Cathepsin S deficiency results in abnormal accumulation of autophagosomes in macrophages and enhances Ang II-induced cardiac inflammation

Longitudinal follow-up of autophagy and inflammation in brain of APPswePS1dE9 transgenic mice

Background

In recent years, studies have sought to understand the mechanisms involved in the alteration of autophagic flux in Alzheimer's disease (AD). Alongside the recent description of the impairment of lysosomal acidification, we wanted to study the relationships between inflammation and autophagy, two physiological components deregulated in AD. Therefore, a longitudinal study was performed in APPswePS1dE9 transgenic mice at three, six and twelve months of age.

Methods

Autophagic markers (Beclin-1, p62 and LC3) and the activation of mammalian Target of Rapamycin (mTOR) signaling pathway were quantified by western blot. Cytokine levels (IL-1β, TNF-α and IL-6) were measured by ELISA. Transmission electron microscopy was performed to detect autophagic vacuoles. Mann-Whitney tests were used to compare wild-type (WT) versus APPswePS1dE9 mice. Longitudinal changes in parameters were analyzed with a Kruskal-Wallis test followed by a post-hoc Dunn’s test. Correlation between two parameters was assessed using a Spearman test.

Results

Compared to 12-month old WT mice, 12-month old APPswePS1dE9 mice had higher levels of IL-1β and TNF-α, a greater inhibition of the mTOR signaling pathway and lower levels of Beclin-1 expression both in cortex and hippocampus. Regarding the relationship of the various parameters in 12-month old APPswePS1dE9 mice, Beclin-1 rates were positively correlated with IL-1β and TNF-α levels. And, on the contrary, TNF-α levels were inversely correlated with the levels of mTOR activation. Altogether, these results suggest that inflammation could induce autophagy in APPswePS1dE9 mice. However, these transgenic mice displayed a large accumulation of autophagic vesicles within dystrophic neurons in cortex and hippocampus, indicating a terminal failure in the autophagic process.

Conclusions

This first demonstration of relationships between inflammation and autophagy in in vivo models of AD should be taken into account in new therapeutic strategies to prevent inflammation and/or stimulate autophagy in advanced neurodegenerative process such as AD.

Impairment of autophagy in the central nervous system during lipopolysaccharide-induced inflammatory stress in mice

Background

Current evidence suggests a central role for autophagy in many neurodegenerative diseases including Alzheimer’s disease, Huntington’s disease, Parkinson’s disease and amyotrophic lateral sclerosis. Furthermore, it is well admitted that inflammation contributes to the progression of these diseases. Interestingly, crosstalks between autophagy and inflammation have been reported in vitro and at the peripheral level such as in Crohn’s disease. However, the impact of systemic inflammation on autophagic components in the brain remains to be documented. Therefore, this study monitored autophagy markers after acute and chronic lipopolysaccharide (LPS)-induced inflammatory stress in mice.

Results

We showed that acute inflammation, 24 h post-intraperitoneal 10 mg/kg LPS, substantially increased cytokine production (Interleukin(IL)-1β, Tumor necrosis factor (TNF)-α and IL-6), decreased the levels of autophagy markers (Beclin-1, p62 and LC3 II) and reduced p70S6K activation in cortex and hippocampus. In hippocampus, IL-1β levels and LC3 II expression were positively and highly correlated and a negative correlation was noted between TNF-α levels and p70S6K activation. Chronic inflammation by injection of 0.5 mg/kg LPS every three days during three months led to a moderate IL-1β production and decreased TNF-α levels. Interestingly, Beclin-1 and LC3 II levels decreased while those of p62 increased. Cortical IL-1β levels positively correlated with Beclin-1 and LC3 II and on the contrary inversely correlated with p62.

Conclusion

The present study is the first showing links between IL-1β-mediated inflammation and autophagy in the brain. It could open to new therapeutic strategies in brain diseases where regulation impairment of inflammation and autophagy progress with the severity of diseases.

