Leutinizing Hormone Releasing Hormone Research Articles

Luteinizing hormone-releasing hormone peptide tethered nanoparticulate system for enhanced antitumoral efficacy of paclitaxel.

Paclitaxel (PTX) is an effective anticancer agent used in the therapy of a wide variety of cancers. However, the drug is difficult to formulate due to its low solubility, and therefore, it is administered under slow infusion with castor oil/ethanol solution as surfactant that causes serious side effects. This investigation investigates leutinizing hormone releasing hormone (LHRH)-tethered nanparticulate system as modality for cancer-specific delivery of PTX and therefore minimizing the adverse effects. LHRH-tethered poly(lactic-co-glycolic acid) copolymer with poly ethylene glycol side chain was synthesized, characterized and employed to formulate PTX-loaded nanoparticulate system. The developed nanoparticulate appears to be proficient in carrying as well as targeted delivery of PTX with improved therapeutic efficacy and better safety.

Chitosan-nanoconjugated hormone nanoparticles for sustained surge of gonadotropins and enhanced reproductive output in female fish.

A controlled release delivery system helps to overcome the problem of short life of the leutinizing hormone releasing hormone (LHRH) in blood and avoids use of multiple injections to enhance reproductive efficacy. Chitosan- and chitosan-gold nanoconjugates of salmon LHRH of desired size, dispersity and zeta potential were synthesized and evaluated at half the dose rate against full dose of bare LHRH for their reproductive efficacy in the female fish, Cyprinus carpio. Whereas injections of both the nanoconjugates induced controlled and sustained surge of the hormones with peak (P<0.01) at 24 hrs, surge due to bare LHRH reached its peak at 7 hrs and either remained at plateau or sharply declined thereafter. While the percentage of relative total eggs produced by fish were 130 and 67 per cent higher, that of fertilised eggs were 171 and 88 per cent higher on chitosan- and chitosan-gold nanoconjugates than bare LHRH. Chitosan nanoconjugates had a 13 per cent higher and chitosan gold preparation had a 9 per cent higher fertilization rate than bare LHRH. Histology of the ovaries also attested the pronounced effect of nanoparticles on reproductive output. This is the first report on use of chitosan-conjugated nanodelivery of gonadotropic hormone in fish.

Rational design of novel antiandrogens for neutralizing androgen receptor function in hormone refractory prostate cancer

The standard hormonal therapy with currently available antiandrogens and the leutinizing hormone releasing hormone (LHRH) analogs is not effective in the hormone-refractory stage of prostate cancer due to changes in androgen receptor (AR) signaling axis. In this refractory stage, AR continues to play a significant role in the growth of cancer cells even though the cancer cells are no longer dependent on the level of circulating androgens. A series of 11beta-Delta(9)-19 nortestosterone compounds were designed through structure-based rationale and tested for their binding affinity against AR and glucocorticoid receptor (GR) using fluorescence polarization assays, their agonistic ability to induce AR dependent transcription using PSA-driven report gene assays, and their growth inhibitory affects against a series of AR positive (LAPC4, LNCap, and CWR22R) and negative human prostate cancer cell lines (PC3) using MTT cell proliferation assays. This study proposes the design of novel bifunctional antiandrogens based on the conjugation of 11beta and/or 7alpha-Delta(9)-19 nortestosterone class of steroidal compounds to the synthetic ligand for FK506-binding proteins. As a critical step towards the development of bifunctional antiandrogens, highly potent and AR-specific lead compounds were identified using in vitro data. The lead compounds identified in this study possessed low binding affinity for GR, indicating the absence of undesirable antiglucocorticoid activity. The results of this study validate our drug discovery rationale based on the structural biology of AR and pave the pay for future development of bifunctional compounds in order to block AR function in hormone refractory stage of prostate cancer.

