Biomedical subjects

A R Morrison

Publications and source records attributed to A R Morrison.

At least 19 recordsLinked to original sources

PubMed1996

Interleukin-1 beta activates PI 3-kinase in renal mesangial cells.

Interleukin-1 beta rapidly stimulates the activation of phosphatidylinositol 3-hydroxyl kinase in renal mesangial cells. This interleukin-1 beta dependent activation is associated with a rapid increase in phosphatidyl inositol 3,4,5 phosphate in renal mesangial cells. The increase in PI 3-kinase activity is inhibited by wortmannin. In addition wortmannin partially inhibited IL-1 beta induced PGE2 production and potentiated IL-1 beta induced nitric oxide production. These experiments suggest that IL-1 beta can activate PI 3-kinase in renal mesangial cells and that the enzyme plays a role in IL-1 beta induced PGE2 and NO formation in the renal mesangial cell.

Androstadienes↗

PubMed1996

Interleukin-1beta activates protein kinase C zeta in renal mesangial cells. Potential role in prostaglandin E2 up-regulation.

Protein kinase C (PKC) plays a role in signal transduction mediated by interleukin-1beta (IL-1beta) leading to the increase in prostaglandin E2 (PGE2) production. In the present study we suggest that there are at least two distinct PKC isotypes involved in the signaling mechanism. Staurosporine potentiated the effect of IL-1beta on coxII mRNA expression while calphostin C totally inhibited mRNA expression. The down-regulation of PKC by growing mesangial cells in the presence of phorbol 12-myristate 13-acetate for 24 h failed to modify the up-regulated response in PGE2 formation by IL-1beta. Furthermore, incubation of mesangial cells with IL-1beta causes translocation of PKCzeta from cytosol to a presumed membrane compartment, and this translocation phenomenon was not inhibited by incubating the cells with staurosporine but was inhibited with calphostin C. Gel retardation assays also demonstrated that staurosporine did not inhibit the IL-1beta-stimulated binding of nuclear extracts to the NFkappaB motif. In contrast, calphostin C inhibited binding to the kappaB motif in a dose-dependent manner. Finally, antisense oligonucleotides to PKCzeta partially inhibited the IL-1beta-induced PGE2 formation while control sense oligonucleotides were without effect. Taken together, these data suggest that PKCzeta is involved in the IL-1beta signaling responses.

Alkaloids↗

PubMed1996

Antioxidants inhibit interleukin-1-induced cyclooxygenase and nitric-oxide synthase expression in rat mesangial cells. Evidence for post-transcriptional regulation.

Glomerular mesangial cells produce reactive oxygen intermediates when stimulated by interleukin-1 (IL-1) or tumor necrosis factor. Recent observations suggest that reactive oxygen intermediates may play a role in IL-1 and tumor necrosis factor signaling and may upregulate gene expression. We therefore evaluated the effects of antioxidants on IL-1beta-induced cyclooxygenase-2 (Cox-2) and inducible nitric-oxide synthase (iNOS) expression in rat mesangial cells. The oxidant scavenger, pyrrolidine dithiocarbamate (PDTC), inhibited iNOS expression at the transcriptional level, since PDTC abolished iNOS mRNA accumulation. In contrast, PDTC inhibited Cox-2 expression at the post-transcriptional level, since PDTC did not affect IL-1beta-induced Cox-2 mRNA levels but inhibited Cox-2 protein expression and prostaglandin E2 production. Another antioxidant, rotenone, which inhibits reactive oxygen intermediate production by inhibiting the mitochondrial electron transport system, did not inhibit IL-1beta-induced iNOS and Cox-2 mRNA expression but inhibited iNOS and Cox-2 protein expression, suggesting a post-transcriptional target for the inhibition of NOS and Cox-2 expression induced by IL-1beta. These results suggest that not only transcriptional regulation but also post-transcriptional mechanisms are involved in redox-sensitive inhibition of cytokine induced Cox-2 and NOS expression. These results suggest a novel approach for intervention in cytokine-mediated inflammatory processes.

