Induction Of Heat Shock Protein 27 Research Articles

Porphyromonas gingivalis activates Heat-Shock-Protein 27 to drive a LC3C-specific probacterial form of select autophagy that is redox sensitive for intracellular bacterial survival in human gingival mucosa.

Porphyromonas gingivalis , a major oral pathobiont, evades canonical host pathogen clearance in human primary gingival epithelial cells (GECs) by initiating a non-canonical variant of autophagy consisting of Microtubule-associated protein 1A/1B-light chain 3 (LC3)-rich autophagosomes, which then act as replicative niches. Simultaneously, P. gingivalis inhibits apoptosis and oxidative-stress, including extracellular-ATP (eATP)-mediated reactive-oxygen-species (ROS) production via phosphorylating Heat Shock Protein 27 (HSp27) with the bacterial nucleoside-diphosphate-kinase (Ndk). Here, we have mechanistically identified that P. gingivalis -mediated induction of HSp27 is crucial for the recruitment of the LC3 isoform, LC3C, to drive the formation of live P. gingivalis -containing Beclin1-ATG14-rich autophagosomes that are redox sensitive and non-degrading. HSp27 depletions of both infected GECs and gingiva-mimicking organotypic-culture systems resulted in the collapse of P. gingivalis -mediated autophagosomes, and abolished P. gingivalis -induced LC3C-specific autophagic-flux in a HSp27-dependent manner. Concurrently, HSp27 depletion accompanied by eATP treatment abrogated protracted Beclin 1-ATG14 partnering and decreased live intracellular P. gingivalis levels. These events were only partially restored via treatments with the antioxidant N-acetyl cysteine (NAC), which rescued the cellular redox environment independent of HSp27. Moreover, the temporal phosphorylation of HSp27 by the bacterial Ndk results in HSp27 tightly partnering with LC3C, hindering LC3C canonical cleavage, extending Beclin 1-ATG14 association, and halting canonical maturation. These findings pinpoint how HSp27 pleiotropically serves as a major platform-molecule, redox regulator, and stepwise modulator of LC3C during P. gingivalis -mediated non-canonical autophagy. Thus, our findings can determine specific molecular strategies for interfering with the host-adapted P. gingivalis ' successful mucosal colonization and oral dysbiosis.

Abstract 1761: Dual inhibition of HSP27 and FAO as a novel therapeutic strategy for cisplatin-resistant ovarian cancer

Abstract Cisplatin is the most commonly employed chemotherapeutic drug for ovarian cancer treatment. However, most ovarian cancer patients experience recurrent cisplatin-resistant cancer, for which treatment options are limited. We have previously shown that inhibition of heat shock protein 27 (HSP27) or fatty acid oxidation (FAO) sensitizes cisplatin-resistant ovarian cancer cells to cisplatin. However, it is unknown if HSP27 and FAO pathways interact to promote cisplatin resistance in ovarian cancer cells. Therefore, we tested whether cisplatin-resistant ovarian cancer cells are sensitive to concurrent HSP27 and FAO inhibition. Strikingly, dual inhibition of HSP27 and FAO, with the clinically employed drugs ivermectin and perhexiline respectively, dramatically decreased the viability of A2780CIS, a cisplatin-resistant ovarian cancer cell line. We also found that HSP27 knockdown cancer cells are more sensitive to cisplatin and perhexiline dual treatment. Thus, we sought to test the hypothesis that cisplatin-resistant ovarian cancer cells rely on FAO upon HSP27 inhibition to maintain cisplatin resistance. To test if FAO is affected by HSP27 inhibition, we measured AMPK activity and CPT1A expression, an inducer of FAO and the rate limiting enzyme of FAO respectively. We found that AMPK is activated and CPT1A is upregulated in HSP27 knockdown cancer cells. It has been shown that cisplatin induces reactive oxygen species (ROS) and that HSP27 is a negative regulator of ROS. Thus, we treated HSP27 knockdown cancer cells with cisplatin and measured the levels of mitochondrial and cellular ROS, oxidized/reduced lipids, and reduced thiols using MitoSOX, CellROX, Image -iT Lipid Peroxidation, and ThiolTracker fluorescent dyes, respectively. Our data demonstrates that HSP27 inhibition increases mitochondrial ROS, cellular ROS, and the ratio of oxidized to reduced lipids in cisplatin-treated cells. Additionally, HSP27 inhibition decreases levels of reduced thiols in this context. Our preliminary data also suggests that cisplatin-treated HSP27 knockdown cells have decreased expression of glucose-6-phosphate dehydrogenase (G6PD) and glutathione reductase (GSR), key enzymes that facilitate the reduction of glutathione into its reduced form (GSH). Additionally, we demonstrate that attenuation of cisplatin-induced ROS with N-Acetyl cysteine (NAC) prevented cisplatin-induced apoptosis and ferroptosis. NAC also attenuated cisplatin-mediated induction of HSP27 and FAO gene expression in cisplatin-resistant ovarian cancer cells. Collectively, our results demonstrate that HSP27 and FAO are two parallel pathways that promote cisplatin resistance in ovarian cancer cells by attenuating cisplatin-induced ROS. Future studies will determine the in vivo efficacy of this combination therapy and if dual inhibition leads to synergistic cell death through a ROS based mechanism. Citation Format: James P. Heiserman, Zenab Minhas, Dong-Joo Cheon. Dual inhibition of HSP27 and FAO as a novel therapeutic strategy for cisplatin-resistant ovarian cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 1761.