The Notch γ-secretase inhibitor ameliorates kidney fibrosis via inhibition of TGF-β/Smad2/3 signaling pathway activation

Kidney fibrosis is a common feature of chronic kidney disease (CKD). A recent study suggests that abnormal Notch signaling activation contributes to the development of renal fibrosis. However, the molecular mechanism that regulates this process remains unexplored. Unilateral ureteral obstruction (UUO) or sham-operated C57BL6 mice (aged 10 weeks) were randomly assigned to receive dibenzazepine (DBZ, 250 μg/100g/d) or vehicle for 7 days. Histologic examinations were performed on the kidneys using Masson's trichrome staining and immunohistochemistry. Real-time PCR and western blot analysis were used for detection of mRNA expression and protein phosphorylation. The expression of Notch 1, 3, and 4, Notch intracellular domain (NICD), and its target genes Hes1 and HeyL were upregulated in UUO mice, while the increase in NICD protein was significantly attenuated by DBZ. After 7 days, the severity of renal fibrosis and expression of fibrotic markers, including collagen 1α1/3α1, fibronectin, and α-smooth muscle actin, were markedly increased in UUO compared with sham mice. In contrast, administration of DBZ markedly attenuated these effects. Furthermore, DBZ significantly inhibited UUO-induced expression of transforming growth factor (TGF)-β, phosphorylated Smad 2, and Smad 3. Mechanistically, Notch signaling activation in tubular epithelial cells enhanced fibroblast proliferation and activation in a coculture experiment. Our study provides evidence that Notch signaling is implicated in renal fibrogenesis. The Notch inhibitor DBZ can ameliorate this process via inhibition of the TGF-β/Smad2/3 signaling pathway, and might be a novel drug for preventing chronic kidney disease.

Inhibition of platelet activation by clopidogrel prevents hypertension-induced cardiac inflammation and fibrosis

Purpose

Platelets are essential for primary hemostasis; however, platelet activation also plays an important proinflammatory role. Inflammation promotes the development of cardiac fibrosis and heart failure induced by hypertension. In this study, we aimed to determine whether inhibiting platelet activation using clopidogrel could inhibit hypertension-induced cardiac inflammation and fibrosis.

Methods

Using a mouse model of angiotensin II (Ang II) infusion (1,500 ng/[kg·min] for 7 days), we determined the role of platelet activation in Ang II infusion-induced cardiac inflammation and fibrosis using a P2Y₁₂ receptor inhibitor, clopidogrel (50 mg/[kg·day]).

Results

CD41 staining showed that platelets accumulated in Ang II-infused hearts. Clopidogrel treatment inhibited Ang II infusion-induced accumulation of α-SMA⁺ myofibroblasts and cardiac fibrosis (4.17 ± 1.26 vs. 1.46 ± 0.81, p < 0.05). Infiltration of inflammatory cells, including Mac-2⁺ macrophages and CD45⁺Ly6G⁺ neutrophils (30.38 ± 4.12 vs. 18.7 ± 2.38, p < 0.05), into Ang II-infused hearts was also suppressed by platelet inhibition. Real-time PCR and immunohistochemical staining showed that platelet inhibition significantly decreased the expression of interleukin-1β and transforming growth factor-β. Acute injection of Ang II or PE stimulated platelet activation and platelet-leukocyte conjugation, which were abolished by clopidogrel treatment.

Conclusion

Thus, inhibition of platelet activation by clopidogrel prevents cardiac inflammation and fibrosis in response to Ang II. Taken together, our results indicate Ang II infusion-induced hypertension stimulated platelet activation and platelet-leukocyte conjugation, which initiated inflammatory responses that contributed to cardiac fibrosis.

Adiponectin suppresses angiotensin II-induced inflammation and cardiac fibrosis through activation of macrophage autophagy

Previous studies have indicated that adiponectin (APN) protects against cardiac remodeling, but the underlying mechanism remains unclear. The present study aimed to elucidate how APN regulates inflammatory responses and cardiac fibrosis in response to angiotensin II (Ang II). Male APN knockout (APN KO) mice and wild-type (WT) C57BL/6 littermates were sc infused with Ang II at 750 ng/kg per minute. Seven days after Ang II infusion, both APN KO and WT mice developed equally high blood pressure levels. However, APN KO mice developed more severe cardiac fibrosis and inflammation compared with WT mice. This finding was demonstrated by the up-regulation of collagen I, α-smooth muscle actin, IL-1β, and TNF-α and increased macrophage infiltration in APN KO mice. Moreover, there were substantially fewer microtubule-associated protein 1 light chain 3-positive autophagosomes in macrophages in the hearts of Ang II-infused APN KO mice. Additional in vitro studies also revealed that globular APN treatment induced autophagy, inhibited Ang II-induced nuclear factor-κB activity, and enhanced the expression of antiinflammatory cytokines, including IL-10, macrophage galactose N-acetyl-galactosamine specific lectin 2, found in inflammatory zone 1, and type-1 arginase in macrophages. In contrast, APN-induced autophagy and antiinflammatory cytokine expression was diminished in Atg5-knockdown macrophages or by Compound C, an inhibitor of adenosine 5'-monophosphate-activated protein kinase. Our study indicates that APN activates macrophage autophagy through the adenosine 5'-monophosphate-activated protein kinase pathway and suppresses Ang II-induced inflammatory responses, thereby reducing the extent of cardiac fibrosis.