Animals↗

PubMed1996

Nitric oxide amplifies interleukin 1-induced cyclooxygenase-2 expression in rat mesangial cells.

Interleukin 1 and nitric oxide (NO) from infiltrating macrophages and activated mesangial cells may act in concert to sustain and promote glomerular damage. To evaluate if such synergy occurs, we evaluated the effect if IL-1 beta and NO on the formation of prostaglandin (PG)E2 and cyclooxygenase (COX) expression. The NO donors, sodium nitroprusside and S-nitroso-N-acetylpenicillamine, alone did not increase basal PGE2 formation. However, these compounds amplified IL-1 beta-induced PGE2 production. Similarly, sodium nitroprusside and S-nitroso-N-acetylpenicillamine by themselves did not induce mRNA and protein for COX-2, the inducible isoform of COX; however, they both potentiated IL-1 beta-induced mRNA and protein expression of COX-2. The stimulatory effect of NO is likely to be mediated by cGMP since (a) an inhibitor of the soluble guanylate cyclase, methylene blue, reversed the stimulatory effect of NO donors on COX-2 mRNA expression; (b) the membrane-permeable cGMP analogue, 8-Br-cGMP, mimicked the stimulatory effect of NO donors on COX-2-mRNA expression; and (c) atrial natriuretic peptide, which increases cellular cGMP by activating the membrane-bound guanylate cyclase, also amplified IL-1 beta-induced COX-2 mRNA expression. These data indicate a novel interaction between NO and COX pathways.

Animals↗

PubMed1996

Tyrosine kinase inhibitors, genistein and herbimycin A, do not block interleukin-1 beta-induced activation of NF-kappa B in rat mesangial cells.

We have previously demonstrated that interleukin-1 beta (IL-1 beta) rapidly induces tyrosine phosphorylation of several proteins in the renal mesangial cell. Two mechanistically distinct tyrosine kinase inhibitors, genistein and herbimycin A, block the induction of cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS) by IL-1 beta in rat mesangial cells. Since both COX-2 and iNOS promoters have a kappa B binding motif, we have evaluated the effects of tyrosine kinase inhibitors on IL-1 beta-induced nuclear factor-kappa B (NF-kappa B) activation by electromobility shift assays. IL-1 beta rapidly induced the translocation of NF-kappa B in rat mesangial cells. However, the tyrosine kinase inhibitors, genistein and herbimycin A, failed to block the translocation of NF-kappa B at concentrations which abolish COX-2 and iNOS mRNA expression. These data suggest that an upstream tyrosine kinase pathway may not be required for IL-1 beta-induced NF-kappa B activation and that the tyrosine kinase pathway may converge with the NF-kappa B pathway down-stream of NF-kappa B activation in rat mesangial cells.

Animals↗

PubMed1996

Elicited PGO waves in rats: lack of 5-HT1A inhibition in putative pontine generator region.

Ponto-geniculo-occipital (PGO) waves and an elicited analogue (PGOE) may be recorded in the pons of rats. Cholinergic cells in the pedunculopontine tegmental (PPT) and laterodorsal tegmental (LDT) nuclei are implicated in the generation of PGO waves. Serotonin (5-HT) may inhibit the generation of PGO waves, and possibly PGOE. We examined the role of 5-HT1A receptor mechanisms in the generation of auditory-elicited PGOE in rats. Administration of 8-OH-DPAT [8-hydroxy-2-(n-dipropylamino)tetralin] into PPT did not significantly affect PGOE amplitude or response frequency. Binding of [3H]CN-IMI ([3H]cyanoimipramine) to 5-HT uptake sites located presynaptically was used as a measure of 5-HT innervation. Quantitative autoradiographic analysis of [3H]CN-IMI binding indicated a moderate to low degree of 5-HT innervation of PPT and a moderately high innervation of LDT compared to the dorsal raphe nucleus (DRN). Binding of [3H]8-OH-DPAT to 5-HT1A receptors revealed few receptor sites in PPT, and a low to moderate number of receptors in LDT compared to binding in DRN. The results suggest that inhibitory serotonergic modulation of PGOE is probably not mediated through a 5-HT1A receptor mechanism in PPT.