Artificial Propagation and Induction of Triploidy in Largemouth Bass Micropterus salmoides and Ploidy Discrimination using Erythrocyte Length

AbstractWe describe an artificial propagation procedure and simple ploidy discrimination techniques using erythrocyte major axis length for largemouth bass Micropterus salmoides. Hormonal treatments of 5 mg/kg of carp pituitary and 50 μg/kg of leutinizing hormone‐releasing hormone (LHRH) produced viable gametes in 21‐24 h, and triploidy was induced using a pressure treatment of 563 kg/cm2 on embryos for a 1‐min duration exactly 5 min following fertilization. We produced about 500 fingerling triploids and about 500 diploid controls, and verified genetic status of a subset of each group using flow cytometry. Erythrocyte length was measured for 10 known diploid and 10 known triploid individuals. Remaining fish were internally microtagged with group‐specific tags and mixed to test the model. We developed ploidy discrimination intervals based on the 99% confidence limits of mean erythrocyte length (MEL, N= 25 erythrocytes) for individual fish, which were 14.43‐16.66 μ.m for triploids, and 10.23‐13.62 μm for diploids. Logistic regression provided the discrimination model: Ploidy status (±) = ‐196.16 + 13.97 x MEL, with positive (+) outcomes considered triploid. Both discrimination techniques were 100% effective at differentiating ploidy of the 22 microtagged largemouth bass recollected from the mixed population. We did not observe a significant change in erythrocyte length as fish size increased, indicating that erythrocyte length is an accurate predictor of ploidy for all sizes of largemouth bass.

Galanin/GALP and galanin receptors: role in central control of feeding, body weight/obesity and reproduction?

Scientific and commercial pharmacological interest in the role of galanin and galanin receptors in the regulation of food intake, energy balance, and obesity has waned recently, following initial enthusiasm during the 1980–1990s. It has been replaced by efforts to understand the role of newly discovered peptide systems such as the hypocretin/orexins, melanocortins and cocaine- and amphetamine-regulated transcript (CART) and their relationship to the important hormones, leptin and insulin. Thus, while numerous studies have revealed the ability of galanin to stimulate food intake via actions at sites within the hypothalamus, and shown reliable changes in hypothalamic galanin synthesis in response to food ingestion; findings including the lack of a ‘body weight/obesity’ phenotype in galanin transgenic mouse strains and a lack of agonists/antagonists for galanin receptor subtypes have probably served to reduce enthusiasm. However, as more is learnt about the general and galanin-related neurochemistry of brain pathways involved in feeding, metabolism and body weight control, the potential importance of galanin systems is again in focus. Studies of the newly discovered galanin family peptide, ‘galanin-like peptide’ (GALP), highlight the likely role of galanin peptides and receptors in the physiological coupling of body weight, adiposity and reproductive function. GALP is produced by a discrete population of neurons within the basomedial arcuate nucleus (and median eminence) that send projections to the anterior paraventricular nucleus and that make close contacts with leutinizing hormone-releasing hormone (LHRH) neurons in basal forebrain. Furthermore, GALP neurons express leptin receptors and respond to leptin treatment by increasing their expression of GALP mRNA. Centrally administered GALP activates LHRH-immunoreactive neurons and increases plasma LH levels. These findings suggest a direct stimulatory action of endogenous GALP on gonadotropin secretion via actions within the hypothalamus/basal forebrain, with leptin actions linking this system to body adipose levels.

Combination endocrine therapy in the management of breast cancer.

