Modulation of Systemic Metabolism by MMP‐2: From MMP‐2 Deficiency in Mice to MMP‐2 Deficiency in Patients

Role of MMP-2 and MMP-9 in the Relationship between Inflammation, Fibrosis, and Apoptosis during Progression of Non-Alcoholic Fatty Liver Disease and Diagnostic Significance of Plasma Levels of Their Active Forms

MMP-2 and MMP-9 play an important role in pathogenesis of chronic liver diseases, participating in the processes of inflammation and fibrosis. Their role in progression of non-alcoholic fatty liver disease (NAFLD) is poorly understood. Analysis of MMP-2, -9 levels in the blood plasma of patients with different forms of NAFLD [liver steatosis (LS) and non-alcoholic steatohepatitis (NASH) of weak (-WA), moderate (MA), high (-HA) activity without pronounced fibrosis] was performed. Correlations between the levels of MMP-2, -9 and mRNA of the genes MMP2, MMP9, ADAM17, NLRP3, caspase 3 activity in peripheral blood leukocytes (PBL), TNFα, IL-6, sIL-6R, cytokeratin-18 fragments in plasma were assessed. In steatosis, the levels of MMP2 gene mRNA in PBL and MMP-2 in plasma are lower than in the control, and expression of the NLRP3 gene in PBL is increased relative to other groups. In the NASH-WA, the level of MMP-9 is higher than in the control, in LS, and in NASH-MA, which could be associated with activation of inflammation during transformation of LS into NASH. The plasma level of MMP-9 over 389.50 pg/ml has been shown to be diagnostically significant for identification of NASH-WA among the patients with steatosis (AUC ROC = 0.818, 95% CI = 0.689-0.948, p < 0.001). In NAFLD, the level of MMP-9 could be associated not only with inflammation, but also with apoptosis. ADAM17 probably plays a certain role in this regard. In the advanced NASH, hepatocyte apoptosis is increased, the level of caspase 3 activity in PBL is increased, the level of MMP-9 in the blood is reduced to the level of the control and LS. In the NASH-HA, the level of mRNA of the ADAM17 gene in PBL is increased compared to the control, NASH-WA, and NASH-MA. Thus, MMP-2 and MMP-9 are involved in pathogenesis of NAFLD already at the early stages and their level in blood could be associated with the presence and severity of inflammation in the liver parenchyma.

Proteomic study of localized tissue necrosis by Naja atra venom

Naja atra bites often result in immediate and severe illness. The venom of N. atra contains a complex mixture of toxins that can cause significant damage to the patient's skin tissue. If left untreated, this condition can progress to localized necrosis, potentially resulting in impairment or even amputation in severe cases. Despite the known effects of the venom, the exact mechanisms underlying this tissue necrosis are not fully understood. This study aimed to investigate the protein components responsible for tissue necrosis induced by N. atra venom at both the organism-wide and molecular levels. To achieve this, venom was injected into Bama miniature pigs to cause ulcers, and exudate samples were collected at various time points after injection. Label-free proteomics analysis identified 1119, 1016, 938, 864, and 855 proteins in the exudate at 6, 12, 24, 36, and 48 h post-injection, respectively. Further analysis revealed 431 differentially expressed proteins, with S100A8, MMP-2, MIF, and IDH2 identified as proteins associated with local tissue necrosis. In this study, we established a Bama miniature pig model for N. atra venom injection and performed proteomic analysis of the wound exudate, which provides important insights into the molecular pathology of snakebite-induced tissue necrosis and potential theoretical bases for clinical treatment. Proteomic data from this study can be accessed through ProteomeXchange using the identifier PXD052498.

Role of matrix metalloproteinases in bone regeneration: Narrative review

Background

Matrix metalloproteinases (MMPs) not only work as enzymes but also as degrading enzymes that have been shown to play an important function in extracellular matrix (ECM) regeneration, including bone regeneration. To generate new bone tissue, bone regeneration or repair relies on a series of regulated processes in which MMPs play an important role. Bone cells express the MMPs in an active state, and these MMPs are assumed to have a crucial role, not only for the viability and functionality of osteoclasts, osteoblasts, and osteocytes but also for the formation and development of chondrocytes.

Objective

This study aimed to review and present the roles of matrix metalloproteinases in bone regeneration.

Methods

An analysis of the scientific literature on the topics of matrix metalloproteinases in bone regeneration was done on PubMed and Google Scholar. Search results were screened for articles that described or investigated the impacts matrix metalloproteinases have on bones in relation to dentistry. The journals' cited papers were also assessed for relevance and included if they complied with the criteria for inclusion. Accessibility to the full document was one of the prerequisites for admission.

Result

Bone regeneration are intricate ongoing processes involving numerous MMPs, especially MMP 2, 9 and 13. MMP-2 appears to alter bone growth through influencing osteoclast and osteoblast activity and proliferation, MMP-9-deficient animals have abnormal bone formation exclusively during endochondral ossification, MMP 13 is responsible for osteoclast receptor activation, has been linked to the breakdown bone resorption.

Conclusions

MMP 2, 9, and 13 play a major protective role in osteogenesis and bone regeneration.