8-Hydroxy-2-(di-n-propylamino)tetralin↗

PubMed1996

Histamine in human epidermal cells is induced by ultraviolet light injury.

Human epidermal cell cultures were examined to determine whether they were capable of histamine release. Results of these studies indicated that keratinocytes contain and release significant amounts of histamine. In the skin of some individuals, histamine content was induced after ultraviolet B light injury, and 40% of subjects demonstrated high basal histamine levels. Mass spectrometric analysis of cell supernatants showed that the histamine was released into the extracellular environment. Such release may contribute to common itching or intensify the inflammatory response in vivo.

Adult↗

PubMed1996

Interleukin-1 beta activates c-jun NH2-terminal kinase subgroup of mitogen-activated protein kinases in mesangial cells.

We investigated whether JNK is activated by interleukin-1 beta (IL-1 beta) in mesangial cells. We performed in-gel kinase assays with His-c-jun-(1-79), which contains the amino-terminal activation domain of c-jun and a mutant His-c-jun in which Ser-63 and Ser-73 of His-c-jun were mutated to Ala as the substrates. JNK1 (p45) and JNK2 (p54) isoforms phosphorylated His-c-jun in mesangial cells. IL-1 beta produced a time- and concentration-dependent increase in JNK activity. IL-1 beta did not phosphorylated the mutant, His-c-jun. The IL-1 beta-activated JNK activity was independent of serum and suppressed by neither tyrosine kinase inhibitors nor protein kinase C inhibitors. JNK was also stimulated by anisomycin and okadaic acid but not by phorbol 12-myristate 13-acetate. The protein synthesis inhibitors and okadaic acid potentiated the IL-1 beta-induced JNK activity. Together, these studies indicate that the novel JNK group of protein kinases may play an important role in the signal transduction pathway initiated by proinflammatory cytokines, such as IL-1 beta in mesangial cells.

Animals↗

PubMed1996

Relationship of ventricular tachycardia to sleep/wakefulness in a model of sudden cardiac death.

Death from some childhood disorders such as sudden infant death syndrome and the congenital long QT syndrome are associated with specific behaviors such as sleep or emotional stress. We studied young German shepherd dogs that die suddenly during presumed sleep. These dogs have inherited ventricular tachycardia (VT) which is most frequent during sinus bradycardia and sinus arrhythmia. We hypothesized that the number of VT complexes (three or more consecutive ectopic complexes) would be greatest during sleep. Moreover, we hypothesized that pauses in the sinus rhythm of greater than 1000 ms would be greatest in the behavior with the most frequent VT. Behavioral states [excited, ambulatory, sitting, lying, rapid eye movement (REM) sleep] were quantified from 24-h video recordings of seven dogs. VT and pauses were quantified for each behavior using simultaneously recorded ECGs. A multivariate model was used to analyze the results. After controlling for time of day, lying, and REM sleep were significantly (p < 0.02) associated with VT, whereas more active behaviors were not. Time of day also independently affected the number of VT complexes. However, behavior and time of day did not account for all of the variability in the number of VT complexes. Pauses were significantly associated with behavior, with the highest number of pauses occurring during lying and REM sleep. However, pauses were not always associated with VT, indicating that a pause was a necessary, but not sufficient, condition for the development of VT. These results suggest that modulation of VT incidence in these animals is multifactorial and that the highest number of VT complexes is associated with the bradycardia that accompanies REM sleep.

Animals↗

PubMed1996

Enhanced prostaglandin synthesis after ultraviolet-B exposure modulates DNA synthesis of lens epithelial cells and lowers intraocular pressure in vivo.