Human Cytomegalovirus Stimulates Monocyte-to-Macrophage Differentiation via the Temporal Regulation of Caspase 3

Monocytes are primary targets for human cytomegalovirus (HCMV) infection and are proposed to be responsible for hematogenous dissemination of the virus. Biologically, monocytes have a short life span of 48 h in the circulation, a period of time during which monocytes must make a cell fate decision on whether to undergo apoptosis or differentiate into a macrophage. We have previously shown that HCMV infection stimulates monocyte-to-macrophage differentiation; however, the mechanism(s) by which HCMV-infected monocytes simultaneously navigate the 48-h "viability gate" and undergo macrophagic differentiation has remained elusive. Studies have demonstrated that the level of caspase 3 and 8 activities in monocytes may mediate the delicate balance between apoptosis and macrophage colony-stimulating factor (M-CSF)-induced myeloid differentiation. Here, we show that HCMV infection, unlike M-CSF treatment, does not induce caspase 8 activity to promote myeloid differentiation. However, HCMV infection does induce a temporal activation of caspase 3, with only a low level of active caspase 3 being observed after the 48-h viability checkpoint. Consistent with the role of a time-dependent activation of caspase 3 in promoting myeloid differentiation, the inhibition of caspase 3 blocked HCMV-induced monocyte-to-macrophage differentiation. Temporal transcriptome and functional analyses identified heat shock protein 27 (HSP27) and Mcl-1, two known regulators of caspase 3 activation, as being upregulated prior to the 48-h viability gate following HCMV infection. Using small interfering RNAs (siRNAs), we demonstrate that HCMV targets the rapid induction of HSP27 and Mcl-1, which cooperatively function to precisely control caspase 3 activity in order to allow for HCMV-infected monocytes to successfully traverse the 48-h cell fate decision checkpoint and commence macrophage maturation. Overall, this study highlights a unique regulatory mechanism employed by HCMV to tightly modulate the caspase 3 activity needed to promote myeloid differentiation, a key process in the viral dissemination and persistence strategy.

Abstract B42: Heat Shock Protein 27 (HSP27, HSPB1) is up-regulated by MET kinase inhibition and limits the effectiveness of inhibitors