Mitochondrial KATP channel involvement in angiotensin II-induced autophagy in vascular smooth muscle cells

Autophagy has emerged as a powerful process in the response to cellular injury. The present study was designed to investigate signal transduction pathways in angiotensin II (Ang II)-induced autophagy. Rat vascular smooth muscle cells (VSMCs) were stimulated with different doses of Ang II (10(-9)-10(-5) mol/L) for different time periods (6-72 h). Incubation with Ang II increased the production of reactive oxygen species (ROS), increased the LC3-II to LC3-I ratio, increased beclin-1 expression, and decreased SQSTM1/p62 expression in a dose- and time-dependent manner. In addition, Ang II increased autophagosome formation. Increased ROS production induced by Ang II was inhibited by Ang II type 1 receptor (AT1) blockers (Olmesartan and Candesartan, ARB), a NADPH Oxidase inhibitor (apocynin), and mitochondrial KATP channels inhibitor (5-hydroxydecanoate, 5HD). Ang II (10(-7) mol/L, 48 h)-induced increase in the LC3-II to LC3-I ratio, the formation of autophagosomes, expression of beclin-1 and decrease in the expression of SQSTM1/p62 were also inhibited by pretreatment with 3-methyladenine or bafilomycin A1 (inhibitors of autophagy), olmesartan and candesartan (in dose-dependent manners), apocynin, 5HD, and siRNA Atg5. Our results indicate that Ang II increases autophagy levels via activation of AT1 receptor and NADPH oxidase. Mitochondrial KATP channels also play an important role in Ang II-induced autophagy. Our results may provide a new strategy for treatment of cardiovascular diseases with Ang II.

Atg5 deficiency-mediated mitophagy aggravates cardiac inflammation and injury in response to angiotensin II

OBJECTIVE

Hypertension induces end-organ damage through inflammation, and autophagy plays a crucial role in the regulation of cellular homeostasis. In the present study, we aimed to define the role of autophagy in the development of inflammation and cardiac injury induced by angiotensin II (Ang II).

METHODS AND RESULTS

Autophagy protein 5 (Atg5) haplodeficiency (Atg5(+/-)) and age-matched wild-type (WT) C57BL/6J mice were infused with Ang II (1500 ng/kg/min) or saline for 7 days. Heart sections were stained with hematoxylin and eosin (H&E), Masson's trichrome, and immunohistochemical stains. Cytokine and LC3 levels were measured using real-time PCR or western blot analysis. After Ang II infusion, the WT mice exhibited marked macrophage accumulation, cytokine expression, and reactive oxygen species (ROS) production compared with saline-infused controls. However, these effects induced by Ang II infusion were aggravated in Atg5(+/-) mice. These effects were associated with Atg5-mediated impaired autophagy, accompanied by increased production of ROS and activation of nuclear factor-κB (NF-κB) in macrophages. Finally, increased cardiac inflammation in Atg5 haplodeficient mice was associated with increased cardiac fibrosis.

CONCLUSION

Atg5 deficiency-mediated autophagy increases ROS production and NF-κB activity in macrophages, thereby contributing to cardiac inflammation and injury. Thus, improving autophagy may be a novel therapeutic strategy to ameliorate hypertension-induced inflammation and organ damage.

The role of autophagy in the intracellular survival of Campylobacter concisus

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Autophagy is involved in host clearance of Campylobacter concisus.

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C. concisus can be found within Campylobacter-containing vacuoles.

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Some C. concisus strains may subvert autophagy to survive intracellularly.

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Proteins specific to invasive C. concisus may be involved in autophagy subversion.