PURPOSE: To study the functional significance of prostaglandin synthesis after ultraviolet-B (UVB) exposure of cultured human lens epithelial cells and rabbit eyes in vivo. METHODS: Prostaglandin E2 (PGE2) was assayed using a radioimmunoassay (RIA) and mass spectroscopy. An immortalized human lens epithelial cell line (HLE-B3) was exposed to UV irradiation, and the synthesis of PGE2 was compared with the rabbit lens epithelial cell line N/N1003A. Intact human lenses were exposed to UVB in organ culture. [3H]Thymidine incorporation was measured in cultured lens epithelial cells by incubation with the radiolabel. The effects of isobutyl methyl xanthine (IBMX), an inhibitor of phosphodiesterase and of dibutyryl cyclic adenosine monophosphate (cAMP), an analog of cAMP, on PGE2 synthesis and DNA synthesis, were determined. Rabbit eyes were exposed to UVB radiation in vivo. Intraocular pressure was measured at specific times after exposure. Aqueous humor was remove from rabbit eyes, and its PGE2 content was measured by RIA. RESULTS: Cultured human lens epithelial cells (HLE), like rabbit lens epithelial cells (RLE), showed a dose-dependent increase in basal PGE2 synthesis 24 hours after UVB exposure. However, the amount of PGE2 synthesis was 2000-fold higher in the rabbit cells. Ultraviolet-B radiation enhanced the incorporation of [3H]thymidine in lens epithelial cells. Pretreatment of cells with indomethacin reduce PGE2 synthesis and [3H]thymidine incorporation. The human and rabbit cells responded in a similar manner to changes in DNA synthesis after UVB exposure. The addition of IBMX or dbcAMP to indomethacin-treated, UVB-exposed cells restored DNA synthesis toward the levels observed in the UVB-exposed cells. An increase in the concentration of cAMP was observed in lens epithelial cells exposed to exogenous PGE2. PGE2 synthesis in intact human lenses also increased twofold 24 hours after UVB exposure. Exposure of the rabbit eye in vivo to an optimal dose of UVB produced an increase in the PGE2 levels of the lens and the aqueous humor. Measurements of the intraocular pressure (IOP) of the animals showed a decrease in IOP by 2.21 +/- 0.66 and 6.45 +/- 0.79 mm Hg (mean +/- SEM, P = 0.004, t-test) at 6 and 24 hours after UVB exposure, respectively. The decrease in IOP was prevented by pretreatment with indomethacin. Exposure of the rabbit lens to UVB radiation in vivo enhanced [3H]thymidine incorporation twofold into the lens. Pretreatment of rabbits with indomethacin before exposure reduced this response. CONCLUSIONS: Results indicate that UVB exposure enhances PGE2 synthesis in HLE cultures as well as in rabbit lenses irradiated in vivo. This increased PGE2 synthesis is related to the increase in DNA synthesis observed after UVB treatment. The modulation of DNA synthesis in cultured lens epithelial cells after UVB exposure may be mediated by a cAMP-dependent mechanism.

1-Methyl-3-isobutylxanthine↗

PubMed1996

The role of prostaglandins E2 and F2 alpha in ultraviolet radiation-induced cortical cataracts in vivo.