Abstract The receptor for the hepatocyte growth factor (HGF) is encoded by the MET oncogene and its activation results in cell growth, survival, motility and invasiveness. Deregulated HGF/MET signaling is observed in many tumors and both HGF and MET are attractive candidates for targeted therapies. Unexpectedly, we found that in ovarian cancer cells the activation of the MET receptor downmodulated the expression of the small heat shock protein 27 (HSP27), which functions as a molecular chaperone and as an antiapoptotic protein. In MET addicted gastric carcinoma cells, where MET is constitutively active, MET kinase inhibition by JNJ-38877605 up-regulated HSP27 expression. More importantly, in these gastric carcinoma cells suppression of HSP27 was alone able to induce cell death and increased cell susceptibility to MET inhibition. HSP27 suppression did not affect MET stability and phosphorylation, but increased activation of caspase 3, which is a known HSP27 client protein. Regulation of HSP27 expression by MET signaling occurred at transcriptional level, as confirmed by the use of HSP27 promoter in a reporter assay. It was not due to the engagement of HSF1, the master key transcription factor regulating HSPs expression, but depended on MEK activation and resulting HIF 1alpha stabilization. MEK inhibition and HIF 1 alpha silencing resulted in the induction of HSP27, suggesting a direct or indirect transcriptional repression. Altogether data show that MET activation down-regulates and MET inhibition up-regulates HSP27 expression, and that HSP27 increased expression protects cells from death induced by MET inhibitors. Therefore, in therapies with MET targeting agents, HSP27 increase might impair the effectiveness of MET inhibitors. As it is known that HSP27 protects cells for chemotherapeutics, data suggest that HSP27 might strongly affect combinatorial treatments.

Sphingosine kinase 1 protects against renal ischemia–reperfusion injury in mice by sphingosine-1-phosphate1 receptor activation

The roles of sphingosine kinases SK1 and SK2 in ischemia-reperfusion injury have not been fully elucidated since studies have found beneficial effects of SK1 while others showed no role in this injury. To help resolve this, we used SK1 or SK2 knockout mice and confirmed that renal ischemia-reperfusion injury induced SK1, but not SK2, in the kidneys. Furthermore, knockout or pharmacological inhibition of SK1 increased injury after renal ischemia-reperfusion injury. In contrast, lack of SK2 conferred renal protection following injury. In addition, we used lentiviral gene delivery to selectively express enhanced green fluorescent protein (EGFP) or human SK1 coexpressed with EGFP (EGFP-huSK1) in the kidney. Mice with kidney-specific overexpression of EGFP-huSK1 had significantly improved renal function with lower plasma creatinine, renal necrosis, apoptosis, and inflammation. Moreover, EGFP-huSK1 overexpression in cultured human proximal tubule (HK-2) cells protected against peroxide-induced necrosis. Selective overexpression of EGFP-huSK1 led to increased HSP27 mRNA and protein expression in vivo and in vitro. Functional protection as well as induction of HSP27 with EGFP-huSK1 overexpression in vivo was blocked with sphingosine-1-phosphate-1 receptor(1) (S1P(1)) antagonism. Thus, our findings suggest that SK1 is renoprotective by S1P(1) activation and perhaps HSP27 induction. Kidney-specific expression of SK1 through lentiviral delivery may be a viable therapeutic option to attenuate renal ischemia-reperfusion injury.

Role of heat shock protein 27 in transforming growth factor-β-stimulated vascular endothelial growth factor release in osteoblasts

We have previously reported that transforming growth factor-β (TGF-β) stimulates heat shock protein27 (HSP27) induction via p44/p42 mitogen-activated protein (MAP) kinase, p38 MAP kinase and stress-activated protein kinase/c-Jun N-terminal kinase in osteoblast-like MC3T3-E1 cells, and that the release of vascular endothelial growth factor (VEGF) is induced by TGF-β in these cells. In the present study, we investigated the effect of HSP27 knockdown on the TGF-β-stimulated VEGF release in these cells. Gene silencing using short interfering RNA against HSP27 (HSP27-siRNA) significantly suppressed the TGF-β-induced VEGF release. Immunofluorescence microscopy also revealed that HSP27-siRNA suppressed the TGF-β-stimulated VEGF induction as well as the reduction of HSP27 induction in these cells. However, the mRNA expression of VEGF stimulated by TGF-β was not reduced even in cells transfected with HSP27-siRNA. These results strongly suggest that HSP27 induction is critical for TGF-β-induced VEGF release in osteoblasts.

