Administration of the calcineurin inhibitor cyclosporine modulates cocaine-induced locomotor activity in rats

Treatment with the calcineurin inhibitor and immunosuppressant cyclosporine A impairs sensorimotor gating in Dark Agouti rats

RATIONALE

Calcineurin is a protein regulating cytokine expression in T lymphocytes and calcineurin inhibitors such as cyclosporine A (CsA) are widely used for immunosuppressive therapy. It also plays a functional role in distinct neuronal processes in the central nervous system. Disturbed information processing as seen in neuropsychiatric disorders is reflected by deficient sensorimotor gating, assessed as prepulse inhibition (PPI) of the acoustic startle response (ASR).

OBJECTIVE

Patients who require treatment with immunosuppressive drugs frequently display neuropsychiatric alterations during treatment with calcineurin inhibitors. Importantly, knockout of calcineurin in the forebrain of mice is associated with cognitive impairments and symptoms of schizophrenia-like psychosis as seen after treatment with stimulants.

METHODS

The present study investigated in rats effects of systemic acute and subchronic administration of CsA on sensorimotor gating. Following a single injection with effective doses of CsA, adult healthy male Dark Agouti rats were tested for PPI. For subchronic treatment, rats were injected daily with the same doses of CsA for 1 week before PPI was assessed. Since calcineurin works as a modulator of the dopamine pathway, activity of the enzyme tyrosine hydroxylase was measured in the prefrontal cortex and striatum after accomplishment of the study.

RESULTS

Acute and subchronic treatment with the calcineurin inhibitor CsA disrupted PPI at a dose of 20 mg/kg. Concomitantly, following acute CsA treatment, tyrosine hydroxylase activity was reduced in the prefrontal cortex, which suggests that dopamine synthesis was downregulated, potentially reflecting a stimulatory impact of CsA on this neurotransmitter system.

CONCLUSIONS

The results support experimental and clinical evidence linking impaired calcineurin signaling in the central nervous system to the pathophysiology of neuropsychiatric symptoms. Moreover, these findings suggest that therapy with calcineurin inhibitors may be a risk factor for developing neurobehavioral alterations as observed after the abuse of psychomotor stimulant drugs.

Chronic interstitial nephritis in agricultural communities is a toxin-induced proximal tubular nephropathy

Almost 30 years after the detection of chronic interstitial nephritis in agricultural communities (CINAC) its etiology remains unknown. To help define this we examined 34 renal biopsies from Sri Lanka, El Salvador, India and France of patients with chronic kidney disease 2-3 and diagnosed with CINAC by light and electron microscopy. In addition to known histopathology, we identified a unique constellation of proximal tubular cell findings including large dysmorphic lysosomes with a light-medium electron-dense matrix containing dispersed dark electron-dense non-membrane bound "aggregates". These aggregates associated with varying degrees of cellular/tubular atrophy, apparent cell fragment shedding and no-weak proximal tubular cell proliferative capacity. Identical lysosomal lesions, identifiable by electron microscopy, were observed in 9% of renal transplant implantation biopsies, but were more prevalent in six month (50%) and 12 month (67%) protocol biopsies and in indication biopsies (76%) of calcineurin inhibitor treated transplant patients. The phenotype was also found associated with nephrotoxic drugs (lomustine, clomiphene, lithium, cocaine) and in some patients with light chain tubulopathy, all conditions that can be directly or indirectly linked to calcineurin pathway inhibition or modulation. One hundred biopsies of normal kidneys, drug/toxin induced nephropathies, and overt proteinuric patients of different etiologies to some extent could demonstrate the light microscopic proximal tubular cell changes, but rarely the electron microscopic lysosomal features. Rats treated with the calcineurin inhibitor cyclosporine for four weeks developed similar proximal tubular cell lysosomal alterations, which were absent in a dehydration group. Overall, the finding of an identical proximal tubular cell (lysosomal) lesion in CINAC and calcineurin inhibitor nephrotoxicity in different geographic regions suggests a common paradigm where CINAC patients undergo a tubulotoxic mechanism similar to calcineurin inhibitor nephrotoxicity.

Aberrant behavioral sensitization by methamphetamine in junctophilin-deficient mice

Junctophilins (JPs) expressed in the endoplasmic/sarcoplasmic reticulum (ER/SR) interact with the plasma membrane, thereby constructing junctional membrane complexes (JMC). We here reported that double-knockout mice lacking both JP3 and JP4 (JP-DKO mice) exhibit aberrant synaptic plasticity in the corticostriatal circuits and irregular methamphetamine (METH)-induced behavioral sensitization when METH (1.0 mg/kg) was administrated six consecutive days and assessed the striatal glutamatergic population spike (PS) by stimulation of cortical white matter. When we assessed the striatal PS by stimulation of cortical white matter, the long-term depression (LTD) was observed in JP-DKO mouse striatum similar to that in control (JP-double hetero mice (JP-DHE mice)). Importantly, LTD converted to long-term potentiation (LTP) following chronic METH treatment concomitant with behavioral sensitization in JP-DHE mice. LTD in JP-DKO mice, however failed to convert to LTP with lacks of behavioral sensitization. LTP impairment in JP-DKO mice was restored by pretreatment with FK506, calcineurin (CaN) inhibitor, but not with apamin, SK channel inhibitor. In immunoblotting analyses, calcium/calmodulin-dependent protein kinase II (CaMKII) autophosphorylation was significantly increased following METH treatment in the striatum of JP-DHE mice. However, CaMKII autophosphorylation did not changed by METH treatment in the striatum of JP-DKO mouse. The increased CaMKII autophosphorylation was closely associated with elevated CaN activity in JP-DKO mice. The lack of increased CaMKII activity in JP-DKO mice was correlated with the impaired METH-induced behavioral sensitization. Thus, elevated CaN and aberrant CaMKII activities in the striatum of JP-DKO mice likely accounts for lack of METH-induced behavioral sensitization.

Role of calcineurin in the VTA in rats behaviorally sensitized to methamphetamine

RATIONALE

Chronic psychostimulant administration increases locomotor activity, which is referred to as locomotor sensitization. Calcineurin has been suggested to participate in psychostimulant-induced sensitization, but the underlying neurobiological mechanism is poorly understood.

OBJECTIVES

This study was designed to examine whether calcineurin activity and its substrates participate in methamphetamine (METH)-induced locomotor sensitization in rats.

MATERIALS AND METHODS

Two weeks daily METH (1 mg/kg, i.p.) was administrated to rats to induce locomotor sensitization, activity of calcineurin and its substrates Synapsin and glycogen synthase kinase-3β (GSK-3β) were detected. The initiation and expression of locomotor sensitization were tested by inhibition of calcineurin activity systematically or locally in the ventral tegmental area (VTA).

RESULTS

Expression of the calcineurin A subunit (catalytic subunit) increased in the VTA but not prefrontal cortex, nucleus accumbens, or hippocampus in rats sensitized to METH. The calcineurin inhibitor cyclosporine A, systemically administered or microinfused into the VTA, suppressed the initiation but not expression of METH-induced locomotor sensitization. Chronic METH exposure upregulated the expression of the calcineurin A subunit in the VTA, which was negatively associated with downregulation of the phosphorylation of Synapsin and GSK-3β. Moreover, the related molecular changes were blocked by systemically administered cyclosporine A or microinjections into the VTA.

CONCLUSIONS

These data elucidate the critical role of calcineurin in the neurobiological mechanism underlying METH-induced locomotor sensitization, suggesting that calcineurin might participate in the initiation of METH-induced locomotor sensitization by negatively regulating the activity of Synapsin and GSK-3β in the VTA.