Organotypic cultures of chick dorsal root ganglia in a semi-solid medium: A model for neurotoxicity testing

Neurotoxicity of Seven MEIC Chemicals Evaluated in Organotypic Cultures of Chick Embryonic Dorsal Root Ganglia

The neurotoxic effects of seven selected Multicenter Evaluation of In Vitro Cytotoxicity programme chemicals (methanol, ethanol, isopropanol, sodium chloride, potassium chloride, iron [II] sulphate and chloroform) were evaluated in organotypic cultures of chick embryonic dorsal root ganglia (DRG), maintained in a soft agar culture medium. Two growth parameters of neurite outgrowth from the ganglia — the mean radial length of neurites and the area of neurite outgrowth — were used to evaluate the toxicities of the chemicals. Dose-dependent decreases of both parameters were observed in all experiments. IC50 values (the concentration causing 50% inhibition of growth) were calculated from the dose-response curves established at three time-points during culture, i.e. 24, 48 and 72 hours. The lowest toxic effect was observed in cultures exposed to methanol (the IC50 ranging from 580mM to 1020mM). The highest toxic effect was observed in cultures exposed to iron (II) sulphate (the IC50 ranging from 1.2mM to 1.7mM). The results of other recent experiments suggest that organotypic cultures of DRG can be used during in vitro studies on target organ toxicity within the peripheral nervous system. Moreover, these cultures preserve the internal organisation of the tissue, maintain intercellular contacts, and thus reflect the in vitro situation, more precisely than other cell cultures.

Imbalance between sympathetic and sensory innervation in peritoneal endometriosis

To investigate possible mechanisms of pain pathophysiology in patients with peritoneal endometriosis, a clinical study on sensory and sympathetic nerve fibre sprouting in endometriosis was performed. Peritoneal lesions (n=40) and healthy peritoneum (n=12) were immunostained and analysed with anti-protein gene product 9.5 (PGP 9.5), anti-substance P (SP) and anti-tyrosine hydroxylase (TH), specific markers for intact nerve fibres, sensory nerve fibres and sympathetic nerve fibres, respectively, to identify the ratio of sympathetic and sensory nerve fibres. In addition, immune cell infiltrates in peritoneal endometriotic lesions were analysed and the nerve growth factor (NGF) and interleukin (IL)-1β expression was correlate with the nerve fibre density. Peritoneal fluids from patients with endometriosis (n=40) and without endometriosis (n=20) were used for the in vitro neuronal growth assay. Cultured chicken dorsal root ganglia (DRG) and sympathetic ganglia were stained with anti-growth associated protein 43 (anti-GAP 43), anti-SP and anti-TH. We could detect an increased sensory and decreased sympathetic nerve fibres density in peritoneal lesions compared to healthy peritoneum. Peritoneal fluids of patients with endometriosis compared to patients without endometriosis induced an increased sprouting of sensory neurites from DRG and decreased neurite outgrowth from sympathetic ganglia. In conclusion, this study demonstrates an imbalance between sympathetic and sensory nerve fibres in peritoneal endometriosis, as well as an altered modulation of peritoneal fluids from patients with endometriosis on sympathetic and sensory innervation which might directly be involved in the maintenance of inflammation and pain.

Neurotoxicity of tetraphenylporphinesulfonate (TPPS4) and a hematoporphyrin derivative (Photosan) in organotypic cultures of chick embryonic dorsal root ganglia

The neurotoxic effect of tetraphenylporphinesulfonate (TPPS4) and a hematoporphyrin derivative (HPD, Photosan) has been studied in organotypic cultures of chick dorsal root ganglia maintained in a semi-solid culture medium. The changes in two characteristics of neurite outgrowth, the mean radial length of neurites growing out from the ganglia and the area of neurite outgrowths, are used as parameters to evaluate the toxic effect. The porphyrins are tested over the concentration range 10-160 micrograms ml-1. TPPS4 is slightly more toxic than the HPD Photosan. The median inhibitory concentration (IC50) for TPPS4 is 45-50 micrograms ml-1 and for the HPD Photosan 50-60 micrograms ml-1, respectively. Nevertheless, the toxicity of the two drugs is relatively low compared to that of commonly used anticancer drugs, such as cisplatin or taxol.