Genetic Variants Associated with Acne Vulgaris

Acne vulgaris (AV) ranks among the common chronic inflammatory disorders that impact the sebaceous components of hair follicles. Acne vulgaris is characterised by cardinal manifestations such as the presence of pimples, nodules, pustules, and cysts, which have the potential to lead to the development of acne scarring and pigmentation. The phenomenon is influenced by polygenic inheritance or can be ascribed to the interplay between multiple genes and environmental factors. In recent years, some researchers have found that some genes (such as IL, TNF, RETN, CYP family, MMPs and TIMPs genes et al) are associated with acne vulgaris and may affect the progression and prognosis of the disease. The number of reviews addressing acne-associated genetic variants, however, is limited. In that case, we have compiled a list of prevalent genes associated with acne in recent times. This helps us understand acne's genetic basis and lets us step in early for people prone to severe acne, lowering the chance of acne scars.

Expression dynamics of metalloproteinases during mandibular bone formation: association with Myb transcription factor

As the dentition forms and becomes functional, the alveolar bone is remodelled. Metalloproteinases are known to contribute to this process, but new regulators are emerging and their contextualization is challenging. This applies to Myb, a transcription factor recently reported to be involved in bone development and regeneration. The regulatory effect of Myb on Mmps expression has mostly been investigated in tumorigenesis, where Myb impacted the expression of Mmp1, Mmp2, Mmp7, and Mmp9. The aim of this investigation was to evaluate the regulatory influence of the Myb on Mmps gene expression, impacting osteogenesis and mandibular bone formation. For that purpose, knock-out mouse model was used. Gene expression of bone-related Mmps and the key osteoblastic transcription factors Runx2 and Sp7 was analysed in Myb knock-out mice mandibles at the survival limit. Out of the metalloproteinases under study, Mmp13 was significantly downregulated. The impact of Myb on the expression of Mmp13 was confirmed by the overexpression of Myb in calvarial-derived cells causing upregulation of Mmp13. Expression of Mmp13 in the context of other Mmps during mandibular/alveolar bone development was followed in vivo along with Myb, Sp7 and Runx2. The most significant changes were observed in the expression of Mmp9 and Mmp13. These MMPs and MYB were further localized in situ by immunohistochemistry and were identified in pre/osteoblastic cells as well as in pre/osteocytes. In conclusion, these results provide a comprehensive insight into the expression dynamics of bone related Mmps during mandibular/alveolar bone formation and point to Myb as another potential regulator of Mmp13.

Matrix metalloproteinases induce extracellular matrix degradation through various pathways to alleviate hepatic fibrosis

Liver fibrosis is the common consequence of various chronic liver injuries and is mainly characterized by the imbalance between the production and degradation of extracellular matrix, which leads to the accumulation of interstitial collagen and other matrix components. Matrix metalloproteinases (MMPs) and their specific inhibitors, that is, tissue inhibitors of metalloproteinases (TIMPs), play a crucial role in collagen synthesis and lysis. Previous in vivo and in vitro studies of our laboratory found repressing extracellular matrix (ECM) accumulation by restoring the balance between MMPs and TIMPs can alleviate liver fibrosis. We conducted a review of articles published in PubMed and Science Direct in the last decade until February 1, 2023, which were searched for using these words "MMPs/TIMPs" and "Hepatic Fibrosis." Through a literature review, this article reviews the experimental studies of liver fibrosis based on MMPs/TIMPs, summarizes the components that may exert an anti-liver fibrosis effect by affecting the expression or activity of MMPs/TIMPs, and attempts to clarify the mechanism of MMPs/TIMPs in regulating collagen homeostasis, so as to provide support for the development of anti-liver fibrosis drugs. We found the MMP-TIMP-ECM interaction can result in better understanding of the pathogenesis and progression of hepatic fibrosis from a different angle, and targeting this interaction may be a promising therapeutic strategy for hepatic fibrosis. Additionally, we summarized and analyzed the drugs that have been found to reduce liver fibrosis by changing the ratio of MMPs/TIMPs, including medicine natural products.

TMT proteomics analysis of cerebrospinal fluid from patients with cerebral venous sinus thrombosis

CVST is a type of venous stroke that mainly affects young adults with no reliable diagnostic markers and effective treatment strategies for secondary pathologies. However, the underlying pathological molecular mechanisms remain unclear. Here, we systematically analyzed the molecule profiling of the cerebrospinal fluid (CSF) in CVST patients via tandem mass tag (TMT)-based proteomics for the first time, aiming to reveal the pathogenesis and provide evidence for the diagnosis and treatment of CVST. Five CVST patients and five control patients were selected, and CSF samples were analyzed by TMT proteomics. Differentially expressed proteins (DEPs) were acquired and bioinformatics analysis was performed. Besides, parallel reaction monitoring (PRM) was utilized to validate the DEPs. 468 differentially expressed proteins were screened, 185 of which were up-regulated and 283 were down-regulated (fold change >1.2, P < 0.05). Bioinformatics analysis displayed that these proteins were significantly enriched in multiple pathways related to a variety of pathophysiological processes. PRM verification showed that apolipoprotein E, MMP-2, neuroserpin, clusterin, and several other molecules were down-regulated. These identified proteins reveal unique pathophysiological characteristics secondary to CVST. Further characterization of these proteins in future research could enable their application as potential therapeutic targets and biomarkers in CVST therapy. SIGNIFICANCE: Cerebral venous sinus thrombosis (CVST) is an underrated and potentially fatal cause of stroke with a reported mortality of 5-10% worldwide. Currently, in addition to anticoagulant and thrombolytic therapy, effective treatments targeting the injured brain parenchyma after CVST remain limited. Besides, accurate diagnostic markers are still sorely lacking. In the present study, we will detect the alterations of the CSF protein spectrum of CVST patients by TMT technique, screen differentially expressed proteins, analyze the functions of these signals through bioinformatics methods, and finally validate the key molecules through parallel reaction monitoring (PRM) technique. Collectively, the study aimed to offer a reference for the discovery of specific protein/pathway alterations in the CSF of CVST patients and further reveal the underlying pathogenesis, thereby providing evidence for the diagnosis and treatment of CVST.