Rho-kinase regulates prostaglandin D2-stimulated heat shock protein 27 induction in osteoblasts

We previously reported that prostaglandin D(2) (PGD(2)) stimulates heat shock protein 27 (HSP27) induction through p44/p42 mitogen-activated protein (MAP) kinase, p38 MAP kinase and stress-activated protein kinase/c-Jun N-terminal kinase (SAPK/JNK) in osteoblast-like MC3T3-E1 cells. In addition, we recently showed that PGD(2) activates Rho-kinase, resulting in the regulation of interleukin-6 synthesis via activation of p38 MAP kinase but not p44/p42 MAP kinase in these cells. In the present study, in order to investigate whether Rho-kinase is involved in the PGD(2)-stimulated HSP27 induction in MC3T3-E1 cells, we examined the effects of Rho-kinase inhibitors on HSP27 induction. Y27632 and fasudil, Rho-kinase inhibitors, markedly suppressed the HSP27 induction stimulated by PGD(2) in a dose-dependent manner without affecting levels of HSP70 in the presence of PGD(2). Immunofluorescence microscopy studies also revealed that Y27632 and fasudil markedly suppressed the induction of HSP27. Y27632 and fasudil attenuated the PGD(2)-induced phosphorylation levels of SAPK/JNK. In conclusion, Rho-kinase inhibitors regulate PGD(2)-stimulated HSP27 induction via activation of both SAPK/JNK and p38 MAP kinase in osteoblasts.

Involvement of Rho-kinase in TGF-β-stimulated heat shock protein 27 induction in osteoblasts

We previously reported that transforming growth factor-β (TGF-β) stimulates heat shock protein 27 (HSP27) induction through p44/p42 mitogen-activated protein (MAP) kinase, p38 MAP kinase and stress-activated protein kinase/ c-Jun N-terminal kinase (SAPK/JNK) in osteoblast-like MC3T3-E1 cells. In addition, we recently reported that the Rho-kinase inhibitors Y27632 and fasudil suppressed the TGF-β-induced phosphorylation of SAPK/JNK, but not p44/p42 MAP kinase, p38 MAP kinase or Smad2. In the present study, to investigate whether Rho-kinase is involved in TGF-β-stimulated HSP27 induction in MC3T3-E1 cells, we examined the effects of Rho-kinase inhibitors on HSP27 induction. Y27632 and fasudil significantly suppressed the HSP27 induction stimulated by TGF-β in a dose-dependent manner, without affecting the protein levels of HSP70 or HSP90. Immunofluorescence microscopy also revealed that TGF-β clearly stimulated, while Y27632 and fasudil markedly suppressed, HSP27 induction in the cytosol of these cells. Taken together, these findings indicate that Rho-kinase regulates TGF-β-stimulated HSP27 induction via SAPK/JNK activation in osteoblasts.

(−)-Epigallocatechin gallate attenuates the induction of HSP27 stimulated by sphingosine 1-phosphate via suppression of phosphatidylinositol 3-kinase/Akt pathway in osteoblasts

We previously reported that sphingosine 1-phosphate stimulates the induction of heat shock protein 27 (HSP27) through p38 mitogen-activated protein (MAP) kinase and phosphatidylinositol 3-kinase/Akt in osteoblast-like MC3T3-E1 cells. In the present study, we investigated whether (-)-epigallocatechin gallate (EGCG), the major polyphenol found in green tea, affects the induction of HSP27 in these cells and its mechanism, since it was previously reported that catechin, including EGCG, suppresses bone resorption. EGCG significantly reduced the induction of HSP27 stimulated by sphingosine 1-phosphate in a dose-dependent manner between 10 and 30 microM. Immunofluorescence microscopy studies revealed that sphingosine 1-phosphate certainly stimulated the induction of HSP27 in the cytosol of these cells, and that EGCG clearly suppressed its induction. However, sphingosine 1-phosphate-stimulated phosphorylation of p38 MAP kinase or MAPKAP-2 was not affected by EGCG. By contrast, EGCG markedly suppressed the phosphorylations of both Akt and glycogen synthase kinase-3beta stimulated by sphingosine 1-phosphate. These results strongly suggest that EGCG suppresses the induction of HSP27 stimulated by sphingosine 1-phosphate via attenuation of, not the p38 MAP kinase pathway, but of the phosphatidylinositol 3-kinase/Akt pathway in osteoblasts.

