Spatially Resolved Identification of Transglutaminase Substrates by Proteomics in Pulmonary Fibrosis

Idiopathic pulmonary fibrosis (IPF) is characterized by the invariably progressive deposition of fibrotic tissue in the lungs and overall poor prognosis. TG2 (transglutaminase 2) is an enzyme that crosslinks glutamine and lysine residues and is involved in IPF pathogenesis. Despite the accumulating evidence implicating TG2 as a critical enzyme, the causative function and direct target of TG2 relating to this pathogenesis remain unelucidated. Here, we clarified the distributions of TG2 protein/activity and conducted quantitative proteomics analyses of possible substrates crosslinked by TG2 on unfixed lung sections in a mouse pulmonary fibrosis model. We identified 126 possible substrates as markedly TG2-dependently increased in fibrotic lung. Gene ontology analysis revealed that these identified proteins were mostly enriched in the lipid metabolic process, immune system process, and protein transport. In addition, these proteins were enriched in 21 pathways, including phagosome, lipid metabolism, several immune responses, and protein processing in endoplasmic reticulum. Furthermore, the network analyses screened out the six clusters and top 20 hub proteins with higher scores, which are related to endoplasmic reticulum stress and peroxisome proliferator-activated receptor signals. Several enriched pathways and categories were identified, some of which were the same terms based on transcription analysis in IPF. Our results provide novel pathological molecular networks driven by protein crosslinking via TG2, which can lead to the development of new therapeutic targets for IPF.

Spatially Resolved Identification of Transglutaminase Substrates by Proteomics in Pulmonary Fibrosis

Idiopathic pulmonary fibrosis (IPF) is characterized by the invariably progressive deposition of fibrotic tissue in the lungs and overall poor prognosis. Transglutaminase 2 (TG2) is an enzyme that crosslinks glutamine and lysine residues and is involved in IPF pathogenesis. Despite the accumulating evidence implicating TG2 as a critical enzyme, the causative function and direct target of TG2 relating to this pathogenesis remain unelucidated. Here, we clarified the distributions of TG2 protein/activity and conducted quantitative proteomics analyses of possible substrates crosslinked by TG2 on unfixed lung sections in a mouse pulmonary fibrosis model. We identified 126 possible substrates as markedly increased TG2-dependently in fibrotic lung. Gene ontology analysis revealed that these identified proteins were mostly enriched in the lipid metabolic process, immune system process, and protein transport. In addition, these proteins enriched in the 21 pathways including phagosome, lipid metabolism, several immune responses, and protein processing in endoplasmic reticulum. Furthermore, the network analyses screened out the 6 clusters and top 20 hub proteins with higher scores, which are related to ER stress and peroxisome proliferator-activated receptor signals. Several enriched pathways and categories were identified, and some of which were the same terms based on transcription analysis in IPF. Our results provide novel pathological molecular networks driven by protein crosslinking via TG2, which can lead to the development of new therapeutic targets for IPF.

Experimental chemonucleolysis with recombinant human matrix metalloproteinase 7 in human herniated discs and dogs

BACKGROUND CONTEXT

Chemonucleolysis has been proposed as a less invasive technique than surgery for patients with lumbar disc herniation. Once chymopapain had been approved as a chemonucleolysis drug, it was withdrawn because of serious complications. A novel agent with fewer complications would be desirable.

PURPOSE

The purpose of this study was to investigate the effects of recombinant human matrix metalloproteinase 7 (rhMMP-7) in experimental chemonucleolysis in vitro and in vivo and examine its effects on tissue damage.

STUDY DESIGN

The study design is the experimental study using human herniated discs and enzyme substrates in vitro and dogs in vivo.

METHODS

The effects of rhMMP-7 on the degradation of human herniated discs were examined by measuring the wet weight in vitro. The correlations between the decrease in wet weight by rhMMP-7 and the conditions associated with herniated discs were also analyzed. The effects of rhMMP-7 on the proteoglycan and water contents were respectively examined with alcian blue staining and T2-weighted magnetic resonance imaging at 7 days after intradiscal injection in dogs. The distribution of [125I]-labeled rhMMP-7 was investigated by autoradioluminography at 7 days after intradiscal injection in dogs. An epidural injection study with rhMMP-7 was performed to evaluate the effects on the tissue damage around the discs at 1 and 13 weeks after the treatment in dogs. The Type 1 and 2 collagen cleavage rates were measured and compared with those of aggrecan in vitro.

RESULTS

Recombinant human matrix metalloproteinase 7 concentration dependently decreased the wet weight of herniated discs in vitro. The decrease in wet weight of the discs by rhMMP-7 did not significantly correlate with the conditions associated with herniated discs. Intradiscal injection of rhMMP-7 reduced the proteoglycan and water contents, with an increase in the serum keratan sulfate levels. Radioactivity of [125I]-labeled rhMMP-7 was detected in the nucleus pulposus and annulus fibrosus but not in the muscle. Epidural injection of rhMMP-7 had no effect on the injection site or the nerve tissues. The Type 1 and 2 collagen cleavage rates of rhMMP-7 were 1,000-fold weaker than those of aggrecan.