Physiological consequences of space flight, including abnormal bone metabolism, space radiation injury, and circadian clock dysregulation: Implications of melatonin use and regulation as a countermeasure

Exposure to the space environment induces a number of pathophysiological outcomes in astronauts, including bone demineralization, sleep disorders, circadian clock dysregulation, cardiovascular and metabolic dysfunction, and reduced immune system function. A recent report describing experiments aboard the Space Shuttle mission, STS-132, showed that the level of melatonin, a hormone that provides the biochemical signal of darkness, was decreased during microgravity in an in vitro culture model. Additionally, abnormal lighting conditions in outer space, such as low light intensity in orbital spacecraft and the altered 24-h light-dark cycles, may result in the dysregulation of melatonin rhythms and the misalignment of the circadian clock from sleep and work schedules in astronauts. Studies on Earth have demonstrated that melatonin regulates various physiological functions including bone metabolism. These data suggest that the abnormal regulation of melatonin in outer space may contribute to pathophysiological conditions of astronauts. In addition, experiments with high-linear energy transfer radiation, a ground-based model of space radiation, showed that melatonin may serve as a protectant against space radiation. Gene expression profiling using an in vitro culture model exposed to space flight during the STS-132 mission, showed that space radiation alters the expression of DNA repair and oxidative stress response genes, indicating that melatonin counteracts the expression of these genes responsive to space radiation to promote cell survival. These findings implicate the use of exogenous melatonin and the regulation of endogenous melatonin as countermeasures for the physiological consequences of space flight.

Matrix Metalloproteinases on Severe COVID-19 Lung Disease Pathogenesis: Cooperative Actions of MMP-8/MMP-2 Axis on Immune Response through HLA-G Shedding and Oxidative Stress

Patients with COVID-19 predominantly have a respiratory tract infection and acute lung failure is the most severe complication. While the molecular basis of SARS-CoV-2 immunopathology is still unknown, it is well established that lung infection is associated with hyper-inflammation and tissue damage. Matrix metalloproteinases (MMPs) contribute to tissue destruction in many pathological situations, and the activity of MMPs in the lung leads to the release of bioactive mediators with inflammatory properties. We sought to characterize a scenario in which MMPs could influence the lung pathogenesis of COVID-19. Although we observed high diversity of MMPs in lung tissue from COVID-19 patients by proteomics, we specified the expression and enzyme activity of MMP-2 in tracheal-aspirate fluid (TAF) samples from intubated COVID-19 and non-COVID-19 patients. Moreover, the expression of MMP-8 was positively correlated with MMP-2 levels and possible shedding of the immunosuppression mediator sHLA-G and sTREM-1. Together, overexpression of the MMP-2/MMP-8 axis, in addition to neutrophil infiltration and products, such as reactive oxygen species (ROS), increased lipid peroxidation that could promote intensive destruction of lung tissue in severe COVID-19. Thus, the inhibition of MMPs can be a novel target and promising treatment strategy in severe COVID-19.

Bioreactors for Vocal Fold Tissue Engineering

It is estimated that almost one-third of the United States population will be affected by a vocal fold (VF) disorder during their lifespan. Promising therapies to treat VF injury and scarring are mostly centered on VF tissue engineering strategies such as the injection of engineered biomaterials and cell therapy. VF tissue engineering, however, is a challenging field as the biomechanical properties, structure, and composition of the VF tissue change upon exposure to mechanical stimulation. As a result, the development of long-term VF treatment strategies relies on the characterization of engineered tissues under a controlled mechanical environment. In this review, we highlight the importance of bioreactors as a powerful tool for VF tissue engineering with a focus on the current state of the art of bioreactors designed to mimic phonation in vitro. We discuss the influence of the phonatory environment on the development, function, injury, and healing of the VF tissue and its importance for the development of efficient therapeutic strategies. A concise and comprehensive overview of bioreactor designs, principles, operating parameters, and scalability are presented. An in-depth analysis of VF bioreactor data to date reveals that mechanical stimulation significantly influences cell viability and the expression of proinflammatory and profibrotic genes in vitro. Although the precision and accuracy of bioreactors contribute to generating reliable results, diverse gene expression profiles across the literature suggest that future efforts should focus on the standardization of bioreactor parameters to enable direct comparisons between studies. Impact statement We present a comprehensive review of bioreactors for vocal fold (VF) tissue engineering with a focus on the influence of the phonatory environment on the development, function, injury, and healing of the VFs and the importance of mimicking phonation on engineered VF tissues in vitro. Furthermore, we put forward a strong argument for the continued development of bioreactors in this area with an emphasis on the standardization of bioreactor designs, principles, operating parameters, and oscillatory regimes to enable comparisons between studies.