Combination endocrine therapy has long been sought after as a means to better treat breast cancer. Agents that suppress estrogen production are given with agents that suppress estrogenic activity at the cellular level. Historically, these combinations have resulted in initial improvements in response rates, but relapse-free and overall survival were not significantly improved. Also, the increased toxicity seen with these regimens was limiting. New endocrine therapies with more potent activity and less toxicity have led to a resurgence of this idea in the management of breast cancer. Complete estrogen blockade has been compared with single-agent treatments in many different settings. The endocrine effects of this type of therapy are intriguing, but apparently do not readily predict a clinical advantage. The combination of an aromatase inhibitor and an antiestrogen, despite pharmacokinetic interactions, may prove to be beneficial. Results from ongoing trials are eagerly awaited to further address this question in postmenopausal breast cancer patients. For premenopausal breast cancer patients the options are more complex. Clinical outcomes with leutinizing hormone releasing hormone (LHRH) agonists plus aromatase inhibitors are limited to very small phase II studies and are not clearly superior to single-agent therapy. Clinical data in the metastatic setting with premenopausal patients favor the use of an LHRH agonist with tamoxifen over the use of an LHRH agonist alone. However, a similar comparison with tamoxifen alone is lacking with only one trial including this as a treatment arm. Adjuvant therapy with this combined endocrine approach (LHRH agonist plus antiestrogen) has been more extensively studied, but lacks crucial comparisons necessary for making complex treatment decisions. Hopefully, through investigative diligence and ingenuity this issue can be adequately understood. However, many exciting new agents are on the horizon that offer hope to further advance the progress made to date although further confounding the questions already answered.

Gonadotropin-Releasing Hormone Genes: Phylogeny, Structure, and Functions

Gonadotropin-releasing hormone (GnRH, previously called leutinizing hormone-releasing hormone, LHRH) is the final common signaling molecule used by the brain to regulate reproduction in all vertebrates. Recently, genes encoding two other GnRH forms have been discovered. Here we present a phylogenetic analysis that shows that the GnRH genes fall naturally into three distinct branches, each of which shares not only a molecular signature but also characteristic expression sites in the brain. The GnRH genes appear to have arisen through gene duplication from a single ancestral GnRH whose origin predates vertebrates. Several lines of data support this suggestion, including the fact that all three genes share an identical exonic structure. The existence of three distinct GnRH families suggests a new, natural nomenclature for the genes, and in addition, we present a logical proposal for naming the peptide sequences. The two recently discovered GnRH genes are unusual because they encode decapeptides that are identical in all the species in which they have been found. The control of gene expression also differs among the three gene families as might be expected since they have had separate evolutionary trajectories for perhaps 500 million years.

Endocrine mechanism of action of toremifene at the level of the central nervous system in advanced breast cancer patients

To differentiate the antagonistic and agonistic effect of toremifene at the level of the hypothalamus-hypophysis axis a leutinizing hormone-releasing hormone (LHRH) test was performed during a phase II clinical trial. In 15 postmenopausal patients with advanced breast cancer, follicle-stimulating hormone (FSH) and LH release--induced by an LHRH agonist (Suprefact injection, 0.5 mg s.c.)--was monitored during a 16-week period of toremifene treatment (60 mg/day p.o.). Prolactin, estradiol, and sex hormone-binding globulin (SHBG) levels were also measured. The functional test was carried out prior to toremifene therapy and then 4, 8, 12, and 16 weeks afterward. The drug sensitized the pituitary to the action of the gonadotrophins; the LHRH-induced FSH and LH release showed a considerably increasing tendency during the toremifene therapy. Estradiol levels decreased statistically significantly and SHBG levels showed a statistically significant increase. A decreased level of prolactin is the sign of an antiestrogenic effect of toremifene on the hypophysis and, as a result, provides evidence for a direct influence of toremifene upon the pituitary. An increase in LH and prolactin release in response to the LHRH test was characteristic in the responders. According to the LHRH test, the antagonistic effect of toremifene seems to be more dominant than the concomitantly existing agonistic property. Neither clinical nor endocrinological side effects could be observed at the level of the CNS during a prolonged period of toremifene administration.

Structure-based search for peptide ligands that cross-react with melanocortin receptors.

