Grzegorz Rosiński

Proctolin, an insect neuropeptide

Synthetic, biological and conformational studies on the insect neuropeptide proctolin (Arg‐Tyr‐Leu‐Pro‐Thr) and some of its analogues are reviewed. Copyright

Differences in trehalase activity in the intestine of fed and starved larvae of Tenebrio molitor L.

Abstract Studies made on trehalase activity in some tissues of Tenebrio molitor larvae have shown that enzyme activity is highest in the intestine, with a low level of activity in the fat body and muscles and traces of activity in the haemolymph. Higher intestinal trehalase activity was found in larvae fed on flaked oats with the addition of brewers yeast and fresh carrot (diet A) than in larvae fed the same diet without carrot (diet B). Starvation of larvae previously reared on diet A caused a decrease in trehalase activity in all the examined tissues except the haemolymph where traces remained. Refeeding starved larvae on diet A caused an increase in intestinal trehalase activity after as little as 2 hr.

Hyperglycaemic and myoactive factors in the corpora cardiaca of the mealworm, Tenebrio molitor

Abstract The corpus cardiacum-corpus allatum complex of Tenebrio molitor contains factors causing hyperglycaemia, stimulating carbohydrate release from the fat body in vitro, and accelerating heart beat in the donor insect. However, no adipokinetic response can be demonstrated upon injection of extracts of this complex in larvae or young imagines. The carbohydrate elevation in the haemolymph is time- and dose-dependent, with a maximal effect about 90–180 min after injection. About 0.03–0.05 gland equivalents are needed to produce a significant increase in the larval and imaginal bioassays; maximal responses in both systems were reached with about 0.5 gland equivalents. Fat body treated in vitro with an extract of 0.5 gland equivalents releases about 130% more carbohydrate into 1 ml physiological saline after 1 h than paired tissue controls. The characteristic response of a semi-isolated adult heart to the endogenous myoactive factor(s) of the corpus cardiacum-allatum extract was an increase in heart beat frequency and a decrease in the amplitude of contraction. The response was dose-dependent and 0.05 gland equivalents were needed to exert a stimulatory effect on the myocardium. Fractionation of a methanolic extract of endocrine complex from Tenebrio molitor by RP-HPLC shows that the hyperglycaemic activity is confined to two regions. A myoactive factor appears to elute just after the second hyperglycaemic material, whereas a cardio-inhibitory factor has more hydrophobic properties. Synthetic neuropeptides adipokinetic hormone I and red pigment concentrating hormone injected as a dose of 8 pmol produce a weak hyperglycaemic effect, whereas myoactive factors I and II and hypertrehalosaemic factor II cause no hyperglycaemia. No adipokinetic response was shown upon injection of any of the neuropeptides tested. A very small stimulation of the adult heart beat frequency was observed upon administration of 20 pmol adipokinetic hormone I and myoactive factor I; all other peptides were without effect. In conclusion, the bioassays with Tenebrio appear to show some species-specificity and the hyperglycaemic/myoactive factors present in the corpus cardiacum-allatum neurosecretory complex may possess distinctive properties compared with adipokinetic hormone I, red pigment concentrating hormone, myoactive factors I and II, and hypertrehalosaemic factor II.

The primary structure of the hypertrehalosemic neuropeptide from tenebrionid beetles: a novel member of the AKH/RPCH family.

A hypertrehalosemic neuropeptide from the corpora cardiac of the two tenebrionid beetle species, Tenebrio molitor and Zophobas rugipes, was purified by high performance liquid chromatography, and its sequence determined by pulsed-liquid phase sequencing employing Edman degradation after deblocking enzymatically the N-terminal pyroglutamate residue. Additionally, the C-terminus of the peptide was blocked as shown by the lack of breakdown using carboxypeptidase. In both species an identical octapeptide, designated Tem-HrTH, with the following amino acid sequence, was found: pGlu-Leu-Asn-Phe-Ser-Pro-Asn-Trp-NH2. This primary sequence has an 88% homology with the hypertrehalosemic hormone I (Pea-CAH-I) from the American cockroach as well as with the red pigment-concentrating hormone (RPCH) of prawns. Injection of the synthetic peptide into larvae or young adults of T. molitor or adult Z. rugipes increases the hemolymph carbohydrate levels in a dose-dependent manner. Thin layer chromatography identified the elevated sugar component of the hemolymph as the disaccharide trehalose. Carbohydrate release from larval fat body in vitro was also shown upon administration of a low concentration of synthetic Tem-HrTH.