Structure-based molecular insights into matrix metalloproteinase inhibitors in cancer treatments

Protease inhibitors are of considerable interest as anticancer agents. Matrix metalloproteinases (MMPs) were the earliest type of proteases considered as anticancer targets. The developments of MMP inhibitors (MMPIs) by pharmaceutical companies can be dated from the early 1980s. Thus far, none of the over 50 MMPIs entering clinical trials have been approved. This work summarizes the reported studies on the structure of MMPs and complexes with ligands and inhibitors, based on which, the authors analyzed the clinical failures of MMPIs in a structural biological manner. Furthermore, MMPs were systematically compared with urokinase, a protease-generating plasmin, which plays similar pathological roles in cancer development; the reasons for the clinical successes of urokinase inhibitors and the clinical failures of MMPIs are discussed.

Impact of High Serum Levels of MMP-7, MMP-9, TGF-β and PDGF Macrophage Activation Markers on Severity of COVID-19 in Obese-Diabetic Patients

OBJECTIVE

The aim of this study was to identify an association between the severity of COVID-19 in obese-diabetic patients and altered serum levels of MMP-7, MMP-9, TGF-β, and PDGF macrophage activation markers.

METHODOLOGY

The study included 70 COVID-19 patients, divided into two groups: Group 1 included: Obese COVID-19 patients with type 2 diabetes mellitus (T2D, n=22 patients) and group 2 included; non-obese, non-diabetic COVID-19 patients as an age- and sex-matched control group (n=48 patients). Serum levels of the tested biomarkers were measured by ELISA at admission and after one weak follow-up.

RESULTS

There was a significant reduction in the serum levels of LBP in obese-diabetic COVID-19 patients versus the control group (8.34±3.94 vs 20.78±7.61) (p 0.0001). Significant elevation of MMP-7, MMP-9, PDGF and TGF-β was detected in obese diabetic COVID-19 patients compared to the non-obese non-diabetic group: 1044.7±519.6 vs 405.6±164.1, 483.05±46.5 vs 173.31±76.26, 154.5±62.78 vs 39.77±21.52, and 603.05±258.82 vs 180.29±97.17, respectively. The serum levels of macrophage activation markers in obese-diabetic patients one week after admission revealed that patients with acute respiratory distress syndrome (ARDS) had significantly higher serum levels of MMP-7 and MMP-9 than non-ARDS patients (p 0.02 and p 0.01 respectively).

CONCLUSION

Macrophages were mainly polarized towards the M2 phenotype in obese-diabetic COVID-19 patients with significant upregulation of the pro-fibrotic markers MMP-7, MMP-9, PDGF, and TGF-β. Thus, high levels of MMP-7 and MMP-9 are associated with ARDS in severe COVID-19 disease among obese-diabetic patients.

Peri-Surgical Inflammatory Profile Associated with Mini-Invasive or Standard Open Lumbar Interbody Fusion Approaches

BACKGROUND

Different surgical approaches are available for lumbar interbody fusion (LIF) to treat disc degeneration. However, a quantification of their invasiveness is lacking, and the definition of minimally invasive surgery (MIS) has not been biochemically detailed. We aimed at characterizing the inflammatory, hematological, and clinical peri-surgical responses to different LIF techniques.

METHODS

68 healthy subjects affected by single-level discopathy (L3 to S1) were addressed to MIS, anterior (ALIF, n = 21) or lateral (LLIF, n = 23), and conventional approaches, transforaminal (TLIF, n = 24), based on the preoperative clinical assessment. Venous blood samples were taken 24 h before the surgery and 24 and 72 h after surgery to assess a wide panel of inflammatory and hematological markers.

RESULTS

martial (serum iron and transferrin) and pro-angiogenic profiles (MMP-2, TWEAK) were improved in ALIF and LLIF compared to TLIF, while the acute phase response (C-reactive protein, sCD163) was enhanced in LLIF.

CONCLUSIONS

MIS procedures (ALIF and LLIF) associated with a reduced incidence of post-operative anemic status, faster recovery, and enhanced pro-angiogenic stimuli compared with TLIF. LLIF associated with an earlier activation of innate immune mechanisms than ALIF and TLIF. The trend of the inflammation markers confirms that the theoretically defined mini-invasive procedures behave as such.

An mTORC1-GRASP55 signaling axis controls unconventional secretion to reshape the extracellular proteome upon stress

Cells communicate with their environment via surface proteins and secreted factors. Unconventional protein secretion (UPS) is an evolutionarily conserved process, via which distinct cargo proteins are secreted upon stress. Most UPS types depend upon the Golgi-associated GRASP55 protein. However, its regulation and biological role remain poorly understood. Here, we show that the mechanistic target of rapamycin complex 1 (mTORC1) directly phosphorylates GRASP55 to maintain its Golgi localization, thus revealing a physiological role for mTORC1 at this organelle. Stimuli that inhibit mTORC1 cause GRASP55 dephosphorylation and relocalization to UPS compartments. Through multiple, unbiased, proteomic analyses, we identify numerous cargoes that follow this unconventional secretory route to reshape the cellular secretome and surfactome. Using MMP2 secretion as a proxy for UPS, we provide important insights on its regulation and physiological role. Collectively, our findings reveal the mTORC1-GRASP55 signaling hub as the integration point in stress signaling upstream of UPS and as a key coordinator of the cellular adaptation to stress.