PURPOSE: Previous work has shown that exposure of lens epithelial cells or rabbit eyes in vivo to ultraviolet B (UVB) radiation enhanced prostaglandin (PG)E2 synthesis. Such enhanced PGE2 synthesis was related to the increased DNA synthesis that followed UVB exposure. The current study examined the relationship between enhanced prostaglandin synthesis and UVB-induced cataract formation. METHODS: Seventy albino (New Zealand white) rabbit eyes were exposed to UVB radiation in vivo. Fluence of radiation at the cornea was 2.8 J/cm2, 5.6 J/cm2, or 11.2 J/cm2. Eyes were examined 24 hours after UVB exposure and for as long as 10 days by slit lamp biomicroscopy. Mass spectrometry was used to measure PGE2, PGF2 alpha, and 6-keto-PGF1 alpha content of the lens and iris-ciliary body using authentic standards. To determine the effect of inhibition of prostaglandin synthesis on UVB-induced cataract formation, animals were given indomethacin intraperitoneally. Other pharmacologic agents, such as PGE2, PGF2 alpha, and misoprostol, were applied topically to the eye. The effect of UVB on K+ pump was determined by incubating isolated lenses with [86Rb+]. RESULTS: Twenty-four hours after UVB exposure, PGE2 and PGF2 alpha concentrations in aqueous humor were increased by 100- and 30-fold, respectively. Lens PGE2 and PGF2 alpha increased by 6- and 4-fold, respectively, after UVB radiation exposure. Pretreatment of animals with indomethacin prevented the rise in lens and aqueous humor PGE2 and PGF2 alpha levels. Furthermore, indomethacin was partially protective against UVB cataract formation and lowered cataract severity from stage 3 to stage 1, but it did not prevent UVB-induced lens changes completely. Topical application of PGE2 before UVB exposure completely prevented cataract formation in the UVB-exposed eye. In contrast, topical administration of PGF2 alpha increased cataract severity. UVB-induced cataract formation preceded changes in [86Rb]+ uptake in lenses subsequently incubated in K(+)-free Tyrode's. CONCLUSIONS: Enhanced synthesis of cyclooxygenase products of arachidonic acid metabolism in the lens is associated with UVB-induced cataract formation in albino rabbit eyes, and inhibition of cyclooxygenase by indomethacin decreased the severity of cataracts. PGE2, the principal arachidonic acid metabolite, appears to have a protective role because pretreatment of the eye with topical PGE2 completely prevented UVB-induced cataract formation, whereas PGF2 alpha increased the severity of the cataract. The evidence presented for a role of PGF2 alpha in the development of cataract suggests that caution be exercised in the use of PGF2 alpha derivatives in the therapy of glaucoma.

6-Ketoprostaglandin F1 alpha↗

PubMed1995

REM sleep inhibition by desipramine: evidence for an alpha-1 adrenergic mechanism.

The acute administration of drugs that block norepinephrine (NE) reuptake suppresses rapid eye movement (REM) sleep in cats and other mammals. The mechanism is presumed to involve NE acting on cells in a pontine REM sleep-generator region. Postsynaptic noradrenergic receptor mechanisms have not been identified. In the present experiments, we tested the ability of the alpha-1 antagonist prazosin and the beta antagonist propranolol to reverse the REM sleep suppression produced by the NE reuptake blocker desipramine (DMI) in the cat. DMI reduced the number of REM sleep episodes, the REM percentage (REM sleep time/total sleep time), and the average REM sleep episode duration. The co-administration of prazosin, but not propranolol, increased the REM percentage and the average REM sleep episode duration toward the placebo level. The co-administration of the peripherally-acting, anti-hypertensive agent hydralazine did not reverse the DMI-induced REM sleep suppression. While the identity of the brain region(s) involved in mediating the alpha-1 noradrenergic suppression of REM sleep by DMI remains unclear, there is reason to consider forebrain structures including the amygdala as well as the pontine areas that generally have been implicated in REM sleep control.

Adrenergic Uptake Inhibitors↗

PubMed1995

Regulation of heme oxygenase mRNA in mesangial cells: prostaglandin E2 negatively modulates interleukin-1-induced heme oxygenase-1 mRNA.