Mice that overexpress human heat shock protein 27 have increased renal injury following ischemia reperfusion

We previously showed that activation of the A1 adenosine receptor protected the kidney against ischemia-reperfusion injury by induction and phosphorylation of heat shock protein 27 (HSP27). Here, we used mice that overexpress human HSP27 (huHSP27) to determine if kidneys from these mice were protected against injury. Proximal tubule cells cultured from the transgenic mice had increased resistance to peroxide-induced necrosis compared to cells from wild-type mice. However, after renal ischemic injury, HSP27 transgenic mice had decreased renal function compared to wild-type mice, along with increased renal expression of mRNAs of pro-inflammatory cytokines (TNF-alpha, ICAM-1, MCP-1) and increased plasma and kidney keratinocyte-derived cytokine. Following ischemic injury, neutrophils infiltrated the kidneys earlier in the transgenic mice. Flow cytometric analysis of lymphocyte subsets showed that those isolated from the kidneys of transgenic mice had increased CD3(+), CD4(+), CD8(+), and NK1.1(+) cells 3 h after injury. When splenocytes or NK1.1(+) cells were isolated from transgenic mice and adoptively transferred into wild-type mice there was increased renal injury. Further, depletion of lymphocytes by splenectomy or neutralization of NK1.1(+) cells resulted in improved renal function in the transgenic mice following reperfusion. Our study shows that induction of HSP27 in renal tubular cells protects against necrosis in vitro, but its systemic increase counteracts this protection by exacerbating renal and systemic inflammation in vivo.

(−)-Epigallocatechin gallate reduces transforming growth factor β-stimulated HSP27 induction through the suppression of stress-activated protein kinase/c-Jun N-terminal kinase in osteoblasts

We previously reported that transforming growth factor-β (TGF-β) stimulates heat shock protein 27 (HSP27) induction through p38 mitogen-activated protein (MAP) kinase and extracellular signal-regulated kinase 1/2 (ERK1/2) in osteoblast-like MC3T3-E1 cells. In the present study, we investigated whether (−)-epigallocatechin gallate (EGCG), the major polyphenol found in green tea, affects the TGF-β-stimulated induction of HSP27 in these cells, and its underlying mechanism. EGCG significantly suppressed the HSP27 induction stimulated by TGF-β in a dose-dependent manner between 10 and 30 µM without affecting the HSP70 levels. TGF-β with or without EGCG did not affect the advanced oxidation protein products. The TGF-β-induced phosphorylation of p38 MAP kinase and ERK1/2 was not affected by EGCG. SP600125, a specific inhibitor of stress-activated protein kinase (SAPK)/c-Jun N-terminal kinase (JNK), markedly reduced the HSP27 expression induced by TGF-β. EGCG significantly suppressed the TGF-β-induced phosphorylation of SAPK/JNK without affecting the phosphorylation of Smad2. EGCG attenuated the phosphorylation of both MKK4 and TAK1 induced by TGF-β. These results strongly suggest that EGCG suppresses the TGF-β-stimulated induction of HSP27 via the attenuation of the SAPK/JNK pathway in osteoblasts, and that this effect is exerted at a point upstream from TAK1.

Acute and delayed renal protection against renal ischemia and reperfusion injury with A1adenosine receptors

We showed previously that activation of A(1) adenosine receptors (AR) protects against renal ischemia-reperfusion (IR) injury in rats and mice. In the heart, transient A(1)AR activation produces biphasic protective effects: acute protection wanes after several hours but protective effects return 24-72 h later (second window of protection). In this study, we determined whether A(1)AR activation produces delayed renal protection and elucidated the mechanisms of acute and delayed renal protection. A(1)AR wild-type mice were subjected to 30-min renal ischemia and 24 h of reperfusion to produce acute renal failure. Pretreatment with a selective A(1)AR agonist 2-chloro-N(6)-cyclopentyladenosine (CCPA; 0.1 mg/kg bolus ip) either 15 min or 24 h before renal ischemia protected against renal IR injury and reduced renal corticomedullary necrosis, apoptosis, and inflammation. Transient A(1)AR activation led to phosphorylation of extracellular signal-regulated protein kinase mitogen-activated protein kinase (ERK MAPK), Akt, and heat shock protein 27 (HSP27). Moreover, induction of HSP27 and Akt occurred with CCPA treatment. Inhibition of PKC with chelerythrine prevented acute but not delayed renal protection with A(1)AR activation. Moreover, deletion of PI3Kgamma or inhibition of Akt, but not inhibition of ERK, prevented delayed and acute renal protection with A(1)AR activation. Inhibition of G(i/o) with pertussis toxin obliterated both acute and delayed A(1)AR-mediated renal protection. In contrast to renal protection with delayed ischemic preconditioning, nitric oxide synthase activity was not induced with delayed A(1)AR-mediated renal protection. Therefore, transient activation of renal A(1)AR led to acute as well as delayed protective effects against renal IR injury via distinct signaling pathways.