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mTORC1 phosphorylates GRASP55 directly at the Golgi in non-stressed cells

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mTORC1 inactivation by stress leads to GRASP55 dephosphorylation and relocalization

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GRASP55 relocalization to autophagosomes and MVBs drives UPS of selected cargo

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mTORC1-GRASP55 link cellular stress to changes in the extracellular proteome via UPS

Metabolic syndrome and the plasma proteome: from association to causation

Background

The metabolic syndrome (MetS), defined by the simultaneous clustering of cardio-metabolic risk factors, is a significant worldwide public health burden with an estimated 25% prevalence worldwide. The pathogenesis of MetS is not entirely clear and the use of molecular level data could help uncover common pathogenic pathways behind the observed clustering.

Methods

Using a highly multiplexed aptamer-based affinity proteomics platform, we examined associations between plasma proteins and prevalent and incident MetS in the KORA cohort (n = 998) and replicated our results for prevalent MetS in the HUNT3 study (n = 923). We applied logistic regression models adjusted for age, sex, smoking status, and physical activity.

We used the bootstrap ranking algorithm of least absolute shrinkage and selection operator (LASSO) to select a predictive model from the incident MetS associated proteins and used area under the curve (AUC) to assess its performance. Finally, we investigated the causal effect of the replicated proteins on MetS using two-sample Mendelian randomization.

Results

Prevalent MetS was associated with 116 proteins, of which 53 replicated in HUNT. These included previously reported proteins like leptin, and new proteins like NTR domain-containing protein 2 and endoplasmic reticulum protein 29. Incident MetS was associated with 14 proteins in KORA, of which 13 overlap the prevalent MetS associated proteins with soluble advanced glycosylation end product-specific receptor (sRAGE) being unique to incident MetS. The LASSO selected an eight-protein predictive model with an (AUC = 0.75; 95% CI = 0.71–0.79) in KORA.

Mendelian randomization suggested causal effects of three proteins on MetS, namely apolipoprotein E2 (APOE2) (Wald-Ratio = − 0.12, Wald-p = 3.63e−13), apolipoprotein B (APOB) (Wald-Ratio = − 0.09, Wald-p = 2.54e−04) and proto-oncogene tyrosine-protein kinase receptor (RET) (Wald-Ratio = 0.10, Wald-p = 5.40e−04).

Conclusions

Our findings offer new insights into the plasma proteome underlying MetS and identify new protein associations. We reveal possible casual effects of APOE2, APOB and RET on MetS. Our results highlight protein candidates that could potentially serve as targets for prevention and therapy.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12933-021-01299-2.

Matrix Metalloproteinases and Arterial Hypertension: Role of Oxidative Stress and Nitric Oxide in Vascular Functional and Structural Alterations

Various pathophysiological mechanisms have been implicated in hypertension, but those resulting in vascular dysfunction and remodeling are critical and may help to identify critical pharmacological targets. This mini-review article focuses on central mechanisms contributing to the vascular dysfunction and remodeling of hypertension, increased oxidative stress and impaired nitric oxide (NO) bioavailability, which enhance vascular matrix metalloproteinase (MMP) activity. The relationship between NO, MMP and oxidative stress culminating in the vascular alterations of hypertension is examined. While the alterations of hypertension are not fully attributable to these pathophysiological mechanisms, there is strong evidence that such mechanisms play critical roles in increasing vascular MMP expression and activity, thus resulting in abnormal degradation of extracellular matrix components, receptors, peptides, and intracellular proteins involved in the regulation of vascular function and structure. Imbalanced vascular MMP activity promotes vasoconstriction and impairs vasodilation, stimulating vascular smooth muscle cells (VSMC) to switch from contractile to synthetic phenotypes, thus facilitating cell growth or migration, which is associated with the deposition of extracellular matrix components. Finally, the protective effects of MMP inhibitors, antioxidants and drugs that enhance vascular NO activity are briefly discussed. Newly emerging therapies that address these essential mechanisms may offer significant advantages to prevent vascular remodeling in hypertensive patients.

Targeting MMP-Regulation of Inflammation to Increase Metabolic Tolerance to COVID-19 Pathologies: A Hypothesis

Many individuals infected with the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) develop no or only mild symptoms, but some can go on onto develop a spectrum of pathologies including pneumonia, acute respiratory distress syndrome, respiratory failure, systemic inflammation, and multiorgan failure. Many pathogens, viral and non-viral, can elicit these pathologies, which justifies reconsidering whether the target of therapeutic approaches to fight pathogen infections should be (a) the pathogen itself, (b) the pathologies elicited by the pathogen interaction with the human host, or (c) a combination of both. While little is known about the immunopathology of SARS-CoV-2, it is well-established that the above-mentioned pathologies are associated with hyper-inflammation, tissue damage, and the perturbation of target organ metabolism. Mounting evidence has shown that these processes are regulated by endoproteinases (particularly, matrix metalloproteinases (MMPs)). Here, we review what is known about the roles played by MMPs in the development of COVID-19 and postulate a mechanism by which MMPs could influence energy metabolism in target organs, such as the lung. Finally, we discuss the suitability of MMPs as therapeutic targets to increase the metabolic tolerance of the host to damage inflicted by the pathogen infection, with a focus on SARS-CoV-2.