To define sequence motifs that can be used to identify peptide ligands of the melanocortin receptor (MCR). Screening of combinatorial libraries has led to identification of D-Trp-Nle-NH2 (Nle, norleucine) and D-Trp-Arg-NH2 as the smallest structures known to antagonize the amphibian MCR (1). As the basis of a search paradigm, peptide-ligands containing these or similar motifs within their larger primary structure were examined for ability to antagonize amphibian and recombinant human MCRs. Compounds examined include analogs of substance P, leutinizing-hormone releasing-hormone, endothelin, neurotensin, and opioid-somatostatin. Of seven compounds tested containing the predetermined search motif D-Trp-AAx (where AAx is Arg, Leu, Nle, or Ile), six were found to have previously unrecognized antagonist activity at the amphibian MCR (Kd 30 to 5000 nM). In contrast, of 14 similar control peptides lacking the D-Trp-AAx search motif, only somatostatin displayed measurable antagonist potency. The anticancer peptide, [Arg8, D-Trp7.9, N-methyl-Phe8]-substance P, was the most potent of the motif-containing peptides with a Kd of 31 nM. The mu-opioid antagonist D-Phe-cyclic[Cys-Tyr-D-Trp-Arg-Thr-Pen]-Thr-NH2 (CTAP) also blocked the amphibian MCR (Kd 1 microM), but the related mu-antagonist CTOP, different only by only by substitution of Arg with ornithine within the search motif, was found to agonize the amphibian MCR (EC50 67 nM). CTAP and the anticancer peptide were also tested on human MCRs (hMCRs); while CTAP competed with alpha-MSH at the hMC1 receptor, the anticancer peptide had no effect or was slightly stimulatory. We have identified dipeptide motifs that help distinguish antagonist ligands of the amphibian MCR from ligands known to interact with other G-protein coupled receptors. This approach might be generally applicable if motifs can identified for other receptors and their subtypes. In studies employing CTAP and CTOP, analogs previously considered highly selective for the mu-opioid receptor, cross-reaction with MCRs must be considered.

Iontophoresis of nafarelin: Effects of current density and concentration on electrotransport in vitro

The effects of administered concentration and applied current density on the iontophoresis of the leutinizing hormone releasing hormone (LHRH) analog, Nafarelin, have been studied in vitro. Peptide electrotransport, at fixed current density as a function of concentration, and at fixed concentration as a function of current density, has been measured across hairless mouse skin. The results indicate that Nafarelin delivery does not increase linearly with applied concentration: while there is an increase when the donor concentration is doubled from 0.5 to 1.0 mg/ml, further increments in applied peptide level result in decreased transport. At constant concentration, Nafarelin flux does increase with increasing current density (up to 0.63 mA/cm 2), but the dependence is very weak. Further experiments utilizing radiolabeled mannitol as a neutral marker of electroosmosis revealed that Nafarelin electrotransport is very sensitive to the extent and direction of convective flow. With increasing amounts of applied Nafarelin, reversal of electroosmosis (from the anode-to-cathode to the cathode-to-anode direction) was apparent; it appeared that the cationic peptide associated strongly with, and neutralized, the net negative charge on the skin, thereby resulting in depression and, ultimately, reversal of the convective flow. This, in turn, inhibits Nafarelin transport by the electroosmotic mechanism and explains, we believe, both the inverse dependence of flux upon concentration and the only weakly dependent behavior upon current density (where, although more current delivers more ions, more current also drives more peptide into the skin and thereby diminishes electroosmosis). Overall, then, this research emphasizes the complicated interplay between peptide structure, skin electrical properties and formulation variables which must be carefully considered in the development and optimization of an iontophoretic drug delivery device.

Characterization of convective solvent flow during iontophoresis.