Cardioacceleratory action of tachykinin-related neuropeptides and proctolin in two coleopteran insect species.

Several cardioactive peptides have been identified in insects and most of them are likely to act on the heart as neurohormones. Here we have investigated the cardioactive properties of members of a family of insect tachykinin-related peptides (TRPs) in heterologous bioassays with two coleopteran insects, Tenebrio molitor and Zophobas atratus. Their effects were compared with the action of the pentapeptide proctolin. We tested the cardiotropic activity of LemTRP-4 isolated from the midgut of the cockroach Leucophaea maderae, CavTK-I and CavTK-II isolated from the blowfly Calliphora vomitoria. The semi-isolated hearts of the two coleopteran species were strongly stimulated by proctolin. We observed a dose dependent increase in heartbeat frequency (a positive chronotropic effect) and a decrease in amplitude of contractions (a negative inotropic effect). In both beetles the TRPs are less potent cardiostimulators and exert lower maximal frequency responses than proctolin. LemTRP-4 applied at 10(-9)-10(-6) M was cardiostimulatory in both species inducing an increase of heart beat frequency. The amplitude of contractions was stimulated only in Z. atratus. CavTK-I and CavTK-II also exerted cardiostimulatory effects in Z. atratus at 10(-9)-10(-6) M. Both peptides stimulated the frequency, but only CavTK-II increased the amplitude of the heart beat. In T. molitor, however, the CavTKs induced no significant effect on the heart. Immunocytochemistry with antisera to the locust TRPs LomTK-I and LomTK-II was employed to identify the source of TRPs acting on the heart. No innervation of the heart by TRP immunoreactive axons could detected, instead it is possible that TRPs reach the heart by route of the circulation. The likely sources of circulating TRPs in these insects are TRP-immunoreactive neurosecretory cells of the median neurosecretory cell group in the brain with terminations in the corpora cardiaca and endocrine cells in the midgut. In conclusion, LemTRP-4, CavTK-I and CavTK-II are less potent cardiostimulators than proctolin and also exert stimulatory rather than inhibitory action on amplitude of contractions. The differences in the responses to proctolin and TRPs suggest that the peptides regulate heart activity by different mechanisms.

Insects Antiviral and Anticancer Peptides: New Leads for the Future?

Insect produce wide range of protein and peptides as a first fast defense line against pathogen infection. These agents act in different ways including insect immune system activation or by direct impact on the target tumor cells or viruses. It has been shown that some of the insect peptides suppress viral gene and protein expression, rybosilate DNA, whereas others cause membrane lysis, induce apoptosis or arrest cell cycle. Several of the purified and characterized peptides of insect origin are very promising in treating of serious human diseases like human immunodeficiency virus (HIV), herpex simplex virus (HSV) or leukaemia. However, some obstacles need to be overcome. Cytotoxic activity of peptides, susceptibility to proteases or high cost of production remain still unsolved problems. Reports on the peptides antiviral and antitumour mechanisms are scanty. Thus, in this review we present characteristic, mode of action and potential medical applications of insects origin peptides with the antiviral and antitumour activity.

Developmental changes in cellular and humoral responses of the burying beetle Nicrophorus vespilloides (Coleoptera, Silphidae).

Necrophagous beetles of the genus Nicrophorus have developed various defence mechanisms that reduce the negative effects of adverse environmental conditions. However, many physiological and ecological aspects, including the functioning of the immune system in burying beetles, are still unknown. In this study, we show developmental changes in cellular and humoral responses of larvae, pupae, and adults of Nicrophorus vespilloides. We assessed changes in total haemocyte count, phenoloxidase activity, and phagocytic ability of haemocytes. We found that during larval development there is a progressive increase in humoral and cellular activities, and these responses are correlated with alterations of total haemocyte counts in the haemolymph. In the pupal stage, a sharp drop in the number of phagocytic haemocytes and an increase in phenoloxidase activity were observed. In adults, cellular and humoral responses remained at a lower level. It is probable that high lytic activity of anal and oral secretions produced by parents supports a lower response of the immune system in the initial phase of larval development. In the studied stages, we also observed differences in polymerisation of F-actin cytoskeleton of haemocytes, number of haemocytes forming filopodia, and filopodia length. These results suggest that the differences in immune responses during various stages of development of N. vespilloides are associated with a dynamically changing environment and different risks of infection. For the first time a detailed analysis of stage-specific alterations in immune system activity during development of the burying beetle is presented.