Multifunctional intracellular matrix metalloproteinases: implications in disease

Matrix metalloproteinases (MMPs) are zinc-dependent endopeptidases that were first discovered as proteases, which target and cleave extracellular proteins. During the past 20 years, however, intracellular roles of MMPs were uncovered and research on this new aspect of their biology expanded. MMP-2 is the first of this protease family to be reported to play a crucial intracellular role where it cleaves several sarcomeric proteins inside cardiac myocytes during oxidative stress-induced injury. Beyond MMP-2, currently at least eleven other MMPs are known to function intracellularly including MMP-1, MMP-3, MMP-7, MMP-8, MMP-9, MMP-10, MMP-11, MMP-12, MMP-14, MMP-23 and MMP-26. These intracellular MMPs are localized to different compartments inside the cell including the cytosol, sarcomere, mitochondria, and the nucleus. Intracellular MMPs contribute to the pathogenesis of various diseases. Cardiovascular renal disorders, inflammation, and malignancy are some examples. They also exert antiviral and bactericidal effects. Interestingly, MMPs can act intracellularly through both protease-dependent and protease-independent mechanisms. In this review, we will highlight the intracellular mechanisms of MMPs activation, their numerous subcellular locales, substrates, and roles in different pathological conditions. We will also discuss the future direction of MMP research and the necessity to exploit the knowledge of their intracellular targets and actions for the design of targeted inhibitors.

Different roles of matrix metalloproteinase 2 in osteolysis of skeletal dysplasia and bone metastasis (Review)

Matrix metalloproteinase 2 (MMP2) is a well-characterized protein that is indispensable for extracellular matrix remodeling and other pathological processes, such as tumor progression and skeletal dysplasia. Excessive activation of MMP2 promotes osteolytic metastasis and bone destruction in late-stage cancers, while its loss-of-function mutations result in the decreased bone mineralization and generalized osteolysis occurring progressively in skeletal developmental disorders, particularly in multicentric osteolysis, nodulosis and arthropathy (MONA). Either upregulation or downregulation of MMP2 activity can result in the same osteolytic effects. Thus, different functions of MMP2 have been recently identified that could explain this observation. While MMP2 can degrade bone matrix, facilitate osteoclastogenesis and amplify various signaling pathways that enhance osteolysis in bone metastasis, its role in maintaining the number of bone cells, supporting osteocytic canalicular network formation and suppressing leptin-mediated inhibition of bone formation has been implicated in osteolytic disorders caused by MMP2 deficiency. Furthermore, the proangiogenic activity of MMP2 is one of the potential mechanisms that are associated with both pathological situations. In the present article, the latest research on MMP2 in bone homeostasis is reviewed and the mechanisms underlying the role of this protein in skeletal metastasis and developmental osteolysis are discussed.

Comparative Serum Analyses Identify Cytokines and Hormones Commonly Dysregulated as Well as Implicated in Promoting Osteolysis in MMP-2-Deficient Mice and Children

Deficiency of matrix metalloproteinase 2 (MMP-2) causes a complex syndrome characterized by multicentric osteolysis, nodulosis, and arthropathy (MONA) as well as cardiac valve defects, dwarfism and hirsutism. MMP-2 deficient (Mmp2 -/-) mice are a model for this rare multisystem pediatric syndrome but their phenotype remains incompletely characterized. Here, we extend the phenotypic characterization of MMP-2 deficiency by comparing the levels of cytokines and chemokines, soluble cytokine receptors, angiogenesis factors, bone development factors, apolipoproteins and hormones in mice and humans. Initial screening was performed on an 8-year-old male presenting a previously unreported deletion mutation c1294delC (Arg432fs) in the MMP2 gene and diagnosed with MONA. Of eighty-one serum biomolecules analyzed, eleven were upregulated (>4-fold), two were downregulated (>4-fold) and sixty-eight remained unchanged, compared to unaffected controls. Specifically, Eotaxin, GM-CSF, M-CSF, GRO-α, MDC, IL-1β, IL-7, IL-12p40, MIP-1α, MIP-1β, and MIG were upregulated and epidermal growth factor (EGF) and ACTH were downregulated in this patient. Subsequent analysis of five additional MMP-2 deficient patients confirmed the upregulation in Eotaxin, IL-7, IL-12p40, and MIP-1α, and the downregulation in EGF. To establish whether these alterations are bona fide phenotypic traits of MMP-2 deficiency, we further studied Mmp2 -/- mice. Among 32 cytokines measured in plasma of Mmp2 -/- mice, the cytokines Eotaxin, IL-1β, MIP-1α, and MIG were commonly upregulated in mice as well as patients with MMP-2 deficiency. Moreover, bioactive cortisol (a factor that exacerbates osteoporosis) was also elevated in MMP-2 deficient mice and patients. Among the factors we have identified to be dysregulated in MMP-2 deficiency many are osteoclastogenic and could potentially contribute to bone disorder in MONA. These new molecular phenotypic traits merit being targeted in future research aimed at understanding the pathological mechanisms elicited by MMP-2 deficiency in children.

