Growth hormone secretagogues prevent dysregulation of skeletal muscle calcium homeostasis in a rat model of cisplatin‐induced cachexia

Abstract

BackgroundCachexia is a wasting condition associated with cancer types and, at the same time, is a serious and dose‐limiting side effect of cancer chemotherapy. Skeletal muscle loss is one of the main characteristics of cachexia that significantly contributes to the functional muscle impairment. Calcium‐dependent signaling pathways are believed to play an important role in skeletal muscle decline observed in cachexia, but whether intracellular calcium homeostasis is affected in this situation remains uncertain. Growth hormone secretagogues (GHS), a family of synthetic agonists of ghrelin receptor (GHS‐R1a), are being developed as a therapeutic option for cancer cachexia syndrome; however, the exact mechanism by which GHS interfere with skeletal muscle is not fully understood.MethodsBy a multidisciplinary approach ranging from cytofluorometry and electrophysiology to gene expression and histology, we characterized the calcium homeostasis in fast‐twitch extensor digitorum longus (EDL) muscle of adult rats with cisplatin‐induced cachexia and established the potential beneficial effects of two GHS (hexarelin and JMV2894) at this level. Additionally, in vivo measures of grip strength and of ultrasonography recordings allowed us to evaluate the functional impact of GHS therapeutic intervention.ResultsCisplatin‐treated EDL muscle fibres were characterized by a ~18% significant reduction of the muscle weight and fibre diameter together with an up‐regulation of atrogin1/Murf‐1 genes and a down‐regulation of Pgc1‐a gene, all indexes of muscle atrophy, and by a two‐fold increase in resting intracellular calcium, [Ca2+]i, compared with control rats. Moreover, the amplitude of the calcium transient induced by caffeine or depolarizing high potassium solution as well as the store‐operated calcium entry were ~50% significantly reduced in cisplatin‐treated rats. Calcium homeostasis dysregulation parallels with changes of functional ex vivo (excitability and resting macroscopic conductance) and in vivo (forelimb force and muscle volume) outcomes in cachectic animals. Administration of hexarelin or JMV2894 markedly reduced the cisplatin‐induced alteration of calcium homeostasis by both common as well as drug‐specific mechanisms of action. This effect correlated with muscle function preservation as well as amelioration of various atrophic indexes, thus supporting the functional impact of GHS activity on calcium homeostasis.ConclusionsOur findings provide a direct evidence that a dysregulation of calcium homeostasis plays a key role in cisplatin‐induced model of cachexia gaining insight into the etiopathogenesis of this form of muscle wasting. Furthermore, our demonstration that GHS administration efficaciously prevents cisplatin‐induced calcium homeostasis alteration contributes to elucidate the mechanism of action through which GHS could potentially ameliorate chemotherapy‐associated cachexia.

Growth hormone secretagogues hexarelin and JMV2894 protect skeletal muscle from mitochondrial damages in a rat model of cisplatin-induced cachexia

“…This change was completely inhibited by the administration of both GHS. Similar results, concerning the EDL muscle, were recently obtained 18 . No significant alteration were observed in heart and kidney weight in all treatment groups.…”

“…Since mitochondrial Ca 2+ signaling depends on interactions between mitochondria and ER/SR, via formation of MFN2 complexes, it is conceivable that alteration of MFN2 protein level can affect Ca 2+ signaling. Thus the Ca 2+ dysregulation observed in the same cachectic animal model 18 , can be related with the here reported increased expression of MFN2 and the occurrence of muscle weakness that we observed in vivo after cisplatin administration 18 may result from a combined effect of mitochondria and SR dysfunctions.…”

“…The reduction in body weight was associated with a significant decrease in cumulative food intake in cisplatin-treated rats, which was partially antagonized by GHS administration 18 .…”

“…Cisplatin-treated animals are a suitable animal model to study muscle derangements specifically associated with chemotherapy 13,14 and can be used for testing new therapies for cachexia 6,15–18 . Using a rat model of cisplatin-induced cachexia, we recently demonstrated that, consistently with the loss of skeletal muscle mass and occurrence of muscle weakness, the extensor digitorum longus (EDL) muscle of cachectic rats is characterized by a disrupted sarcoplasmic reticulum (SR) calcium signaling and an alteration of sarcolemma excitability 18 . Furthermore, according to the multiple actions proposed for ghrelin and GHS 11 , we demonstrated that administration of JMV2894, a novel peptidomimetic GHS, and hexarelin, a well-known synthetic hexapeptide, antagonized cisplatin-induced muscle wasting.…”

“…Furthermore, according to the multiple actions proposed for ghrelin and GHS 11 , we demonstrated that administration of JMV2894, a novel peptidomimetic GHS, and hexarelin, a well-known synthetic hexapeptide, antagonized cisplatin-induced muscle wasting. This was obtained by efficaciously preventing calcium homeostasis dysregulation both in terms of calcium movements and gene expression regulation of specific calcium-related proteins 18 .…”