Marked relationship between matrix metalloproteinase 7 and brain atrophy in HIV infection

Serum levels of matrix metalloproteinase 2 and its inhibitor after tonic-clonic seizures

Damage to the blood-brain barrier (BBB) may result from on-going neuroinflammation, which can lead to leakage of blood components, such as leukocytes and serum proteins, into the brain, resulting in disturbed brain homeostasis. The aim of the project was to examine the involvement of modulatory proteins in the processes of BBB integration after epileptic seizures. We investigated serum changes in the levels of MMP-2 and MMP-7 and its inhibitors after seizures in epilepsy patients. Concentrations of these proteins were measured by ELISA in 50 patients at 1-3, 24, and 72 h after generalized tonic-clonic seizures and once in participants of the control group. The level of MMP-2 in serum was slightly higher after seizures (at 1-3 h time point), but the difference was not statistically significant. The levels of trombospondine (TSP) - 1 and - 2 were decreased at 1-3 h after seizures. The expression of TIMP-2 was increased 1 and 24 h after seizures. There were no significant changes in the level of α2-macroglobulin and MMP-7. Changes in the expression of both specific and non-specific inhibitors indicate the initiation of repair processes of the blood-brain barrier and improvement of its integrity. Since we performed serum analysis, further studies are necessary to investigate the correlation with the expression of the investigated markers in the brain. Perhaps this will allow for the identification of new biomarkers associated with epileptic seizures.

Relationship between Cerebrospinal Fluid Matrix Metalloproteinases Levels and Brain Amyloid Deposition in Mild Cognitive Impairment

This study aimed to explore whether cerebrospinal fluid (CSF) levels of matrix metalloproteinases (MMPs), and their inhibitors (TIMPs) were associated with brain amyloid deposition, cortical glucose metabolism, and white matter lesions (WMLs) in individuals with amnestic mild cognitive impairment (MCI). A total of 33 individuals with amnestic MCI (mean age, 75.6 years) underwent ¹¹C-Pittsburgh compound B positron emission tomography (PiB-PET), ¹⁸F-fluorodeoxyglucose positron emission tomography, magnetic resonance imaging or computed tomography, and CSF analysis. PET uptake of the frontal and temporoparietal lobes and posterior cingulate gyrus was assessed using the cerebellar cortex as the reference region. WMLs were assessed by the Fazekas scale. CSF levels of MMPs and TIMPs were measured with bead-based multiplex assays. After adjusting for covariates, multiple linear regression analysis showed that CSF levels of MMP-2 were negatively correlated with global PiB uptake (p = 0.035), especially in the parietotemporal lobe and posterior cingulate gyrus (p = 0.016 and p = 0.041, respectively). Moreover, CSF levels of MMP-7 were positively correlated with the severity of WMLs (p = 0.033). CSF levels of MMP-2 and MMP-7 are associated with brain amyloid deposition and severity of WMLs, respectively. These findings provide valuable insights into the role of MMPs in amyloid β catabolism and blood-brain barrier integration at the MCI stage.

Impact of Plasma IP-10/CXCL10 and RANTES/CCL5 Levels on Neurocognitive Function in HIV Treatment-Naive Patients

Immune activation, which is accompanied by the production of proinflammatory cytokines, is a strong predictor of disease progression in HIV infection. Inflammation is critical in neuronal damage linked to HIV-associated neurocognitive disorders. We examined the relationship between plasma cytokine levels and deficits in neurocognitive function. Multiplex profiling by Luminex^® technology was used to quantify 27 cytokines/chemokines from 139 plasma samples of people living with HIV (PLWH). The relationship of plasma cytokine markers, clinical parameters, and cognitive impairment, was assessed using Spearman correlations. Partial least squares regression and variable importance in projection scores were used for further evaluation of the association. Forty-nine (35.3%) participants exhibited neurocognitive impairment based on a global deficit score (GDS) of at least 0.5 and 90 (64.7%) were classified as nonimpaired. Twenty-three (16.5%) initiated on combination antiretroviral therapy for 4 weeks before cognitive assessment and 116 (83.5%) were not on treatment. We identified five proinflammatory cytokines that were significant predictors of GDS namely, IP-10 (β = 0.058; p = .007), RANTES (β = 0.049; p = .005), IL-2 (β = 0.047, p = .006), Eotaxin (β = 0.042, p = .003), and IL-7 (β = 0.039, p = .003). IP-10 and RANTES were the strongest predictors of GDS. Both cytokines correlated with plasma viral load and lymphocyte proviral load and were inversely correlated with CD4⁺ T cell counts. IP-10 and RANTES formed a separate cluster with highest proximity. Study findings describe novel associations among IP-10, RANTES, cognitive status, plasma viral load, and cell-associated viral load.