(−)-Epigallocatechin gallate inhibits prostaglandin D 2-stimulated HSP27 induction via suppression of the p44/p42 MAP kinase pathway in osteoblasts

We previously reported that prostaglandin D 2 (PGD 2) stimulates heat shock protein 27 (HSP27) induction through p38 mitogen-activated protein (MAP) kinase, stress-activated protein kinase (SAPK)/c-Jun N-terminal kinase (JNK) and p44/p42 MAP kinase in osteoblast-like MC3T3-E1 cells. In the present study, we investigated whether (−)-epigallocatechin gallate (EGCG), the major polyphenol found in green tea, affects the induction of HSP27 in these cells and the mechanism. EGCG significantly reduced the HSP27 induction stimulated by PGD 2 without affecting the levels of HSP70. The PGD 2-induced phosphorylation of p38 MAP kinase or SAPK/JNK was not affected by EGCG. On the contrary, EGCG markedly suppressed the PGD 2-induced phosphorylation of p44/p42 MAP kinase and MEK1/2. However, the PGD 2-induced phosphorylation of Raf-1 was not inhibited by EGCG. These results strongly suggest that EGCG suppresses the PGD 2-stimulated induction of HSP27 at the point between Raf-1 and MEK1/2 in osteoblasts.

Heat shock protects cardiac cells from doxorubicin-induced toxicity by activating p38 MAPK and phosphorylation of small heat shock protein 27.

Doxorubicin (DOX) and its derivatives are used as chemotherapeutic drugs to treat cancer patients. However, production of DOX-mediated reactive oxygen species (ROS) by prolonged use of these drugs has been found to cause dilative cardiomyopathy and congestive heart failure. Thus various preventive modalities have been developed to avoid this side effect. We have found that the DOX-mediated oxidant-induced toxicity in cardiac cells could be minimized by hyperthermia-induced small heat shock protein 27 (HSP27); that is, this protein acts as an endogenous antioxidant against DOX-derived oxidants such as H(2)O(2). Heat shock-induced HSP27 was found to act as an antiapoptotic protein (reducing ROS and Bax-to-Bcl2 ratio) against DOX, and its phosphorylated isoforms stabilized F-actin remodeling in DOX-treated cardiac cells and, hence, attenuated the toxicity. Protein kinase assays and proteomic analyses suggested that higher expression of HSP27 and its phosphorylation are responsible for the protection in heat-shocked cells. Two-dimensional gel electrophoresis showed six isoforms (nonphosphorylated and phosphorylated) of HSP27. Matrix-assisted laser desorption/ionization time of flight analyses showed alpha- and beta-isoforms of HSP27, which are phosphorylated by various protein kinases. Ser(15) and Ser(85) phosphorylation of HSP27 by MAPK-assisted protein kinase 2 was found to be the key mechanism in reduction of apoptosis and facilitation of F-actin remodeling. The present study illustrates that hyperthermia protects cells from DOX-induced death through induction and phosphorylation of HSP27 and its antiapoptotic and actin-remodeling activities.

Phosphatidylinositol 3‐kinase/Akt plays a role in sphingosine 1‐phosphate‐stimulated HSP27 induction in osteoblasts

We previously reported that p38 mitogen-activated protein (MAP) kinase plays a part in sphingosine 1-phosphate-stimulated heat shock protein 27 (HSP27) induction in osteoblast-like MC3T3-E1 cells. In the present study, we investigated whether phosphatidylinositol 3-kinase (PI3K)/protein kinase B (Akt) is involved in the induction of HSP27 in these cells. Sphingosine 1-phosphate time dependently induced the phosphorylation of Akt. Akt inhibitor, 1L-6-hydroxymethyl-chiro-inositol 2-(R)-2-O-methyl-3-O-octadecylcarbonate, reduced the HSP27 induction stimulated by sphingosine 1-phosphate. The sphingosine 1-phosphate-induced phosphorylation of GSK-3beta was suppressed by Akt inhibitor. The sphingosine 1-phosphate-induced HSP27 levels were attenuated by LY294002 or wortmannin, PI3K inhibitors. Furthermore, LY294002 or Akt inhibitor did not affect the sphingosine 1-phosphate-induced phosphorylation of p38 MAP kinase and SB203580, a p38 MAP kinase inhibitor, had little effect on the phosphorylation of Akt. These results suggest that PI3K/Akt plays a part in the sphingosine 1-phosphate-stimulated induction of HSP27, maybe independently of p38 MAP kinase, in osteoblasts.