During iontophoresis under neutral pH conditions, there is a net convective flow of volume (electroosmosis) from anode to cathode leading to the enhanced transport of dissolved polar (but uncharged) solutes in the same direction. The objective of this study was to address the following unresolved questions with respect to electroosmotic transport: [1] Whether the efficiency of electroosmotic transport is solute size-dependent and, if so, how severe is this dependence? [2] Is electroosmosis linearly related to current density in the same way that the iontophoretic flux of charged species appears to be? [3] Are positively charged permeants able to influence their own electrotransport across the skin (by modifying the net charge on the membrane and altering, as a result, the permselectivity) and, if so, why and to what extent? Electroosmosis was assessed from the iontophoreically driven fluxes of mannitol, sucrose and lactose across hairless mouse skin in vitro. It was found that:- (a) The electroosmotic transport rate of mannitol is similar to that of the disaccharides, sucrose and lactose, when examined under identical conditions. The dependence of electroosmotic flux upon molecular size requires study of solutes having a wider range of MW than those considered here. (b) Electroosmotic flow from anode-to-cathode increases with applied current density; similarly, convective flow in the opposite direction diminishes with increasing current density. Apparently, there is correlation between the net movement of solvent and the total flux of ions across the skin. (c) The permselectivity of skin can be 'neutralized' by driving, iontophoretically, a cationic, lipophilic peptide (specifically the leutinizing hormone releasing hormone (LHRH) analog, Nafarelin) into the membrane.(ABSTRACT TRUNCATED AT 250 WORDS)

J tuning of SUPERCOSY as an aid to resonance assignments

Nuclear magnetic resonance spectroscopy has been extensively used for conformational analysis of biological molecules (I). With the advent of two-dimensional NMR techniques, it has become possible to obtain individual resonance assignments and detailed structural information on large molecules having molecular weights of the order of 6000-7000 (2-15). Recently a pulse sequence has been proposed (26) which is superior to the normal COSY (I 7, 18) scheme for observation of coupling correlations in complicated spin systems. The new pulse scheme has the sequence: 90-t,-A-180-A-90-A-180-At2, where A is a fixed delay and t, and t2, are, respectively, the usual evolution and detection periods of two-dimensional spectroscopy. The value of A depends upon the nature of the spin systems and the magnitudes of the coupling constants (J) between the spins. For an AX spin system, the optimum value of A is 1/4J and for an AX2 system, it is 1/2J. The main advantage of SUPERCOSY over the COSY scheme lies in the fact that the cross-peaks and the diagonal peaks in SUPERCOSY consist of in-phase and antiphase components respectively, while exactly the opposite is true in the COSY spectrum. Consequently, under conditions of overlap or poor digital resolution, cross-peaks build much faster in intensity, while the diagonal peaks tend to grow relatively slower. The fact that the fixed delay A in the SUPERCOSY pulse scheme depends on the value of J enables one to tune the experiment to a particular value of J which may be of special interest. In other words, cross-peaks arising from particular values of J can be selectively enhanced. We have used this principle here to observe selective proton couplings so as to arrive at a unique resonance assignment of the ring protons in the tryptophan residue of a decapeptide, leutinizing hormone releasing hormone (LHRH). Figure 1 shows SUPERCOSY spectra for two different values of A, 30 ms (A) and 40 ms (B). While the complete analysis will be published separately, the intention of this note is to demonstrate how J tuning of SUPERCOSY can be used as an aid in resonance assignment procedures. The two spectra shown in Fig. 1 depict variations in the intensities of several cross-peaks and diagonal peaks. Figure 2 shows expansions of the aromatic regions of the spectra (02 = 6.4-l 1 .O ppm; WI = 6.4-l 1 .O ppm). The peaks labeled A, B, C, D, etc, identify the J-coupling correlations between various ring protons. For example, in the spectrum of Fig. 2A,

Diurnal and circannual rhythms in leutinizing hormone-releasing hormone (lhrh) like material in the pineal gland of seasonally breeding indian weaver bird

Diurnal and circannual rhythms in leutinizing hormone-releasing hormone (lhrh) like material in the pineal gland of seasonally breeding indian weaver bird