Heme oxygenase (EC 1.14.99.3) is the rate-limiting enzyme in heme catabolism. Several lines of evidence suggest a possible role for heme oxygenase in the inflammatory process and in cellular signaling. We have evaluated the regulation of heme oxygenase-1 mRNA induction by the inflammatory stimuli, phorbol 12,13-myristate acetate, heat shock and interleukin-1 beta in cultured rat mesangial cells. Phorbol 12,13-myristate acetate and heat shock rapidly (maximal at 2-3 hrs) induced heme oxygenase-1 mRNA. The effect of interleukin-1 beta on heme oxygenase-1 mRNA induction was slower (maximal at 12 hrs) and modest. However, in the presence of a cyclooxygenase inhibitor, indomethacin, interleukin-1 beta strongly induced heme oxygenase-1 mRNA. The addition of exogenous PGE2 reversed the effect of indomethacin. These data suggest that pro-inflammatory stimuli increase heme oxygenase-1 mRNA expression in rat mesangial cells and that interleukin-1 beta-induced heme oxygenase-1 mRNA level is negatively modulated by PGE2.

Animals↗

PubMed1995

Stimulus-elicited behavior in rapid eye movement sleep without atonia.

Alert wakefulness (W) and rapid eye movement sleep (REM) are remarkably similar on several measures of brain activity, but 2 differences in REM are reduced sensory responsiveness and atonia in postural muscles. Pontine tegmental lesions create REM without atonia (REM-A), releasing motor behavior. In 9 cats, we studied the acoustic startle reflex (ASR), orienting (OR), and ponto-geniculo-occipital waves (PGOE) elicited by tones during W, REM, REM-A, and non-REM (NREM). OR occurred in W and REM-A, being most complete in cats with the most elaborate spontaneous behavior. ASR occurred in W, NREM, and REM-A in lesioned cats. In normal cats, ASR rarely appeared in NREM and REM. PGOE had similar characteristics in both groups. The similarity of REM to W is particularly obvious when cats lack motoneuronal inhibition.

Acoustic Stimulation↗

PubMed1995

IL-1 beta regulates rat mesangial cyclooxygenase II gene expression by tyrosine phosphorylation.

The pro-inflammatory cytokine, interleukin-1 beta, induces the mRNA for prostaglandin endoperoxide synthase II gene in renal mesangial cells. This inductive effect is selective for prostaglandin endoperoxide synthase II and not prostaglandin endoperoxide synthase I. In the present experiments IL-1 beta increased COX II mRNA, and this was inhibited by genistein and herbimycin A, both inhibitors of protein tyrosine kinases. The dose dependent effect of genistein on inhibition of mRNA for COX II correlated with the inhibition of the release of PGE2 into the media. Induction of COX II by interleukin-1 beta was mimicked by incubating the cells in the presence of a protein tyrosine phosphatase inhibitor, vanadate. These experiments also illustrate selective induction of COX II mRNA without induction of COX I mRNA. Western analysis utilizing antiphosphotyrosine antibodies demonstrated in whole lysates of mesangial cells treated with interleukin-1 beta that the transient phosphorylation of several proteins occurred. Interleukin-1 beta induced the transient phosphorylation of a protein of about 39/40 kD. Similarly, vanadate also produced a rapid and transient phosphorylation of a protein of about 39/40 kD in addition to other proteins. Immunoprecipitation of mesangial cell lysates with agarose conjugated antiphosphotyrosine antibody and Western analysis of precipitated proteins with anti-ERK2 antibody demonstrate that the 39/40 kD protein phosphorylated on tyrosine is ERK2 and suggests participation of one of the MAP kinase family of extracellular receptor kinases in IL-1 beta stimulated induction of the COX II gene.

Animals↗

PubMed1995

Tyrosine kinase activation is necessary for inducible nitric oxide synthase expression by interleukin-1 beta.

The inflammatory cytokine interleukin-1 (IL-1) induces the inducible form of nitric oxide synthase (iNOS) with an increase in nitric oxide in rat mesangial cells. However, the cellular mechanisms that underlie the induction of iNOS by IL-1 beta in mesangial cells has not been clarified. Because we have shown that tyrosine kinase inhibitors attenuate IL-1 beta-induced cyclooxygenase expression and prostaglandin production, we investigated the effect of tyrosine kinase inhibitors on IL-1 beta-induced nitrite production and iNOS mRNA expression in rat mesangial cells. The tyrosine kinase inhibitors genistein and herbimycin A attenuated IL-1 beta-induced nitrite production in a dose-dependent manner. In addition, both of these inhibitors blocked IL-1 beta-induced iNOS mRNA expression. These data suggest that tyrosine kinase(s) plays a central role in IL-1 beta signaling to induce iNOS in rat mesangial cells.