Increased matrix metalloproteinase levels and perineuronal net proteolysis in the HIV-infected brain; relevance to altered neuronal population dynamics

HIV-associated neurocognitive disorders (HAND) continue to persist despite effective control of viral replication. Although the mechanisms underlying HAND are poorly understood, recent attention has focused on altered neuronal population activity as a correlate of impaired cognition. However, while alterations in neuronal population activity in the gamma frequency range are noted in the setting of HAND, the underlying mechanisms for these changes is unclear. Perineuronal nets (PNNs) are a specialized extracellular matrix that surrounds a subset of inhibitory neurons important to the expression of neuronal oscillatory activity. In the present study, we observe that levels of PNN-degrading matrix metalloproteinases (MMPs) are elevated in HIV-infected post-mortem human brain tissue. Furthermore, analysis of two PNN components, aggrecan and brevican, reveals increased proteolysis in HIV-infected brains. In addition, local field potential recordings from ex vivo mouse hippocampal slices demonstrate that the power of carbachol-induced gamma activity is increased following PNN degradation. Together, these results provide a possible mechanism whereby increased MMP proteolysis of PNNs may stimulate altered neuronal oscillatory activity and contribute to HAND symptoms.

HIV-1 Tat promotes astrocytic release of CCL2 through MMP/PAR-1 signaling

The HIV-1 protein Tat is continually released by HIV-infected cells despite effective combination antiretroviral therapies (cART). Tat promotes neurotoxicity through enhanced expression of proinflammatory molecules from resident and infiltrating immune cells. These molecules include matrix metalloproteinases (MMPs), which are pathologically elevated in HIV, and are known to drive central nervous system (CNS) injury in varied disease settings. A subset of MMPs can activate G-protein coupled protease-activated receptor 1 (PAR-1), a receptor that is highly expressed on astrocytes. Although PAR-1 expression is increased in HIV-associated neurocognitive disorder (HAND), its role in HAND pathogenesis remains understudied. Herein, we explored Tat's ability to induce expression of the PAR-1 agonists MMP-3 and MMP-13. We also investigated MMP/PAR-1-mediated release of CCL2, a chemokine that drives CNS entry of HIV infected monocytes and remains a significant correlate of cognitive dysfunction in the era of cART. Tat exposure significantly increased the expression of MMP-3 and MMP-13. These PAR-1 agonists both stimulated the release of astrocytic CCL2, and both genetic knock-out and pharmacological inhibition of PAR-1 reduced CCL2 release. Moreover, in HIV-infected post-mortem brain tissue, within-sample analyses revealed a correlation between levels of PAR-1-activating MMPs, PAR-1, and CCL2. Collectively, these findings identify MMP/PAR-1 signaling to be involved in the release of CCL2, which may underlie Tat-induced neuroinflammation.

Impact of variants of MMP-7(-181A>G) gene in susceptibility to the development of HIV-associated neurocognitive disorder and its severity

