. This article aims to summarize the relevant mechanism pathways of COVID-19 and pulmonary fibrosis, explore the interrelationships and possible mechanisms, and discuss the value and risks of existing and potential COVID-19-related pulmonary fibrosis treatment drugs, to provide reference for anti-fibrosis treatment for patients.

COVID-19: Immunohistochemical Analysis of TGF-β Signaling Pathways in Pulmonary Fibrosis

Acute respiratory distress syndrome (ARDS) followed by repair with lung remodeling is observed in COVID-19. These findings can lead to pulmonary terminal fibrosis, a form of irreversible sequelae. There is evidence that TGF-β is intimately involved in the fibrogenic process. When activated, TGF-β promotes the differentiation of fibroblasts into myofibroblasts and regulates the remodeling of the extracellular matrix (ECM). In this sense, the present study evaluated the histopathological features and immunohistochemical biomarkers (ACE-2, AKT-1, Caveolin-1, CD44v6, IL-4, MMP-9, α-SMA, Sphingosine-1, and TGF-β1 tissue expression) involved in the TGF-β1 signaling pathways and pulmonary fibrosis. The study consisted of 24 paraffin lung samples from patients who died of COVID-19 (COVID-19 group), compared to 10 lung samples from patients who died of H1N1pdm09 (H1N1 group) and 11 lung samples from patients who died of different causes, with no lung injury (CONTROL group). In addition to the presence of alveolar septal fibrosis, diffuse alveolar damage (DAD) was found to be significantly increased in the COVID-19 group, associated with a higher density of Collagen I (mature) and III (immature). There was also a significant increase observed in the immunoexpression of tissue biomarkers ACE-2, AKT-1, CD44v6, IL-4, MMP-9, α-SMA, Sphingosine-1, and TGF-β1 in the COVID-19 group. A significantly lower expression of Caveolin-1 was also found in this group. The results suggest the participation of TGF-β pathways in the development process of pulmonary fibrosis. Thus, it would be plausible to consider therapy with TGF-β inhibitors in those patients recovered from COVID-19 to mitigate a possible development of pulmonary fibrosis and its consequences for post-COVID-19 life quality.

Virus infection induced pulmonary fibrosis

Pulmonary fibrosis is the end stage of a broad range of heterogeneous interstitial lung diseases and more than 200 factors contribute to it. In recent years, the relationship between virus infection and pulmonary fibrosis is getting more and more attention, especially after the outbreak of SARS-CoV-2 in 2019, however, the mechanisms underlying the virus-induced pulmonary fibrosis are not fully understood. Here, we review the relationship between pulmonary fibrosis and several viruses such as Human T-cell leukemia virus (HTLV), Human immunodeficiency virus (HIV), Cytomegalovirus (CMV), Epstein–Barr virus (EBV), Murine γ-herpesvirus 68 (MHV-68), Influenza virus, Avian influenza virus, Middle East Respiratory Syndrome (MERS)-CoV, Severe acute respiratory syndrome (SARS)-CoV and SARS-CoV-2 as well as the mechanisms underlying the virus infection induced pulmonary fibrosis. This may shed new light on the potential targets for anti-fibrotic therapy to treat pulmonary fibrosis induced by viruses including SARS-CoV-2.

Pentoxifylline as a Potential Adjuvant Therapy for COVID-19: Impeding the Burden of the Cytokine Storm

The outburst of inflammatory response and hypercoagulability are among the factors contributing to increased mortality in severe COVID-19 cases. Pentoxifylline (PTX), a xanthine-derived drug registered for the treatment of vascular claudication, has been reported to display broad-spectrum anti-inflammatory and immunomodulatory properties via adenosine A2A receptor (A2AR)-related mechanisms, in parallel to its rheological actions. Prior studies have indicated the efficacy of PTX in the treatment of various pulmonary diseases, including the management of acute respiratory distress syndrome of infectious causes. Therefore, PTX has been proposed to have potential benefits in the treatment of SARS-CoV-2 symptoms, as well as its complications. The aim of this review is to discuss available knowledge regarding the role of PTX as a complementary therapeutic in SARS-CoV-2.

Mangostanin Derivatives as Novel and Orally Active Phosphodiesterase 4 Inhibitors for the Treatment of Idiopathic Pulmonary Fibrosis with Improved Safety

Idiopathic pulmonary fibrosis (IPF) is a progressive lung disease, and its incidence rate is rapidly rising. However, effective therapies for the treatment of IPF are still lacking. Phosphodiesterase 4 (PDE4) inhibitors were reported to be potential anti-fibrotic agents, but their clinical use was hampered by side effects like emesis and nausea. Herein, structure-based hit-to-lead optimizations of natural mangostanin resulted in the novel and orally active PDE4 inhibitor 18a with potent inhibitory affinity (IC50 = 4.2 nM), favorable physico-chemical properties, and a different binding pattern from roflumilast. Emetic activity tests on dogs demonstrated that 18a cannot cause emesis even at an oral dose of 10 mg/kg, whereas rolipram had severe emetic effects at an oral dose of 1 mg/kg. Finally, the oral administration of 18a (10 mg/kg) exhibited comparable anti-pulmonary fibrosis effects with pirfenidone (150 mg/kg) in a bleomycin-induced IPF rat model, indicating its potential as a novel anti-IPF agent with improved safety.