Characteristics of Neuropeptide-Containing Innervation, Tissue Remodeling, Growth, and Vascularity in Noses of Patients With Cleft Lip and Palate

OBJECTIVE

To detect the appearance and distribution of factors regulating remodeling, innervation, growth, and vascularity of the nasal tissue affected by cleft lip and palate (CLP).

DESIGN

Morphological analysis of human tissue.

SETTING

Cleft and craniofacial center.

PARTICIPANTS

Fifteen patients who underwent CLP rhinoplasty, 7 control patients.

INTERVENTIONS

Rhinoplasty.

MAIN OUTCOME MEASURES

Immunohistochemistry was performed with protein gene product (PGP) 9.5, transforming growth factor β1 (TGFβ1), vascular endothelial growth factor (VEGF), cluster of differentiation 34 (CD34), matrix metalloproteinase 2 (MMP2), MMP9, and tissue inhibitor of metalloproteinase 2 (TIMP2). The results were evaluated semiquantitatively. Spearman rank order correlation coefficient and Mann-Whitney U test were used for statistical analysis.

RESULTS

Cleft lip and palate-affected tissue revealed dense and loose connective tissue, adipose cells, and hyaline cartilage, along with numerous CD34-positive endotheliocytes and regions of VEGF-positive neoangiogenesis. We observed moderate to numerous PGP 9.5-positive nerve fibers. Transforming growth factor β1, MMP2, MMP9, and TIMP2 were found in cartilage and connective tissue. Cleft lip and palate-affected tissue compared to control samples showed a statistically significant difference in PGP 9.5 (P = .006), VEGF (P = .001), MMP2 (P = .002), MMP9 (P = .013), and TIMP2 (P < .001) expression. We observed a strong, positive correlation between VEGF and MMP9 (P = .027; r _S = 0.705).

CONCLUSIONS

The moderate expression of TGFβ1 and increased distribution of VEGF, MMP2, MMP9, and TIMP2 demonstrate an active extracellular matrix remodeling and angiogenesis, performed by proteases. The cartilaginous septum of the nose is an example of balance between tissue degradation and its suppression, demonstrated by the relationship between MMPs and TIMPs and the presence of VEGF.

Destroy to Rebuild: The Connection Between Bone Tissue Remodeling and Matrix Metalloproteinases

Bone is a dynamic organ that undergoes constant remodeling, an energetically costly process by which old bone is replaced and localized bone defects are repaired to renew the skeleton over time, thereby maintaining skeletal health. This review provides a general overview of bone’s main players (bone lining cells, osteocytes, osteoclasts, reversal cells, and osteoblasts) that participate in bone remodeling. Placing emphasis on the family of extracellular matrix metalloproteinases (MMPs), we describe how: (i) Convergence of multiple protease families (including MMPs and cysteine proteinases) ensures complexity and robustness of the bone remodeling process, (ii) Enzymatic activity of MMPs affects bone physiology at the molecular and cellular levels and (iii) Either overexpression or deficiency/insufficiency of individual MMPs impairs healthy bone remodeling and systemic metabolism. Today, it is generally accepted that proteolytic activity is required for the degradation of bone tissue in osteoarthritis and osteoporosis. However, it is increasingly evident that inactivating mutations in MMP genes can also lead to bone pathology including osteolysis and metabolic abnormalities such as delayed growth. We argue that there remains a need to rethink the role played by proteases in bone physiology and pathology.

Role of MMP-2(-1306 C/T) and TIMP-2(-418G/C) Polymorphism in Chinese Han Patients with Acne Vulgaris

Acne is the most common chronic inflammatory skin diseases. Multiple factors, such as hormonal, environmental, immunological, and genetic factors, are thought to be involved in acne. However, genetic studies have yet to elucidate the full mechanism of acne. The aim of this study was to investigate the association of MMP-2 (-1306C/T) and TIMP-2 (-418G/C) polymorphisms with the risk of acne vulgaris in a Chinese Han population. We also analyzed the correlation of clinical parameters and family history in patients with acne vulgaris. This study included 251 acne patients and 121 age- and sex-matched healthy controls. Genomic DNA was extracted from peripheral blood, and genotyping was performed by PCR and DNA sequencing techniques. There is a significant correlation between the MMP-2 (-1306C/T) polymorphism and the acne vulgaris (P<0.001). Although no association was found between the TIMP-2 (-418G/C) polymorphism and the acne vulgaris, patients with the MMP-2 CT/TIMP-2 GG or GC allele are at higher risk of acne vulgaris. There is also a significant difference in the severity of the disease between acne vulgaris patients with and without family history (P<0.001). This study indicated that the MMP-2 (-1306C/T) polymorphism, in combination with the TIMP-2 (-418G/C) polymorphism, contributes to acne vulgaris susceptibility in the Chinese Han population.