The HIV-1-induced neurological toxicity has been associated with the deficiency of matrix metalloproteinases. Tat protein of HIV up regulates MMP-7 release and activation, leading to neurotoxicity. The SNP -181A>G of MMP-7 is known to have functional effects on its promoter activity. Therefore, we aimed to evaluate the association of variants of MMP-7 -181A>G gene in HIV-associated neurocognitive disorder (HAND). In the present case-control study, we recruited 50 HIV-infected individuals with HAND, 130 HIV-infected individuals without HAND and 150 unrelated healthy individuals. Polymorphism for MMP-7 -181A>G gene was genotyped by PCR-RFLP method. Frequency of -181GG and G allele of MMP-7 did not differ significantly between patients with HAND and without HAND (8.0% vs 13.1%, p = 0.22 and 31% vs 38.1%, p = 0.21). Individuals with -181 AG, -181GG genotype, and G allele of MMP-7 were found to have reduced the risk of development of HAND but not significant (50.0% vs 51.9%, p = 0.09, OR = 0.54; 13.1% vs 19.0%, p = 0.33, OR = 0.71 and 38.1% vs 44.9%, p = 0.09, OR = 0.75). Individuals in early HIV disease stage having -181AG genotype and -181AG + GG combined genotype of MMP-7 were not associated with the development of HAND (OR = 1.27, p = 0.25 and OR = 1.25, p = 0.17). Tobacco and alcohol consumption among individuals with any genotype of MMP-7 was not associated with the risk of development of HAND. In conclusion, individuals with -181GG genotype and G allele had no impact on susceptibility to the development of HAND and its severity.

Determinants of HIV-induced brain changes in three different periods of the early clinical course: A data mining analysis

To inform an understanding of brain status in HIV infection, quantitative imaging measurements were derived at structural, microstructural and macromolecular levels in three different periods of early infection and then analyzed simultaneously at each stage using data mining. Support vector machine recursive feature elimination was then used for simultaneous analysis of subject characteristics, clinical and behavioral variables, and immunologic measures in plasma and CSF to rank features associated with the most discriminating brain alterations in each period. The results indicate alterations beginning in initial infection and in all periods studied. The severity of immunosuppression in the initial virus host interaction was the most highly ranked determinant of earliest brain alterations. These results shed light on the initial brain changes induced by a neurotropic virus and their subsequent evolution. The pattern of ongoing alterations occurring during and beyond the period in which virus is suppressed in the systemic circulation supports the brain as a viral reservoir that may preclude eradication in the host. Data mining capabilities that can address high dimensionality and simultaneous analysis of disparate information sources have considerable utility for identifying mechanisms underlying onset of neurological injury and for informing new therapeutic targets.

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The brain was examined in initial stages of HIV using imaging and data mining.

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Brain alterations were identified in all studied periods of the early course.

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Severity of immunosuppression was the highest ranked determinant of onset.

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MMP-1 and CD33+CD36+ monocytes were identified as determinants in every period.

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The brain may represent an early reservoir that precludes viral eradication.

Dynamic nature of the p75 neurotrophin receptor in response to injury and disease

Neurotrophins and their respective tropomyosin related kinase (Trk) receptors (TrkA, TrkB, and TrkC) and the p75 neurotrophin receptor (p75(NTR)) play a fundamental role in the development and maintenance of the nervous system making them important targets for treatment of neurodegenerative diseases. Whereas Trk receptors are directly activated by specific neurotrophins, the p75(NTR) is a multifunctional receptor that exerts its effects via heterodimeric interactions with TrkA, TrkB, TrkC, sortilin or the Nogo receptor to regulate a wide array of cellular functions. By partnering with different receptors the p75(NTR) regulates binding of mature versus pro-neurotrophins and activation of different signaling pathways with outcomes ranging from growth and survival to cell death. While the developmental downregulation of the p75(NTR) has raised questions regarding its role in the mature nervous system, recent data have revealed widespread expression of low levels, a role in synaptic plasticity and adult neurogenesis and upregulation in response to injury or disease. Studies are needed to better understand these processes, particularly in the damaged nervous system, but will be complicated by expression of p75(NTR) on immune cells including macrophages and microglia that are intimately involved in disease and repair processes. Recent approaches that regulate p75(NTR) function with small non-peptide ligands have demonstrated potent neuroprotection in models of injury and neurodegenerative diseases that highlight the importance of the p75(NTR) as a therapeutic target. Future studies hold the promise of revealing a wealth of information on the multifaceted actions of the p75(NTR) that will inform the design of new neurotrophin-based therapies.