The pro-apoptotic action of the peptide hormone, Neb -colloostatin, on insect haemocytes

SUMMARY The gonadoinhibitory peptide hormone Neb-colloostatin was first isolated from ovaries of the flesh fly Neobellieria bullata. This 19-mer peptide is thought to be a cleaved product of a collagen-like precursor molecule that is formed during remodelling of the extracellular matrix. In this study, we report that upon injection of picomolar and nanomolar doses, this peptide exerts a pro-apoptotic action on haemocytes of Tenebrio molitor adults, as visualized by changes in morphology and viability. The F-actin cytoskeleton was found to aggregate into distinctive patches. This may be responsible for the observed inhibition of adhesion of haemocytes and for the stimulation of filopodia formation. However, Neb-colloostatin injection did not induce the formation of autophagic vacuoles. Our results suggest that physiological concentrations of Neb-colloostatin play an important role in controlling the quantity and activity of haemocytes in insect haemolymph. They also suggest that during periods in which Neb-colloostatin is released, this peptide may cause a weakening of the insects’ immune system. This is the first report that exposure to a peptide hormone causes apoptosis in insect haemocytes.

Mono- and polynuclear copper(II) complexes of alloferons 1 with point mutations (H6A) and (H12A): stability structure and cytotoxicity.

Mononuclear and polynuclear copper(II) complexes of the alloferons 1 (Allo1) with point mutations (H6A) H(1)GVSGA(6)GQH(9)GVH(12)G-COOH (Allo6A) and (H12A) H(1)GVSGH(6)GQH(9)GVA(12)G-COOH (Allo12A) have been studied by potentiometric, UV-visible, CD, EPR spectroscopic, and mass spectrometry (MS) methods. Complete complex speciation at different metal-to-ligand ratios ranging from 1:1 to 3:1 was obtained. At physiological pH 7.4 and a 1:1 metal-to-ligand molar ratio, the Allo6A and Allo12A peptides form CuL complexes with the 4N {NH2, N(Im)-H(1),2N(Im)} binding mode. The amine nitrogen donor and the imidazole nitrogen atoms (H(9)H(12) or H(6)H(9)) can be considered to be independent metal-binding sites in the species formed for the systems studied. As a consequence, di- and trinuclear complexes for the metal-to-ligand 2:1 and 3:1 molar ratios dominate in solution, respectively. The induction of apoptosis in vivo in Tenebrio molitor cells by the ligands and their copper(II) complexes at pH 7.4 was studied. The biological results show that copper(II) ions in vivo did not cause any apparent apoptotic features. The most active was the Cu(II)-Allo12A complex formed at pH 7.4 with a {NH2, N(Im)-H(1),N(Im)-H(6),N(Im)-H(9)} binding site. It exhibited 123% higher of caspase activity in hemocytes than the native peptide, Allo1.

UCP4 expression changes in larval and pupal fat bodies of the beetle Zophobas atratus under adipokinetic hormone treatment

We investigated the influence of adipokinetic hormone (AKH), an insect neurohormone, on uncoupling protein 4 (ZaUCP4) expression and activity in larval and pupal fat body mitochondria of the beetle Zophobas atratus in relation to intermediary metabolism. Homologous Tenmo-AKH was administered to the beetle larvae and pupae as either a single dose or as two doses of 20pmol during a 24h interval. In the larval and pupal fat bodies, downregulation of ZaUCP4 expression at the mRNA and protein levels was observed 24h and 48h after AKH treatment, respectively. In both developmental stages, ZaUCP4 activity was lowered in fat body mitochondria 48h after AKH treatment. In the AKH-injected larvae, changes in ZaUCP4 expression were accompanied by the mobilization of carbohydrate reserves, no change in the concentration of total lipids and an increase in the free fatty acid level. In contrast, AKH had no effect on carbohydrate metabolism in the pupal fat body but induced lipid mobilization. It seems that AKH influences ZaUCP4 expression by triggering multiple events and that it has different physiological roles in controlling intermediary metabolism in the fat body of the beetle larvae and pupae.