Amino Acid Oxidoreductases↗

PubMed1995

Metabolic effects of fatty acid-bearing albumin on a proximal tubule cell line.

In glomerular disease, fatty acids carried on albumin are taken up by the proximal tubule with filtered albumin. We postulate that the fatty acids carried on filtered albumin could contribute to the deleterious effects of proteinuria. The effects of fatty acid-albumin complexes on lipid metabolism have been studied in opossum kidney (OK) cells, a proximal tubule cell line. OK cells transported two-thirds of [14C]palmitate-albumin (5 mg/ml) intracellularly within 16 h. [14C]palmitate-albumin was distributed into phosphatidylcholines, phosphatidylinositols, and tri- and diglycerides. 14C-labeled unsaturated fatty acid albumins (oleate, linoleate, and arachidonate) showed preferential incorporation into triglycerides, with lesser incorporation into phospholipids. Studies of total lipid pools showed that fatty acid-albumin uptake produced a particularly marked increase in total triglyceride levels (approximately 10-fold). Oil red O staining of OK cells cultured with oleate-albumin showed a marked increase in intracellular lipid droplets, compared with cells cultured with delipidated albumin, consistent with triglyceride accumulation. Less than 1% of [14C]palmitate taken up was isolated as intracellular free fatty acid. Less than 5% of [14C]palmitate internalized was oxidized to 14CO2. Different fatty acids, when taken up by the OK cell, have distinct metabolic fates. Each fatty acid is incorporated in a characteristic fashion into certain complex lipids, possibly dependent on the presence or absence of double bonds. We propose that this may have functional consequences for the proximal tubule in the human nephrotic syndrome.

Animals↗

PubMed1995

Interleukin-1 beta induces interstitial collagenase gene expression and protein secretion in renal mesangial cells.

Degradation and tissue remodeling of the extracellular matrix in the normal glomerulus occur through the coordinate action of neutral metalloproteinases, which are in turn regulated by specific inhibitors. Many of these proteins can be secreted by mesangial cells. In the current study, gene regulation of a rat matrix metalloproteinase, interstitial collagenase and its tissue inhibitor of metalloproteinase-1 (TIMP-1), was investigated by Northern blot analysis. Stimulation of rat mesangial cell (RMC) collagenase by interleukin 1 beta (IL-1 beta) produced an increase (> 45-fold) in mRNA which peaked at 12 h. Lesser effects on the TIMP-1 mRNA expression were observed in response to IL-1 beta. Indomethacin did not influence the effect of IL-1 beta on collagenase, and exogenous prostaglandin E2 had no significant effect either on basal or IL-1 beta-stimulated mRNA levels. Collagenase was secreted into the media and showed minimal gelatinolytic activity at 36-h stimulation with IL-1 beta by zymography. By Western immunoblotting, we demonstrated with 24 h of stimulation the secretion of the active form of collagenase, which further increased after 36 h with IL-1 beta compared with the control. When RMC were retreated with genistein and herbimycin A, both inhibited collagenase mRNA induction by IL-1 beta. These data suggest that IL-1 beta stimulates interstitial collagenase synthesis and activation and that a tyrosine kinase pathway is involved in the signal transduction mechanisms and is not dependent on endogenous prostaglandin biosynthesis. Recently, a third interstitial collagenase (collagenase-3) has been identified from breast carcinoma. This cDNA is 84% identical to the rat interstitial collagenase cDNA probe we have utilized in this study and thus may represent the rat homologue of the human collagenase-3 now called matrix metalloproteinase (MMP)-13.

Animals↗