Noncontiguous Protein Interaction Domains in Osteopontin Contribute to Enhance HIV-1 Replication

Osteopontin (OPN) is a proinflammatory cytokine produced by T-cells, macrophages, osteoclasts, and several other cell types, which confers immunity to many intracellular pathogens. OPN was first identified as an early marker of cellular activation of T-lymphocytes and subsequently was shown to play a role in cancer through its ability to promote cell survival and inflammation. OPN levels are elevated in the plasma and cerebrospinal fluid of HIV-infected individuals and even more so in those suffering from HIV-related neurocognitive impairment. The infiltration of monocytes and macrophages both infected and uninfected into the brain is the first step in HIV pathogenesis of the central nervous system. Inhibition of OPN in macrophages significantly impairs HIV replication. In an effort to identify and understand the role of OPN in the neuropathogenesis of HIV infection, we are using a combination of in vitro, ex vivo and in vivo approaches. In this study we have used a molecular approach and a surrogate cell culture model to identify the domains of OPN that are required to enhance HIV replication. We found that N- and C-terminal fragments, encoding multiple motifs including sequences involved in binding integrins and CD44, a domain know to promote adhesion contribute to OPN's ability to increase HIV replication. Use of inhibitors against c-Jun N-terminal kinase (JNK) and phosphoinositide 3-kinase (PI-3K) impaired the ability of OPN to increase the integrin subunit 1 or CD29 on the surface of HIV-infected and bystander cells. These results suggest that multiple OPN-regulated cellular pathways are commandeered by HIV to promote productive replication and cell-to-cell spread.

Matrix metalloproteinase levels in early HIV infection and relation to in vivo brain status

Matrix metalloproteinases (MMPs) have been implicated in human immunodeficiency virus (HIV)-associated neurological injury; however, this relationship has not been studied early in infection. Plasma levels of MMP-1, MMP-2, MMP-7, MMP-9, and MMP-10 measured using Luminex technology (Austin, TX, USA) were compared in 52 HIV and 21 seronegative participants of the Chicago Early HIV Infection study. MMP levels were also examined in HIV subgroups defined by antibody reactivity, viremia, and antiretroviral status, as well as in available cerebrospinal fluid (CSF) samples (n = 9). MMPs were evaluated for patterns of relationship to cognitive function and to quantitative magnetic resonance measurements of the brain derived in vivo. Plasma MMP-2 levels were significantly reduced in early HIV infection and correlated with altered white matter integrity and atrophic brain changes. MMP-9 levels were higher in the treated subgroup than in the naïve HIV subgroup. Only MMP-2 and MMP-9 were detected in the CSF; CSF MMP-2 correlated with white matter integrity and with volumetric changes in basal ganglia. Relationships with cognitive function were also identified. MMP-2 levels in plasma and in CSF correspond to early changes in brain structure and function. These findings establish a link between MMPs and neurological status previously unidentified in early HIV infection.

Expression of substance P, neurokinin-1 receptor and immune markers in the brains of individuals with HIV-associated neuropathology

The tachykinin neuropeptide substance P (SP) has an important signaling role in both the nervous and the immune systems. Two naturally occurring variants of the neurokinin-1 receptor (NK1R) mediate the effects of SP, full-length receptor (NK1R-F) and a truncated form (NK1R-T) that lacks 96 amino acid residues at the C-terminus. We previously reported decreased expression of the NK1R-F in the CNS of HIV-positive individuals in comparison to HIV-negative control subjects. There were no differences in the expression of the NK1R-T in the same groups. In the current study, we quantified the expressions of SP precursor mRNA preprotachykinin (TAC1), NK1R (full and truncated forms), viral load (HIV-gag) and several proinflammatory and immune markers (CD4, CCR5, CXCR4, fractalkine, IL-6, IL-10, CCL2, CCL20 and CD163) in the frontal cortex of autopsied brains from HIV-1-positive individuals with or without HIV-associated neuropathology. The expressions of SP and, to lesser extent, NK1R-F were decreased while the expressions of CXCR4, CCR5 and CCL2 were increased in CNS of individuals with HIV-associated neuropathology. There was no change in HIV loads associated with neuropathology; however, we found a positive correlation between viral loads and the expression of haptoglobin-hemoglobin scavenger receptor CD163. An analysis of CSF from corresponding samples demonstrated an increase in proinflammatory markers (CCL2 MIP-1α and MIP-1β) associated with neuropathology. Although our data confirm the overall inflammatory nature of HIV-associated neuropathology, we observed a decrease in the expression of SP and NK1R-F, which is also associated with other forms of neuroinflammation.