COVID-19 and Parkinson's disease: Defects in neurogenesis as the potential cause of olfactory system impairments and anosmia

Anosmia, a neuropathogenic condition of loss of smell, has been recognized as a key pathogenic hallmark of the current pandemic SARS-CoV-2 infection responsible for COVID-19. While the anosmia resulting from olfactory bulb (OB) pathology is the prominent clinical characteristic of Parkinson's disease (PD), SARS-CoV-2 infection has been predicted as a potential risk factor for developing Parkinsonism-related symptoms in a significant portion of COVID-19 patients and survivors. SARS-CoV-2 infection appears to alter the dopamine system and induce the loss of dopaminergic neurons that have been known to be the cause of PD. However, the underlying biological basis of anosmia and the potential link between COVID-19 and PD remains obscure. Ample experimental studies in rodents suggest that the occurrence of neural stem cell (NSC) mediated neurogenesis in the olfactory epithelium (OE) and OB is important for olfaction. Though the occurrence of neurogenesis in the human forebrain has been a subject of debate, considerable experimental evidence strongly supports the incidence of neurogenesis in the human OB in adulthood. To note, various viral infections and neuropathogenic conditions including PD with olfactory dysfunctions have been characterized by impaired neurogenesis in OB and OE. Therefore, this article describes and examines the recent reports on SARS-CoV-2 mediated OB dysfunctions and defects in the dopaminergic system responsible for PD. Further, the article emphasizes that COVID-19 and PD associated anosmia could result from the regenerative failure in the replenishment of the dopaminergic neurons in OB and olfactory sensory neurons in OE.

Long Noncoding RNAs as Emerging Regulators of COVID-19

Coronavirus disease 2019 (COVID-19), which has high incidence rates with rapid rate of transmission, is a pandemic that spread across the world, resulting in more than 3,000,000 deaths globally. Currently, several drugs have been used for the clinical treatment of COVID-19, such as antivirals (radecivir, baritinib), monoclonal antibodies (tocilizumab), and glucocorticoids (dexamethasone). Accumulating evidence indicates that long noncoding RNAs (lncRNAs) are essential regulators of virus infections and antiviral immune responses including biological processes that are involved in the regulation of COVID-19 and subsequent disease states. Upon viral infections, cellular lncRNAs directly regulate viral genes and influence viral replication and pathology through virus-mediated changes in the host transcriptome. Additionally, several host lncRNAs could help the occurrence of viral immune escape by inhibiting type I interferons (IFN-1), while others could up-regulate IFN-1 production to play an antiviral role. Consequently, understanding the expression and function of lncRNAs during severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection will provide insights into the development of lncRNA-based methods. In this review, we summarized the current findings of lncRNAs in the regulation of the strong inflammatory response, immune dysfunction and thrombosis induced by SARS-CoV-2 infection, discussed the underlying mechanisms, and highlighted the therapeutic challenges of COVID-19 treatment and its future research directions.

Bovine Serum Albumin-Coated Niclosamide-Zein Nanoparticles as Potential Injectable Medicine against COVID-19

(1) Background: COVID-19 has affected millions of people worldwide, but countries with high experimental anti-SARS-CoV-2 vaccination rates among the general population respectively show progress in achieving general herd immunity in the population (a combination of natural and vaccine-induced acquired immunity), resulting in a significant reduction in both newly detected infections and mortality rates. However, the longevity of the vaccines’ ability to provide protection against the ongoing pandemic is still unclear. Therefore, it is of utmost importance to have new medications to fight against the pandemic at the earliest point possible. Recently, it has been found that repurposing already existing drugs could, in fact, be an ideal strategy to formulate effective medication for COVID-19. Though there are many FDA-approved drugs, it has been found that niclosamide (NIC), an anthelmintic drug, has significantly high potential against the SARS-CoV-2 virus. (2) Methods: Here we deployed a simple self-assembling technique through which Zein nanoparticles were successfully used to encapsulate NIC, which was then coated with bovine serum albumin (BSA) in order to improve the drugs’ stability, injectablity, and selectivity towards the virus-infected cells. (3) Results: The particle size for the BSA-stabilized Zein-NIC nanohybrid was found to be less than 200 nm, with excellent colloidal stability and sustained drug release properties. In addition, the nanohybrid showed enhanced drug release behavior under serum conditions, indicating that such a hybrid drug delivery system could be highly beneficial for treating COVID-19 patients suffering from high endothelial glycocalyx damage followed by a cytokine storm related to the severe inflammations.

Inhibiting TGF-[Formula: see text] 1-Mediated Cellular Processes as an Effective Strategy for the Treatment of Pulmonary Fibrosis with Chinese Herbal Medicines

Pulmonary fibrosis (PF) is a chronic and irreversible interstitial lung disease that even threatens the lives of some patients infected with COVID-19. PF is a multicellular pathological process, including the initial injuries of epithelial cells, recruitment of inflammatory cells, epithelial-mesenchymal transition, activation and differentiation of fibroblasts, etc. TGF-[Formula: see text]1 acts as a key effect factor that participates in these cellular processes of PF. Recently, much attention was paid to inhibiting TGF-[Formula: see text]1 mediated cell processes in the treatment of PF with Chinese herbal medicines (CHM), an important part of traditional Chinese medicine. Here, this review first summarized the effects of TGF-[Formula: see text]1 in different cellular processes of PF. Then, this review summarized the recent research on CHM (compounds, multi-components, single medicines and prescriptions) to directly and/or indirectly inhibit TGF-[Formula: see text]1 signaling (TLRs, PPARs, micrRNA, etc.) in PF. Most of the research focused on CHM natural compounds, including but not limited to alkaloids, flavonoids, phenols and terpenes. After review, the research perspectives of CHM on TGF-[Formula: see text]1 inhibition in PF were further discussed. This review hopes that revealing the inhibiting effects of CHM on TGF-[Formula: see text]1-mediated cellular processes of PF can promote CHM to be better understood and utilized, thus transforming the therapeutic activities of CHM into practice.