Lanthanum suppresses arachidonic acid-induced cell death and mitochondrial depolarization in PC12 cells

Biodegradable Zn-5Dy Alloy with Enhanced Osteo/Angio-Genic Activity and Osteointegration Effect via Regulation of SIRT4-Dependent Mitochondrial Function

Zinc (Zn)-dysprosium (Dy) binary alloys are promising biodegradable bone fracture fixation implants owing to their attractive biodegradability and mechanical properties. However, their clinical application is a challenge for bone fracture healing, due to the lack of Zn-Dy alloys with tailored proper bio-mechanical and osteointegration properties for bone regeneration. A Zn-5Dy alloy with high strength and ductility and a degradation rate aligned with the bone remodeling cycle is developed. Here, mechanical stability is further confirmed, proving that Zn-5Dy alloy can resist aging in the degradation process, thus meeting the mechanical requirements of fracture fixation. In vitro cellular experiments reveal that the Zn-5Dy alloy enhances osteogenesis and angiogenesis by elevating SIRT4-mediated mitochondrial function. In vivo Micro-CT, SEM-EDS, and immunohistochemistry analyses further indicate good biosafety, suitable biodegradation rate, and great osteointegration of Zn-5Dy alloy during bone healing, which also depends on the upregulation of SIRT4-mediated mitochondrial events. Overall, the study is the first to report a Zn-5Dy alloy that exerts remarkable osteointegration properties and has a strong potential to promote bone healing. Furthermore, the results highlight the importance of mitochondrial modulation and shall guide the future development of mitochondria-targeting materials in enhancing bone fracture healing.

The Toxic Effect of Lanthanum on Planaria Is Mediated by a Variety of Ion Channels

The effect of toxic concentrations of La³⁺ on the Ca, K, Na, Mg, and Cl channels of planaria was investigated through the use of various agonists and antagonists to those channels. It was demonstrated that La exerts its toxic effects through L-type, but not T-type, Ca channels. La also demonstrated activity at Na, K, Mg, and Cl channels, but, these effects were most likely mediated by other effects of La on Ca activity. However, these interactions appear to be very complex and confounded by oxidative stresses. The study also introduces a planaria stress scale which allows the effects of toxic substances to be examined on a continuum.

Effects of Hsp90 inhibitors, geldanamycin and its analog, on ceramide metabolism and cytotoxicity in PC12 cells

The inhibitors of heat shock protein-90 (Hsp90), geldanamycin (GA) and 17-(allylamino)-17-desmethoxygeldanamycin, show various cellular effects including destabilization of Hsp90 clients and expression of other chaperones, etc. and modulate cytotoxicity depending on cell types and stimuli. In this study, we investigated the effects of Hsp90 inhibitors on survival of PC12 cells with and without cytotoxic stimuli including orthovanadate, Na(3)VO(4). Treatment with Hsp90 inhibitors at 2 µM for 16 hr did not cause cell detachment and leakage of lactate dehydrogenase, and at concentrations greater than 5 µM resulted in cytotoxicity. The inhibitors at 2 µM enhanced the cytotoxicity of 1 mM Na(3)VO(4), and did not protect PC12 cells at any concentrations against Na(3)VO(4). Next, the effects of Hsp90 inhibitors on the intracellular metabolism of ceramide and arachidonic acid (AA) were examined, since these processes also regulate cytotoxicity. In cells treated with 4-nitrobenzo-2-oxa-1,3-diazole (NBD)-labeled C6-ceramide, Hsp90 inhibitors reduced the formation of NBD-glucosylceramide and Na(3)VO(4)-induced formation of NBD-caproic acid, a counterpart of sphingosine, without affecting other metabolites including NBD-sphingomyelin. GA treatment did not change the amounts of AA released in PC12 cells with and without Na(3)VO(4). In HeLa cells, however, GA treatment decreased the release of AA via cytosolic phospholipase A(2)α's activation probably because of dysfunctional Hsp90 clients. Our results suggest the possible involvement of ceramide metabolism, not AA release, in GA-induced cytotoxicity in PC12 cells.

Apoptosis caused by imidazolium-based ionic liquids in PC12 cells

The cytotoxicity of alkylmethylimidazolium-based ionic liquids on rat pheochromocytoma (PC12) cells was evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, lactate dehydrogenase release (LDH), and acridine orange staining in the present study. Mitochondrial depolarization, DNA fragmentation, reactive oxygen species (ROS) levels, and caspase-3 activity were also determined. The results showed dose-dependent cytotoxicity of ionic liquids on PC12 cells, and the ionic liquids with longer lateral chains had stronger cytotoxicity. Additionally, we found that exposure to the ionic liquid 1-octyl-3-methylimidazolium bromide ([C(8)mim]Br) provoked cellular LDH release, increased mitochondrial depolarization, induced cellular transmogrification, nuclear shrinkage and DNA fragmentation, and promoted caspase-3 activity and ROS levels in PC12 cells. These results suggest that [C(8)mim]Br may induce PC12 cell apoptosis triggered by excessive ROS and mediated by mitochondrial depolarization and permeability transition. Our result may be helpful for illuminating the cytotoxicity mechanism of alkylmethylimidazolium-based ionic liquids and safely using them in the future.

Toxic cytological alteration and mitochondrial dysfunction in PC12 cells induced by 1-octyl-3-methylimidazolium chloride

Ionic liquids have recently received considerable attention due to their negligible vapor pressure and substitute for conventional organic solvents. However, their solubility in water and a great deal of literature regarding their toxicity on aquatic organisms have caused much concern in recent years. This study aims to evaluate the cytotoxicity of 1-octyl-3-methylimidazolium chloride ([C(8)mim][Cl]) on the rat pheochromocytoma (PC12) cell line by cell viability assay and to determine the cytological alterations and damages in PC12 cells after 24h of exposure at the concentrations of 0.07, 0.14, and 0.28 mM of [C(8)mim][Cl]. The results show that [C(8)mim][Cl] inhibits PC12 cell growth and decreases their viabilities in a remarkable dose-dependent manner, and the 24h EC(50) of [C(8)mim][Cl] for PC12 cells is calculated to be around 0.56 mM. Our results also reveal that [C(8)mim][Cl]-exposure induces DNA damage, sustained increase of intracellular Ca(2+), overproduction of reactive oxygen species, gradually exhausted cellular ATP, mitochondrial permeability transition, and apoptosis in PC12 cells. We suppose that mitochondrial permeability transition and mitochondrial dysfunction maybe the major cytotoxicity mechanism of [C(8)mim]Cl for PC12 cells.