CONCLUSIONS

This study demonstrated experimental chemonucleolysis with rhMMP-7 in vitro and in vivo. The effects of rhMMP-7 were not affected by the conditions associated with herniated discs. The epidural injection study together with the autoradioluminography and in vitro enzyme assay suggests that intradiscal injection of rhMMP-7 may not induce tissue damage around the discs because of its distribution and substrate selectivity. Recombinant human matrix metalloproteinase 7 may be a novel and promising chemonucleolysis agent.

[Participation of endogenous brain histamine on learning and memory]

It is well known that histamines play an important role as a neurotransmitter in the central nervous system and participate in several physiological functions, such as the regulation of body temperature, food intake, circadian rhythm and analgesia. Since the first report by de Almeida and Izquierdo that histamines facilitate memory performance in mice, it has been revealed that the histaminergic nervous system in the brain plays a crucial role in learning and memory functions. First, we demonstrate the effects of histamines and histaminergic drugs on learning and memory using active avoidance and 8-arm radial maze tests. Many reports suggest that acetylcholine and N-methyl-D-aspartate (NMDA) receptors play an important role in learning and memory. In this report, we also describe the interaction between histamine-induced memory facilitation and acetylcholine or NMDA receptors.

Inhibitory effects of propolis granular A P C on 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone-induced lung tumorigenesis in A/J mice

We examined the effect of propolis granular A. P. C on lung tumorigenesis in female A/J mice. Lung tumors were induced by the tobacco-specific carcinogen, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) administered in drinking water for 7 weeks in mice maintained on an AIN-76A semi-synthetic diet. Propolis granular A. P. C (100 mg/kg body wt.) was administered orally daily for 6 days/week from 1 week before NNK administration and throughout the experiment. Sixteen weeks after the NNK treatment, the mice were killed and the number of surface lung tumors was measured. The number of lung tumors in mice treated with NNK alone for 7 weeks (9.4 mg/mouse) was significantly more than in that observed in control mice. Propolis granular A. P. C significantly decreased the number of lung tumors induced by NNK. These results indicate that propolis granular A. P. C is effective in suppressing NNK-induced lung tumorigenesis in mice.

Ameliorative effects of histamine on 7-chlorokynurenic acid-induced spatial memory deficits in rats

RATIONALE

Histamine plays an important role in modulating acquisition and retention in learning and memory process in experimental animals.

OBJECTIVES

We examined the effects of polyamine and histamine on the N-methyl- d-aspartate (NMDA) receptor glycine site antagonist 7-chlorokynurenic acid-induced spatial memory deficits in radial maze performance in rats.

METHOD

Effects of histamine (0.5 or 1 nmol/site intracerebroventricularly), spermidine (1 nmol/site, intracerebroventricularly) and spermine (1 nmol/site, intracerebroventricularly) on spatial memory deficit in 9-week-old-male Wistar rats were observed. Both reference and working memory errors occurred in radial maze performance in rats, following intracerebroventricular injection of 7-chlorokynurenic acid (10 nmol/site).

RESULTS

Spermidine (1 nmol/site, intracerebroventricularly) or spermine (1 nmol/site, intracerebroventricularly) antagonized 7-chlorokynurenic acid-induced deficits on working memory but not on reference memory errors. Intracerebroventricular histamine (0.5 or 1 nmol/site) or thioperamide (100 nmol/site) also ameliorated 7-chlorokynurenic acid-induced working memory deficits. To determine whether the effects of histamine involve histamine receptors, the effects of some methylhistamines were examined. The effects of R-alpha-methylhistamine on radial maze performance were mimicked by histamine. N(alpha)-methylhistamine had no effect on 7-chlorokynurenic acid-induced memory deficits, whereas 1-methylhistamine, but not 3-methylhistamine reversed 7-chlorokynurenic acid-induced working memory deficits.

CONCLUSION

These results suggest that the amelioration of 7-chlorokynurenic acid-induced working memory deficits by histamine may involve a direct action of histamine at the polyamine sites on NMDA receptors.