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Proteins of interest in C. concisus infection: ATG4B, ATG7, ATG9B, CTSD and LAMP1.

Campylobacter concisus is an emerging pathogen that has been associated with gastrointestinal diseases. Given the importance of autophagy for the elimination of intracellular bacteria and the subversion of this process by pathogenic bacteria, we investigated the role of autophagy in C. concisus intracellular survival. Gentamicin protection assays were employed to assess intracellular levels of C. concisus within Caco-2 cells, following autophagy induction and inhibition. To assess the interaction between C. concisus and autophagosomes, confocal microscopy, scanning electron microscopy, and transmission electron microscopy were employed. Expression levels of 84 genes involved in the autophagy process were measured using qPCR. Autophagy inhibition resulted in two- to four-fold increases in intracellular levels of C. concisus within Caco-2 cells, while autophagy induction resulted in a significant reduction in intracellular levels or bacterial clearance. C. concisus strains with low intracellular survival levels showed a dramatic increase in these levels upon autophagy inhibition. Confocal microscopy showed co-localization of the bacterium with autophagosomes, while transmission electron microscopy identified intracellular bacteria persisting within autophagic vesicles. Further, qPCR showed that following infection, 13 genes involved in the autophagy process were significantly regulated, and a further five showed borderline results, with an overall indication towards a dampening effect exerted by the bacterium on this process. Our data collectively indicates that while autophagy is important for the clearance of C. concisus, some strains may manipulate this process to benefit their intracellular survival.

Cathepsin S-mediated autophagic flux in tumor-associated macrophages accelerate tumor development by promoting M2 polarization

BACKGROUND

Tumor-associated macrophages (TAMs) are the major component of tumor-infiltrating leukocytes. TAMs are heterogeneous, with distinct phenotypes influenced by the microenvironment surrounding tumor tissues, but relatively little is known about the key molecular in these cells that contribute to malignant phenotypes. Autophagic activity is a critical factor in tumor development that contributes to enhancing cellular fitness and survival in the hostile tumor microenvironment. However, the molecular basis and relations between autophagy and TAMs polarization remain unclear.

METHODS

Cathepsin S (Cat S) expression was analyzed in human colon carcinoma and normal colon tissues. In vivo effects were evaluated using PancO2 subcutaneous tumor model and SL4 hepatic metastasis model. Immunofluorescence staining, flow cytometry and real-time PCR were done to examine TAMs polarization. Western blotting assay, transmission electron microscopy, mCherry-GFP-LC3 transfection and DQ-BSA degradation assays were carried out to determine its role in regulating autophagy.

RESULTS

In the present study, we showed that the enhanced expression of Cat S correlated with the severity of histologic grade as well as clinical stage, metastasis, and recurrence, which are known indicators of a relatively poor prognosis of human colon carcinoma. Cat S knockout led to decreased tumor growth and metastasis. Moreover, Cat S knockout inhibited M2 macrophage polarization during tumor development. We further demonstrated that Cat S was required for not only autophagic flux but also the fusion processes of autophagosomes and lysosomes in TAMs. Importantly, we found that Cat S contributed to tumor development by regulating the M2 phenotype of TAMs through the activation of autophagy.

CONCLUSIONS

These results indicated that Cat S-mediated autophagic flux is an important mechanism for inducing M2-type polarization of TAMs, which leads to tumor development. These data provide strong evidence for a tumor-promoting role of autophagy in TAMs and suggest Cat S could be a potential target for cancer therapy.

Serum lipocalin-2, cathepsin S and chemerin levels and nonalcoholic fatty liver disease

Several novel circulating adipokines are associated with insulin resistance and inflammation. Little information exists in NAFLD about three recently recognized adipokines lipocalin-2, cathepsin S and chemerin. To assess the relationship between serum lipocalin-2, cathepsin S and chemerin levels and the development of non-alcoholic fatty liver in Chinese subjects, we measured serum lipocalin-2, cathepsin S and chemerin levels in 903 Chinese subjects by ELISA. Among the study population, 436 patients are with B-mode ultrasound-proven NAFLD and 467 controls. Levels of lipocalin-2, but not cathepsin S and chemerin, were significantly elevated in NAFLD versus control [lipocalin-2, 89.67 ± 4.47 vs. 68.70 ± 3.65 ng/mL (p < 0.001)]. After stepwise linear regression analysis adjusting for potential cofounders, further revealed that serum lipocalcin-2 was an independent predictor of NAFLD in whole cohort (standardized β = 0.114, t = 2.347, p = 0.02). Lipocalin-2 levels correlated with insulin resistance (homeostasis model assessment of insulin resistance) and inflammation (CRP) in whole cohorts and NAFLD, whereas cathepsin S and chemerin only correlated positively with insulin resistance and inflammation in whole cohorts. Our results indicated that circulating lipocalin-2, produced by adipocytes, are elevated and may contribute to the development of NAFLD. Serum lipocalin-2, which correlates with inflammation and insulin resistance, may have a direct pathogenic link to disease progression.