Identification of fibrinogen as a natural inhibitor of MMP-2

Non-genetic MMP-2 insufficiency is a relatively unexplored condition which could be induced by pathological overexpression of endogenous MMP-2 inhibitors such as TIMPs and/or the acute phase reactant alpha-2-macroglobulin. Here, we investigate the hypothesis that human fibrinogen (FBG) – an acute phase reactant – inhibits human MMP-2. Following an unexpected observation where sera from human donors including arthritis patients with increased levels of serum FBG exhibited reduced binding of serum proMMP-2 to gelatin, we found that human FBG (0 to 3.6 mg/mL i.e., 0 to 10.6 μM) concentration-dependently inhibited human proMMP-2 and MMP2 from binding to gelatin. Moreover, at normal physiological concentrations, FBG (5.29–11.8 μM) concentration-dependently inhibited (40–70% inhibition) the cleavage of fluorescein-conjugated gelatin by MMP-2, but not MMP-9. Indicative of a mixed-type (combination of competitive and non-competitive) inhibition mechanism, FBG reduced the V_max (24.9 ± 0.7 min⁻¹ to 17.7 ± 0.9 min⁻¹, P < 0.05) and increased the Michaelis-Menten constant K_M (204 ± 6 n_M to 478 ± 50 nM, P < 0.05) for the reaction of MMP-2 cleavage of fluorescein-conjugated gelatin. In silico analyses and studies of FBG neutralization with anti-FBG antibodies implicated the domains D and E of FBG in the inhibition of MMP-2. In conclusion, FBG is a natural selective MMP-2 inhibitor, whose pathological elevation could lead to MMP-2 insufficiency in humans.

Pathologies of matrix metalloproteinase-2 underactivity: a perspective on a neglected condition 1

A member of the matrix metalloproteinase family, matrix metalloproteinase-2 (MMP-2, gelatinase A), has been extensively studied for its role in both normal physiology and pathological processes. Whereas most research efforts in recent years have investigated the pathologies associated with MMP-2 overactivity, the pathological mechanisms elicited by MMP-2 underactivity are less well understood. Here, we distinguish between 2 states and describe their causes: (i) MMP-2 deficiency (complete loss of MMP-2 activity) and (ii) MMP-2 insufficiency (defined as MMP-2 activity below baseline levels). Further, we review the biology of MMP-2, summarizing the current literature on MMP-2 underactivity in both mice and humans, and describe research being conducted by our lab towards improving our understanding of the pathological mechanisms elicited by MMP-2 deficiency/insufficiency. We think that this research could stimulate the discovery of new therapeutic approaches for managing pathologies associated with MMP-2 underactivity. Moreover, similar concepts could apply to other members of the matrix metalloproteinase family.

MMP-2: is too low as bad as too high in the cardiovascular system?

Matrix metalloproteinase (MMP)-2 cleaves a broad spectrum of substrates, including extracellular matrix components (responsible for normal tissue remodeling) and cytokines (modulators of the inflammatory response to physiological insults such as tissue damage). MMP-2 expression is elevated in many cardiovascular pathologies (e.g., myocardial infarction, hypertensive heart disease) where tissue remodeling and inflammatory responses are perturbed. Thus, it has generally been assumed that blockade of MMP-2 activity will yield therapeutic effects. Here, we provide a counterargument to this dogma based on 1) preclinical studies on Mmp2-null ( Mmp2−/−) mice and 2) clinical studies on patients with inactivating MMP2 gene mutations. Furthermore, we put forward the hypothesis that, when MMP-2 activity falls below baseline, the bioavailability of proinflammatory cytokines normally cleaved and inactivated by MMP-2 increases, leading to the production of cytokines and cardiac secretion of phospholipase A2activity into the circulation, which stimulate systemic inflammation that perturbs lipid metabolism in target organs. Finally, we suggest that insufficient understanding of the consequences of MMP-2 deficiency remains a major factor in the failure of MMP-2 inhibitor-based therapeutic approaches. This paucity of knowledge precludes our ability to effectively intervene in cardiovascular and noncardiovascular pathologies at the level of MMP-2.

Matrix Metalloproteinases in Bone Resorption, Remodeling, and Repair

Matrix metalloproteinases (MMPs) are the major protease family responsible for the cleavage of the matrisome (global composition of the extracellular matrix (ECM) proteome) and proteins unrelated to the ECM, generating bioactive molecules. These proteins drive ECM remodeling, in association with tissue-specific and cell-anchored inhibitors (TIMPs and RECK, respectively). In the bone, the ECM mediates cell adhesion, mechanotransduction, nucleation of mineralization, and the immobilization of growth factors to protect them from damage or degradation. Since the first description of an MMP in bone tissue, many other MMPs have been identified, as well as their inhibitors. Numerous functions have been assigned to these proteins, including osteoblast/osteocyte differentiation, bone formation, solubilization of the osteoid during bone resorption, osteoclast recruitment and migration, and as a coupling factor in bone remodeling under physiological conditions. In turn, a number of pathologies, associated with imbalanced bone remodeling, arise mainly from MMP overexpression and abnormalities of the ECM, leading to bone osteolysis or bone formation. In this review, we will discuss the functions of MMPs and their inhibitors in bone cells, during bone remodeling, pathological bone resorption (osteoporosis and bone metastasis), bone repair/regeneration, and emergent roles in bone bioengineering.