Matrix metalloproteinases and their tissue inhibitors in serum and cerebrospinal fluid of children with Japanese encephalitis virus infection

The expression of matrix metalloproteinases (MMPs) is tightly regulated at the level of gene transcription, conversion of pro-enzyme to active MMPs, and the action of tissue inhibitors of metalloproteinases (TIMPs). The present study aimed to investigate the expression of some specific MMPs (2, 7, 9) and TIMPs (1, 2, 3) in serum and cerebrospinal fluid (CSF) of children with Japanese encephalitis virus (JEV) infection. Serum and CSF levels of MMPs and TIMPs in children with JEV infection and disease control (DC) were compared. The CSF and serum concentrations of MMP-2, TIMP-2 and TIMP-3 were significantly higher in children with JEV infection compared to DC. The concentration of MMP-9 in serum was significantly higher in children with JEV infection than in the DC and healthy control (HC), while in the CSF, no significant difference was observed compared to DC. The MMP-7 serum concentration was significantly higher in children with JEV infection compared to HC, but no significant difference was observed compared to DC. MMP-7 concentration was undetectable in CSF in both groups. The TIMP-1 CSF concentration was significantly higher, while the serum concentration was significantly lower, in children with JEV infection compared to DC. No correlation was found between the levels of each biomolecule measured in CSF and serum, suggesting that the levels in CSF represent local production within the CNS rather than production in the periphery. We also observed leucocytosis, mononuclear pleocytosis and elevated protein concentrations in the CSF of children with JEV infection compared to DC.

Human matrix metalloproteinases: an ubiquitarian class of enzymes involved in several pathological processes

Human matrix metalloproteinases (MMPs) belong to the M10 family of the MA clan of endopeptidases. They are ubiquitarian enzymes, structurally characterized by an active site where a Zn(2+) atom, coordinated by three histidines, plays the catalytic role, assisted by a glutamic acid as a general base. Various MMPs display different domain composition, which is very important for macromolecular substrates recognition. Substrate specificity is very different among MMPs, being often associated to their cellular compartmentalization and/or cellular type where they are expressed. An extensive review of the different MMPs structural and functional features is integrated with their pathological role in several types of diseases, spanning from cancer to cardiovascular diseases and to neurodegeneration. It emerges a very complex and crucial role played by these enzymes in many physiological and pathological processes.

Platelet decline as a predictor of brain injury in HIV infection

An association between platelet decline and increased risk of progression to dementia has been observed in an advanced HIV infection cohort study. This investigation evaluated the prognostic significance of platelet decline for dementia, for psychomotor slowing, and for brain injury, as quantified in vivo, in a much larger population of HIV+ men. Platelet counts and neurocognitive data were available from biannual visits of 2,125 HIV+ men participating in the prospective, Multicenter AIDS Cohort Study from 1984 to 2009. Brain volumetric data were also available from an imaging substudy of 83 seropositive participants aged 50 and older. The association of platelet counts with neurocognitive outcome was assessed using Cox proportional hazard models where change in platelet count from baseline was a time-updated variable. Marked platelet decline was associated with increased risk of dementia in univariate analysis (hazard ratio [HR] = 2.5, 95% confidence interval [CI] = 1.8-3.5), but not after adjustment for CD4 cell count, HIV viral load, age, study site, hemoglobin, race, education, smoking, and alcohol use (HR = 1.4, 95% CI = 0.78-2.5). Platelet decline did not predict psychomotor slowing in either univariate (HR = 0.79, 95% CI = 0.58-1.08) or multivariate (HR = 1.10, 95% CI = 0.73-1.67) analysis. Analysis of brain volumetric data, however, indicated a relationship between platelet decline and reduced gray matter volume fraction in univariate (p = 0.06) and multivariate (p < 0.05) analyses. Platelet decline was not an independent predictor of dementia or psychomotor slowing, after adjusting for stage of disease. Findings from a structural brain imaging substudy of older participants, however, support a possible relationship between platelet decline and reduced gray matter.