Bilateral, vascular and perivascular glial upregulation of heat shock protein-27 after repeated epileptic seizures

Heat shock protein-27 (HSP-27) is an inducible stress response protein. It inhibits apoptotic cell death and is a reliable marker for oxidative stress. We studied the induction of HSP-27 in rat brains on days 1, 4 and 14 after repeated, pentylenetetrazole (PTZ)-induced seizures using immunohistochemisty. Saline treated control rats showed no induction of HSP-27. HSP-27 reactive astrocytes were rarely seen 1 or 4 days after PTZ injection. When present, single astrocytes were located in the cortex and/or the hippocampus. After 14 days PTZ treatment, a bilateral distribution of HSP-27 immunoreactive glia was present in piriform and entorhinal cortices and in the dentate gyrus of most brains. Rats with most intense HSP-27 upregulation showed HSP-27 in amygdala and thalamic nuclei. Astrocytes associated with blood vessels presented strongest HSP-27 staining, but did not show upregulation of gial fibrillary acidic protein and none responded with HSP-47 expression. Additionally, HSP-27 immunoreactivity increased in the endothelial cells of blood vessels in the affected brain regions, although no neuronal induction occurred. Contrastingly, a subconvulsive dose of the glutamine synthetase inhibitor l-methionine sulfoxime, which acts directly on astrocytes, resulted in a rapid, homogeneous astrocyte-specific HSP-27 upregulation within 24 h. Thus, repeated PTZ-induced seizure activity elicits a focal “heat shock” response in endothelial cells and astrocytes of selected cerebral regions indicating that expression of HSP-27 occurred in a seizure-dependent manner within the affected cerebral circuitries. Therefore, this PTZ-model of repeated seizure activity exhibited a cortical pattern of HSP-27 expression which is most comparable to that known from patients with epilepsy.

1α,25-Dihydroxy-vitamin D 3 in combination with 17β-estradiol lowers the cortical expression of heat shock protein-27 following experimentally induced focal cortical ischemia in rats

1α,25-(OH) 2-vitamin-D 3 (1,25-D 3) and 17β-estradiol are both known to act neuroprotective in certain experimental in vitro and in vivo settings. We studied the effects of 1,25-D 3 or 17β-estradiol or their combined application on heat shock protein-27 (HSP-27) distribution after focal cortical ischemia using the photothrombosis model. HSP-27 is a well-established marker of the cerebral oxidative stress response and a potent inhibitor of apoptosis. Lesioned rats were injected i.p. one hour after injury with either 1 μg 1,25-D 3/kg or 7 μg 17β-estradiol/kg or a combination of both steroids. Groups of non-lesioned steroid-treated rats and lesioned, solvent-treated rats served as controls. Treatment with both steroids did not affect the size of the lesion. In addition, 17β-estradiol resulted in significant reduction of HSP-27 induction, whereas the combination of 1,25-D 3 + 17β-estradiol resulted in a highly significant reduction of HSP-27 within the infracted cerebral cortex, indicating that both steroids act synergistically in a protective manner.