Organotypic spinal cord culture in serum-free fibrin gel: a new approach to study three-dimensional neurite outgrowth and of neurotoxicity testing: Effects of modulating the actin and tubulin dynamics and protein kinase activities

Spinal cord explants from embryonic day seven (E7) chicken embryos were cultured without serum and in the presence of aprotinine, in a three-dimensional fibrin matrix. These conditions promote a robust, radial, unfasciculated outgrowth of neurites that are tipped by elaborate growth cones. Routinely after 5 days, the neurite outgrowth intensity (NOI) was determined by measuring the optical density of the immunostained neurites (image analysis program OPTIMAS version 5.2) within defined areas, extending radially for up to 3 mm from the explant border. A dose-dependent inhibition of NOI was determined for the cytoskeleton-affecting drugs nocodazole (half maximal inhibition ([I50]), 0.02 microM), taxol ([I50], 0.016 microM), cytochalasin D ([I50], 0.006 microM), and tetramethyl lead ([I50], 0.05 microM). Likewise, NOI was decreased in a dose-dependent fashion by ML-9 and RO-31-8220, inhibitors of myosin-light chain kinase and protein kinase C (PKC), respectively. The addition of 1,2-dioctanoyl-s,n-glycerol, a potent activator of PKC, led, at 5 microM, to an increase and at 30 and 60 microM to a decrease in NOI. The described system provides a rapid, reproducible, and quantitative assay for the effects of exogenous factors on the mode and intensity of neurite outgrowth.

ACTH-related peptides: receptors and signal transduction systems involved in their neurotrophic and neuroprotective actions

ACTH-related peptides are promising neurotrophic and neuroprotective agents, as demonstrated in many in vivo and in vitro studies. They accelerate nerve repair after injury, improving both sensor and motor function. Furthermore, ACTH-related peptides have neuroprotective properties against cisplatin- and taxol-induced neurotoxicity, they improve neuronal function in animals with neuropathy due to experimental diabetes, and they prevent degeneration of myelinated axons in rats suffering from experimental allergic neuritis, a model of peripheral demyelinating neuropathy. Studies in neuronal cultures have corroborated these clinical observations and serve to investigate the mechanism of action of the ACTH-related peptide effects. This paper reviews both in vitro and in vivo effects and emphasizes the mechanism of action. Recent data on melanotrophic receptors and signal transduction systems will be discussed in this context.

Protection by an ACTH4-9 analogue against the toxic effects of cisplatin and taxol on sensory neurons and glial cells in vitro

Sensory neuropathy is a serious side effect of anti-tumour drugs such as cisplatin and taxol. There are indications that an analogue of the adrenocorticotrophic hormone 4-9 fragment (ACTH4-9: Met(O2)-Glu-His-Phe-D-Lys-Phe) can prevent these neurotoxic effects. We studied the potential protective effects of this analogue in cultures of chick dorsal root ganglia and rat Schwann cells treated with cisplatin or taxol to gain insight into the mode of action and characteristics of this neuroprotection. Neurite outgrowth of sensory neurons in vitro was dose-dependently inhibited by cisplatin and taxol; after 48 hr, 10 micrograms/ml cisplatin reduced outgrowth from 431 +/- 17 microns to 220 +/- 6 microns and 0.01 micrograms/ml taxol from 344 +/- 3 microns to 200 +/- 43 microns. Co-treatment of 10 micrograms/ml cisplatin with the ACTH4-9 analogue (0.1 nM-1 nM) resulted in about 35% more outgrowth than cisplatin alone. In contrast, the analogue could not prevent taxol neurotoxicity. Migration of neurons and satellite cells from the DRG-body is completely inhibited by 10 micrograms/ml cisplatin. Taxol had no effect on the migration of these cells. In addition, cisplatin was more toxic to Schwann cells than taxol; 3-10 micrograms/ml cisplatin significantly reduced their laminin content, total protein, 2',3'-cyclic nucleotide 3'-phosphodiesterase activity, and cell division. The ACTH4-9 analogue (0.01 nM-100 nM) had no effect on the migration of cells out of the DRGs and could not prevent the toxic effect on the Schwann cells. These data support our hypothesis that the neuroprotective effect of ACTH4-9 analogue is brought about by a direct action on neurons, possibly by replacing a Schwann-/satellite-cell derived trophic factor.