Notch γ-secretase inhibitor dibenzazepine attenuates angiotensin II-induced abdominal aortic aneurysm in ApoE knockout mice by multiple mechanisms

Abdominal aortic aneurysm (AAA) is a life-threatening aortic disease in the elderly. Activation of Notch1 pathway plays a critical role in the development of AAA, but the underlying mechanisms remain poorly understood. In the present study, we explored the mechanisms by which Notch1 activation regulates angiotensin II (Ang II)-induced AAA formation and evaluated the therapeutic potential of a new Notch γ-secretase inhibitor, dibenzazepine (DBZ), for the treatment of AAA. Apolipoprotein E knockout (Apo E(-/-)) mice infused for 4 weeks with Ang II (1000 ng/kg/min, IP) using osmotic mini-pumps were received an intraperitoneal injection of either vehicle or 1 mg/kg/d DBZ. Notch1 signaling was activated in AAA tissue from both Ang II-infused Apo E(-/-) mice and human undergoing AAA repair in vivo, with increased expression of Notch intracellular domain (NICD) and its target gene Hes1, and this effect was effectively blocked by DBZ. Moreover, infusion of Ang II markedly increased the incidence and severity of AAA in Apo E(-/-) mice. In contrast, inhibition of Notch activation by DBZ prevented AAA formation in vivo. Furthermore, DBZ markedly prevented Ang II-stimulated accumulation of macrophages and CD4(+) T cells, and ERK-mediated angiogenesis, simultaneously reversed Th2 response, in vivo. In conclusion, these findings provide new insight into the multiple mechanisms of Notch signaling involved in AAA formation and suggest that γ-secretase inhibitor DBZ might be a novel therapeutic drug for treating AAAS.

Cathepsins: a new culprit behind abdominal aortic aneurysm

Abdominal aortic aneurysm (AAA) is a fatal disease defined as an abdominal aortic diameter of 3.0 cm or more, where the abdominal aorta exceeds the normal diameter by more than 50%. Histopathological changes of AAA mainly include extracellular matrix (ECM) remodeling at the abdominal aorta wall, but there is lack of specific drugs to treat AAA. Recent studies have reported that lysosomal cathepsins could induce vascular remodeling and AAA formation by regulating vascular inflammation, medial smooth muscle cell apoptosis, neovascularization, and protease expression. Thus, cathepsins are expected to become a new therapeutic target for AAA treatment.

Inhibition of cathepsin S produces neuroprotective effects after traumatic brain injury in mice

Cathepsin S (CatS) is a cysteine protease normally present in lysosomes. It has long been regarded as an enzyme that is primarily involved in general protein degradation. More recently, mounting evidence has shown that it is involved in Alzheimer disease, seizures, age-related inflammatory processes, and neuropathic pain. In this study, we investigated the time course of CatS protein and mRNA expression and the cellular distribution of CatS in a mouse model of traumatic brain injury (TBI). To clarify the roles of CatS in TBI, we injected the mice intraventricularly with LHVS, a nonbrain penetrant, irreversible CatS inhibitor, and examined the effect on inflammation and neurobehavioral function. We found that expression of CatS was increased as early as 1 h after TBI at both protein and mRNA levels. The increased expression was detected in microglia and neurons. Inhibition of CatS significantly reduced the level of TBI-induced inflammatory factors in brain tissue and alleviated brain edema. Additionally, administration of LHVS led to a decrease in neuronal degeneration and improved neurobehavioral function. These results imply that CatS is involved in the secondary injury after TBI and provide a new perspective for preventing secondary injury after TBI.