Effects of second-generation histamine H1 receptor antagonists on the active avoidance response in rats

1. The aim of the present study was to establish a new schedule of active avoidance response in rats to estimate the central effects of second-generation histamine H1 receptor antagonists. 2. With the new schedule, a rat was placed into a dark room. A sliding door was opened after a delay of 5 s and, unless the animal moved into the lit room, an electric shock was delivered for 3 s. With the conventional schedule, the sliding door was opened immediately after the rat was placed into the dark room. 3. Ketotifen, at a dose of 50 mg/kg, showed no significant effect on the retrieval of active avoidance response with the conventional schedule. However, with the new schedule, the drug caused significant inhibition of retrieval of the response, even at a dose of 10 mg/kg. 4. Epinastine showed no significant effect on retrieval of the active avoidance response, even at a dose of 50 mg/kg with the new schedule. 5. Cetirizine, at a dose of 50 mg/kg, caused a significant effect, indicating that cetirizine, at this dose, markedly inhibits memory retrieval. 6. Both olopatadine and loratadine had potent effects; at doses of 20 and 50 mg/kg, respectively, these agents showed significant inhibitory effects on retrieval of the response. 7. In conclusion, we have developed a new schedule of active avoidance response that can be used to estimate the central effects of second-generation histamine H1 receptor antagonists.

Effects of NMDA antagonist MK-801 on radial maze performance in Zucker rats

We examined the participation of the NMDA receptor in the histaminergic system using radial maze performance in Zucker rats. Although pyrilamine caused a significant effect on spatial memory deficit in lean rats, no significant spatial memory deficit was observed in obese rats. On the other hand, MK-801 caused significant spatial memory deficits in obese rats in comparison with lean rats. These results indicate that the histaminergic neuron is not closely related with the radial maze performance in obese rats. In addition, the potent effect of MK-801 observed in obese rats compared with lean rats may be responsible for the activation of NMDA receptors in obese rats.

Effect of docosahexaenoic acid-fortified Chlorella vulgaris strain CK22 on the radial maze performance in aged mice

Effect of docosahexaenoic acid (DHA) [22: 6(n-3)]-fortified Chlorella oil fraction on radial maze performance was studied in aged mice. Male ICR mice aged 9 months were fed a diet containing 2 g DHA-fortified Chlorella oil fraction/100 g diet or normal diet (Control group) for 2 months. Two months after the start of feeding, the mice were tested for learning ability related to 2 types of memory, reference memory and working memory, with the partially (4 of 8) baited eight-arm radial maze. Reference memory is a kind of information that should be retained until the next trial. Working memory is a kind of information that disappears in a short time. Entry into the unbaited arms and repeated entry into the visited arms were defined as reference memory errors and working memory errors, respectively. DHA-fortified Chlorella oil fraction administration to mice for 2 months resulted in a significant decrease in the number of working memory errors without affecting the number of reference memory errors. A significant increase in the DHA content in the brain was also observed. These results suggest that the intake of DHA-fortified Chlorella oil fraction effectively enhances working memory in maze performance.

Effects of the NMDA antagonist MK-801 on radial maze performance in histidine-deficient rats

We examined the effects of a histidine-deficient diet on brain histamine contents as well as on learning and memory using the eight-arm radial maze in rats. A significant decrease in histamine content in the hippocampus was observed after long-term feeding of rats with a histidine-deficient diet. At the same time, significant enhancement of the acquisition process in radial maze performance was also observed. Pyrilamine did not show a significant effect on radial maze performance in histidine-deficient rats. On the other hand, pyrilamine caused a significant spatial memory deficit in control rats. Scopolamine was effective in inhibiting spatial memory in both histidine-deficient and control rats. MK-801 caused spatial memory deficits more potently in histidine-deficient rats than in controls. Brain glycine contents showed a significant increase in the hippocampus in histidine-deficient rats. These results indicated that the spatial memory deficits induced by MK-801 in histidine-deficient rats are closely related to increased glycine levels and activation of NMDA receptors.

Effects of histidine on working memory deficits induced by the 5-HT1A-receptor agonist 8-OH-DPAT

We investigated the effects of histidine on spatial memory deficits induced by the 5-HT1A-receptor agonist, 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT). Working memory deficits were elicited by 8-OH-DPAT without affecting reference memory. Histidine improved the working memory deficit induced by 8-OH-DPAT at doses causing a significant increase in brain histamine content. This finding suggests that the histaminergic system regulates 8-OH-DPAT-induced working memory deficit.

Effects of vasopressin on histamine H(1) receptor antagonist-induced spatial memory deficits in rats

The effects of [Arg(8)] vasopressin on histamine H(1) receptor antagonist-induced memory deficits were investigated using the eight-arm radial maze performance test in rats. Pyrilamine and diphenhydramine as well as scopolamine induced memory deficits characterized by increases in the number of total errors, reference memory errors and working memory errors. [Arg(8)] vasopressin improved not only scopolamine--but also pyrilamine--and diphenhydramine-induced memory deficits, although a high dose of [Arg(8)] vasopressin was needed to antagonize pyrilamine-induced memory deficits. The effects of pyrilamine on the brain [Arg(8)] vasopressin content were studied, and the hippocampus [Arg(8)] vasopressin content was shown to be decreased after pyrilamine injection. From these observations, it seems likely that [Arg(8)] vasopressin participates in not only the cholinergic system but also the histaminergic system in spatial memory.