Heat Shock Protein‐27 Is Upregulated in the Temporal Cortex of Patients with Epilepsy

Heat shock protein-27 (HSP-27) belongs to the group of small heat shock proteins that become induced in response to various pathologic conditions. HSP-27 has been shown to protect cells and subcellular structures, particularly mitochondria, and serves as a carrier for estradiol. It is a reliable marker for tissues affected by oxidative stress. Oxidative stress and related cellular defence mechanisms are currently thought to play a major role during experimentally induced epileptic neuropathology. We addressed the question whether HSP-27 becomes induced in the neocortex resected from patients with pharmacoresistant epilepsy. Human epileptic temporal neocortex was obtained during neurosurgery, and control tissue was obtained at autopsy from subjects without known neurologic diseases. The tissues were either frozen for Western blot analysis or fixed in Zamboni's fixative for the topographic detection of HSP-27 at the cellular level by means of immunohistochemistry. HSP-27 was highly expressed in all epilepsy specimens and in the cortex of a patient who died in the final stage of multiple sclerosis (positive control), whereas only low amounts of HSP-27 were detectable in control brains. In epilepsy patients, HSP-27 was present in astrocytes and in the walls of blood vessels. The intracortical distribution patterns varied strongly among the epilepsy specimens. These results demonstrate that HSP-27 becomes induced in response to epileptic pathology. Although the functional aspects of HSP-27 induction during human epilepsy have yet to be elucidated, it can be concluded that HSP-27 is a marker for cortical regions in which a stress response has been caused by seizures.

Methotrexate enhances prostaglandin [formula omitted]-stimulated heat shock protein 27 induction in osteoblasts

As for the pathogenesis of rheumatoid arthritis (RA), prostaglandins (PGs) act as important mediators of inflammation and joint destruction. Among them, PGD 2 is well recognized as a potent regulator of osteoblastic functions. We previously showed that PGD 2 stimulates the induction of heat shock protein 27 (HSP27) via protein kinase C (PKC)-dependent p38 mitogen-activated protein (MAP) kinase and p44/p42 MAP kinase in osteoblast-like MC3T3-E1 cells. Therefore, it is a current topic to clarify how HSP27 plays a role for regulating osteoblastic functions in the lesion of RA. On the other hand, methotrexate (MTX) is one of the most effective medicines for the treatment of RA. Here, we examined the effect of MTX on PGD 2 -stimulated HSP27 induction in MC3T3-E1 cells. The cells were pretreated with various doses of MTX including therapeutic dosage for RA, and then stimulated by PGD 2 . MTX significantly enhanced the PGD 2 - increased levels of HSP27 in a dose-dependent manner, although MTX alone had no effect on the levels of HSP27. In addition, MTX amplified the PGD 2 -increased levels of HSP27 mRNA. On the contrary, MTX had little effect on PGD 2 -induced formation of inositol phosphates, PKC activation and phosphorylations of MAP kinases. Our results strongly suggest that MTX enhances PGD 2 -stimulated HSP27 induction at a point downstream from MAP kinases in osteoblasts.

Endothelial barrier dysfunction caused by LPS correlates with phosphorylation of HSP27 in vivo.

Lung edema during sepsis is triggered by formation of gaps between endothelial cells followed by macrophage infiltration. Endothelial gap formation has been proposed to involve changes in the structure of the actin filament cytoskeleton. Heat shock protein 27 (HSP27) is believed to modulate actin filament dynamics or structure, in a manner dependent on its phosphorylation status. We hypothesized that HSP27 may play a role in endothelial gap formation, by affecting actin dependent events in endothelial cells. As there has been no report concerning HSP27 in lung edema in vivo, we examined induction and phosphorylation of HSP27 in lung following LPS injection, as a model of sepsis. In lung, HSP27 mainly localized in capillary endothelial cells of the alveolus, and in smooth muscle cells of pulmonary arteries. HSP27 became significantly more phosphorylated at 3 h after LPS treatment, while the distribution of HSP27 remained unchanged. Pre-treatment with anti-TNFalpha antibody, which has been shown to reduce lung injury, blocked increases in HSP27 phosphorylation at 3 h. HSP27 phosphorylation was also increased in cultured rat pulmonary arterial endothelial cells (RPAEC) by treatment with TNFalpha, LPS, or H2O2. This phosphorylation was blocked by pre-treatment with SB203580, an inhibitor of the upstream kinase, p38 MAP kinase. Increased endothelial permeability caused by H2O2 in vitro was also blocked by SB203580. The amount of actin associated with HSP27 was reduced after treatment with LPS, or H2O2. In summary, HSP27 phosphorylation temporally correlated with LPS induced pathological endothelial cell gap formation in vivo and in a cell culture model system. This is the first report of increased HSP27 phosphorylation associated with pathological lung injury in an animal model of sepsis.