Chitosan oligosaccharides block LPS-induced O-GlcNAcylation of NF-κB and endothelial inflammatory response

It is known that chitosan oligosaccharides (COS) suppress LPS-induced vascular endothelial inflammatory response by mechanism involving NF-κB blockade. It remains unknown how COS inhibit NF-κB. We provided evidence both in cultured endothelial cells and mouse model supporting a new mechanism. Regardless of the endothelial cell types, the LPS-induced NF-κB-dependent inflammatory gene expression was suppressed by COS, which was associated with reduced NF-κB nucleus translocation. LPS enhanced O-GlcNAc modification of NF-κB/p65 and activated NF-κB pathway, which could be prevented either by siRNA knockdown of O-GlcNAc transferase (OGT) or pretreatment with COS. Inhibition of either mitogen-activated protein kinase or superoxide generation abolishes LPS-induced NF-κB O-GlcNAcylation. Consistently, aortic tissues from LPS-treated mice presented enhanced NF-κB/p65 O-GlcNAcylation in association with upregulated gene expression of inflammatory cytokines in vascular tissues; however, pre-administration of COS prevented these responses. In conclusion, COS decreased OGT-dependent O-GlcNAcylation of NF-κB and thereby attenuated LPS-induced vascular endothelial inflammatory response.

Cysteine protease cathepsins and matrix metalloproteinases in the development of abdominal aortic aneurysms

Both cysteine protease cathepsins and matrix metalloproteinases are implicated in the pathogenesis of abdominal aortic aneurysms (AAAs) in humans and animals. Blood and aortic tissues from humans or animals with AAAs contain much higher levels of these proteases, and often lower levels of their endogenous inhibitors, than do blood and aortic tissues from healthy subjects. Protease- and protease inhibitor-deficient mice and synthetic protease inhibitors have affirmed that cysteinyl cathepsins and matrix metalloproteinases both participate directly in AAA development in several experimental model systems. Here, we summarize our current understanding of how proteases contribute to the pathogenesis of AAA, and discuss whether proteases or their inhibitors may serve as diagnostic biomarkers or potential therapeutic targets for this common human arterial disease.

Amphisomal route of MHC class I cross-presentation in bacteria-infected dendritic cells

Dendritic cells (DCs) are among the first professional APCs encountered by the obligate intracellular bacterium Chlamydia during infection. Using an established mouse bone marrow-derived DC line, we show that DCs control chlamydial infection in multiple small inclusions characterized by restricted bacterial growth, impaired cytosolic export of the virulence factor chlamydial protease-like activity factor, and interaction with guanylate-binding protein 1, a host cell factor involved in the initiation of autophagy. During maturation of infected DCs, chlamydial inclusions disintegrate, likely because they lack chlamydial protease-like activity factor-mediated protection. Released cytosolic Chlamydia are taken up by autophagosomes and colocalize with cathepsin-positive amphisomal vacuoles, to which peptide transporter TAP and upregulated MHC class I (MHC I) are recruited. Chlamydial Ags are subsequently generated through routes involving preprocessing in amphisomes via cathepsins and entry into the cytosol for further processing by the proteasome. Finally, bacterial peptides are reimported into the endosomal pathway for loading onto recycling MHC I. Thus, we unravel a novel pathway of MHC I-mediated cross-presentation that is initiated with a host cellular attack physically disrupting the parasitophorous vacuole, involves autophagy to collect cytosolic organisms into autophagosomes, and concludes with complex multistep antigenic processing in separate cellular compartments.

Differential toxic responses between pristine and functionalized multiwall nanotubes involve induction of autophagy accumulation in murine lung

Carbon nanotubes (CNT) are becoming commonly used in industrial applications. However, the toxicity associated with this material remains to be established. The aim of this study was to investigate the potential toxic mechanisms associated with multiwall carbon nanotubes (MWCNT) in normal mouse lung. A total of 100 μg of two types of MWCNT, namely, pristine MWCNT (PMWCNT) and acid-treated-MWCNT (TMWCNT), was administered to male C57BL/6 mice via intratracheal (IT) instillation for a period of 6 mo. Our results indicated that PMWCNT induced pulmonary autophagy accumulation and resulted in more potent tumorigenic effects compared to TMWCNT. Accordingly, MWCNT may exert differential toxicity attributed to various physicochemical properties. Data emphasize the need for careful regulation of production and use of CNT.